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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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SPDX-License-Identifier: GPL-2.0-only/* * kernel/lockdep.c * * Runtime locking correctness validator * * Started by Ingo Molnar: * * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra * * this code maps all the lock dependencies as they occur in a live kernel * and will warn about the following classes of locking bugs: * * - lock inversion scenarios * - circular lock dependencies * - hardirq/softirq safe/unsafe locking bugs * * Bugs are reported even if the current locking scenario does not cause * any deadlock at this point. * * I.e. if anytime in the past two locks were taken in a different order, * even if it happened for another task, even if those were different * locks (but of the same class as this lock), this code will detect it. * * Thanks to Arjan van de Ven for coming up with the initial idea of * mapping lock dependencies runtime. */#define DISABLE_BRANCH_PROFILING#include <linux/mutex.h>#include <linux/sched.h>#include <linux/sched/clock.h>#include <linux/sched/task.h>#include <linux/sched/mm.h>#include <linux/delay.h>#include <linux/module.h>#include <linux/proc_fs.h>#include <linux/seq_file.h>#include <linux/spinlock.h>#include <linux/kallsyms.h>#include <linux/interrupt.h>#include <linux/stacktrace.h>#include <linux/debug_locks.h>#include <linux/irqflags.h>#include <linux/utsname.h>#include <linux/hash.h>#include <linux/ftrace.h>#include <linux/stringify.h>#include <linux/bitmap.h>#include <linux/bitops.h>#include <linux/gfp.h>#include <linux/random.h>#include <linux/jhash.h>#include <linux/nmi.h>#include <linux/rcupdate.h>#include <linux/kprobes.h>#include <linux/lockdep.h>#include <linux/context_tracking.h>#include <linux/console.h>#include <linux/kasan.h>
#include <asm/sections.h>
#include "lockdep_internals.h"#include "lock_events.h"
#include <trace/events/lock.h>
#ifdef CONFIG_PROVE_LOCKINGstatic int prove_locking = 1;module_param(prove_locking, int, 0644);#else#define prove_locking 0#endif
#ifdef CONFIG_LOCK_STATstatic int lock_stat = 1;module_param(lock_stat, int, 0644);#else#define lock_stat 0#endif
#ifdef CONFIG_SYSCTLstatic const struct ctl_table kern_lockdep_table[] = {#ifdef CONFIG_PROVE_LOCKING { .procname = "prove_locking", .data = &prove_locking, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, },#endif /* CONFIG_PROVE_LOCKING */#ifdef CONFIG_LOCK_STAT { .procname = "lock_stat", .data = &lock_stat, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, },#endif /* CONFIG_LOCK_STAT */};
static __init int kernel_lockdep_sysctls_init(void){ register_sysctl_init("kernel", kern_lockdep_table); return 0;}late_initcall(kernel_lockdep_sysctls_init);#endif /* CONFIG_SYSCTL */
DEFINE_PER_CPU(unsigned int, lockdep_recursion);EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
static __always_inline bool lockdep_enabled(void){ if (!debug_locks) return false;
if (this_cpu_read(lockdep_recursion)) return false;
if (current->lockdep_recursion) return false;
return true;}
/* * lockdep_lock: protects the lockdep graph, the hashes and the * class/list/hash allocators. * * This is one of the rare exceptions where it's justified * to use a raw spinlock - we really dont want the spinlock * code to recurse back into the lockdep code... */static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;static struct task_struct *__owner;
static inline void lockdep_lock(void){ DEBUG_LOCKS_WARN_ON(!irqs_disabled());
__this_cpu_inc(lockdep_recursion); arch_spin_lock(&__lock); __owner = current;}
static inline void lockdep_unlock(void){ DEBUG_LOCKS_WARN_ON(!irqs_disabled());
if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current)) return;
__owner = NULL; arch_spin_unlock(&__lock); __this_cpu_dec(lockdep_recursion);}
#ifdef CONFIG_PROVE_LOCKINGstatic inline bool lockdep_assert_locked(void){ return DEBUG_LOCKS_WARN_ON(__owner != current);}#endif
static struct task_struct *lockdep_selftest_task_struct;
static int graph_lock(void){ lockdep_lock(); lockevent_inc(lockdep_lock); /* * Make sure that if another CPU detected a bug while * walking the graph we dont change it (while the other * CPU is busy printing out stuff with the graph lock * dropped already) */ if (!debug_locks) { lockdep_unlock(); return 0; } return 1;}
static inline void graph_unlock(void){ lockdep_unlock();}
/* * Turn lock debugging off and return with 0 if it was off already, * and also release the graph lock: */static inline int debug_locks_off_graph_unlock(void){ int ret = debug_locks_off();
lockdep_unlock();
return ret;}
unsigned long nr_list_entries;static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
/* * All data structures here are protected by the global debug_lock. * * nr_lock_classes is the number of elements of lock_classes[] that is * in use. */#define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)#define KEYHASH_SIZE (1UL << KEYHASH_BITS)static struct hlist_head lock_keys_hash[KEYHASH_SIZE];unsigned long nr_lock_classes;unsigned long nr_zapped_classes;unsigned long nr_dynamic_keys;unsigned long max_lock_class_idx;struct lock_class lock_classes[MAX_LOCKDEP_KEYS];DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
static inline struct lock_class *hlock_class(struct held_lock *hlock){ unsigned int class_idx = hlock->class_idx;
/* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */ barrier();
if (!test_bit(class_idx, lock_classes_in_use)) { /* * Someone passed in garbage, we give up. */ DEBUG_LOCKS_WARN_ON(1); return NULL; }
/* * At this point, if the passed hlock->class_idx is still garbage, * we just have to live with it */ return lock_classes + class_idx;}
#ifdef CONFIG_LOCK_STATstatic DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
static inline u64 lockstat_clock(void){ return local_clock();}
static int lock_point(unsigned long points[], unsigned long ip){ int i;
for (i = 0; i < LOCKSTAT_POINTS; i++) { if (points[i] == 0) { points[i] = ip; break; } if (points[i] == ip) break; }
return i;}
static void lock_time_inc(struct lock_time *lt, u64 time){ if (time > lt->max) lt->max = time;
if (time < lt->min || !lt->nr) lt->min = time;
lt->total += time; lt->nr++;}
static inline void lock_time_add(struct lock_time *src, struct lock_time *dst){ if (!src->nr) return;
if (src->max > dst->max) dst->max = src->max;
if (src->min < dst->min || !dst->nr) dst->min = src->min;
dst->total += src->total; dst->nr += src->nr;}
void lock_stats(struct lock_class *class, struct lock_class_stats *stats){ int cpu, i;
memset(stats, 0, sizeof(struct lock_class_stats)); for_each_possible_cpu(cpu) { struct lock_class_stats *pcs = &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
for (i = 0; i < ARRAY_SIZE(stats->contention_point); i++) stats->contention_point[i] += pcs->contention_point[i];
for (i = 0; i < ARRAY_SIZE(stats->contending_point); i++) stats->contending_point[i] += pcs->contending_point[i];
lock_time_add(&pcs->read_waittime, &stats->read_waittime); lock_time_add(&pcs->write_waittime, &stats->write_waittime);
lock_time_add(&pcs->read_holdtime, &stats->read_holdtime); lock_time_add(&pcs->write_holdtime, &stats->write_holdtime);
for (i = 0; i < ARRAY_SIZE(stats->bounces); i++) stats->bounces[i] += pcs->bounces[i]; }}
void clear_lock_stats(struct lock_class *class){ int cpu;
for_each_possible_cpu(cpu) { struct lock_class_stats *cpu_stats = &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
memset(cpu_stats, 0, sizeof(struct lock_class_stats)); } memset(class->contention_point, 0, sizeof(class->contention_point)); memset(class->contending_point, 0, sizeof(class->contending_point));}
static struct lock_class_stats *get_lock_stats(struct lock_class *class){ return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];}
static void lock_release_holdtime(struct held_lock *hlock){ struct lock_class_stats *stats; u64 holdtime;
if (!lock_stat) return;
holdtime = lockstat_clock() - hlock->holdtime_stamp;
stats = get_lock_stats(hlock_class(hlock)); if (hlock->read) lock_time_inc(&stats->read_holdtime, holdtime); else lock_time_inc(&stats->write_holdtime, holdtime);}#elsestatic inline void lock_release_holdtime(struct held_lock *hlock){}#endif
/* * We keep a global list of all lock classes. The list is only accessed with * the lockdep spinlock lock held. free_lock_classes is a list with free * elements. These elements are linked together by the lock_entry member in * struct lock_class. */static LIST_HEAD(all_lock_classes);static LIST_HEAD(free_lock_classes);
/** * struct pending_free - information about data structures about to be freed * @zapped: Head of a list with struct lock_class elements. * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements * are about to be freed. */struct pending_free { struct list_head zapped; DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);};
/** * struct delayed_free - data structures used for delayed freeing * * A data structure for delayed freeing of data structures that may be * accessed by RCU readers at the time these were freed. * * @rcu_head: Used to schedule an RCU callback for freeing data structures. * @index: Index of @pf to which freed data structures are added. * @scheduled: Whether or not an RCU callback has been scheduled. * @pf: Array with information about data structures about to be freed. */static struct delayed_free { struct rcu_head rcu_head; int index; int scheduled; struct pending_free pf[2];} delayed_free;
/* * The lockdep classes are in a hash-table as well, for fast lookup: */#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)#define classhashentry(key) (classhash_table + __classhashfn((key)))
static struct hlist_head classhash_table[CLASSHASH_SIZE];
/* * We put the lock dependency chains into a hash-table as well, to cache * their existence: */#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
static struct hlist_head chainhash_table[CHAINHASH_SIZE];
/* * the id of held_lock */static inline u16 hlock_id(struct held_lock *hlock){ BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));}
static inline __maybe_unused unsigned int chain_hlock_class_idx(u16 hlock_id){ return hlock_id & (MAX_LOCKDEP_KEYS - 1);}
/* * The hash key of the lock dependency chains is a hash itself too: * it's a hash of all locks taken up to that lock, including that lock. * It's a 64-bit hash, because it's important for the keys to be * unique. */static inline u64 iterate_chain_key(u64 key, u32 idx){ u32 k0 = key, k1 = key >> 32;
__jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
return k0 | (u64)k1 << 32;}
void lockdep_init_task(struct task_struct *task){ task->lockdep_depth = 0; /* no locks held yet */ task->curr_chain_key = INITIAL_CHAIN_KEY; task->lockdep_recursion = 0;}
static __always_inline void lockdep_recursion_inc(void){ __this_cpu_inc(lockdep_recursion);}
static __always_inline void lockdep_recursion_finish(void){ if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion))) __this_cpu_write(lockdep_recursion, 0);}
void lockdep_set_selftest_task(struct task_struct *task){ lockdep_selftest_task_struct = task;}
/* * Debugging switches: */
#define VERBOSE 0#define VERY_VERBOSE 0
#if VERBOSE# define HARDIRQ_VERBOSE 1# define SOFTIRQ_VERBOSE 1#else# define HARDIRQ_VERBOSE 0# define SOFTIRQ_VERBOSE 0#endif
#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE/* * Quick filtering for interesting events: */static int class_filter(struct lock_class *class){#if 0 /* Example */ if (class->name_version == 1 && !strcmp(class->name, "lockname")) return 1; if (class->name_version == 1 && !strcmp(class->name, "&struct->lockfield")) return 1;#endif /* Filter everything else. 1 would be to allow everything else */ return 0;}#endif
static int verbose(struct lock_class *class){#if VERBOSE return class_filter(class);#endif return 0;}
static void print_lockdep_off(const char *bug_msg){ printk(KERN_DEBUG "%s\n", bug_msg); printk(KERN_DEBUG "turning off the locking correctness validator.\n");#ifdef CONFIG_LOCK_STAT printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");#endif}
unsigned long nr_stack_trace_entries;
#ifdef CONFIG_PROVE_LOCKING/** * struct lock_trace - single stack backtrace * @hash_entry: Entry in a stack_trace_hash[] list. * @hash: jhash() of @entries. * @nr_entries: Number of entries in @entries. * @entries: Actual stack backtrace. */struct lock_trace { struct hlist_node hash_entry; u32 hash; u32 nr_entries; unsigned long entries[] __aligned(sizeof(unsigned long));};#define LOCK_TRACE_SIZE_IN_LONGS \ (sizeof(struct lock_trace) / sizeof(unsigned long))/* * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock. */static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2){ return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries && memcmp(t1->entries, t2->entries, t1->nr_entries * sizeof(t1->entries[0])) == 0;}
static struct lock_trace *save_trace(void){ struct lock_trace *trace, *t2; struct hlist_head *hash_head; u32 hash; int max_entries;
BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE); BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries); max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries - LOCK_TRACE_SIZE_IN_LONGS;
if (max_entries <= 0) { if (!debug_locks_off_graph_unlock()) return NULL;
nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!"); dump_stack(); nbcon_cpu_emergency_exit();
return NULL; } trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
hash = jhash(trace->entries, trace->nr_entries * sizeof(trace->entries[0]), 0); trace->hash = hash; hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1)); hlist_for_each_entry(t2, hash_head, hash_entry) { if (traces_identical(trace, t2)) return t2; } nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries; hlist_add_head(&trace->hash_entry, hash_head);
return trace;}
/* Return the number of stack traces in the stack_trace[] array. */u64 lockdep_stack_trace_count(void){ struct lock_trace *trace; u64 c = 0; int i;
for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) { hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) { c++; } }
return c;}
/* Return the number of stack hash chains that have at least one stack trace. */u64 lockdep_stack_hash_count(void){ u64 c = 0; int i;
for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) if (!hlist_empty(&stack_trace_hash[i])) c++;
return c;}#endif
unsigned int nr_hardirq_chains;unsigned int nr_softirq_chains;unsigned int nr_process_chains;unsigned int max_lockdep_depth;
#ifdef CONFIG_DEBUG_LOCKDEP/* * Various lockdep statistics: */DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);#endif
#ifdef CONFIG_PROVE_LOCKING/* * Locking printouts: */
#define __USAGE(__STATE) \ [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \ [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \ [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\ [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
static const char *usage_str[] ={#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)#include "lockdep_states.h"#undef LOCKDEP_STATE [LOCK_USED] = "INITIAL USE", [LOCK_USED_READ] = "INITIAL READ USE", /* abused as string storage for verify_lock_unused() */ [LOCK_USAGE_STATES] = "IN-NMI",};#endif
const char *__get_key_name(const struct lockdep_subclass_key *key, char *str){ return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);}
static inline unsigned long lock_flag(enum lock_usage_bit bit){ return 1UL << bit;}
static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit){ /* * The usage character defaults to '.' (i.e., irqs disabled and not in * irq context), which is the safest usage category. */ char c = '.';
/* * The order of the following usage checks matters, which will * result in the outcome character as follows: * * - '+': irq is enabled and not in irq context * - '-': in irq context and irq is disabled * - '?': in irq context and irq is enabled */ if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) { c = '+'; if (class->usage_mask & lock_flag(bit)) c = '?'; } else if (class->usage_mask & lock_flag(bit)) c = '-';
return c;}
void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS]){ int i = 0;
#define LOCKDEP_STATE(__STATE) \ usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \ usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);#include "lockdep_states.h"#undef LOCKDEP_STATE
usage[i] = '\0';}
static void __print_lock_name(struct held_lock *hlock, struct lock_class *class){ char str[KSYM_NAME_LEN]; const char *name;
name = class->name; if (!name) { name = __get_key_name(class->key, str); printk(KERN_CONT "%s", name); } else { printk(KERN_CONT "%s", name); if (class->name_version > 1) printk(KERN_CONT "#%d", class->name_version); if (class->subclass) printk(KERN_CONT "/%d", class->subclass); if (hlock && class->print_fn) class->print_fn(hlock->instance); }}
static void print_lock_name(struct held_lock *hlock, struct lock_class *class){ char usage[LOCK_USAGE_CHARS];
get_usage_chars(class, usage);
printk(KERN_CONT " ("); __print_lock_name(hlock, class); printk(KERN_CONT "){%s}-{%d:%d}", usage, class->wait_type_outer ?: class->wait_type_inner, class->wait_type_inner);}
static void print_lockdep_cache(struct lockdep_map *lock){ const char *name; char str[KSYM_NAME_LEN];
name = lock->name; if (!name) name = __get_key_name(lock->key->subkeys, str);
printk(KERN_CONT "%s", name);}
static void print_lock(struct held_lock *hlock){ /* * We can be called locklessly through debug_show_all_locks() so be * extra careful, the hlock might have been released and cleared. * * If this indeed happens, lets pretend it does not hurt to continue * to print the lock unless the hlock class_idx does not point to a * registered class. The rationale here is: since we don't attempt * to distinguish whether we are in this situation, if it just * happened we can't count on class_idx to tell either. */ struct lock_class *lock = hlock_class(hlock);
if (!lock) { printk(KERN_CONT "<RELEASED>\n"); return; }
printk(KERN_CONT "%px", hlock->instance); print_lock_name(hlock, lock); printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);}
static void lockdep_print_held_locks(struct task_struct *p){ int i, depth = READ_ONCE(p->lockdep_depth);
if (!depth) printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p)); else printk("%d lock%s held by %s/%d:\n", depth, str_plural(depth), p->comm, task_pid_nr(p)); /* * It's not reliable to print a task's held locks if it's not sleeping * and it's not the current task. */ if (p != current && task_is_running(p)) return; for (i = 0; i < depth; i++) { printk(" #%d: ", i); print_lock(p->held_locks + i); }}
static void print_kernel_ident(void){ printk("%s %.*s %s\n", init_utsname()->release, (int)strcspn(init_utsname()->version, " "), init_utsname()->version, print_tainted());}
static int very_verbose(struct lock_class *class){#if VERY_VERBOSE return class_filter(class);#endif return 0;}
/* * Is this the address of a static object: */#ifdef __KERNEL__static int static_obj(const void *obj){ unsigned long addr = (unsigned long) obj;
if (is_kernel_core_data(addr)) return 1;
/* * keys are allowed in the __ro_after_init section. */ if (is_kernel_rodata(addr)) return 1;
/* * in initdata section and used during bootup only? * NOTE: On some platforms the initdata section is * outside of the _stext ... _end range. */ if (system_state < SYSTEM_FREEING_INITMEM && init_section_contains((void *)addr, 1)) return 1;
/* * in-kernel percpu var? */ if (is_kernel_percpu_address(addr)) return 1;
/* * module static or percpu var? */ return is_module_address(addr) || is_module_percpu_address(addr);}#endif
/* * To make lock name printouts unique, we calculate a unique * class->name_version generation counter. The caller must hold the graph * lock. */static int count_matching_names(struct lock_class *new_class){ struct lock_class *class; int count = 0;
if (!new_class->name) return 0;
list_for_each_entry(class, &all_lock_classes, lock_entry) { if (new_class->key - new_class->subclass == class->key) return class->name_version; if (class->name && !strcmp(class->name, new_class->name)) count = max(count, class->name_version); }
return count + 1;}
/* used from NMI context -- must be lockless */static noinstr struct lock_class *look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass){ struct lockdep_subclass_key *key; struct hlist_head *hash_head; struct lock_class *class;
