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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/irq_work.h>#include <linux/rcupdate.h>#include <linux/rculist.h>#include <linux/kernel.h>#include <linux/export.h>#include <linux/percpu.h>#include <linux/init.h>#include <linux/interrupt.h>#include <linux/gfp.h>#include <linux/smp.h>#include <linux/cpu.h>#include <linux/sched.h>#include <linux/sched/idle.h>#include <linux/hypervisor.h>#include <linux/sched/clock.h>#include <linux/nmi.h>#include <linux/sched/debug.h>#include <linux/jump_label.h>#include <linux/string_choices.h>
#include <trace/events/ipi.h>#define CREATE_TRACE_POINTS#include <trace/events/csd.h>#undef CREATE_TRACE_POINTS
#include "smpboot.h"#include "sched/smp.h"
#define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK)
struct call_function_data { call_single_data_t __percpu *csd; cpumask_var_t cpumask; cpumask_var_t cpumask_ipi;};
static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data);
static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue);
static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1);
static void __flush_smp_call_function_queue(bool warn_cpu_offline);
int smpcfd_prepare_cpu(unsigned int cpu){ struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, cpu_to_node(cpu))) return -ENOMEM; if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, cpu_to_node(cpu))) { free_cpumask_var(cfd->cpumask); return -ENOMEM; } cfd->csd = alloc_percpu(call_single_data_t); if (!cfd->csd) { free_cpumask_var(cfd->cpumask); free_cpumask_var(cfd->cpumask_ipi); return -ENOMEM; }
return 0;}
int smpcfd_dead_cpu(unsigned int cpu){ struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
free_cpumask_var(cfd->cpumask); free_cpumask_var(cfd->cpumask_ipi); free_percpu(cfd->csd); return 0;}
int smpcfd_dying_cpu(unsigned int cpu){ /* * The IPIs for the smp-call-function callbacks queued by other CPUs * might arrive late, either due to hardware latencies or because this * CPU disabled interrupts (inside stop-machine) before the IPIs were * sent. So flush out any pending callbacks explicitly (without waiting * for the IPIs to arrive), to ensure that the outgoing CPU doesn't go * offline with work still pending. * * This runs with interrupts disabled inside the stopper task invoked by * stop_machine(), ensuring mutually exclusive CPU offlining and IPI flush. */ __flush_smp_call_function_queue(false); irq_work_run(); return 0;}
void __init call_function_init(void){ int i;
for_each_possible_cpu(i) init_llist_head(&per_cpu(call_single_queue, i));
smpcfd_prepare_cpu(smp_processor_id());}
static __always_inline voidsend_call_function_single_ipi(int cpu){ if (call_function_single_prep_ipi(cpu)) { trace_ipi_send_cpu(cpu, _RET_IP_, generic_smp_call_function_single_interrupt); arch_send_call_function_single_ipi(cpu); }}
static __always_inline voidsend_call_function_ipi_mask(struct cpumask *mask){ trace_ipi_send_cpumask(mask, _RET_IP_, generic_smp_call_function_single_interrupt); arch_send_call_function_ipi_mask(mask);}
static __always_inline voidcsd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd){ trace_csd_function_entry(func, csd); func(info); trace_csd_function_exit(func, csd);}
static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled);
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
/* * Parse the csdlock_debug= kernel boot parameter. * * If you need to restore the old "ext" value that once provided * additional debugging information, reapply the following commits: * * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging") * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging") */static int __init csdlock_debug(char *str){ int ret; unsigned int val = 0;
ret = get_option(&str, &val); if (ret) { if (val) static_branch_enable(&csdlock_debug_enabled); else static_branch_disable(&csdlock_debug_enabled); }
return 1;}__setup("csdlock_debug=", csdlock_debug);
static DEFINE_PER_CPU(call_single_data_t *, cur_csd);static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);static DEFINE_PER_CPU(void *, cur_csd_info);
static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */module_param(csd_lock_timeout, ulong, 0644);static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */module_param(panic_on_ipistall, int, 0644);
static atomic_t csd_bug_count = ATOMIC_INIT(0);
/* Record current CSD work for current CPU, NULL to erase. */static void __csd_lock_record(call_single_data_t *csd){ if (!csd) { smp_mb(); /* NULL cur_csd after unlock. */ __this_cpu_write(cur_csd, NULL); return; } __this_cpu_write(cur_csd_func, csd->func); __this_cpu_write(cur_csd_info, csd->info); smp_wmb(); /* func and info before csd. */ __this_cpu_write(cur_csd, csd); smp_mb(); /* Update cur_csd before function call. */ /* Or before unlock, as the case may be. */}