if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) { instrumentation_begin(); debug_locks_off(); nbcon_cpu_emergency_enter(); printk(KERN_ERR "BUG: looking up invalid subclass: %u\n", subclass); printk(KERN_ERR "turning off the locking correctness validator.\n"); dump_stack(); nbcon_cpu_emergency_exit(); instrumentation_end(); return NULL; }
/* * If it is not initialised then it has never been locked, * so it won't be present in the hash table. */ if (unlikely(!lock->key)) return NULL;
/* * NOTE: the class-key must be unique. For dynamic locks, a static * lock_class_key variable is passed in through the mutex_init() * (or spin_lock_init()) call - which acts as the key. For static * locks we use the lock object itself as the key. */ BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(struct lockdep_map));
key = lock->key->subkeys + subclass;
hash_head = classhashentry(key);
/* * We do an RCU walk of the hash, see lockdep_free_key_range(). */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return NULL;
hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) { if (class->key == key) { /* * Huh! same key, different name? Did someone trample * on some memory? We're most confused. */ WARN_ONCE(class->name != lock->name && lock->key != &__lockdep_no_validate__, "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n", lock->name, lock->key, class->name); return class; } }
return NULL;}
/* * Static locks do not have their class-keys yet - for them the key is * the lock object itself. If the lock is in the per cpu area, the * canonical address of the lock (per cpu offset removed) is used. */static bool assign_lock_key(struct lockdep_map *lock){ unsigned long can_addr, addr = (unsigned long)lock;
#ifdef __KERNEL__ /* * lockdep_free_key_range() assumes that struct lock_class_key * objects do not overlap. Since we use the address of lock * objects as class key for static objects, check whether the * size of lock_class_key objects does not exceed the size of * the smallest lock object. */ BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));#endif
if (__is_kernel_percpu_address(addr, &can_addr)) lock->key = (void *)can_addr; else if (__is_module_percpu_address(addr, &can_addr)) lock->key = (void *)can_addr; else if (static_obj(lock)) lock->key = (void *)lock; else { /* Debug-check: all keys must be persistent! */ debug_locks_off(); nbcon_cpu_emergency_enter(); pr_err("INFO: trying to register non-static key.\n"); pr_err("The code is fine but needs lockdep annotation, or maybe\n"); pr_err("you didn't initialize this object before use?\n"); pr_err("turning off the locking correctness validator.\n"); dump_stack(); nbcon_cpu_emergency_exit(); return false; }
return true;}
#ifdef CONFIG_DEBUG_LOCKDEP
/* Check whether element @e occurs in list @h */static bool in_list(struct list_head *e, struct list_head *h){ struct list_head *f;
list_for_each(f, h) { if (e == f) return true; }
return false;}
/* * Check whether entry @e occurs in any of the locks_after or locks_before * lists. */static bool in_any_class_list(struct list_head *e){ struct lock_class *class; int i;
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { class = &lock_classes[i]; if (in_list(e, &class->locks_after) || in_list(e, &class->locks_before)) return true; } return false;}
static bool class_lock_list_valid(struct lock_class *c, struct list_head *h){ struct lock_list *e;
list_for_each_entry(e, h, entry) { if (e->links_to != c) { printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s", c->name ? : "(?)", (unsigned long)(e - list_entries), e->links_to && e->links_to->name ? e->links_to->name : "(?)", e->class && e->class->name ? e->class->name : "(?)"); return false; } } return true;}
#ifdef CONFIG_PROVE_LOCKINGstatic u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];#endif
static bool check_lock_chain_key(struct lock_chain *chain){#ifdef CONFIG_PROVE_LOCKING u64 chain_key = INITIAL_CHAIN_KEY; int i;
for (i = chain->base; i < chain->base + chain->depth; i++) chain_key = iterate_chain_key(chain_key, chain_hlocks[i]); /* * The 'unsigned long long' casts avoid that a compiler warning * is reported when building tools/lib/lockdep. */ if (chain->chain_key != chain_key) { printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n", (unsigned long long)(chain - lock_chains), (unsigned long long)chain->chain_key, (unsigned long long)chain_key); return false; }#endif return true;}
static bool in_any_zapped_class_list(struct lock_class *class){ struct pending_free *pf; int i;
for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) { if (in_list(&class->lock_entry, &pf->zapped)) return true; }
return false;}
static bool __check_data_structures(void){ struct lock_class *class; struct lock_chain *chain; struct hlist_head *head; struct lock_list *e; int i;
/* Check whether all classes occur in a lock list. */ for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { class = &lock_classes[i]; if (!in_list(&class->lock_entry, &all_lock_classes) && !in_list(&class->lock_entry, &free_lock_classes) && !in_any_zapped_class_list(class)) { printk(KERN_INFO "class %px/%s is not in any class list\n", class, class->name ? : "(?)"); return false; } }
/* Check whether all classes have valid lock lists. */ for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { class = &lock_classes[i]; if (!class_lock_list_valid(class, &class->locks_before)) return false; if (!class_lock_list_valid(class, &class->locks_after)) return false; }
/* Check the chain_key of all lock chains. */ for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) { head = chainhash_table + i; hlist_for_each_entry_rcu(chain, head, entry) { if (!check_lock_chain_key(chain)) return false; } }
/* * Check whether all list entries that are in use occur in a class * lock list. */ for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { e = list_entries + i; if (!in_any_class_list(&e->entry)) { printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n", (unsigned int)(e - list_entries), e->class->name ? : "(?)", e->links_to->name ? : "(?)"); return false; } }
/* * Check whether all list entries that are not in use do not occur in * a class lock list. */ for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { e = list_entries + i; if (in_any_class_list(&e->entry)) { printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n", (unsigned int)(e - list_entries), e->class && e->class->name ? e->class->name : "(?)", e->links_to && e->links_to->name ? e->links_to->name : "(?)"); return false; } }
return true;}
int check_consistency = 0;module_param(check_consistency, int, 0644);
static void check_data_structures(void){ static bool once = false;
if (check_consistency && !once) { if (!__check_data_structures()) { once = true; WARN_ON(once); } }}
#else /* CONFIG_DEBUG_LOCKDEP */
static inline void check_data_structures(void) { }
#endif /* CONFIG_DEBUG_LOCKDEP */
static void init_chain_block_buckets(void);
/* * Initialize the lock_classes[] array elements, the free_lock_classes list * and also the delayed_free structure. */static void init_data_structures_once(void){ static bool __read_mostly ds_initialized, rcu_head_initialized; int i;
if (likely(rcu_head_initialized)) return;
if (system_state >= SYSTEM_SCHEDULING) { init_rcu_head(&delayed_free.rcu_head); rcu_head_initialized = true; }
if (ds_initialized) return;
ds_initialized = true;
INIT_LIST_HEAD(&delayed_free.pf[0].zapped); INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
for (i = 0; i < ARRAY_SIZE(lock_classes); i++) { list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes); INIT_LIST_HEAD(&lock_classes[i].locks_after); INIT_LIST_HEAD(&lock_classes[i].locks_before); } init_chain_block_buckets();}
static inline struct hlist_head *keyhashentry(const struct lock_class_key *key){ unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
return lock_keys_hash + hash;}
/* Register a dynamically allocated key. */void lockdep_register_key(struct lock_class_key *key){ struct hlist_head *hash_head; struct lock_class_key *k; unsigned long flags;
if (WARN_ON_ONCE(static_obj(key))) return; hash_head = keyhashentry(key);
raw_local_irq_save(flags); if (!graph_lock()) goto restore_irqs; hlist_for_each_entry_rcu(k, hash_head, hash_entry) { if (WARN_ON_ONCE(k == key)) goto out_unlock; } hlist_add_head_rcu(&key->hash_entry, hash_head); nr_dynamic_keys++;out_unlock: graph_unlock();restore_irqs: raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lockdep_register_key);
/* Check whether a key has been registered as a dynamic key. */static bool is_dynamic_key(const struct lock_class_key *key){ struct hlist_head *hash_head; struct lock_class_key *k; bool found = false;
if (WARN_ON_ONCE(static_obj(key))) return false;
/* * If lock debugging is disabled lock_keys_hash[] may contain * pointers to memory that has already been freed. Avoid triggering * a use-after-free in that case by returning early. */ if (!debug_locks) return true;
hash_head = keyhashentry(key);
rcu_read_lock(); hlist_for_each_entry_rcu(k, hash_head, hash_entry) { if (k == key) { found = true; break; } } rcu_read_unlock();
return found;}
/* * Register a lock's class in the hash-table, if the class is not present * yet. Otherwise we look it up. We cache the result in the lock object * itself, so actual lookup of the hash should be once per lock object. */static struct lock_class *register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force){ struct lockdep_subclass_key *key; struct hlist_head *hash_head; struct lock_class *class; int idx;
DEBUG_LOCKS_WARN_ON(!irqs_disabled());
class = look_up_lock_class(lock, subclass); if (likely(class)) goto out_set_class_cache;
if (!lock->key) { if (!assign_lock_key(lock)) return NULL; } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) { return NULL; }
key = lock->key->subkeys + subclass; hash_head = classhashentry(key);
if (!graph_lock()) { return NULL; } /* * We have to do the hash-walk again, to avoid races * with another CPU: */ hlist_for_each_entry_rcu(class, hash_head, hash_entry) { if (class->key == key) goto out_unlock_set; }
init_data_structures_once();
/* Allocate a new lock class and add it to the hash. */ class = list_first_entry_or_null(&free_lock_classes, typeof(*class), lock_entry); if (!class) { if (!debug_locks_off_graph_unlock()) { return NULL; }
nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!"); dump_stack(); nbcon_cpu_emergency_exit(); return NULL; } nr_lock_classes++; __set_bit(class - lock_classes, lock_classes_in_use); debug_atomic_inc(nr_unused_locks); class->key = key; class->name = lock->name; class->subclass = subclass; WARN_ON_ONCE(!list_empty(&class->locks_before)); WARN_ON_ONCE(!list_empty(&class->locks_after)); class->name_version = count_matching_names(class); class->wait_type_inner = lock->wait_type_inner; class->wait_type_outer = lock->wait_type_outer; class->lock_type = lock->lock_type; /* * We use RCU's safe list-add method to make * parallel walking of the hash-list safe: */ hlist_add_head_rcu(&class->hash_entry, hash_head); /* * Remove the class from the free list and add it to the global list * of classes. */ list_move_tail(&class->lock_entry, &all_lock_classes); idx = class - lock_classes; if (idx > max_lock_class_idx) max_lock_class_idx = idx;
if (verbose(class)) { graph_unlock();
nbcon_cpu_emergency_enter(); printk("\nnew class %px: %s", class->key, class->name); if (class->name_version > 1) printk(KERN_CONT "#%d", class->name_version); printk(KERN_CONT "\n"); dump_stack(); nbcon_cpu_emergency_exit();
if (!graph_lock()) { return NULL; } }out_unlock_set: graph_unlock();
out_set_class_cache: if (!subclass || force) lock->class_cache[0] = class; else if (subclass < NR_LOCKDEP_CACHING_CLASSES) lock->class_cache[subclass] = class;
/* * Hash collision, did we smoke some? We found a class with a matching * hash but the subclass -- which is hashed in -- didn't match. */ if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass)) return NULL;
return class;}
#ifdef CONFIG_PROVE_LOCKING/* * Allocate a lockdep entry. (assumes the graph_lock held, returns * with NULL on failure) */static struct lock_list *alloc_list_entry(void){ int idx = find_first_zero_bit(list_entries_in_use, ARRAY_SIZE(list_entries));
if (idx >= ARRAY_SIZE(list_entries)) { if (!debug_locks_off_graph_unlock()) return NULL;
nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!"); dump_stack(); nbcon_cpu_emergency_exit(); return NULL; } nr_list_entries++; __set_bit(idx, list_entries_in_use); return list_entries + idx;}
/* * Add a new dependency to the head of the list: */static int add_lock_to_list(struct lock_class *this, struct lock_class *links_to, struct list_head *head, u16 distance, u8 dep, const struct lock_trace *trace){ struct lock_list *entry; /* * Lock not present yet - get a new dependency struct and * add it to the list: */ entry = alloc_list_entry(); if (!entry) return 0;
entry->class = this; entry->links_to = links_to; entry->dep = dep; entry->distance = distance; entry->trace = trace; /* * Both allocation and removal are done under the graph lock; but * iteration is under RCU-sched; see look_up_lock_class() and * lockdep_free_key_range(). */ list_add_tail_rcu(&entry->entry, head);
return 1;}
/* * For good efficiency of modular, we use power of 2 */#define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
/* * The circular_queue and helpers are used to implement graph * breadth-first search (BFS) algorithm, by which we can determine * whether there is a path from a lock to another. In deadlock checks, * a path from the next lock to be acquired to a previous held lock * indicates that adding the <prev> -> <next> lock dependency will * produce a circle in the graph. Breadth-first search instead of * depth-first search is used in order to find the shortest (circular) * path. */struct circular_queue { struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE]; unsigned int front, rear;};
static struct circular_queue lock_cq;
unsigned int max_bfs_queue_depth;
static unsigned int lockdep_dependency_gen_id;
static inline void __cq_init(struct circular_queue *cq){ cq->front = cq->rear = 0; lockdep_dependency_gen_id++;}
static inline int __cq_empty(struct circular_queue *cq){ return (cq->front == cq->rear);}
static inline int __cq_full(struct circular_queue *cq){ return ((cq->rear + 1) & CQ_MASK) == cq->front;}
static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem){ if (__cq_full(cq)) return -1;
cq->element[cq->rear] = elem; cq->rear = (cq->rear + 1) & CQ_MASK; return 0;}
/* * Dequeue an element from the circular_queue, return a lock_list if * the queue is not empty, or NULL if otherwise. */static inline struct lock_list * __cq_dequeue(struct circular_queue *cq){ struct lock_list * lock;
if (__cq_empty(cq)) return NULL;
lock = cq->element[cq->front]; cq->front = (cq->front + 1) & CQ_MASK;
return lock;}
static inline unsigned int __cq_get_elem_count(struct circular_queue *cq){ return (cq->rear - cq->front) & CQ_MASK;}
static inline void mark_lock_accessed(struct lock_list *lock){ lock->class->dep_gen_id = lockdep_dependency_gen_id;}
static inline void visit_lock_entry(struct lock_list *lock, struct lock_list *parent){ lock->parent = parent;}
static inline unsigned long lock_accessed(struct lock_list *lock){ return lock->class->dep_gen_id == lockdep_dependency_gen_id;}
static inline struct lock_list *get_lock_parent(struct lock_list *child){ return child->parent;}
static inline int get_lock_depth(struct lock_list *child){ int depth = 0; struct lock_list *parent;
while ((parent = get_lock_parent(child))) { child = parent; depth++; } return depth;}
/* * Return the forward or backward dependency list. * * @lock: the lock_list to get its class's dependency list * @offset: the offset to struct lock_class to determine whether it is * locks_after or locks_before */static inline struct list_head *get_dep_list(struct lock_list *lock, int offset){ void *lock_class = lock->class;
return lock_class + offset;}/* * Return values of a bfs search: * * BFS_E* indicates an error * BFS_R* indicates a result (match or not) * * BFS_EINVALIDNODE: Find a invalid node in the graph. * * BFS_EQUEUEFULL: The queue is full while doing the bfs. * * BFS_RMATCH: Find the matched node in the graph, and put that node into * *@target_entry. * * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry * _unchanged_. */enum bfs_result { BFS_EINVALIDNODE = -2, BFS_EQUEUEFULL = -1, BFS_RMATCH = 0, BFS_RNOMATCH = 1,};
/* * bfs_result < 0 means error */static inline bool bfs_error(enum bfs_result res){ return res < 0;}
/* * DEP_*_BIT in lock_list::dep * * For dependency @prev -> @next: * * SR: @prev is shared reader (->read != 0) and @next is recursive reader * (->read == 2) * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader * SN: @prev is shared reader and @next is non-recursive locker (->read != 2) * EN: @prev is exclusive locker and @next is non-recursive locker * * Note that we define the value of DEP_*_BITs so that: * bit0 is prev->read == 0 * bit1 is next->read != 2 */#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
#define DEP_SR_MASK (1U << (DEP_SR_BIT))#define DEP_ER_MASK (1U << (DEP_ER_BIT))#define DEP_SN_MASK (1U << (DEP_SN_BIT))#define DEP_EN_MASK (1U << (DEP_EN_BIT))
static inline unsigned int__calc_dep_bit(struct held_lock *prev, struct held_lock *next){ return (prev->read == 0) + ((next->read != 2) << 1);}
static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next){ return 1U << __calc_dep_bit(prev, next);}
/* * calculate the dep_bit for backwards edges. We care about whether @prev is * shared and whether @next is recursive. */static inline unsigned int__calc_dep_bitb(struct held_lock *prev, struct held_lock *next){ return (next->read != 2) + ((prev->read == 0) << 1);}
static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next){ return 1U << __calc_dep_bitb(prev, next);}
/* * Initialize a lock_list entry @lock belonging to @class as the root for a BFS * search. */static inline void __bfs_init_root(struct lock_list *lock, struct lock_class *class){ lock->class = class; lock->parent = NULL; lock->only_xr = 0;}
/* * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the * root for a BFS search. * * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)-> * and -(S*)->. */static inline void bfs_init_root(struct lock_list *lock, struct held_lock *hlock){ __bfs_init_root(lock, hlock_class(hlock)); lock->only_xr = (hlock->read == 2);}
/* * Similar to bfs_init_root() but initialize the root for backwards BFS. * * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->). */static inline void bfs_init_rootb(struct lock_list *lock, struct held_lock *hlock){ __bfs_init_root(lock, hlock_class(hlock)); lock->only_xr = (hlock->read != 0);}
static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset){ if (!lock || !lock->parent) return NULL;
return list_next_or_null_rcu(get_dep_list(lock->parent, offset), &lock->entry, struct lock_list, entry);}
/* * Breadth-First Search to find a strong path in the dependency graph. * * @source_entry: the source of the path we are searching for. * @data: data used for the second parameter of @match function * @match: match function for the search * @target_entry: pointer to the target of a matched path * @offset: the offset to struct lock_class to determine whether it is * locks_after or locks_before * * We may have multiple edges (considering different kinds of dependencies, * e.g. ER and SN) between two nodes in the dependency graph. But * only the strong dependency path in the graph is relevant to deadlocks. A * strong dependency path is a dependency path that doesn't have two adjacent * dependencies as -(*R)-> -(S*)->, please see: * * Documentation/locking/lockdep-design.rst * * for more explanation of the definition of strong dependency paths * * In __bfs(), we only traverse in the strong dependency path: * * In lock_list::only_xr, we record whether the previous dependency only * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we * filter out any -(S*)-> in the current dependency and after that, the * ->only_xr is set according to whether we only have -(*R)-> left. */static enum bfs_result __bfs(struct lock_list *source_entry, void *data, bool (*match)(struct lock_list *entry, void *data), bool (*skip)(struct lock_list *entry, void *data), struct lock_list **target_entry, int offset){ struct circular_queue *cq = &lock_cq; struct lock_list *lock = NULL; struct lock_list *entry; struct list_head *head; unsigned int cq_depth; bool first;
lockdep_assert_locked();
__cq_init(cq); __cq_enqueue(cq, source_entry);
while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) { if (!lock->class) return BFS_EINVALIDNODE;
/* * Step 1: check whether we already finish on this one. * * If we have visited all the dependencies from this @lock to * others (iow, if we have visited all lock_list entries in * @lock->class->locks_{after,before}) we skip, otherwise go * and visit all the dependencies in the list and mark this * list accessed. */ if (lock_accessed(lock)) continue; else mark_lock_accessed(lock);
/* * Step 2: check whether prev dependency and this form a strong * dependency path. */ if (lock->parent) { /* Parent exists, check prev dependency */ u8 dep = lock->dep; bool prev_only_xr = lock->parent->only_xr;
/* * Mask out all -(S*)-> if we only have *R in previous * step, because -(*R)-> -(S*)-> don't make up a strong * dependency. */ if (prev_only_xr) dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
/* If nothing left, we skip */ if (!dep) continue;
/* If there are only -(*R)-> left, set that for the next step */ lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK)); }
/* * Step 3: we haven't visited this and there is a strong * dependency path to this, so check with @match. * If @skip is provide and returns true, we skip this * lock (and any path this lock is in). */ if (skip && skip(lock, data)) continue;
if (match(lock, data)) { *target_entry = lock; return BFS_RMATCH; }
/* * Step 4: if not match, expand the path by adding the * forward or backwards dependencies in the search * */ first = true; head = get_dep_list(lock, offset); list_for_each_entry_rcu(entry, head, entry) { visit_lock_entry(entry, lock);
/* * Note we only enqueue the first of the list into the * queue, because we can always find a sibling * dependency from one (see __bfs_next()), as a result * the space of queue is saved. */ if (!first) continue;
first = false;
if (__cq_enqueue(cq, entry)) return BFS_EQUEUEFULL;
cq_depth = __cq_get_elem_count(cq); if (max_bfs_queue_depth < cq_depth) max_bfs_queue_depth = cq_depth; } }
return BFS_RNOMATCH;}
static inline enum bfs_result__bfs_forwards(struct lock_list *src_entry, void *data, bool (*match)(struct lock_list *entry, void *data), bool (*skip)(struct lock_list *entry, void *data), struct lock_list **target_entry){ return __bfs(src_entry, data, match, skip, target_entry, offsetof(struct lock_class, locks_after));
}
static inline enum bfs_result__bfs_backwards(struct lock_list *src_entry, void *data, bool (*match)(struct lock_list *entry, void *data), bool (*skip)(struct lock_list *entry, void *data), struct lock_list **target_entry){ return __bfs(src_entry, data, match, skip, target_entry, offsetof(struct lock_class, locks_before));
}
static void print_lock_trace(const struct lock_trace *trace, unsigned int spaces){ stack_trace_print(trace->entries, trace->nr_entries, spaces);}
/* * Print a dependency chain entry (this is only done when a deadlock * has been detected): */static noinline voidprint_circular_bug_entry(struct lock_list *target, int depth){ if (debug_locks_silent) return; printk("\n-> #%u", depth); print_lock_name(NULL, target->class); printk(KERN_CONT ":\n"); print_lock_trace(target->trace, 6);}
static voidprint_circular_lock_scenario(struct held_lock *src, struct held_lock *tgt, struct lock_list *prt){ struct lock_class *source = hlock_class(src); struct lock_class *target = hlock_class(tgt); struct lock_class *parent = prt->class; int src_read = src->read; int tgt_read = tgt->read;
/* * A direct locking problem where unsafe_class lock is taken * directly by safe_class lock, then all we need to show * is the deadlock scenario, as it is obvious that the * unsafe lock is taken under the safe lock. * * But if there is a chain instead, where the safe lock takes * an intermediate lock (middle_class) where this lock is * not the same as the safe lock, then the lock chain is * used to describe the problem. Otherwise we would need * to show a different CPU case for each link in the chain * from the safe_class lock to the unsafe_class lock. */ if (parent != source) { printk("Chain exists of:\n "); __print_lock_name(src, source); printk(KERN_CONT " --> "); __print_lock_name(NULL, parent); printk(KERN_CONT " --> "); __print_lock_name(tgt, target); printk(KERN_CONT "\n\n"); }
printk(" Possible unsafe locking scenario:\n\n"); printk(" CPU0 CPU1\n"); printk(" ---- ----\n"); if (tgt_read != 0) printk(" rlock("); else printk(" lock("); __print_lock_name(tgt, target); printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(NULL, parent); printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(tgt, target); printk(KERN_CONT ");\n"); if (src_read != 0) printk(" rlock("); else if (src->sync) printk(" sync("); else printk(" lock("); __print_lock_name(src, source); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n");}
/* * When a circular dependency is detected, print the * header first: */static noinline voidprint_circular_bug_header(struct lock_list *entry, unsigned int depth, struct held_lock *check_src, struct held_lock *check_tgt){ struct task_struct *curr = current;
if (debug_locks_silent) return;
pr_warn("\n"); pr_warn("======================================================\n"); pr_warn("WARNING: possible circular locking dependency detected\n"); print_kernel_ident(); pr_warn("------------------------------------------------------\n"); pr_warn("%s/%d is trying to acquire lock:\n", curr->comm, task_pid_nr(curr)); print_lock(check_src);
pr_warn("\nbut task is already holding lock:\n");
print_lock(check_tgt); pr_warn("\nwhich lock already depends on the new lock.\n\n"); pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
print_circular_bug_entry(entry, depth);}
/* * We are about to add B -> A into the dependency graph, and in __bfs() a * strong dependency path A -> .. -> B is found: hlock_class equals * entry->class. * * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong * dependency cycle, that means: * * Either * * a) B -> A is -(E*)-> * * or * * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B) * * as then we don't have -(*R)-> -(S*)-> in the cycle. */static inline bool hlock_conflict(struct lock_list *entry, void *data){ struct held_lock *hlock = (struct held_lock *)data;
return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */ (hlock->read == 0 || /* B -> A is -(E*)-> */ !entry->only_xr); /* A -> .. -> B is -(*N)-> */}
static noinline void print_circular_bug(struct lock_list *this, struct lock_list *target, struct held_lock *check_src, struct held_lock *check_tgt){ struct task_struct *curr = current; struct lock_list *parent; struct lock_list *first_parent; int depth;
if (!debug_locks_off_graph_unlock() || debug_locks_silent) return;
this->trace = save_trace(); if (!this->trace) return;
depth = get_lock_depth(target);
nbcon_cpu_emergency_enter();
print_circular_bug_header(target, depth, check_src, check_tgt);
parent = get_lock_parent(target); first_parent = parent;
while (parent) { print_circular_bug_entry(parent, --depth); parent = get_lock_parent(parent); }
printk("\nother info that might help us debug this:\n\n"); print_circular_lock_scenario(check_src, check_tgt, first_parent);
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
static noinline void print_bfs_bug(int ret){ if (!debug_locks_off_graph_unlock()) return;
/* * Breadth-first-search failed, graph got corrupted? */ if (ret == BFS_EQUEUEFULL) pr_warn("Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:\n");
WARN(1, "lockdep bfs error:%d\n", ret);}
static bool noop_count(struct lock_list *entry, void *data){ (*(unsigned long *)data)++; return false;}
static unsigned long __lockdep_count_forward_deps(struct lock_list *this){ unsigned long count = 0; struct lock_list *target_entry;
__bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
return count;}unsigned long lockdep_count_forward_deps(struct lock_class *class){ unsigned long ret, flags; struct lock_list this;
__bfs_init_root(&this, class);
raw_local_irq_save(flags); lockdep_lock(); ret = __lockdep_count_forward_deps(&this); lockdep_unlock(); raw_local_irq_restore(flags);
return ret;}
static unsigned long __lockdep_count_backward_deps(struct lock_list *this){ unsigned long count = 0; struct lock_list *target_entry;
__bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
return count;}
unsigned long lockdep_count_backward_deps(struct lock_class *class){ unsigned long ret, flags; struct lock_list this;
__bfs_init_root(&this, class);
raw_local_irq_save(flags); lockdep_lock(); ret = __lockdep_count_backward_deps(&this); lockdep_unlock(); raw_local_irq_restore(flags);
return ret;}
/* * Check that the dependency graph starting at <src> can lead to * <target> or not. */static noinline enum bfs_resultcheck_path(struct held_lock *target, struct lock_list *src_entry, bool (*match)(struct lock_list *entry, void *data), bool (*skip)(struct lock_list *entry, void *data), struct lock_list **target_entry){ enum bfs_result ret;
ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
if (unlikely(bfs_error(ret))) print_bfs_bug(ret);
return ret;}
static void print_deadlock_bug(struct task_struct *, struct held_lock *, struct held_lock *);
/* * Prove that the dependency graph starting at <src> can not * lead to <target>. If it can, there is a circle when adding * <target> -> <src> dependency. * * Print an error and return BFS_RMATCH if it does. */static noinline enum bfs_resultcheck_noncircular(struct held_lock *src, struct held_lock *target, struct lock_trace **const trace){ enum bfs_result ret; struct lock_list *target_entry; struct lock_list src_entry;
bfs_init_root(&src_entry, src);
debug_atomic_inc(nr_cyclic_checks);
ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
if (unlikely(ret == BFS_RMATCH)) { if (!*trace) { /* * If save_trace fails here, the printing might * trigger a WARN but because of the !nr_entries it * should not do bad things. */ *trace = save_trace(); }
if (src->class_idx == target->class_idx) print_deadlock_bug(current, src, target); else print_circular_bug(&src_entry, target_entry, src, target); }
return ret;}
#ifdef CONFIG_TRACE_IRQFLAGS
/* * Forwards and backwards subgraph searching, for the purposes of * proving that two subgraphs can be connected by a new dependency * without creating any illegal irq-safe -> irq-unsafe lock dependency. * * A irq safe->unsafe deadlock happens with the following conditions: * * 1) We have a strong dependency path A -> ... -> B * * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore * irq can create a new dependency B -> A (consider the case that a holder * of B gets interrupted by an irq whose handler will try to acquire A). * * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a * strong circle: * * For the usage bits of B: * a) if A -> B is -(*N)->, then B -> A could be any type, so any * ENABLED_IRQ usage suffices. * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only * ENABLED_IRQ_*_READ usage suffices. * * For the usage bits of A: * c) if A -> B is -(E*)->, then B -> A could be any type, so any * USED_IN_IRQ usage suffices. * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only * USED_IN_IRQ_*_READ usage suffices. */
/* * There is a strong dependency path in the dependency graph: A -> B, and now * we need to decide which usage bit of A should be accumulated to detect * safe->unsafe bugs. * * Note that usage_accumulate() is used in backwards search, so ->only_xr * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true). * * As above, if only_xr is false, which means A -> B has -(E*)-> dependency * path, any usage of A should be considered. Otherwise, we should only * consider _READ usage. */static inline bool usage_accumulate(struct lock_list *entry, void *mask){ if (!entry->only_xr) *(unsigned long *)mask |= entry->class->usage_mask; else /* Mask out _READ usage bits */ *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
return false;}
/* * There is a strong dependency path in the dependency graph: A -> B, and now * we need to decide which usage bit of B conflicts with the usage bits of A, * i.e. which usage bit of B may introduce safe->unsafe deadlocks. * * As above, if only_xr is false, which means A -> B has -(*N)-> dependency * path, any usage of B should be considered. Otherwise, we should only * consider _READ usage. */static inline bool usage_match(struct lock_list *entry, void *mask){ if (!entry->only_xr) return !!(entry->class->usage_mask & *(unsigned long *)mask); else /* Mask out _READ usage bits */ return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);}
static inline bool usage_skip(struct lock_list *entry, void *mask){ if (entry->class->lock_type == LD_LOCK_NORMAL) return false;
/* * Skip local_lock() for irq inversion detection. * * For !RT, local_lock() is not a real lock, so it won't carry any * dependency. * * For RT, an irq inversion happens when we have lock A and B, and on * some CPU we can have: * * lock(A); * <interrupted> * lock(B); * * where lock(B) cannot sleep, and we have a dependency B -> ... -> A. * * Now we prove local_lock() cannot exist in that dependency. First we * have the observation for any lock chain L1 -> ... -> Ln, for any * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise * wait context check will complain. And since B is not a sleep lock, * therefore B.inner_wait_type >= 2, and since the inner_wait_type of * local_lock() is 3, which is greater than 2, therefore there is no * way the local_lock() exists in the dependency B -> ... -> A. * * As a result, we will skip local_lock(), when we search for irq * inversion bugs. */ if (entry->class->lock_type == LD_LOCK_PERCPU && DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG)) return false;
/* * Skip WAIT_OVERRIDE for irq inversion detection -- it's not actually * a lock and only used to override the wait_type. */
return true;}
/* * Find a node in the forwards-direction dependency sub-graph starting * at @root->class that matches @bit. * * Return BFS_MATCH if such a node exists in the subgraph, and put that node * into *@target_entry. */static enum bfs_resultfind_usage_forwards(struct lock_list *root, unsigned long usage_mask, struct lock_list **target_entry){ enum bfs_result result;
debug_atomic_inc(nr_find_usage_forwards_checks);
result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
return result;}
/* * Find a node in the backwards-direction dependency sub-graph starting * at @root->class that matches @bit. */static enum bfs_resultfind_usage_backwards(struct lock_list *root, unsigned long usage_mask, struct lock_list **target_entry){ enum bfs_result result;
debug_atomic_inc(nr_find_usage_backwards_checks);
result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
return result;}
static void print_lock_class_header(struct lock_class *class, int depth){ int bit;
printk("%*s->", depth, ""); print_lock_name(NULL, class);#ifdef CONFIG_DEBUG_LOCKDEP printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));#endif printk(KERN_CONT " {\n");
for (bit = 0; bit < LOCK_TRACE_STATES; bit++) { if (class->usage_mask & (1 << bit)) { int len = depth;
len += printk("%*s %s", depth, "", usage_str[bit]); len += printk(KERN_CONT " at:\n"); print_lock_trace(class->usage_traces[bit], len); } } printk("%*s }\n", depth, "");
printk("%*s ... key at: [<%px>] %pS\n", depth, "", class->key, class->key);}
/* * Dependency path printing: * * After BFS we get a lock dependency path (linked via ->parent of lock_list), * printing out each lock in the dependency path will help on understanding how * the deadlock could happen. Here are some details about dependency path * printing: * * 1) A lock_list can be either forwards or backwards for a lock dependency, * for a lock dependency A -> B, there are two lock_lists: * * a) lock_list in the ->locks_after list of A, whose ->class is B and * ->links_to is A. In this case, we can say the lock_list is * "A -> B" (forwards case). * * b) lock_list in the ->locks_before list of B, whose ->class is A * and ->links_to is B. In this case, we can say the lock_list is * "B <- A" (bacwards case). * * The ->trace of both a) and b) point to the call trace where B was * acquired with A held. * * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't * represent a certain lock dependency, it only provides an initial entry * for BFS. For example, BFS may introduce a "helper" lock_list whose * ->class is A, as a result BFS will search all dependencies starting with * A, e.g. A -> B or A -> C. * * The notation of a forwards helper lock_list is like "-> A", which means * we should search the forwards dependencies starting with "A", e.g A -> B * or A -> C. * * The notation of a bacwards helper lock_list is like "<- B", which means * we should search the backwards dependencies ending with "B", e.g. * B <- A or B <- C. */
/* * printk the shortest lock dependencies from @root to @leaf in reverse order. * * We have a lock dependency path as follow: * * @root @leaf * | | * V V * ->parent ->parent * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list | * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln| * * , so it's natural that we start from @leaf and print every ->class and * ->trace until we reach the @root. */static void __usedprint_shortest_lock_dependencies(struct lock_list *leaf, struct lock_list *root){ struct lock_list *entry = leaf; int depth;
/*compute depth from generated tree by BFS*/ depth = get_lock_depth(leaf);
do { print_lock_class_header(entry->class, depth); printk("%*s ... acquired at:\n", depth, ""); print_lock_trace(entry->trace, 2); printk("\n");
if (depth == 0 && (entry != root)) { printk("lockdep:%s bad path found in chain graph\n", __func__); break; }
entry = get_lock_parent(entry); depth--; } while (entry && (depth >= 0));}
/* * printk the shortest lock dependencies from @leaf to @root. * * We have a lock dependency path (from a backwards search) as follow: * * @leaf @root * | | * V V * ->parent ->parent * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list | * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln | * * , so when we iterate from @leaf to @root, we actually print the lock * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order. * * Another thing to notice here is that ->class of L2 <- L1 is L1, while the * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call * trace of L1 in the dependency path, which is alright, because most of the * time we can figure out where L1 is held from the call trace of L2. */static void __usedprint_shortest_lock_dependencies_backwards(struct lock_list *leaf, struct lock_list *root){ struct lock_list *entry = leaf; const struct lock_trace *trace = NULL; int depth;
/*compute depth from generated tree by BFS*/ depth = get_lock_depth(leaf);
do { print_lock_class_header(entry->class, depth); if (trace) { printk("%*s ... acquired at:\n", depth, ""); print_lock_trace(trace, 2); printk("\n"); }
/* * Record the pointer to the trace for the next lock_list * entry, see the comments for the function. */ trace = entry->trace;
if (depth == 0 && (entry != root)) { printk("lockdep:%s bad path found in chain graph\n", __func__); break; }
entry = get_lock_parent(entry); depth--; } while (entry && (depth >= 0));}
static voidprint_irq_lock_scenario(struct lock_list *safe_entry, struct lock_list *unsafe_entry, struct lock_class *prev_class, struct lock_class *next_class){ struct lock_class *safe_class = safe_entry->class; struct lock_class *unsafe_class = unsafe_entry->class; struct lock_class *middle_class = prev_class;
if (middle_class == safe_class) middle_class = next_class;
/* * A direct locking problem where unsafe_class lock is taken * directly by safe_class lock, then all we need to show * is the deadlock scenario, as it is obvious that the * unsafe lock is taken under the safe lock. * * But if there is a chain instead, where the safe lock takes * an intermediate lock (middle_class) where this lock is * not the same as the safe lock, then the lock chain is * used to describe the problem. Otherwise we would need * to show a different CPU case for each link in the chain * from the safe_class lock to the unsafe_class lock. */ if (middle_class != unsafe_class) { printk("Chain exists of:\n "); __print_lock_name(NULL, safe_class); printk(KERN_CONT " --> "); __print_lock_name(NULL, middle_class); printk(KERN_CONT " --> "); __print_lock_name(NULL, unsafe_class); printk(KERN_CONT "\n\n"); }