static __always_inline void csd_lock_record(call_single_data_t *csd){ if (static_branch_unlikely(&csdlock_debug_enabled)) __csd_lock_record(csd);}
static int csd_lock_wait_getcpu(call_single_data_t *csd){ unsigned int csd_type;
csd_type = CSD_TYPE(csd); if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC) return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */ return -1;}
static atomic_t n_csd_lock_stuck;
/** * csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long? * * Returns: @true if a CSD-lock acquisition is stuck and has been stuck * long enough for a "non-responsive CSD lock" message to be printed. */bool csd_lock_is_stuck(void){ return !!atomic_read(&n_csd_lock_stuck);}
/* * Complain if too much time spent waiting. Note that only * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, * so waiting on other types gets much less information. */static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages){ int cpu = -1; int cpux; bool firsttime; u64 ts2, ts_delta; call_single_data_t *cpu_cur_csd; unsigned int flags = READ_ONCE(csd->node.u_flags); unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC;
if (!(flags & CSD_FLAG_LOCK)) { if (!unlikely(*bug_id)) return true; cpu = csd_lock_wait_getcpu(csd); pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", *bug_id, raw_smp_processor_id(), cpu); atomic_dec(&n_csd_lock_stuck); return true; }
ts2 = ktime_get_mono_fast_ns(); /* How long since we last checked for a stuck CSD lock.*/ ts_delta = ts2 - *ts1; if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) * (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) || csd_lock_timeout_ns == 0)) return false;
if (ts0 > ts2) { /* Our own sched_clock went backward; don't blame another CPU. */ ts_delta = ts0 - ts2; pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta); *ts1 = ts2; return false; }
firsttime = !*bug_id; if (firsttime) *bug_id = atomic_inc_return(&csd_bug_count); cpu = csd_lock_wait_getcpu(csd); if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) cpux = 0; else cpux = cpu; cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ /* How long since this CSD lock was stuck. */ ts_delta = ts2 - ts0; pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n", firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta, cpu, csd->func, csd->info); (*nmessages)++; if (firsttime) atomic_inc(&n_csd_lock_stuck); /* * If the CSD lock is still stuck after 5 minutes, it is unlikely * to become unstuck. Use a signed comparison to avoid triggering * on underflows when the TSC is out of sync between sockets. */ BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); if (cpu_cur_csd && csd != cpu_cur_csd) { pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)), READ_ONCE(per_cpu(cur_csd_info, cpux))); } else { pr_alert("\tcsd: CSD lock (#%d) %s.\n", *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request"); } if (cpu >= 0) { if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0)) dump_cpu_task(cpu); if (!cpu_cur_csd) { pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu); arch_send_call_function_single_ipi(cpu); } } if (firsttime) dump_stack(); *ts1 = ts2;
return false;}
/* * csd_lock/csd_unlock used to serialize access to per-cpu csd resources * * For non-synchronous ipi calls the csd can still be in use by the * previous function call. For multi-cpu calls its even more interesting * as we'll have to ensure no other cpu is observing our csd. */static void __csd_lock_wait(call_single_data_t *csd){ unsigned long nmessages = 0; int bug_id = 0; u64 ts0, ts1;
ts1 = ts0 = ktime_get_mono_fast_ns(); for (;;) { if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages)) break; cpu_relax(); } smp_acquire__after_ctrl_dep();}
static __always_inline void csd_lock_wait(call_single_data_t *csd){ if (static_branch_unlikely(&csdlock_debug_enabled)) { __csd_lock_wait(csd); return; }
smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));}#elsestatic __always_inline void __csd_lock_wait(call_single_data_t *csd){}
static void csd_lock_record(call_single_data_t *csd){}
static __always_inline void csd_lock_wait(call_single_data_t *csd){ smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));}#endif
static __always_inline void csd_lock(call_single_data_t *csd){ if (IS_ENABLED(CONFIG_CSD_LOCK_WAIT_DEBUG) && static_branch_unlikely(&csdlock_debug_enabled)) {
for (;;) { unsigned int flags;
__csd_lock_wait(csd); flags = READ_ONCE(csd->node.u_flags);
if (!(flags & CSD_FLAG_LOCK) && try_cmpxchg_acquire(&csd->node.u_flags, &flags, flags | CSD_FLAG_LOCK)) break; } } else { csd_lock_wait(csd); csd->node.u_flags |= CSD_FLAG_LOCK; }
/* * prevent CPU from reordering the above assignment * to ->flags with any subsequent assignments to other * fields of the specified call_single_data_t structure: */ smp_wmb();}