printk(" Possible interrupt unsafe locking scenario:\n\n"); printk(" CPU0 CPU1\n"); printk(" ---- ----\n"); printk(" lock("); __print_lock_name(NULL, unsafe_class); printk(KERN_CONT ");\n"); printk(" local_irq_disable();\n"); printk(" lock("); __print_lock_name(NULL, safe_class); printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(NULL, middle_class); printk(KERN_CONT ");\n"); printk(" <Interrupt>\n"); printk(" lock("); __print_lock_name(NULL, safe_class); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n");}
static voidprint_bad_irq_dependency(struct task_struct *curr, struct lock_list *prev_root, struct lock_list *next_root, struct lock_list *backwards_entry, struct lock_list *forwards_entry, struct held_lock *prev, struct held_lock *next, enum lock_usage_bit bit1, enum lock_usage_bit bit2, const char *irqclass){ if (!debug_locks_off_graph_unlock() || debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("=====================================================\n"); pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n", irqclass, irqclass); print_kernel_ident(); pr_warn("-----------------------------------------------------\n"); pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n", curr->comm, task_pid_nr(curr), lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT, curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT, lockdep_hardirqs_enabled(), curr->softirqs_enabled); print_lock(next);
pr_warn("\nand this task is already holding:\n"); print_lock(prev); pr_warn("which would create a new lock dependency:\n"); print_lock_name(prev, hlock_class(prev)); pr_cont(" ->"); print_lock_name(next, hlock_class(next)); pr_cont("\n");
pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n", irqclass); print_lock_name(NULL, backwards_entry->class); pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass); print_lock_name(NULL, forwards_entry->class); pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass); pr_warn("...");
print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
pr_warn("\nother info that might help us debug this:\n\n"); print_irq_lock_scenario(backwards_entry, forwards_entry, hlock_class(prev), hlock_class(next));
lockdep_print_held_locks(curr);
pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass); print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
pr_warn("\nthe dependencies between the lock to be acquired"); pr_warn(" and %s-irq-unsafe lock:\n", irqclass); next_root->trace = save_trace(); if (!next_root->trace) goto out; print_shortest_lock_dependencies(forwards_entry, next_root);
pr_warn("\nstack backtrace:\n"); dump_stack();out: nbcon_cpu_emergency_exit();}
static const char *state_names[] = {#define LOCKDEP_STATE(__STATE) \ __stringify(__STATE),#include "lockdep_states.h"#undef LOCKDEP_STATE};
static const char *state_rnames[] = {#define LOCKDEP_STATE(__STATE) \ __stringify(__STATE)"-READ",#include "lockdep_states.h"#undef LOCKDEP_STATE};
static inline const char *state_name(enum lock_usage_bit bit){ if (bit & LOCK_USAGE_READ_MASK) return state_rnames[bit >> LOCK_USAGE_DIR_MASK]; else return state_names[bit >> LOCK_USAGE_DIR_MASK];}
/* * The bit number is encoded like: * * bit0: 0 exclusive, 1 read lock * bit1: 0 used in irq, 1 irq enabled * bit2-n: state */static int exclusive_bit(int new_bit){ int state = new_bit & LOCK_USAGE_STATE_MASK; int dir = new_bit & LOCK_USAGE_DIR_MASK;
/* * keep state, bit flip the direction and strip read. */ return state | (dir ^ LOCK_USAGE_DIR_MASK);}
/* * Observe that when given a bitmask where each bitnr is encoded as above, a * right shift of the mask transforms the individual bitnrs as -1 and * conversely, a left shift transforms into +1 for the individual bitnrs. * * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0) * instead by subtracting the bit number by 2, or shifting the mask right by 2. * * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2. * * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is * all bits set) and recompose with bitnr1 flipped. */static unsigned long invert_dir_mask(unsigned long mask){ unsigned long excl = 0;
/* Invert dir */ excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK; excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
return excl;}
/* * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ * usage may cause deadlock too, for example: * * P1 P2 * <irq disabled> * write_lock(l1); <irq enabled> * read_lock(l2); * write_lock(l2); * <in irq> * read_lock(l1); * * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible * deadlock. * * In fact, all of the following cases may cause deadlocks: * * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_* * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_* * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ * * As a result, to calculate the "exclusive mask", first we invert the * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*). */static unsigned long exclusive_mask(unsigned long mask){ unsigned long excl = invert_dir_mask(mask);
excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK; excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
return excl;}
/* * Retrieve the _possible_ original mask to which @mask is * exclusive. Ie: this is the opposite of exclusive_mask(). * Note that 2 possible original bits can match an exclusive * bit: one has LOCK_USAGE_READ_MASK set, the other has it * cleared. So both are returned for each exclusive bit. */static unsigned long original_mask(unsigned long mask){ unsigned long excl = invert_dir_mask(mask);
/* Include read in existing usages */ excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK; excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
return excl;}
/* * Find the first pair of bit match between an original * usage mask and an exclusive usage mask. */static int find_exclusive_match(unsigned long mask, unsigned long excl_mask, enum lock_usage_bit *bitp, enum lock_usage_bit *excl_bitp){ int bit, excl, excl_read;
for_each_set_bit(bit, &mask, LOCK_USED) { /* * exclusive_bit() strips the read bit, however, * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need * to search excl | LOCK_USAGE_READ_MASK as well. */ excl = exclusive_bit(bit); excl_read = excl | LOCK_USAGE_READ_MASK; if (excl_mask & lock_flag(excl)) { *bitp = bit; *excl_bitp = excl; return 0; } else if (excl_mask & lock_flag(excl_read)) { *bitp = bit; *excl_bitp = excl_read; return 0; } } return -1;}
/* * Prove that the new dependency does not connect a hardirq-safe(-read) * lock with a hardirq-unsafe lock - to achieve this we search * the backwards-subgraph starting at <prev>, and the * forwards-subgraph starting at <next>: */static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, struct held_lock *next){ unsigned long usage_mask = 0, forward_mask, backward_mask; enum lock_usage_bit forward_bit = 0, backward_bit = 0; struct lock_list *target_entry1; struct lock_list *target_entry; struct lock_list this, that; enum bfs_result ret;
/* * Step 1: gather all hard/soft IRQs usages backward in an * accumulated usage mask. */ bfs_init_rootb(&this, prev);
ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL); if (bfs_error(ret)) { print_bfs_bug(ret); return 0; }
usage_mask &= LOCKF_USED_IN_IRQ_ALL; if (!usage_mask) return 1;
/* * Step 2: find exclusive uses forward that match the previous * backward accumulated mask. */ forward_mask = exclusive_mask(usage_mask);
bfs_init_root(&that, next);
ret = find_usage_forwards(&that, forward_mask, &target_entry1); if (bfs_error(ret)) { print_bfs_bug(ret); return 0; } if (ret == BFS_RNOMATCH) return 1;
/* * Step 3: we found a bad match! Now retrieve a lock from the backward * list whose usage mask matches the exclusive usage mask from the * lock found on the forward list. * * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering * the follow case: * * When trying to add A -> B to the graph, we find that there is a * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M, * that B -> ... -> M. However M is **softirq-safe**, if we use exact * invert bits of M's usage_mask, we will find another lock N that is * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not * cause a inversion deadlock. */ backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
ret = find_usage_backwards(&this, backward_mask, &target_entry); if (bfs_error(ret)) { print_bfs_bug(ret); return 0; } if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH)) return 1;
/* * Step 4: narrow down to a pair of incompatible usage bits * and report it. */ ret = find_exclusive_match(target_entry->class->usage_mask, target_entry1->class->usage_mask, &backward_bit, &forward_bit); if (DEBUG_LOCKS_WARN_ON(ret == -1)) return 1;
print_bad_irq_dependency(curr, &this, &that, target_entry, target_entry1, prev, next, backward_bit, forward_bit, state_name(backward_bit));
return 0;}
#else
static inline int check_irq_usage(struct task_struct *curr, struct held_lock *prev, struct held_lock *next){ return 1;}
static inline bool usage_skip(struct lock_list *entry, void *mask){ return false;}
#endif /* CONFIG_TRACE_IRQFLAGS */
#ifdef CONFIG_LOCKDEP_SMALL/* * We are about to add A -> B into the dependency graph, and in __bfs() a * strong dependency path A -> .. -> B is found: hlock_class equals * entry->class. * * If A -> .. -> B can replace A -> B in any __bfs() search (means the former * is _stronger_ than or equal to the latter), we consider A -> B as redundant. * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the * dependency graph, as any strong path ..-> A -> B ->.. we can get with * having dependency A -> B, we could already get a equivalent path ..-> A -> * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant. * * We need to make sure both the start and the end of A -> .. -> B is not * weaker than A -> B. For the start part, please see the comment in * check_redundant(). For the end part, we need: * * Either * * a) A -> B is -(*R)-> (everything is not weaker than that) * * or * * b) A -> .. -> B is -(*N)-> (nothing is stronger than this) * */static inline bool hlock_equal(struct lock_list *entry, void *data){ struct held_lock *hlock = (struct held_lock *)data;
return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */ (hlock->read == 2 || /* A -> B is -(*R)-> */ !entry->only_xr); /* A -> .. -> B is -(*N)-> */}
/* * Check that the dependency graph starting at <src> can lead to * <target> or not. If it can, <src> -> <target> dependency is already * in the graph. * * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if * any error appears in the bfs search. */static noinline enum bfs_resultcheck_redundant(struct held_lock *src, struct held_lock *target){ enum bfs_result ret; struct lock_list *target_entry; struct lock_list src_entry;
bfs_init_root(&src_entry, src); /* * Special setup for check_redundant(). * * To report redundant, we need to find a strong dependency path that * is equal to or stronger than <src> -> <target>. So if <src> is E, * we need to let __bfs() only search for a path starting at a -(E*)->, * we achieve this by setting the initial node's ->only_xr to true in * that case. And if <prev> is S, we set initial ->only_xr to false * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant. */ src_entry.only_xr = src->read == 0;
debug_atomic_inc(nr_redundant_checks);
/* * Note: we skip local_lock() for redundant check, because as the * comment in usage_skip(), A -> local_lock() -> B and A -> B are not * the same. */ ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
if (ret == BFS_RMATCH) debug_atomic_inc(nr_redundant);
return ret;}
#else
static inline enum bfs_resultcheck_redundant(struct held_lock *src, struct held_lock *target){ return BFS_RNOMATCH;}
#endif
static void inc_chains(int irq_context){ if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT) nr_hardirq_chains++; else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT) nr_softirq_chains++; else nr_process_chains++;}
static void dec_chains(int irq_context){ if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT) nr_hardirq_chains--; else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT) nr_softirq_chains--; else nr_process_chains--;}
static voidprint_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv){ struct lock_class *next = hlock_class(nxt); struct lock_class *prev = hlock_class(prv);
printk(" Possible unsafe locking scenario:\n\n"); printk(" CPU0\n"); printk(" ----\n"); printk(" lock("); __print_lock_name(prv, prev); printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(nxt, next); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); printk(" May be due to missing lock nesting notation\n\n");}
static voidprint_deadlock_bug(struct task_struct *curr, struct held_lock *prev, struct held_lock *next){ struct lock_class *class = hlock_class(prev);
if (!debug_locks_off_graph_unlock() || debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("============================================\n"); pr_warn("WARNING: possible recursive locking detected\n"); print_kernel_ident(); pr_warn("--------------------------------------------\n"); pr_warn("%s/%d is trying to acquire lock:\n", curr->comm, task_pid_nr(curr)); print_lock(next); pr_warn("\nbut task is already holding lock:\n"); print_lock(prev);
if (class->cmp_fn) { pr_warn("and the lock comparison function returns %i:\n", class->cmp_fn(prev->instance, next->instance)); }
pr_warn("\nother info that might help us debug this:\n"); print_deadlock_scenario(next, prev); lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
/* * Check whether we are holding such a class already. * * (Note that this has to be done separately, because the graph cannot * detect such classes of deadlocks.) * * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same * lock class is held but nest_lock is also held, i.e. we rely on the * nest_lock to avoid the deadlock. */static intcheck_deadlock(struct task_struct *curr, struct held_lock *next){ struct lock_class *class; struct held_lock *prev; struct held_lock *nest = NULL; int i;
for (i = 0; i < curr->lockdep_depth; i++) { prev = curr->held_locks + i;
if (prev->instance == next->nest_lock) nest = prev;
if (hlock_class(prev) != hlock_class(next)) continue;
/* * Allow read-after-read recursion of the same * lock class (i.e. read_lock(lock)+read_lock(lock)): */ if ((next->read == 2) && prev->read) continue;
class = hlock_class(prev);
if (class->cmp_fn && class->cmp_fn(prev->instance, next->instance) < 0) continue;
/* * We're holding the nest_lock, which serializes this lock's * nesting behaviour. */ if (nest) return 2;
print_deadlock_bug(curr, prev, next); return 0; } return 1;}
/* * There was a chain-cache miss, and we are about to add a new dependency * to a previous lock. We validate the following rules: * * - would the adding of the <prev> -> <next> dependency create a * circular dependency in the graph? [== circular deadlock] * * - does the new prev->next dependency connect any hardirq-safe lock * (in the full backwards-subgraph starting at <prev>) with any * hardirq-unsafe lock (in the full forwards-subgraph starting at * <next>)? [== illegal lock inversion with hardirq contexts] * * - does the new prev->next dependency connect any softirq-safe lock * (in the full backwards-subgraph starting at <prev>) with any * softirq-unsafe lock (in the full forwards-subgraph starting at * <next>)? [== illegal lock inversion with softirq contexts] * * any of these scenarios could lead to a deadlock. * * Then if all the validations pass, we add the forwards and backwards * dependency. */static intcheck_prev_add(struct task_struct *curr, struct held_lock *prev, struct held_lock *next, u16 distance, struct lock_trace **const trace){ struct lock_list *entry; enum bfs_result ret;
if (!hlock_class(prev)->key || !hlock_class(next)->key) { /* * The warning statements below may trigger a use-after-free * of the class name. It is better to trigger a use-after free * and to have the class name most of the time instead of not * having the class name available. */ WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key, "Detected use-after-free of lock class %px/%s\n", hlock_class(prev), hlock_class(prev)->name); WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key, "Detected use-after-free of lock class %px/%s\n", hlock_class(next), hlock_class(next)->name); return 2; }
if (prev->class_idx == next->class_idx) { struct lock_class *class = hlock_class(prev);
if (class->cmp_fn && class->cmp_fn(prev->instance, next->instance) < 0) return 2; }
/* * Prove that the new <prev> -> <next> dependency would not * create a circular dependency in the graph. (We do this by * a breadth-first search into the graph starting at <next>, * and check whether we can reach <prev>.) * * The search is limited by the size of the circular queue (i.e., * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes * in the graph whose neighbours are to be checked. */ ret = check_noncircular(next, prev, trace); if (unlikely(bfs_error(ret) || ret == BFS_RMATCH)) return 0;
if (!check_irq_usage(curr, prev, next)) return 0;
/* * Is the <prev> -> <next> dependency already present? * * (this may occur even though this is a new chain: consider * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3 * chains - the second one will be new, but L1 already has * L2 added to its dependency list, due to the first chain.) */ list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) { if (entry->class == hlock_class(next)) { if (distance == 1) entry->distance = 1; entry->dep |= calc_dep(prev, next);
/* * Also, update the reverse dependency in @next's * ->locks_before list. * * Here we reuse @entry as the cursor, which is fine * because we won't go to the next iteration of the * outer loop: * * For normal cases, we return in the inner loop. * * If we fail to return, we have inconsistency, i.e. * <prev>::locks_after contains <next> while * <next>::locks_before doesn't contain <prev>. In * that case, we return after the inner and indicate * something is wrong. */ list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) { if (entry->class == hlock_class(prev)) { if (distance == 1) entry->distance = 1; entry->dep |= calc_depb(prev, next); return 1; } }
/* <prev> is not found in <next>::locks_before */ return 0; } }
/* * Is the <prev> -> <next> link redundant? */ ret = check_redundant(prev, next); if (bfs_error(ret)) return 0; else if (ret == BFS_RMATCH) return 2;
if (!*trace) { *trace = save_trace(); if (!*trace) return 0; }
/* * Ok, all validations passed, add the new lock * to the previous lock's dependency list: */ ret = add_lock_to_list(hlock_class(next), hlock_class(prev), &hlock_class(prev)->locks_after, distance, calc_dep(prev, next), *trace);
if (!ret) return 0;
ret = add_lock_to_list(hlock_class(prev), hlock_class(next), &hlock_class(next)->locks_before, distance, calc_depb(prev, next), *trace); if (!ret) return 0;
return 2;}
/* * Add the dependency to all directly-previous locks that are 'relevant'. * The ones that are relevant are (in increasing distance from curr): * all consecutive trylock entries and the final non-trylock entry - or * the end of this context's lock-chain - whichever comes first. */static intcheck_prevs_add(struct task_struct *curr, struct held_lock *next){ struct lock_trace *trace = NULL; int depth = curr->lockdep_depth; struct held_lock *hlock;
/* * Debugging checks. * * Depth must not be zero for a non-head lock: */ if (!depth) goto out_bug; /* * At least two relevant locks must exist for this * to be a head: */ if (curr->held_locks[depth].irq_context != curr->held_locks[depth-1].irq_context) goto out_bug;
for (;;) { u16 distance = curr->lockdep_depth - depth + 1; hlock = curr->held_locks + depth - 1;
if (hlock->check) { int ret = check_prev_add(curr, hlock, next, distance, &trace); if (!ret) return 0;
/* * Stop after the first non-trylock entry, * as non-trylock entries have added their * own direct dependencies already, so this * lock is connected to them indirectly: */ if (!hlock->trylock) break; }
depth--; /* * End of lock-stack? */ if (!depth) break; /* * Stop the search if we cross into another context: */ if (curr->held_locks[depth].irq_context != curr->held_locks[depth-1].irq_context) break; } return 1;out_bug: if (!debug_locks_off_graph_unlock()) return 0;
/* * Clearly we all shouldn't be here, but since we made it we * can reliable say we messed up our state. See the above two * gotos for reasons why we could possibly end up here. */ WARN_ON(1);
return 0;}
struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];unsigned long nr_zapped_lock_chains;unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
/* * The first 2 chain_hlocks entries in the chain block in the bucket * list contains the following meta data: * * entry[0]: * Bit 15 - always set to 1 (it is not a class index) * Bits 0-14 - upper 15 bits of the next block index * entry[1] - lower 16 bits of next block index * * A next block index of all 1 bits means it is the end of the list. * * On the unsized bucket (bucket-0), the 3rd and 4th entries contain * the chain block size: * * entry[2] - upper 16 bits of the chain block size * entry[3] - lower 16 bits of the chain block size */#define MAX_CHAIN_BUCKETS 16#define CHAIN_BLK_FLAG (1U << 15)#define CHAIN_BLK_LIST_END 0xFFFFU
static int chain_block_buckets[MAX_CHAIN_BUCKETS];
static inline int size_to_bucket(int size){ if (size > MAX_CHAIN_BUCKETS) return 0;
return size - 1;}
/* * Iterate all the chain blocks in a bucket. */#define for_each_chain_block(bucket, prev, curr) \ for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \ (curr) >= 0; \ (prev) = (curr), (curr) = chain_block_next(curr))
/* * next block or -1 */static inline int chain_block_next(int offset){ int next = chain_hlocks[offset];
WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
if (next == CHAIN_BLK_LIST_END) return -1;
next &= ~CHAIN_BLK_FLAG; next <<= 16; next |= chain_hlocks[offset + 1];
return next;}
/* * bucket-0 only */static inline int chain_block_size(int offset){ return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];}
static inline void init_chain_block(int offset, int next, int bucket, int size){ chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG; chain_hlocks[offset + 1] = (u16)next;
if (size && !bucket) { chain_hlocks[offset + 2] = size >> 16; chain_hlocks[offset + 3] = (u16)size; }}
static inline void add_chain_block(int offset, int size){ int bucket = size_to_bucket(size); int next = chain_block_buckets[bucket]; int prev, curr;
if (unlikely(size < 2)) { /* * We can't store single entries on the freelist. Leak them. * * One possible way out would be to uniquely mark them, other * than with CHAIN_BLK_FLAG, such that we can recover them when * the block before it is re-added. */ if (size) nr_lost_chain_hlocks++; return; }
nr_free_chain_hlocks += size; if (!bucket) { nr_large_chain_blocks++;
/* * Variable sized, sort large to small. */ for_each_chain_block(0, prev, curr) { if (size >= chain_block_size(curr)) break; } init_chain_block(offset, curr, 0, size); if (prev < 0) chain_block_buckets[0] = offset; else init_chain_block(prev, offset, 0, 0); return; } /* * Fixed size, add to head. */ init_chain_block(offset, next, bucket, size); chain_block_buckets[bucket] = offset;}
/* * Only the first block in the list can be deleted. * * For the variable size bucket[0], the first block (the largest one) is * returned, broken up and put back into the pool. So if a chain block of * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be * queued up after the primordial chain block and never be used until the * hlock entries in the primordial chain block is almost used up. That * causes fragmentation and reduce allocation efficiency. That can be * monitored by looking at the "large chain blocks" number in lockdep_stats. */static inline void del_chain_block(int bucket, int size, int next){ nr_free_chain_hlocks -= size; chain_block_buckets[bucket] = next;
if (!bucket) nr_large_chain_blocks--;}
static void init_chain_block_buckets(void){ int i;
for (i = 0; i < MAX_CHAIN_BUCKETS; i++) chain_block_buckets[i] = -1;
add_chain_block(0, ARRAY_SIZE(chain_hlocks));}
/* * Return offset of a chain block of the right size or -1 if not found. * * Fairly simple worst-fit allocator with the addition of a number of size * specific free lists. */static int alloc_chain_hlocks(int req){ int bucket, curr, size;
/* * We rely on the MSB to act as an escape bit to denote freelist * pointers. Make sure this bit isn't set in 'normal' class_idx usage. */ BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
init_data_structures_once();
if (nr_free_chain_hlocks < req) return -1;
/* * We require a minimum of 2 (u16) entries to encode a freelist * 'pointer'. */ req = max(req, 2); bucket = size_to_bucket(req); curr = chain_block_buckets[bucket];
if (bucket) { if (curr >= 0) { del_chain_block(bucket, req, chain_block_next(curr)); return curr; } /* Try bucket 0 */ curr = chain_block_buckets[0]; }
/* * The variable sized freelist is sorted by size; the first entry is * the largest. Use it if it fits. */ if (curr >= 0) { size = chain_block_size(curr); if (likely(size >= req)) { del_chain_block(0, size, chain_block_next(curr)); if (size > req) add_chain_block(curr + req, size - req); return curr; } }
/* * Last resort, split a block in a larger sized bucket. */ for (size = MAX_CHAIN_BUCKETS; size > req; size--) { bucket = size_to_bucket(size); curr = chain_block_buckets[bucket]; if (curr < 0) continue;
del_chain_block(bucket, size, chain_block_next(curr)); add_chain_block(curr + req, size - req); return curr; }
return -1;}
static inline void free_chain_hlocks(int base, int size){ add_chain_block(base, max(size, 2));}
struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i){ u16 chain_hlock = chain_hlocks[chain->base + i]; unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
return lock_classes + class_idx;}
/* * Returns the index of the first held_lock of the current chain */static inline int get_first_held_lock(struct task_struct *curr, struct held_lock *hlock){ int i; struct held_lock *hlock_curr;
for (i = curr->lockdep_depth - 1; i >= 0; i--) { hlock_curr = curr->held_locks + i; if (hlock_curr->irq_context != hlock->irq_context) break;
}
return ++i;}
#ifdef CONFIG_DEBUG_LOCKDEP/* * Returns the next chain_key iteration */static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key){ u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
printk(" hlock_id:%d -> chain_key:%016Lx", (unsigned int)hlock_id, (unsigned long long)new_chain_key); return new_chain_key;}
static voidprint_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next){ struct held_lock *hlock; u64 chain_key = INITIAL_CHAIN_KEY; int depth = curr->lockdep_depth; int i = get_first_held_lock(curr, hlock_next);
printk("depth: %u (irq_context %u)\n", depth - i + 1, hlock_next->irq_context); for (; i < depth; i++) { hlock = curr->held_locks + i; chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
print_lock(hlock); }
print_chain_key_iteration(hlock_id(hlock_next), chain_key); print_lock(hlock_next);}
static void print_chain_keys_chain(struct lock_chain *chain){ int i; u64 chain_key = INITIAL_CHAIN_KEY; u16 hlock_id;
printk("depth: %u\n", chain->depth); for (i = 0; i < chain->depth; i++) { hlock_id = chain_hlocks[chain->base + i]; chain_key = print_chain_key_iteration(hlock_id, chain_key);
print_lock_name(NULL, lock_classes + chain_hlock_class_idx(hlock_id)); printk("\n"); }}
static void print_collision(struct task_struct *curr, struct held_lock *hlock_next, struct lock_chain *chain){ nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("============================\n"); pr_warn("WARNING: chain_key collision\n"); print_kernel_ident(); pr_warn("----------------------------\n"); pr_warn("%s/%d: ", current->comm, task_pid_nr(current)); pr_warn("Hash chain already cached but the contents don't match!\n");
pr_warn("Held locks:"); print_chain_keys_held_locks(curr, hlock_next);
pr_warn("Locks in cached chain:"); print_chain_keys_chain(chain);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}#endif
/* * Checks whether the chain and the current held locks are consistent * in depth and also in content. If they are not it most likely means * that there was a collision during the calculation of the chain_key. * Returns: 0 not passed, 1 passed */static int check_no_collision(struct task_struct *curr, struct held_lock *hlock, struct lock_chain *chain){#ifdef CONFIG_DEBUG_LOCKDEP int i, j, id;
i = get_first_held_lock(curr, hlock);
if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) { print_collision(curr, hlock, chain); return 0; }
for (j = 0; j < chain->depth - 1; j++, i++) { id = hlock_id(&curr->held_locks[i]);
if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) { print_collision(curr, hlock, chain); return 0; } }#endif return 1;}
/* * Given an index that is >= -1, return the index of the next lock chain. * Return -2 if there is no next lock chain. */long lockdep_next_lockchain(long i){ i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1); return i < ARRAY_SIZE(lock_chains) ? i : -2;}
unsigned long lock_chain_count(void){ return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));}
/* Must be called with the graph lock held. */static struct lock_chain *alloc_lock_chain(void){ int idx = find_first_zero_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains));
if (unlikely(idx >= ARRAY_SIZE(lock_chains))) return NULL; __set_bit(idx, lock_chains_in_use); return lock_chains + idx;}
/* * Adds a dependency chain into chain hashtable. And must be called with * graph_lock held. * * Return 0 if fail, and graph_lock is released. * Return 1 if succeed, with graph_lock held. */static inline int add_chain_cache(struct task_struct *curr, struct held_lock *hlock, u64 chain_key){ struct hlist_head *hash_head = chainhashentry(chain_key); struct lock_chain *chain; int i, j;
/* * The caller must hold the graph lock, ensure we've got IRQs * disabled to make this an IRQ-safe lock.. for recursion reasons * lockdep won't complain about its own locking errors. */ if (lockdep_assert_locked()) return 0;
chain = alloc_lock_chain(); if (!chain) { if (!debug_locks_off_graph_unlock()) return 0;
nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!"); dump_stack(); nbcon_cpu_emergency_exit(); return 0; } chain->chain_key = chain_key; chain->irq_context = hlock->irq_context; i = get_first_held_lock(curr, hlock); chain->depth = curr->lockdep_depth + 1 - i;
BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks)); BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks)); BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
j = alloc_chain_hlocks(chain->depth); if (j < 0) { if (!debug_locks_off_graph_unlock()) return 0;
nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!"); dump_stack(); nbcon_cpu_emergency_exit(); return 0; }
chain->base = j; for (j = 0; j < chain->depth - 1; j++, i++) { int lock_id = hlock_id(curr->held_locks + i);
chain_hlocks[chain->base + j] = lock_id; } chain_hlocks[chain->base + j] = hlock_id(hlock); hlist_add_head_rcu(&chain->entry, hash_head); debug_atomic_inc(chain_lookup_misses); inc_chains(chain->irq_context);
return 1;}
/* * Look up a dependency chain. Must be called with either the graph lock or * the RCU read lock held. */static inline struct lock_chain *lookup_chain_cache(u64 chain_key){ struct hlist_head *hash_head = chainhashentry(chain_key); struct lock_chain *chain;
hlist_for_each_entry_rcu(chain, hash_head, entry) { if (READ_ONCE(chain->chain_key) == chain_key) { debug_atomic_inc(chain_lookup_hits); return chain; } } return NULL;}
/* * If the key is not present yet in dependency chain cache then * add it and return 1 - in this case the new dependency chain is * validated. If the key is already hashed, return 0. * (On return with 1 graph_lock is held.) */static inline int lookup_chain_cache_add(struct task_struct *curr, struct held_lock *hlock, u64 chain_key){ struct lock_class *class = hlock_class(hlock); struct lock_chain *chain = lookup_chain_cache(chain_key);
if (chain) {cache_hit: if (!check_no_collision(curr, hlock, chain)) return 0;
if (very_verbose(class)) { printk("\nhash chain already cached, key: " "%016Lx tail class: [%px] %s\n", (unsigned long long)chain_key, class->key, class->name); }
return 0; }
if (very_verbose(class)) { printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n", (unsigned long long)chain_key, class->key, class->name); }
if (!graph_lock()) return 0;
/* * We have to walk the chain again locked - to avoid duplicates: */ chain = lookup_chain_cache(chain_key); if (chain) { graph_unlock(); goto cache_hit; }
if (!add_chain_cache(curr, hlock, chain_key)) return 0;
return 1;}
static int validate_chain(struct task_struct *curr, struct held_lock *hlock, int chain_head, u64 chain_key){ /* * Trylock needs to maintain the stack of held locks, but it * does not add new dependencies, because trylock can be done * in any order. * * We look up the chain_key and do the O(N^2) check and update of * the dependencies only if this is a new dependency chain. * (If lookup_chain_cache_add() return with 1 it acquires * graph_lock for us) */ if (!hlock->trylock && hlock->check && lookup_chain_cache_add(curr, hlock, chain_key)) { /* * Check whether last held lock: * * - is irq-safe, if this lock is irq-unsafe * - is softirq-safe, if this lock is hardirq-unsafe * * And check whether the new lock's dependency graph * could lead back to the previous lock: * * - within the current held-lock stack * - across our accumulated lock dependency records * * any of these scenarios could lead to a deadlock. */ /* * The simple case: does the current hold the same lock * already? */ int ret = check_deadlock(curr, hlock);
if (!ret) return 0; /* * Add dependency only if this lock is not the head * of the chain, and if the new lock introduces no more * lock dependency (because we already hold a lock with the * same lock class) nor deadlock (because the nest_lock * serializes nesting locks), see the comments for * check_deadlock(). */ if (!chain_head && ret != 2) { if (!check_prevs_add(curr, hlock)) return 0; }
graph_unlock(); } else { /* after lookup_chain_cache_add(): */ if (unlikely(!debug_locks)) return 0; }
return 1;}#elsestatic inline int validate_chain(struct task_struct *curr, struct held_lock *hlock, int chain_head, u64 chain_key){ return 1;}
static void init_chain_block_buckets(void) { }#endif /* CONFIG_PROVE_LOCKING */
/* * We are building curr_chain_key incrementally, so double-check * it from scratch, to make sure that it's done correctly: */static void check_chain_key(struct task_struct *curr){#ifdef CONFIG_DEBUG_LOCKDEP struct held_lock *hlock, *prev_hlock = NULL; unsigned int i; u64 chain_key = INITIAL_CHAIN_KEY;
for (i = 0; i < curr->lockdep_depth; i++) { hlock = curr->held_locks + i; if (chain_key != hlock->prev_chain_key) { debug_locks_off(); /* * We got mighty confused, our chain keys don't match * with what we expect, someone trample on our task state? */ WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n", curr->lockdep_depth, i, (unsigned long long)chain_key, (unsigned long long)hlock->prev_chain_key); return; }
/* * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is * it registered lock class index? */ if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use))) return;
if (prev_hlock && (prev_hlock->irq_context != hlock->irq_context)) chain_key = INITIAL_CHAIN_KEY; chain_key = iterate_chain_key(chain_key, hlock_id(hlock)); prev_hlock = hlock; } if (chain_key != curr->curr_chain_key) { debug_locks_off(); /* * More smoking hash instead of calculating it, damn see these * numbers float.. I bet that a pink elephant stepped on my memory. */ WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n", curr->lockdep_depth, i, (unsigned long long)chain_key, (unsigned long long)curr->curr_chain_key); }#endif}
#ifdef CONFIG_PROVE_LOCKINGstatic int mark_lock(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit new_bit);
static void print_usage_bug_scenario(struct held_lock *lock){ struct lock_class *class = hlock_class(lock);
printk(" Possible unsafe locking scenario:\n\n"); printk(" CPU0\n"); printk(" ----\n"); printk(" lock("); __print_lock_name(lock, class); printk(KERN_CONT ");\n"); printk(" <Interrupt>\n"); printk(" lock("); __print_lock_name(lock, class); printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n");}
static voidprint_usage_bug(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit){ if (!debug_locks_off() || debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("================================\n"); pr_warn("WARNING: inconsistent lock state\n"); print_kernel_ident(); pr_warn("--------------------------------\n");
pr_warn("inconsistent {%s} -> {%s} usage.\n", usage_str[prev_bit], usage_str[new_bit]);
pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n", curr->comm, task_pid_nr(curr), lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT, lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT, lockdep_hardirqs_enabled(), lockdep_softirqs_enabled(curr)); print_lock(this);
pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]); print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
print_irqtrace_events(curr); pr_warn("\nother info that might help us debug this:\n"); print_usage_bug_scenario(this);
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
/* * Print out an error if an invalid bit is set: */static inline intvalid_state(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit){ if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) { graph_unlock(); print_usage_bug(curr, this, bad_bit, new_bit); return 0; } return 1;}
/* * print irq inversion bug: */static voidprint_irq_inversion_bug(struct task_struct *curr, struct lock_list *root, struct lock_list *other, struct held_lock *this, int forwards, const char *irqclass){ struct lock_list *entry = other; struct lock_list *middle = NULL; int depth;
if (!debug_locks_off_graph_unlock() || debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("========================================================\n"); pr_warn("WARNING: possible irq lock inversion dependency detected\n"); print_kernel_ident(); pr_warn("--------------------------------------------------------\n"); pr_warn("%s/%d just changed the state of lock:\n", curr->comm, task_pid_nr(curr)); print_lock(this); if (forwards) pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass); else pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass); print_lock_name(NULL, other->class); pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
pr_warn("\nother info that might help us debug this:\n");
/* Find a middle lock (if one exists) */ depth = get_lock_depth(other); do { if (depth == 0 && (entry != root)) { pr_warn("lockdep:%s bad path found in chain graph\n", __func__); break; } middle = entry; entry = get_lock_parent(entry); depth--; } while (entry && entry != root && (depth >= 0)); if (forwards) print_irq_lock_scenario(root, other, middle ? middle->class : root->class, other->class); else print_irq_lock_scenario(other, root, middle ? middle->class : other->class, root->class);
lockdep_print_held_locks(curr);
pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n"); root->trace = save_trace(); if (!root->trace) goto out; print_shortest_lock_dependencies(other, root);
pr_warn("\nstack backtrace:\n"); dump_stack();out: nbcon_cpu_emergency_exit();}
/* * Prove that in the forwards-direction subgraph starting at <this> * there is no lock matching <mask>: */static intcheck_usage_forwards(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit bit){ enum bfs_result ret; struct lock_list root; struct lock_list *target_entry; enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK; unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
bfs_init_root(&root, this); ret = find_usage_forwards(&root, usage_mask, &target_entry); if (bfs_error(ret)) { print_bfs_bug(ret); return 0; } if (ret == BFS_RNOMATCH) return 1;
/* Check whether write or read usage is the match */ if (target_entry->class->usage_mask & lock_flag(bit)) { print_irq_inversion_bug(curr, &root, target_entry, this, 1, state_name(bit)); } else { print_irq_inversion_bug(curr, &root, target_entry, this, 1, state_name(read_bit)); }
return 0;}
/* * Prove that in the backwards-direction subgraph starting at <this> * there is no lock matching <mask>: */static intcheck_usage_backwards(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit bit){ enum bfs_result ret; struct lock_list root; struct lock_list *target_entry; enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK; unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
bfs_init_rootb(&root, this); ret = find_usage_backwards(&root, usage_mask, &target_entry); if (bfs_error(ret)) { print_bfs_bug(ret); return 0; } if (ret == BFS_RNOMATCH) return 1;
/* Check whether write or read usage is the match */ if (target_entry->class->usage_mask & lock_flag(bit)) { print_irq_inversion_bug(curr, &root, target_entry, this, 0, state_name(bit)); } else { print_irq_inversion_bug(curr, &root, target_entry, this, 0, state_name(read_bit)); }