static __always_inline void csd_unlock(call_single_data_t *csd){ WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK));
/* * ensure we're all done before releasing data: */ smp_store_release(&csd->node.u_flags, 0);}
static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data);
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUGstatic call_single_data_t *get_single_csd_data(int cpu){ if (static_branch_unlikely(&csdlock_debug_enabled) && (unsigned int)cpu < nr_cpu_ids) return per_cpu_ptr(&csd_data, cpu); return this_cpu_ptr(&csd_data);}#elsestatic call_single_data_t *get_single_csd_data(int cpu){ return this_cpu_ptr(&csd_data);}#endif
void __smp_call_single_queue(int cpu, struct llist_node *node){ /* * We have to check the type of the CSD before queueing it, because * once queued it can have its flags cleared by * flush_smp_call_function_queue() * even if we haven't sent the smp_call IPI yet (e.g. the stopper * executes migration_cpu_stop() on the remote CPU). */ if (trace_csd_queue_cpu_enabled()) { call_single_data_t *csd; smp_call_func_t func;
csd = container_of(node, call_single_data_t, node.llist); func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? sched_ttwu_pending : csd->func;
trace_call__csd_queue_cpu(cpu, _RET_IP_, func, csd); }
/* * The list addition should be visible to the target CPU when it pops * the head of the list to pull the entry off it in the IPI handler * because of normal cache coherency rules implied by the underlying * llist ops. * * If IPIs can go out of order to the cache coherency protocol * in an architecture, sufficient synchronisation should be added * to arch code to make it appear to obey cache coherency WRT * locking and barrier primitives. Generic code isn't really * equipped to do the right thing... */ if (llist_add(node, &per_cpu(call_single_queue, cpu))) send_call_function_single_ipi(cpu);}
/* * Insert a previously allocated call_single_data_t element * for execution on the given CPU. data must already have * ->func, ->info, and ->flags set. */static int generic_exec_single(int cpu, call_single_data_t *csd){ /* * Preemption already disabled here so stopper cannot run on this CPU, * ensuring mutually exclusive CPU offlining and last IPI flush. */ if (cpu == smp_processor_id()) { smp_call_func_t func = csd->func; void *info = csd->info; unsigned long flags;
/* * We can unlock early even for the synchronous on-stack case, * since we're doing this from the same CPU.. */ csd_lock_record(csd); csd_unlock(csd); local_irq_save(flags); csd_do_func(func, info, NULL); csd_lock_record(NULL); local_irq_restore(flags); return 0; }
if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { csd_unlock(csd); return -ENXIO; }
__smp_call_single_queue(cpu, &csd->node.llist);
return 0;}
/** * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks * * Invoked by arch to handle an IPI for call function single. * Must be called with interrupts disabled. */void generic_smp_call_function_single_interrupt(void){ __flush_smp_call_function_queue(true);}
/** * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks * * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an * offline CPU. Skip this check if set to 'false'. * * Flush any pending smp-call-function callbacks queued on this CPU. This is * invoked by the generic IPI handler, as well as by a CPU about to go offline, * to ensure that all pending IPI callbacks are run before it goes completely * offline. * * Loop through the call_single_queue and run all the queued callbacks. * Must be called with interrupts disabled. */static void __flush_smp_call_function_queue(bool warn_cpu_offline){ call_single_data_t *csd, *csd_next; struct llist_node *entry, *prev; struct llist_head *head; static bool warned; atomic_t *tbt;
lockdep_assert_irqs_disabled();
/* Allow waiters to send backtrace NMI from here onwards */ tbt = this_cpu_ptr(&trigger_backtrace); atomic_set_release(tbt, 1);
head = this_cpu_ptr(&call_single_queue); entry = llist_del_all(head); entry = llist_reverse_order(entry);
/* There shouldn't be any pending callbacks on an offline CPU. */ if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && !warned && entry != NULL)) { warned = true; WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
/* * We don't have to use the _safe() variant here * because we are not invoking the IPI handlers yet. */ llist_for_each_entry(csd, entry, node.llist) { switch (CSD_TYPE(csd)) { case CSD_TYPE_ASYNC: case CSD_TYPE_SYNC: case CSD_TYPE_IRQ_WORK: pr_warn("IPI callback %pS sent to offline CPU\n", csd->func); break;
case CSD_TYPE_TTWU: pr_warn("IPI task-wakeup sent to offline CPU\n"); break;