return 0;}
void print_irqtrace_events(struct task_struct *curr){ const struct irqtrace_events *trace = &curr->irqtrace;
nbcon_cpu_emergency_enter();
printk("irq event stamp: %u\n", trace->irq_events); printk("hardirqs last enabled at (%u): [<%px>] %pS\n", trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip, (void *)trace->hardirq_enable_ip); printk("hardirqs last disabled at (%u): [<%px>] %pS\n", trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip, (void *)trace->hardirq_disable_ip); printk("softirqs last enabled at (%u): [<%px>] %pS\n", trace->softirq_enable_event, (void *)trace->softirq_enable_ip, (void *)trace->softirq_enable_ip); printk("softirqs last disabled at (%u): [<%px>] %pS\n", trace->softirq_disable_event, (void *)trace->softirq_disable_ip, (void *)trace->softirq_disable_ip);
nbcon_cpu_emergency_exit();}
static int HARDIRQ_verbose(struct lock_class *class){#if HARDIRQ_VERBOSE return class_filter(class);#endif return 0;}
static int SOFTIRQ_verbose(struct lock_class *class){#if SOFTIRQ_VERBOSE return class_filter(class);#endif return 0;}
static int (*state_verbose_f[])(struct lock_class *class) = {#define LOCKDEP_STATE(__STATE) \ __STATE##_verbose,#include "lockdep_states.h"#undef LOCKDEP_STATE};
static inline int state_verbose(enum lock_usage_bit bit, struct lock_class *class){ return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);}
typedef int (*check_usage_f)(struct task_struct *, struct held_lock *, enum lock_usage_bit bit, const char *name);
static intmark_lock_irq(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit new_bit){ int excl_bit = exclusive_bit(new_bit); int read = new_bit & LOCK_USAGE_READ_MASK; int dir = new_bit & LOCK_USAGE_DIR_MASK;
/* * Validate that this particular lock does not have conflicting * usage states. */ if (!valid_state(curr, this, new_bit, excl_bit)) return 0;
/* * Check for read in write conflicts */ if (!read && !valid_state(curr, this, new_bit, excl_bit + LOCK_USAGE_READ_MASK)) return 0;
/* * Validate that the lock dependencies don't have conflicting usage * states. */ if (dir) { /* * mark ENABLED has to look backwards -- to ensure no dependee * has USED_IN state, which, again, would allow recursion deadlocks. */ if (!check_usage_backwards(curr, this, excl_bit)) return 0; } else { /* * mark USED_IN has to look forwards -- to ensure no dependency * has ENABLED state, which would allow recursion deadlocks. */ if (!check_usage_forwards(curr, this, excl_bit)) return 0; }
if (state_verbose(new_bit, hlock_class(this))) return 2;
return 1;}
/* * Mark all held locks with a usage bit: */static intmark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit){ struct held_lock *hlock; int i;
for (i = 0; i < curr->lockdep_depth; i++) { enum lock_usage_bit hlock_bit = base_bit; hlock = curr->held_locks + i;
if (hlock->read) hlock_bit += LOCK_USAGE_READ_MASK;
BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
if (!hlock->check) continue;
if (!mark_lock(curr, hlock, hlock_bit)) return 0; }
return 1;}
/* * Hardirqs will be enabled: */static void __trace_hardirqs_on_caller(void){ struct task_struct *curr = current;
/* * We are going to turn hardirqs on, so set the * usage bit for all held locks: */ if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ)) return; /* * If we have softirqs enabled, then set the usage * bit for all held locks. (disabled hardirqs prevented * this bit from being set before) */ if (curr->softirqs_enabled) mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);}
/** * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts * * Invoked before a possible transition to RCU idle from exit to user or * guest mode. This ensures that all RCU operations are done before RCU * stops watching. After the RCU transition lockdep_hardirqs_on() has to be * invoked to set the final state. */void lockdep_hardirqs_on_prepare(void){ if (unlikely(!debug_locks)) return;
/* * NMIs do not (and cannot) track lock dependencies, nothing to do. */ if (unlikely(in_nmi())) return;
if (unlikely(this_cpu_read(lockdep_recursion))) return;
if (unlikely(lockdep_hardirqs_enabled())) { /* * Neither irq nor preemption are disabled here * so this is racy by nature but losing one hit * in a stat is not a big deal. */ __debug_atomic_inc(redundant_hardirqs_on); return; }
/* * We're enabling irqs and according to our state above irqs weren't * already enabled, yet we find the hardware thinks they are in fact * enabled.. someone messed up their IRQ state tracing. */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return;
/* * See the fine text that goes along with this variable definition. */ if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled)) return;
/* * Can't allow enabling interrupts while in an interrupt handler, * that's general bad form and such. Recursion, limited stack etc.. */ if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context())) return;
current->hardirq_chain_key = current->curr_chain_key;
lockdep_recursion_inc(); __trace_hardirqs_on_caller(); lockdep_recursion_finish();}EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
void noinstr lockdep_hardirqs_on(unsigned long ip){ struct irqtrace_events *trace = ¤t->irqtrace;
if (unlikely(!debug_locks)) return;
/* * NMIs can happen in the middle of local_irq_{en,dis}able() where the * tracking state and hardware state are out of sync. * * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from, * and not rely on hardware state like normal interrupts. */ if (unlikely(in_nmi())) { if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) return;
/* * Skip: * - recursion check, because NMI can hit lockdep; * - hardware state check, because above; * - chain_key check, see lockdep_hardirqs_on_prepare(). */ goto skip_checks; }
if (unlikely(this_cpu_read(lockdep_recursion))) return;
if (lockdep_hardirqs_enabled()) { /* * Neither irq nor preemption are disabled here * so this is racy by nature but losing one hit * in a stat is not a big deal. */ __debug_atomic_inc(redundant_hardirqs_on); return; }
/* * We're enabling irqs and according to our state above irqs weren't * already enabled, yet we find the hardware thinks they are in fact * enabled.. someone messed up their IRQ state tracing. */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return;
/* * Ensure the lock stack remained unchanged between * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on(). */ DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key != current->curr_chain_key);
skip_checks: /* we'll do an OFF -> ON transition: */ __this_cpu_write(hardirqs_enabled, 1); trace->hardirq_enable_ip = ip; trace->hardirq_enable_event = ++trace->irq_events; debug_atomic_inc(hardirqs_on_events);}EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
/* * Hardirqs were disabled: */void noinstr lockdep_hardirqs_off(unsigned long ip){ if (unlikely(!debug_locks)) return;
/* * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep; * they will restore the software state. This ensures the software * state is consistent inside NMIs as well. */ if (in_nmi()) { if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) return; } else if (__this_cpu_read(lockdep_recursion)) return;
/* * So we're supposed to get called after you mask local IRQs, but for * some reason the hardware doesn't quite think you did a proper job. */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return;
if (lockdep_hardirqs_enabled()) { struct irqtrace_events *trace = ¤t->irqtrace;
/* * We have done an ON -> OFF transition: */ __this_cpu_write(hardirqs_enabled, 0); trace->hardirq_disable_ip = ip; trace->hardirq_disable_event = ++trace->irq_events; debug_atomic_inc(hardirqs_off_events); } else { debug_atomic_inc(redundant_hardirqs_off); }}EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
/* * Softirqs will be enabled: */void lockdep_softirqs_on(unsigned long ip){ struct irqtrace_events *trace = ¤t->irqtrace;
if (unlikely(!lockdep_enabled())) return;
/* * We fancy IRQs being disabled here, see softirq.c, avoids * funny state and nesting things. */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return;
if (current->softirqs_enabled) { debug_atomic_inc(redundant_softirqs_on); return; }
lockdep_recursion_inc(); /* * We'll do an OFF -> ON transition: */ current->softirqs_enabled = 1; trace->softirq_enable_ip = ip; trace->softirq_enable_event = ++trace->irq_events; debug_atomic_inc(softirqs_on_events); /* * We are going to turn softirqs on, so set the * usage bit for all held locks, if hardirqs are * enabled too: */ if (lockdep_hardirqs_enabled()) mark_held_locks(current, LOCK_ENABLED_SOFTIRQ); lockdep_recursion_finish();}
/* * Softirqs were disabled: */void lockdep_softirqs_off(unsigned long ip){ if (unlikely(!lockdep_enabled())) return;
/* * We fancy IRQs being disabled here, see softirq.c */ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return;
if (current->softirqs_enabled) { struct irqtrace_events *trace = ¤t->irqtrace;
/* * We have done an ON -> OFF transition: */ current->softirqs_enabled = 0; trace->softirq_disable_ip = ip; trace->softirq_disable_event = ++trace->irq_events; debug_atomic_inc(softirqs_off_events); /* * Whoops, we wanted softirqs off, so why aren't they? */ DEBUG_LOCKS_WARN_ON(!softirq_count()); } else debug_atomic_inc(redundant_softirqs_off);}
/** * lockdep_cleanup_dead_cpu - Ensure CPU lockdep state is cleanly stopped * * @cpu: index of offlined CPU * @idle: task pointer for offlined CPU's idle thread * * Invoked after the CPU is dead. Ensures that the tracing infrastructure * is left in a suitable state for the CPU to be subsequently brought * online again. */void lockdep_cleanup_dead_cpu(unsigned int cpu, struct task_struct *idle){ if (unlikely(!debug_locks)) return;
if (unlikely(per_cpu(hardirqs_enabled, cpu))) { pr_warn("CPU %u left hardirqs enabled!", cpu); if (idle) print_irqtrace_events(idle); /* Clean it up for when the CPU comes online again. */ per_cpu(hardirqs_enabled, cpu) = 0; }}
static intmark_usage(struct task_struct *curr, struct held_lock *hlock, int check){ if (!check) goto lock_used;
/* * If non-trylock use in a hardirq or softirq context, then * mark the lock as used in these contexts: */ if (!hlock->trylock) { if (hlock->read) { if (lockdep_hardirq_context()) if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ_READ)) return 0; if (curr->softirq_context) if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ_READ)) return 0; } else { if (lockdep_hardirq_context()) if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ)) return 0; if (curr->softirq_context) if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ)) return 0; } }
/* * For lock_sync(), don't mark the ENABLED usage, since lock_sync() * creates no critical section and no extra dependency can be introduced * by interrupts */ if (!hlock->hardirqs_off && !hlock->sync) { if (hlock->read) { if (!mark_lock(curr, hlock, LOCK_ENABLED_HARDIRQ_READ)) return 0; if (curr->softirqs_enabled) if (!mark_lock(curr, hlock, LOCK_ENABLED_SOFTIRQ_READ)) return 0; } else { if (!mark_lock(curr, hlock, LOCK_ENABLED_HARDIRQ)) return 0; if (curr->softirqs_enabled) if (!mark_lock(curr, hlock, LOCK_ENABLED_SOFTIRQ)) return 0; } }
lock_used: /* mark it as used: */ if (!mark_lock(curr, hlock, LOCK_USED)) return 0;
return 1;}
static inline unsigned int task_irq_context(struct task_struct *task){ return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() + LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;}
static int separate_irq_context(struct task_struct *curr, struct held_lock *hlock){ unsigned int depth = curr->lockdep_depth;
/* * Keep track of points where we cross into an interrupt context: */ if (depth) { struct held_lock *prev_hlock;
prev_hlock = curr->held_locks + depth-1; /* * If we cross into another context, reset the * hash key (this also prevents the checking and the * adding of the dependency to 'prev'): */ if (prev_hlock->irq_context != hlock->irq_context) return 1; } return 0;}
/* * Mark a lock with a usage bit, and validate the state transition: */static int mark_lock(struct task_struct *curr, struct held_lock *this, enum lock_usage_bit new_bit){ unsigned int new_mask, ret = 1;
if (new_bit >= LOCK_USAGE_STATES) { DEBUG_LOCKS_WARN_ON(1); return 0; }
if (new_bit == LOCK_USED && this->read) new_bit = LOCK_USED_READ;
new_mask = 1 << new_bit;
/* * If already set then do not dirty the cacheline, * nor do any checks: */ if (likely(hlock_class(this)->usage_mask & new_mask)) return 1;
if (!graph_lock()) return 0; /* * Make sure we didn't race: */ if (unlikely(hlock_class(this)->usage_mask & new_mask)) goto unlock;
if (!hlock_class(this)->usage_mask) debug_atomic_dec(nr_unused_locks);
hlock_class(this)->usage_mask |= new_mask;
if (new_bit < LOCK_TRACE_STATES) { if (!(hlock_class(this)->usage_traces[new_bit] = save_trace())) return 0; }
if (new_bit < LOCK_USED) { ret = mark_lock_irq(curr, this, new_bit); if (!ret) return 0; }
unlock: graph_unlock();
/* * We must printk outside of the graph_lock: */ if (ret == 2) { nbcon_cpu_emergency_enter(); printk("\nmarked lock as {%s}:\n", usage_str[new_bit]); print_lock(this); print_irqtrace_events(curr); dump_stack(); nbcon_cpu_emergency_exit(); }
return ret;}
static inline short task_wait_context(struct task_struct *curr){ /* * Set appropriate wait type for the context; for IRQs we have to take * into account force_irqthread as that is implied by PREEMPT_RT. */ if (lockdep_hardirq_context()) { /* * Check if force_irqthreads will run us threaded. */ if (curr->hardirq_threaded || curr->irq_config) return LD_WAIT_CONFIG;
return LD_WAIT_SPIN; } else if (curr->softirq_context) { /* * Softirqs are always threaded. */ return LD_WAIT_CONFIG; }
return LD_WAIT_MAX;}
static intprint_lock_invalid_wait_context(struct task_struct *curr, struct held_lock *hlock){ short curr_inner;
if (!debug_locks_off()) return 0; if (debug_locks_silent) return 0;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("=============================\n"); pr_warn("[ BUG: Invalid wait context ]\n"); print_kernel_ident(); pr_warn("-----------------------------\n");
pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr)); print_lock(hlock);
pr_warn("other info that might help us debug this:\n");
curr_inner = task_wait_context(curr); pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
lockdep_print_held_locks(curr);
pr_warn("stack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();
return 0;}
/* * Verify the wait_type context. * * This check validates we take locks in the right wait-type order; that is it * ensures that we do not take mutexes inside spinlocks and do not attempt to * acquire spinlocks inside raw_spinlocks and the sort. * * The entire thing is slightly more complex because of RCU, RCU is a lock that * can be taken from (pretty much) any context but also has constraints. * However when taken in a stricter environment the RCU lock does not loosen * the constraints. * * Therefore we must look for the strictest environment in the lock stack and * compare that to the lock we're trying to acquire. */static int check_wait_context(struct task_struct *curr, struct held_lock *next){ u8 next_inner = hlock_class(next)->wait_type_inner; u8 next_outer = hlock_class(next)->wait_type_outer; u8 curr_inner; int depth;
if (!next_inner || next->trylock) return 0;
if (!next_outer) next_outer = next_inner;
/* * Find start of current irq_context.. */ for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) { struct held_lock *prev = curr->held_locks + depth; if (prev->irq_context != next->irq_context) break; } depth++;
curr_inner = task_wait_context(curr);
for (; depth < curr->lockdep_depth; depth++) { struct held_lock *prev = curr->held_locks + depth; struct lock_class *class = hlock_class(prev); u8 prev_inner = class->wait_type_inner;
if (prev_inner) { /* * We can have a bigger inner than a previous one * when outer is smaller than inner, as with RCU. * * Also due to trylocks. */ curr_inner = min(curr_inner, prev_inner);
/* * Allow override for annotations -- this is typically * only valid/needed for code that only exists when * CONFIG_PREEMPT_RT=n. */ if (unlikely(class->lock_type == LD_LOCK_WAIT_OVERRIDE)) curr_inner = prev_inner; } }
if (next_outer > curr_inner) return print_lock_invalid_wait_context(curr, next);
return 0;}
#else /* CONFIG_PROVE_LOCKING */
static inline intmark_usage(struct task_struct *curr, struct held_lock *hlock, int check){ return 1;}
static inline unsigned int task_irq_context(struct task_struct *task){ return 0;}
static inline int separate_irq_context(struct task_struct *curr, struct held_lock *hlock){ return 0;}
static inline int check_wait_context(struct task_struct *curr, struct held_lock *next){ return 0;}
#endif /* CONFIG_PROVE_LOCKING */
/* * Initialize a lock instance's lock-class mapping info: */void lockdep_init_map_type(struct lockdep_map *lock, const char *name, struct lock_class_key *key, int subclass, u8 inner, u8 outer, u8 lock_type){ int i;
for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++) lock->class_cache[i] = NULL;
#ifdef CONFIG_LOCK_STAT lock->cpu = raw_smp_processor_id();#endif
/* * Can't be having no nameless bastards around this place! */ if (DEBUG_LOCKS_WARN_ON(!name)) { lock->name = "NULL"; return; }
lock->name = name;
lock->wait_type_outer = outer; lock->wait_type_inner = inner; lock->lock_type = lock_type;
/* * No key, no joy, we need to hash something. */ if (DEBUG_LOCKS_WARN_ON(!key)) return; /* * Sanity check, the lock-class key must either have been allocated * statically or must have been registered as a dynamic key. */ if (!static_obj(key) && !is_dynamic_key(key)) { if (debug_locks) printk(KERN_ERR "BUG: key %px has not been registered!\n", key); DEBUG_LOCKS_WARN_ON(1); return; } lock->key = key;
if (unlikely(!debug_locks)) return;
if (subclass) { unsigned long flags;
if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled())) return;
raw_local_irq_save(flags); lockdep_recursion_inc(); register_lock_class(lock, subclass, 1); lockdep_recursion_finish(); raw_local_irq_restore(flags); }}EXPORT_SYMBOL_GPL(lockdep_init_map_type);
struct lock_class_key __lockdep_no_validate__;EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
struct lock_class_key __lockdep_no_track__;EXPORT_SYMBOL_GPL(__lockdep_no_track__);
#ifdef CONFIG_PROVE_LOCKINGvoid lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn cmp_fn, lock_print_fn print_fn){ struct lock_class *class = lock->class_cache[0]; unsigned long flags;
raw_local_irq_save(flags); lockdep_recursion_inc();
if (!class) class = register_lock_class(lock, 0, 0);
if (class) { WARN_ON(class->cmp_fn && class->cmp_fn != cmp_fn); WARN_ON(class->print_fn && class->print_fn != print_fn);
class->cmp_fn = cmp_fn; class->print_fn = print_fn; }
lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lockdep_set_lock_cmp_fn);#endif
static voidprint_lock_nested_lock_not_held(struct task_struct *curr, struct held_lock *hlock){ if (!debug_locks_off()) return; if (debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("==================================\n"); pr_warn("WARNING: Nested lock was not taken\n"); print_kernel_ident(); pr_warn("----------------------------------\n");
pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr)); print_lock(hlock);
pr_warn("\nbut this task is not holding:\n"); pr_warn("%s\n", hlock->nest_lock->name);
pr_warn("\nstack backtrace:\n"); dump_stack();
pr_warn("\nother info that might help us debug this:\n"); lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
static int __lock_is_held(const struct lockdep_map *lock, int read);
/* * This gets called for every mutex_lock*()/spin_lock*() operation. * We maintain the dependency maps and validate the locking attempt: * * The callers must make sure that IRQs are disabled before calling it, * otherwise we could get an interrupt which would want to take locks, * which would end up in lockdep again. */static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, int trylock, int read, int check, int hardirqs_off, struct lockdep_map *nest_lock, unsigned long ip, int references, int pin_count, int sync){ struct task_struct *curr = current; struct lock_class *class = NULL; struct held_lock *hlock; unsigned int depth; int chain_head = 0; int class_idx; u64 chain_key;
if (unlikely(!debug_locks)) return 0;
if (unlikely(lock->key == &__lockdep_no_track__)) return 0;
lockevent_inc(lockdep_acquire);
if (!prove_locking || lock->key == &__lockdep_no_validate__) { check = 0; lockevent_inc(lockdep_nocheck); }