default: pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", CSD_TYPE(csd)); break; } } }
/* * First; run all SYNC callbacks, people are waiting for us. */ prev = NULL; llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { /* Do we wait until *after* callback? */ if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { smp_call_func_t func = csd->func; void *info = csd->info;
if (prev) { prev->next = &csd_next->node.llist; } else { entry = &csd_next->node.llist; }
csd_lock_record(csd); csd_do_func(func, info, csd); csd_unlock(csd); csd_lock_record(NULL); } else { prev = &csd->node.llist; } }
if (!entry) return;
/* * Second; run all !SYNC callbacks. */ prev = NULL; llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { int type = CSD_TYPE(csd);
if (type != CSD_TYPE_TTWU) { if (prev) { prev->next = &csd_next->node.llist; } else { entry = &csd_next->node.llist; }
if (type == CSD_TYPE_ASYNC) { smp_call_func_t func = csd->func; void *info = csd->info;
csd_lock_record(csd); csd_unlock(csd); csd_do_func(func, info, csd); csd_lock_record(NULL); } else if (type == CSD_TYPE_IRQ_WORK) { irq_work_single(csd); }
} else { prev = &csd->node.llist; } }
/* * Third; only CSD_TYPE_TTWU is left, issue those. */ if (entry) { csd = llist_entry(entry, typeof(*csd), node.llist); csd_do_func(sched_ttwu_pending, entry, csd); }}
/** * flush_smp_call_function_queue - Flush pending smp-call-function callbacks * from task context (idle, migration thread) * * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to * handle queued SMP function calls before scheduling. * * The migration thread has to ensure that an eventually pending wakeup has * been handled before it migrates a task. */void flush_smp_call_function_queue(void){ unsigned int was_pending; unsigned long flags;
if (llist_empty(this_cpu_ptr(&call_single_queue))) return;
local_irq_save(flags); /* Get the already pending soft interrupts for RT enabled kernels */ was_pending = local_softirq_pending(); __flush_smp_call_function_queue(true); if (local_softirq_pending()) do_softirq_post_smp_call_flush(was_pending);
local_irq_restore(flags);}
/** * smp_call_function_single - Run a function on a specific CPU * @cpu: Specific target CPU for this function. * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. * @wait: If true, wait until function has completed on other CPUs. * * Returns: %0 on success, else a negative status code. */int smp_call_function_single(int cpu, smp_call_func_t func, void *info, int wait){ call_single_data_t *csd; call_single_data_t csd_stack = { .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, }; int this_cpu; int err;
/* * Prevent preemption and reschedule on another CPU, as well as CPU * removal. This prevents stopper from running on this CPU, thus * providing mutual exclusion of the below cpu_online() check and * IPI sending ensuring IPI are not missed by CPU going offline. */ this_cpu = get_cpu();
/* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() && !oops_in_progress);
/* * When @wait we can deadlock when we interrupt between llist_add() and * arch_send_call_function_ipi*(); when !@wait we can deadlock due to * csd_lock() on because the interrupt context uses the same csd * storage. */ WARN_ON_ONCE(!in_task());
csd = &csd_stack; if (!wait) { csd = get_single_csd_data(cpu); csd_lock(csd); }
csd->func = func; csd->info = info;#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG csd->node.src = this_cpu; csd->node.dst = cpu;#endif
err = generic_exec_single(cpu, csd);
if (wait) csd_lock_wait(csd);
put_cpu();
return err;}EXPORT_SYMBOL(smp_call_function_single);
/** * smp_call_function_single_async() - Run an asynchronous function on a * specific CPU. * @cpu: The CPU to run on. * @csd: Pre-allocated and setup data structure * * Like smp_call_function_single(), but the call is asynchonous and * can thus be done from contexts with disabled interrupts. * * The caller passes his own pre-allocated data structure * (ie: embedded in an object) and is responsible for synchronizing it * such that the IPIs performed on the @csd are strictly serialized. * * If the function is called with one csd which has not yet been * processed by previous call to smp_call_function_single_async(), the * function will return immediately with -EBUSY showing that the csd * object is still in progress. * * NOTE: Be careful, there is unfortunately no current debugging facility to * validate the correctness of this serialization. * * Return: %0 on success or negative errno value on error */int smp_call_function_single_async(int cpu, call_single_data_t *csd){ int err = 0;
preempt_disable();
if (csd->node.u_flags & CSD_FLAG_LOCK) { err = -EBUSY; goto out; }
csd->node.u_flags = CSD_FLAG_LOCK; smp_wmb();
err = generic_exec_single(cpu, csd);
out: preempt_enable();