if (DEBUG_LOCKS_WARN_ON(subclass >= MAX_LOCKDEP_SUBCLASSES)) return 0;
if (subclass < NR_LOCKDEP_CACHING_CLASSES) class = lock->class_cache[subclass]; /* * Not cached? */ if (unlikely(!class)) { class = register_lock_class(lock, subclass, 0); if (!class) return 0; }
debug_class_ops_inc(class);
if (very_verbose(class)) { nbcon_cpu_emergency_enter(); printk("\nacquire class [%px] %s", class->key, class->name); if (class->name_version > 1) printk(KERN_CONT "#%d", class->name_version); printk(KERN_CONT "\n"); dump_stack(); nbcon_cpu_emergency_exit(); }
/* * Add the lock to the list of currently held locks. * (we dont increase the depth just yet, up until the * dependency checks are done) */ depth = curr->lockdep_depth; /* * Ran out of static storage for our per-task lock stack again have we? */ if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH)) return 0;
class_idx = class - lock_classes;
if (depth && !sync) { /* we're holding locks and the new held lock is not a sync */ hlock = curr->held_locks + depth - 1; if (hlock->class_idx == class_idx && nest_lock) { if (!references) references++;
if (!hlock->references) hlock->references++;
hlock->references += references;
/* Overflow */ if (DEBUG_LOCKS_WARN_ON(hlock->references < references)) return 0;
return 2; } }
hlock = curr->held_locks + depth; /* * Plain impossible, we just registered it and checked it weren't no * NULL like.. I bet this mushroom I ate was good! */ if (DEBUG_LOCKS_WARN_ON(!class)) return 0; hlock->class_idx = class_idx; hlock->acquire_ip = ip; hlock->instance = lock; hlock->nest_lock = nest_lock; hlock->irq_context = task_irq_context(curr); hlock->trylock = trylock; hlock->read = read; hlock->check = check; hlock->sync = !!sync; hlock->hardirqs_off = !!hardirqs_off; hlock->references = references;#ifdef CONFIG_LOCK_STAT hlock->waittime_stamp = 0; hlock->holdtime_stamp = lockstat_clock();#endif hlock->pin_count = pin_count;
if (check_wait_context(curr, hlock)) return 0;
/* Initialize the lock usage bit */ if (!mark_usage(curr, hlock, check)) return 0;
/* * Calculate the chain hash: it's the combined hash of all the * lock keys along the dependency chain. We save the hash value * at every step so that we can get the current hash easily * after unlock. The chain hash is then used to cache dependency * results. * * The 'key ID' is what is the most compact key value to drive * the hash, not class->key. */ /* * Whoops, we did it again.. class_idx is invalid. */ if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use))) return 0;
chain_key = curr->curr_chain_key; if (!depth) { /* * How can we have a chain hash when we ain't got no keys?! */ if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY)) return 0; chain_head = 1; }
hlock->prev_chain_key = chain_key; if (separate_irq_context(curr, hlock)) { chain_key = INITIAL_CHAIN_KEY; chain_head = 1; } chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
if (nest_lock && !__lock_is_held(nest_lock, -1)) { print_lock_nested_lock_not_held(curr, hlock); return 0; }
if (!debug_locks_silent) { WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key); WARN_ON_ONCE(!hlock_class(hlock)->key); }
if (!validate_chain(curr, hlock, chain_head, chain_key)) return 0;
/* For lock_sync(), we are done here since no actual critical section */ if (hlock->sync) return 1;
curr->curr_chain_key = chain_key; curr->lockdep_depth++; check_chain_key(curr);#ifdef CONFIG_DEBUG_LOCKDEP if (unlikely(!debug_locks)) return 0;#endif if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) { debug_locks_off(); nbcon_cpu_emergency_enter(); print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!"); printk(KERN_DEBUG "depth: %i max: %lu!\n", curr->lockdep_depth, MAX_LOCK_DEPTH);
lockdep_print_held_locks(current); debug_show_all_locks(); dump_stack(); nbcon_cpu_emergency_exit();
return 0; }
if (unlikely(curr->lockdep_depth > max_lockdep_depth)) max_lockdep_depth = curr->lockdep_depth;
return 1;}
static void print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock, unsigned long ip){ if (!debug_locks_off()) return; if (debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("=====================================\n"); pr_warn("WARNING: bad unlock balance detected!\n"); print_kernel_ident(); pr_warn("-------------------------------------\n"); pr_warn("%s/%d is trying to release lock (", curr->comm, task_pid_nr(curr)); print_lockdep_cache(lock); pr_cont(") at:\n"); print_ip_sym(KERN_WARNING, ip); pr_warn("but there are no more locks to release!\n"); pr_warn("\nother info that might help us debug this:\n"); lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
static noinstr int match_held_lock(const struct held_lock *hlock, const struct lockdep_map *lock){ if (hlock->instance == lock) return 1;
if (hlock->references) { const struct lock_class *class = lock->class_cache[0];
if (!class) class = look_up_lock_class(lock, 0);
/* * If look_up_lock_class() failed to find a class, we're trying * to test if we hold a lock that has never yet been acquired. * Clearly if the lock hasn't been acquired _ever_, we're not * holding it either, so report failure. */ if (!class) return 0;
/* * References, but not a lock we're actually ref-counting? * State got messed up, follow the sites that change ->references * and try to make sense of it. */ if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock)) return 0;
if (hlock->class_idx == class - lock_classes) return 1; }
return 0;}
/* @depth must not be zero */static struct held_lock *find_held_lock(struct task_struct *curr, struct lockdep_map *lock, unsigned int depth, int *idx){ struct held_lock *ret, *hlock, *prev_hlock; int i;
i = depth - 1; hlock = curr->held_locks + i; ret = hlock; if (match_held_lock(hlock, lock)) goto out;
ret = NULL; for (i--, prev_hlock = hlock--; i >= 0; i--, prev_hlock = hlock--) { /* * We must not cross into another context: */ if (prev_hlock->irq_context != hlock->irq_context) { ret = NULL; break; } if (match_held_lock(hlock, lock)) { ret = hlock; break; } }
out: *idx = i; return ret;}
static int reacquire_held_locks(struct task_struct *curr, unsigned int depth, int idx, unsigned int *merged){ struct held_lock *hlock; int first_idx = idx;
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) return 0;
for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) { switch (__lock_acquire(hlock->instance, hlock_class(hlock)->subclass, hlock->trylock, hlock->read, hlock->check, hlock->hardirqs_off, hlock->nest_lock, hlock->acquire_ip, hlock->references, hlock->pin_count, 0)) { case 0: return 1; case 1: break; case 2: *merged += (idx == first_idx); break; default: WARN_ON(1); return 0; } } return 0;}
static int__lock_set_class(struct lockdep_map *lock, const char *name, struct lock_class_key *key, unsigned int subclass, unsigned long ip){ struct task_struct *curr = current; unsigned int depth, merged = 0; struct held_lock *hlock; struct lock_class *class; int i;
if (unlikely(!debug_locks)) return 0;
depth = curr->lockdep_depth; /* * This function is about (re)setting the class of a held lock, * yet we're not actually holding any locks. Naughty user! */ if (DEBUG_LOCKS_WARN_ON(!depth)) return 0;
hlock = find_held_lock(curr, lock, depth, &i); if (!hlock) { print_unlock_imbalance_bug(curr, lock, ip); return 0; }
lockdep_init_map_type(lock, name, key, 0, lock->wait_type_inner, lock->wait_type_outer, lock->lock_type); class = register_lock_class(lock, subclass, 0); hlock->class_idx = class - lock_classes;
curr->lockdep_depth = i; curr->curr_chain_key = hlock->prev_chain_key;
if (reacquire_held_locks(curr, depth, i, &merged)) return 0;
/* * I took it apart and put it back together again, except now I have * these 'spare' parts.. where shall I put them. */ if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged)) return 0; return 1;}
static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip){ struct task_struct *curr = current; unsigned int depth, merged = 0; struct held_lock *hlock; int i;
if (unlikely(!debug_locks)) return 0;
depth = curr->lockdep_depth; /* * This function is about (re)setting the class of a held lock, * yet we're not actually holding any locks. Naughty user! */ if (DEBUG_LOCKS_WARN_ON(!depth)) return 0;
hlock = find_held_lock(curr, lock, depth, &i); if (!hlock) { print_unlock_imbalance_bug(curr, lock, ip); return 0; }
curr->lockdep_depth = i; curr->curr_chain_key = hlock->prev_chain_key;
WARN(hlock->read, "downgrading a read lock"); hlock->read = 1; hlock->acquire_ip = ip;
if (reacquire_held_locks(curr, depth, i, &merged)) return 0;
/* Merging can't happen with unchanged classes.. */ if (DEBUG_LOCKS_WARN_ON(merged)) return 0;
/* * I took it apart and put it back together again, except now I have * these 'spare' parts.. where shall I put them. */ if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth)) return 0;
return 1;}
/* * Remove the lock from the list of currently held locks - this gets * called on mutex_unlock()/spin_unlock*() (or on a failed * mutex_lock_interruptible()). */static int__lock_release(struct lockdep_map *lock, unsigned long ip){ struct task_struct *curr = current; unsigned int depth, merged = 1; struct held_lock *hlock; int i;
if (unlikely(!debug_locks)) return 0;
depth = curr->lockdep_depth; /* * So we're all set to release this lock.. wait what lock? We don't * own any locks, you've been drinking again? */ if (depth <= 0) { print_unlock_imbalance_bug(curr, lock, ip); return 0; }
/* * Check whether the lock exists in the current stack * of held locks: */ hlock = find_held_lock(curr, lock, depth, &i); if (!hlock) { print_unlock_imbalance_bug(curr, lock, ip); return 0; }
if (hlock->instance == lock) lock_release_holdtime(hlock);
WARN(hlock->pin_count, "releasing a pinned lock\n");
if (hlock->references) { hlock->references--; if (hlock->references) { /* * We had, and after removing one, still have * references, the current lock stack is still * valid. We're done! */ return 1; } }
/* * We have the right lock to unlock, 'hlock' points to it. * Now we remove it from the stack, and add back the other * entries (if any), recalculating the hash along the way: */
curr->lockdep_depth = i; curr->curr_chain_key = hlock->prev_chain_key;
/* * The most likely case is when the unlock is on the innermost * lock. In this case, we are done! */ if (i == depth-1) return 1;
if (reacquire_held_locks(curr, depth, i + 1, &merged)) return 0;
/* * We had N bottles of beer on the wall, we drank one, but now * there's not N-1 bottles of beer left on the wall... * Pouring two of the bottles together is acceptable. */ DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
/* * Since reacquire_held_locks() would have called check_chain_key() * indirectly via __lock_acquire(), we don't need to do it again * on return. */ return 0;}
static __always_inlineint __lock_is_held(const struct lockdep_map *lock, int read){ struct task_struct *curr = current; int i;
for (i = 0; i < curr->lockdep_depth; i++) { struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) { if (read == -1 || !!hlock->read == read) return LOCK_STATE_HELD;
return LOCK_STATE_NOT_HELD; } }
return LOCK_STATE_NOT_HELD;}
static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock){ struct pin_cookie cookie = NIL_COOKIE; struct task_struct *curr = current; int i;
if (unlikely(!debug_locks)) return cookie;
for (i = 0; i < curr->lockdep_depth; i++) { struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) { /* * Grab 16bits of randomness; this is sufficient to not * be guessable and still allows some pin nesting in * our u32 pin_count. */ cookie.val = 1 + (sched_clock() & 0xffff); hlock->pin_count += cookie.val; return cookie; } }
WARN(1, "pinning an unheld lock\n"); return cookie;}
static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie){ struct task_struct *curr = current; int i;
if (unlikely(!debug_locks)) return;
for (i = 0; i < curr->lockdep_depth; i++) { struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) { hlock->pin_count += cookie.val; return; } }
WARN(1, "pinning an unheld lock\n");}
static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie){ struct task_struct *curr = current; int i;
if (unlikely(!debug_locks)) return;
for (i = 0; i < curr->lockdep_depth; i++) { struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock)) { if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n")) return;
hlock->pin_count -= cookie.val;
if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n")) hlock->pin_count = 0;
return; } }
WARN(1, "unpinning an unheld lock\n");}
/* * Check whether we follow the irq-flags state precisely: */static noinstr void check_flags(unsigned long flags){#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) if (!debug_locks) return;
/* Get the warning out.. */ instrumentation_begin();
if (irqs_disabled_flags(flags)) { if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) { printk("possible reason: unannotated irqs-off.\n"); } } else { if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) { printk("possible reason: unannotated irqs-on.\n"); } }
#ifndef CONFIG_PREEMPT_RT /* * We dont accurately track softirq state in e.g. * hardirq contexts (such as on 4KSTACKS), so only * check if not in hardirq contexts: */ if (!hardirq_count()) { if (softirq_count()) { /* like the above, but with softirqs */ DEBUG_LOCKS_WARN_ON(current->softirqs_enabled); } else { /* lick the above, does it taste good? */ DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled); } }#endif
if (!debug_locks) print_irqtrace_events(current);
instrumentation_end();#endif}
void lock_set_class(struct lockdep_map *lock, const char *name, struct lock_class_key *key, unsigned int subclass, unsigned long ip){ unsigned long flags;
if (unlikely(!lockdep_enabled())) return;
raw_local_irq_save(flags); lockdep_recursion_inc(); check_flags(flags); if (__lock_set_class(lock, name, key, subclass, ip)) check_chain_key(current); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_set_class);
void lock_downgrade(struct lockdep_map *lock, unsigned long ip){ unsigned long flags;
if (unlikely(!lockdep_enabled())) return;
raw_local_irq_save(flags); lockdep_recursion_inc(); check_flags(flags); if (__lock_downgrade(lock, ip)) check_chain_key(current); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_downgrade);
/* NMI context !!! */static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass){#ifdef CONFIG_PROVE_LOCKING struct lock_class *class = look_up_lock_class(lock, subclass); unsigned long mask = LOCKF_USED;
/* if it doesn't have a class (yet), it certainly hasn't been used yet */ if (!class) return;
/* * READ locks only conflict with USED, such that if we only ever use * READ locks, there is no deadlock possible -- RCU. */ if (!hlock->read) mask |= LOCKF_USED_READ;
if (!(class->usage_mask & mask)) return;
hlock->class_idx = class - lock_classes;
print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);#endif}
static bool lockdep_nmi(void){ if (raw_cpu_read(lockdep_recursion)) return false;
if (!in_nmi()) return false;
return true;}
/* * read_lock() is recursive if: * 1. We force lockdep think this way in selftests or * 2. The implementation is not queued read/write lock or * 3. The locker is at an in_interrupt() context. */bool read_lock_is_recursive(void){ return force_read_lock_recursive || !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) || in_interrupt();}EXPORT_SYMBOL_GPL(read_lock_is_recursive);
/* * We are not always called with irqs disabled - do that here, * and also avoid lockdep recursion: */void lock_acquire(struct lockdep_map *lock, unsigned int subclass, int trylock, int read, int check, struct lockdep_map *nest_lock, unsigned long ip){ unsigned long flags;
trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
if (!debug_locks) return;
/* * As KASAN instrumentation is disabled and lock_acquire() is usually * the first lockdep call when a task tries to acquire a lock, add * kasan_check_byte() here to check for use-after-free and other * memory errors. */ kasan_check_byte(lock);
if (unlikely(!lockdep_enabled())) { /* XXX allow trylock from NMI ?!? */ if (lockdep_nmi() && !trylock) { struct held_lock hlock;
hlock.acquire_ip = ip; hlock.instance = lock; hlock.nest_lock = nest_lock; hlock.irq_context = 2; // XXX hlock.trylock = trylock; hlock.read = read; hlock.check = check; hlock.hardirqs_off = true; hlock.references = 0;
verify_lock_unused(lock, &hlock, subclass); } return; }
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); __lock_acquire(lock, subclass, trylock, read, check, irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 0); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_acquire);
void lock_release(struct lockdep_map *lock, unsigned long ip){ unsigned long flags;
trace_lock_release(lock, ip);
if (unlikely(!lockdep_enabled() || lock->key == &__lockdep_no_track__)) return;
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); if (__lock_release(lock, ip)) check_chain_key(current); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_release);
/* * lock_sync() - A special annotation for synchronize_{s,}rcu()-like API. * * No actual critical section is created by the APIs annotated with this: these * APIs are used to wait for one or multiple critical sections (on other CPUs * or threads), and it means that calling these APIs inside these critical * sections is potential deadlock. */void lock_sync(struct lockdep_map *lock, unsigned subclass, int read, int check, struct lockdep_map *nest_lock, unsigned long ip){ unsigned long flags;
if (unlikely(!lockdep_enabled())) return;
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); __lock_acquire(lock, subclass, 0, read, check, irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 1); check_chain_key(current); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_sync);
noinstr int lock_is_held_type(const struct lockdep_map *lock, int read){ unsigned long flags; int ret = LOCK_STATE_NOT_HELD;
/* * Avoid false negative lockdep_assert_held() and * lockdep_assert_not_held(). */ if (unlikely(!lockdep_enabled())) return LOCK_STATE_UNKNOWN;
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); ret = __lock_is_held(lock, read); lockdep_recursion_finish(); raw_local_irq_restore(flags);
return ret;}EXPORT_SYMBOL_GPL(lock_is_held_type);NOKPROBE_SYMBOL(lock_is_held_type);
struct pin_cookie lock_pin_lock(struct lockdep_map *lock){ struct pin_cookie cookie = NIL_COOKIE; unsigned long flags;
if (unlikely(!lockdep_enabled())) return cookie;
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); cookie = __lock_pin_lock(lock); lockdep_recursion_finish(); raw_local_irq_restore(flags);
return cookie;}EXPORT_SYMBOL_GPL(lock_pin_lock);
void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie){ unsigned long flags;
if (unlikely(!lockdep_enabled())) return;
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); __lock_repin_lock(lock, cookie); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_repin_lock);
void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie){ unsigned long flags;
if (unlikely(!lockdep_enabled())) return;
raw_local_irq_save(flags); check_flags(flags);
lockdep_recursion_inc(); __lock_unpin_lock(lock, cookie); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_unpin_lock);
#ifdef CONFIG_LOCK_STATstatic void print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock, unsigned long ip){ if (!debug_locks_off()) return; if (debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("=================================\n"); pr_warn("WARNING: bad contention detected!\n"); print_kernel_ident(); pr_warn("---------------------------------\n"); pr_warn("%s/%d is trying to contend lock (", curr->comm, task_pid_nr(curr)); print_lockdep_cache(lock); pr_cont(") at:\n"); print_ip_sym(KERN_WARNING, ip); pr_warn("but there are no locks held!\n"); pr_warn("\nother info that might help us debug this:\n"); lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
static void__lock_contended(struct lockdep_map *lock, unsigned long ip){ struct task_struct *curr = current; struct held_lock *hlock; struct lock_class_stats *stats; unsigned int depth; int i, contention_point, contending_point;
depth = curr->lockdep_depth; /* * Whee, we contended on this lock, except it seems we're not * actually trying to acquire anything much at all.. */ if (DEBUG_LOCKS_WARN_ON(!depth)) return;
if (unlikely(lock->key == &__lockdep_no_track__)) return;
hlock = find_held_lock(curr, lock, depth, &i); if (!hlock) { print_lock_contention_bug(curr, lock, ip); return; }
if (hlock->instance != lock) return;
hlock->waittime_stamp = lockstat_clock();
contention_point = lock_point(hlock_class(hlock)->contention_point, ip); contending_point = lock_point(hlock_class(hlock)->contending_point, lock->ip);
stats = get_lock_stats(hlock_class(hlock)); if (contention_point < LOCKSTAT_POINTS) stats->contention_point[contention_point]++; if (contending_point < LOCKSTAT_POINTS) stats->contending_point[contending_point]++; if (lock->cpu != smp_processor_id()) stats->bounces[bounce_contended + !!hlock->read]++;}
static void__lock_acquired(struct lockdep_map *lock, unsigned long ip){ struct task_struct *curr = current; struct held_lock *hlock; struct lock_class_stats *stats; unsigned int depth; u64 now, waittime = 0; int i, cpu;
depth = curr->lockdep_depth; /* * Yay, we acquired ownership of this lock we didn't try to * acquire, how the heck did that happen? */ if (DEBUG_LOCKS_WARN_ON(!depth)) return;
if (unlikely(lock->key == &__lockdep_no_track__)) return;
hlock = find_held_lock(curr, lock, depth, &i); if (!hlock) { print_lock_contention_bug(curr, lock, _RET_IP_); return; }
if (hlock->instance != lock) return;
cpu = smp_processor_id(); if (hlock->waittime_stamp) { now = lockstat_clock(); waittime = now - hlock->waittime_stamp; hlock->holdtime_stamp = now; }
stats = get_lock_stats(hlock_class(hlock)); if (waittime) { if (hlock->read) lock_time_inc(&stats->read_waittime, waittime); else lock_time_inc(&stats->write_waittime, waittime); } if (lock->cpu != cpu) stats->bounces[bounce_acquired + !!hlock->read]++;
lock->cpu = cpu; lock->ip = ip;}
void lock_contended(struct lockdep_map *lock, unsigned long ip){ unsigned long flags;
trace_lock_contended(lock, ip);
if (unlikely(!lock_stat || !lockdep_enabled())) return;
raw_local_irq_save(flags); check_flags(flags); lockdep_recursion_inc(); __lock_contended(lock, ip); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_contended);
void lock_acquired(struct lockdep_map *lock, unsigned long ip){ unsigned long flags;
trace_lock_acquired(lock, ip);
if (unlikely(!lock_stat || !lockdep_enabled())) return;
raw_local_irq_save(flags); check_flags(flags); lockdep_recursion_inc(); __lock_acquired(lock, ip); lockdep_recursion_finish(); raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(lock_acquired);#endif
/* * Used by the testsuite, sanitize the validator state * after a simulated failure: */
void lockdep_reset(void){ unsigned long flags; int i;
raw_local_irq_save(flags); lockdep_init_task(current); memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock)); nr_hardirq_chains = 0; nr_softirq_chains = 0; nr_process_chains = 0; debug_locks = 1; for (i = 0; i < CHAINHASH_SIZE; i++) INIT_HLIST_HEAD(chainhash_table + i); raw_local_irq_restore(flags);}
/* Remove a class from a lock chain. Must be called with the graph lock held. */static void remove_class_from_lock_chain(struct pending_free *pf, struct lock_chain *chain, struct lock_class *class){#ifdef CONFIG_PROVE_LOCKING int i;
for (i = chain->base; i < chain->base + chain->depth; i++) { if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes) continue; /* * Each lock class occurs at most once in a lock chain so once * we found a match we can break out of this loop. */ goto free_lock_chain; } /* Since the chain has not been modified, return. */ return;
free_lock_chain: free_chain_hlocks(chain->base, chain->depth); /* Overwrite the chain key for concurrent RCU readers. */ WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY); dec_chains(chain->irq_context);
/* * Note: calling hlist_del_rcu() from inside a * hlist_for_each_entry_rcu() loop is safe. */ hlist_del_rcu(&chain->entry); __set_bit(chain - lock_chains, pf->lock_chains_being_freed); nr_zapped_lock_chains++;#endif}
/* Must be called with the graph lock held. */static void remove_class_from_lock_chains(struct pending_free *pf, struct lock_class *class){ struct lock_chain *chain; struct hlist_head *head; int i;
for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) { head = chainhash_table + i; hlist_for_each_entry_rcu(chain, head, entry) { remove_class_from_lock_chain(pf, chain, class); } }}
/* * Remove all references to a lock class. The caller must hold the graph lock. */static void zap_class(struct pending_free *pf, struct lock_class *class){ struct lock_list *entry; int i;
WARN_ON_ONCE(!class->key);
/* * Remove all dependencies this lock is * involved in: */ for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { entry = list_entries + i; if (entry->class != class && entry->links_to != class) continue; __clear_bit(i, list_entries_in_use); nr_list_entries--; list_del_rcu(&entry->entry); } if (list_empty(&class->locks_after) && list_empty(&class->locks_before)) { list_move_tail(&class->lock_entry, &pf->zapped); hlist_del_rcu(&class->hash_entry); WRITE_ONCE(class->key, NULL); WRITE_ONCE(class->name, NULL); /* Class allocated but not used, -1 in nr_unused_locks */ if (class->usage_mask == 0) debug_atomic_dec(nr_unused_locks); nr_lock_classes--; __clear_bit(class - lock_classes, lock_classes_in_use); if (class - lock_classes == max_lock_class_idx) max_lock_class_idx--; } else { WARN_ONCE(true, "%s() failed for class %s\n", __func__, class->name); }
remove_class_from_lock_chains(pf, class); nr_zapped_classes++;}
static void reinit_class(struct lock_class *class){ WARN_ON_ONCE(!class->lock_entry.next); WARN_ON_ONCE(!list_empty(&class->locks_after)); WARN_ON_ONCE(!list_empty(&class->locks_before)); memset_startat(class, 0, key); WARN_ON_ONCE(!class->lock_entry.next); WARN_ON_ONCE(!list_empty(&class->locks_after)); WARN_ON_ONCE(!list_empty(&class->locks_before));}
static inline int within(const void *addr, void *start, unsigned long size){ return addr >= start && addr < start + size;}
static bool inside_selftest(void){ return current == lockdep_selftest_task_struct;}
/* The caller must hold the graph lock. */static struct pending_free *get_pending_free(void){ return delayed_free.pf + delayed_free.index;}
static void free_zapped_rcu(struct rcu_head *cb);
/** See if we need to queue an RCU callback, must called with* the lockdep lock held, returns false if either we don't have* any pending free or the callback is already scheduled.* Otherwise, a call_rcu() must follow this function call.*/static bool prepare_call_rcu_zapped(struct pending_free *pf){ WARN_ON_ONCE(inside_selftest());
if (list_empty(&pf->zapped)) return false;
if (delayed_free.scheduled) return false;
delayed_free.scheduled = true;
WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf); delayed_free.index ^= 1;
return true;}
/* The caller must hold the graph lock. May be called from RCU context. */static void __free_zapped_classes(struct pending_free *pf){ struct lock_class *class;
check_data_structures();
list_for_each_entry(class, &pf->zapped, lock_entry) reinit_class(class);
list_splice_init(&pf->zapped, &free_lock_classes);
#ifdef CONFIG_PROVE_LOCKING bitmap_andnot(lock_chains_in_use, lock_chains_in_use, pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains)); bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));#endif}
static void free_zapped_rcu(struct rcu_head *ch){ struct pending_free *pf; unsigned long flags; bool need_callback;
if (WARN_ON_ONCE(ch != &delayed_free.rcu_head)) return;
raw_local_irq_save(flags); lockdep_lock();
/* closed head */ pf = delayed_free.pf + (delayed_free.index ^ 1); __free_zapped_classes(pf); delayed_free.scheduled = false; need_callback = prepare_call_rcu_zapped(delayed_free.pf + delayed_free.index); lockdep_unlock(); raw_local_irq_restore(flags);
/* * If there's pending free and its callback has not been scheduled, * queue an RCU callback. */ if (need_callback) call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
}
/* * Remove all lock classes from the class hash table and from the * all_lock_classes list whose key or name is in the address range [start, * start + size). Move these lock classes to the zapped_classes list. Must * be called with the graph lock held. */static void __lockdep_free_key_range(struct pending_free *pf, void *start, unsigned long size){ struct lock_class *class; struct hlist_head *head; int i;
/* Unhash all classes that were created by a module. */ for (i = 0; i < CLASSHASH_SIZE; i++) { head = classhash_table + i; hlist_for_each_entry_rcu(class, head, hash_entry) { if (!within(class->key, start, size) && !within(class->name, start, size)) continue; zap_class(pf, class); } }}
/* * Used in module.c to remove lock classes from memory that is going to be * freed; and possibly re-used by other modules. * * We will have had one synchronize_rcu() before getting here, so we're * guaranteed nobody will look up these exact classes -- they're properly dead * but still allocated. */static void lockdep_free_key_range_reg(void *start, unsigned long size){ struct pending_free *pf; unsigned long flags; bool need_callback;
init_data_structures_once();
raw_local_irq_save(flags); lockdep_lock(); pf = get_pending_free(); __lockdep_free_key_range(pf, start, size); need_callback = prepare_call_rcu_zapped(pf); lockdep_unlock(); raw_local_irq_restore(flags); if (need_callback) call_rcu(&delayed_free.rcu_head, free_zapped_rcu); /* * Wait for any possible iterators from look_up_lock_class() to pass * before continuing to free the memory they refer to. */ synchronize_rcu();}
/* * Free all lockdep keys in the range [start, start+size). Does not sleep. * Ignores debug_locks. Must only be used by the lockdep selftests. */static void lockdep_free_key_range_imm(void *start, unsigned long size){ struct pending_free *pf = delayed_free.pf; unsigned long flags;
init_data_structures_once();
raw_local_irq_save(flags); lockdep_lock(); __lockdep_free_key_range(pf, start, size); __free_zapped_classes(pf); lockdep_unlock(); raw_local_irq_restore(flags);}
void lockdep_free_key_range(void *start, unsigned long size){ init_data_structures_once();
if (inside_selftest()) lockdep_free_key_range_imm(start, size); else lockdep_free_key_range_reg(start, size);}
/* * Check whether any element of the @lock->class_cache[] array refers to a * registered lock class. The caller must hold either the graph lock or the * RCU read lock. */static bool lock_class_cache_is_registered(struct lockdep_map *lock){ struct lock_class *class; struct hlist_head *head; int i, j;
for (i = 0; i < CLASSHASH_SIZE; i++) { head = classhash_table + i; hlist_for_each_entry_rcu(class, head, hash_entry) { for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++) if (lock->class_cache[j] == class) return true; } } return false;}
/* The caller must hold the graph lock. Does not sleep. */static void __lockdep_reset_lock(struct pending_free *pf, struct lockdep_map *lock){ struct lock_class *class; int j;
/* * Remove all classes this lock might have: */ for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) { /* * If the class exists we look it up and zap it: */ class = look_up_lock_class(lock, j); if (class) zap_class(pf, class); } /* * Debug check: in the end all mapped classes should * be gone. */ if (WARN_ON_ONCE(lock_class_cache_is_registered(lock))) debug_locks_off();}
/* * Remove all information lockdep has about a lock if debug_locks == 1. Free * released data structures from RCU context. */static void lockdep_reset_lock_reg(struct lockdep_map *lock){ struct pending_free *pf; unsigned long flags; int locked; bool need_callback = false;
raw_local_irq_save(flags); locked = graph_lock(); if (!locked) goto out_irq;
pf = get_pending_free(); __lockdep_reset_lock(pf, lock); need_callback = prepare_call_rcu_zapped(pf);
graph_unlock();out_irq: raw_local_irq_restore(flags); if (need_callback) call_rcu(&delayed_free.rcu_head, free_zapped_rcu);}
/* * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the * lockdep selftests. */static void lockdep_reset_lock_imm(struct lockdep_map *lock){ struct pending_free *pf = delayed_free.pf; unsigned long flags;
raw_local_irq_save(flags); lockdep_lock(); __lockdep_reset_lock(pf, lock); __free_zapped_classes(pf); lockdep_unlock(); raw_local_irq_restore(flags);}
void lockdep_reset_lock(struct lockdep_map *lock){ init_data_structures_once();
if (inside_selftest()) lockdep_reset_lock_imm(lock); else lockdep_reset_lock_reg(lock);}
/* * Unregister a dynamically allocated key. * * Unlike lockdep_register_key(), a search is always done to find a matching * key irrespective of debug_locks to avoid potential invalid access to freed * memory in lock_class entry. */void lockdep_unregister_key(struct lock_class_key *key){ struct hlist_head *hash_head = keyhashentry(key); struct lock_class_key *k; struct pending_free *pf; unsigned long flags; bool found = false; bool need_callback = false;
might_sleep();
if (WARN_ON_ONCE(static_obj(key))) return;
raw_local_irq_save(flags); lockdep_lock();
hlist_for_each_entry_rcu(k, hash_head, hash_entry) { if (k == key) { hlist_del_rcu(&k->hash_entry); found = true; break; } } WARN_ON_ONCE(!found && debug_locks); if (found) { pf = get_pending_free(); __lockdep_free_key_range(pf, key, 1); need_callback = prepare_call_rcu_zapped(pf); nr_dynamic_keys--; } lockdep_unlock(); raw_local_irq_restore(flags);
if (need_callback) call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
/* * Wait until is_dynamic_key() has finished accessing k->hash_entry. * * Some operations like __qdisc_destroy() will call this in a debug * kernel, and the network traffic is disabled while waiting, hence * the delay of the wait matters in debugging cases. Currently use a * synchronize_rcu_expedited() to speed up the wait at the cost of * system IPIs. TODO: Replace RCU with hazptr for this. */ synchronize_rcu_expedited();}EXPORT_SYMBOL_GPL(lockdep_unregister_key);
void __init lockdep_init(void){ pr_info("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
pr_info("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES); pr_info("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH); pr_info("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS); pr_info("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE); pr_info("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES); pr_info("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS); pr_info("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
pr_info(" memory used by lock dependency info: %zu kB\n", (sizeof(lock_classes) + sizeof(lock_classes_in_use) + sizeof(classhash_table) + sizeof(list_entries) + sizeof(list_entries_in_use) + sizeof(chainhash_table) + sizeof(delayed_free)#ifdef CONFIG_PROVE_LOCKING + sizeof(lock_cq) + sizeof(lock_chains) + sizeof(lock_chains_in_use) + sizeof(chain_hlocks)#endif ) / 1024 );
#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) pr_info(" memory used for stack traces: %zu kB\n", (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024 );#endif
pr_info(" per task-struct memory footprint: %zu bytes\n", sizeof(((struct task_struct *)NULL)->held_locks));}
static voidprint_freed_lock_bug(struct task_struct *curr, const void *mem_from, const void *mem_to, struct held_lock *hlock){ if (!debug_locks_off()) return; if (debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("=========================\n"); pr_warn("WARNING: held lock freed!\n"); print_kernel_ident(); pr_warn("-------------------------\n"); pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n", curr->comm, task_pid_nr(curr), mem_from, mem_to-1); print_lock(hlock); lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
static inline int not_in_range(const void* mem_from, unsigned long mem_len, const void* lock_from, unsigned long lock_len){ return lock_from + lock_len <= mem_from || mem_from + mem_len <= lock_from;}
/* * Called when kernel memory is freed (or unmapped), or if a lock * is destroyed or reinitialized - this code checks whether there is * any held lock in the memory range of <from> to <to>: */void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len){ struct task_struct *curr = current; struct held_lock *hlock; unsigned long flags; int i;
if (unlikely(!debug_locks)) return;
raw_local_irq_save(flags); for (i = 0; i < curr->lockdep_depth; i++) { hlock = curr->held_locks + i;
if (not_in_range(mem_from, mem_len, hlock->instance, sizeof(*hlock->instance))) continue;
print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock); break; } raw_local_irq_restore(flags);}EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
static void print_held_locks_bug(void){ if (!debug_locks_off()) return; if (debug_locks_silent) return;
nbcon_cpu_emergency_enter();
pr_warn("\n"); pr_warn("====================================\n"); pr_warn("WARNING: %s/%d still has locks held!\n", current->comm, task_pid_nr(current)); print_kernel_ident(); pr_warn("------------------------------------\n"); lockdep_print_held_locks(current); pr_warn("\nstack backtrace:\n"); dump_stack();
nbcon_cpu_emergency_exit();}
void debug_check_no_locks_held(void){ if (unlikely(current->lockdep_depth > 0)) print_held_locks_bug();}EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
#ifdef __KERNEL__void debug_show_all_locks(void){ struct task_struct *g, *p;
if (unlikely(!debug_locks)) { pr_warn("INFO: lockdep is turned off.\n"); return; } pr_warn("\nShowing all locks held in the system:\n");
rcu_read_lock(); for_each_process_thread(g, p) { if (!p->lockdep_depth) continue; lockdep_print_held_locks(p); touch_nmi_watchdog(); touch_all_softlockup_watchdogs(); } rcu_read_unlock();
pr_warn("\n"); pr_warn("=============================================\n\n");}EXPORT_SYMBOL_GPL(debug_show_all_locks);#endif
/* * Careful: only use this function if you are sure that * the task cannot run in parallel! */void debug_show_held_locks(struct task_struct *task){ if (unlikely(!debug_locks)) { printk("INFO: lockdep is turned off.\n"); return; } lockdep_print_held_locks(task);}EXPORT_SYMBOL_GPL(debug_show_held_locks);
asmlinkage __visible void lockdep_sys_exit(void){ struct task_struct *curr = current;
if (unlikely(curr->lockdep_depth)) { if (!debug_locks_off()) return; nbcon_cpu_emergency_enter(); pr_warn("\n"); pr_warn("================================================\n"); pr_warn("WARNING: lock held when returning to user space!\n"); print_kernel_ident(); pr_warn("------------------------------------------------\n"); pr_warn("%s/%d is leaving the kernel with locks still held!\n", curr->comm, curr->pid); lockdep_print_held_locks(curr); nbcon_cpu_emergency_exit(); }
/* * The lock history for each syscall should be independent. So wipe the * slate clean on return to userspace. */ lockdep_invariant_state(false);}
void lockdep_rcu_suspicious(const char *file, const int line, const char *s){ struct task_struct *curr = current; int dl = READ_ONCE(debug_locks); bool rcu = warn_rcu_enter();
/* Note: the following can be executed concurrently, so be careful. */ nbcon_cpu_emergency_enter(); pr_warn("\n"); pr_warn("=============================\n"); pr_warn("WARNING: suspicious RCU usage\n"); print_kernel_ident(); pr_warn("-----------------------------\n"); pr_warn("%s:%d %s!\n", file, line, s); pr_warn("\nother info that might help us debug this:\n\n"); pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s", !rcu_lockdep_current_cpu_online() ? "RCU used illegally from offline CPU!\n" : "", rcu_scheduler_active, dl, dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
/* * If a CPU is in the RCU-free window in idle (ie: in the section * between ct_idle_enter() and ct_idle_exit(), then RCU * considers that CPU to be in an "extended quiescent state", * which means that RCU will be completely ignoring that CPU. * Therefore, rcu_read_lock() and friends have absolutely no * effect on a CPU running in that state. In other words, even if * such an RCU-idle CPU has called rcu_read_lock(), RCU might well * delete data structures out from under it. RCU really has no * choice here: we need to keep an RCU-free window in idle where * the CPU may possibly enter into low power mode. This way we can * notice an extended quiescent state to other CPUs that started a grace * period. Otherwise we would delay any grace period as long as we run * in the idle task. * * So complain bitterly if someone does call rcu_read_lock(), * rcu_read_lock_bh() and so on from extended quiescent states. */ if (!rcu_is_watching()) pr_warn("RCU used illegally from extended quiescent state!\n");
lockdep_print_held_locks(curr); pr_warn("\nstack backtrace:\n"); dump_stack(); nbcon_cpu_emergency_exit(); warn_rcu_exit(rcu);}EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);