return err;}EXPORT_SYMBOL_GPL(smp_call_function_single_async);
/** * smp_call_function_any - Run a function on any of the given cpus * @mask: The mask of cpus it can run on. * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. * @wait: If true, wait until function has completed. * * Selection preference: * 1) current cpu if in @mask * 2) nearest cpu in @mask, based on NUMA topology * * Returns: %0 on success, else a negative status code (if no cpus were online). */int smp_call_function_any(const struct cpumask *mask, smp_call_func_t func, void *info, int wait){ unsigned int cpu; int ret;
/* Try for same CPU (cheapest) */ cpu = get_cpu(); if (!cpumask_test_cpu(cpu, mask)) cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu));
ret = smp_call_function_single(cpu, func, info, wait); put_cpu(); return ret;}EXPORT_SYMBOL_GPL(smp_call_function_any);
/* * Flags to be used as scf_flags argument of smp_call_function_many_cond(). * * %SCF_WAIT: Wait until function execution is completed * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask */#define SCF_WAIT (1U << 0)#define SCF_RUN_LOCAL (1U << 1)
static void smp_call_function_many_cond(const struct cpumask *mask, smp_call_func_t func, void *info, unsigned int scf_flags, smp_cond_func_t cond_func){ int cpu, last_cpu, this_cpu = smp_processor_id(); struct call_function_data *cfd; bool wait = scf_flags & SCF_WAIT; int nr_cpus = 0; bool run_remote = false;
lockdep_assert_preemption_disabled();
/* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ if (cpu_online(this_cpu) && !oops_in_progress && !early_boot_irqs_disabled) lockdep_assert_irqs_enabled();
/* * When @wait we can deadlock when we interrupt between llist_add() and * arch_send_call_function_ipi*(); when !@wait we can deadlock due to * csd_lock() on because the interrupt context uses the same csd * storage. */ WARN_ON_ONCE(!in_task());
/* Check if we need remote execution, i.e., any CPU excluding this one. */ if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) { cfd = this_cpu_ptr(&cfd_data); cpumask_and(cfd->cpumask, mask, cpu_online_mask); __cpumask_clear_cpu(this_cpu, cfd->cpumask);
cpumask_clear(cfd->cpumask_ipi); for_each_cpu(cpu, cfd->cpumask) { call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
if (cond_func && !cond_func(cpu, info)) { __cpumask_clear_cpu(cpu, cfd->cpumask); continue; }
/* Work is enqueued on a remote CPU. */ run_remote = true;
csd_lock(csd); if (wait) csd->node.u_flags |= CSD_TYPE_SYNC; csd->func = func; csd->info = info;#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG csd->node.src = this_cpu; csd->node.dst = cpu;#endif trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
/* * Kick the remote CPU if this is the first work * item enqueued. */ if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { __cpumask_set_cpu(cpu, cfd->cpumask_ipi); nr_cpus++; last_cpu = cpu; } }
/* * Choose the most efficient way to send an IPI. Note that the * number of CPUs might be zero due to concurrent changes to the * provided mask. */ if (nr_cpus == 1) send_call_function_single_ipi(last_cpu); else if (likely(nr_cpus > 1)) send_call_function_ipi_mask(cfd->cpumask_ipi); }
/* Check if we need local execution. */ if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) && (!cond_func || cond_func(this_cpu, info))) { unsigned long flags;
local_irq_save(flags); csd_do_func(func, info, NULL); local_irq_restore(flags); }
if (run_remote && wait) { for_each_cpu(cpu, cfd->cpumask) { call_single_data_t *csd;
csd = per_cpu_ptr(cfd->csd, cpu); csd_lock_wait(csd); } }}
/** * smp_call_function_many() - Run a function on a set of CPUs. * @mask: The set of cpus to run on (only runs on online subset). * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. * @wait: If true, wait (atomically) until function has completed * on other CPUs. * * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. Preemption * must be disabled when calling this function. * * @func is not called on the local CPU even if @mask contains it. Consider * using on_each_cpu_cond_mask() instead if this is not desirable. */void smp_call_function_many(const struct cpumask *mask, smp_call_func_t func, void *info, bool wait){ smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL);}EXPORT_SYMBOL(smp_call_function_many);
/** * smp_call_function() - Run a function on all other CPUs. * @func: The function to run. This must be fast and non-blocking. * @info: An arbitrary pointer to pass to the function. * @wait: If true, wait (atomically) until function has completed * on other CPUs. * * If @wait is true, then returns once @func has returned; otherwise * it returns just before the target cpu calls @func. * * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. */void smp_call_function(smp_call_func_t func, void *info, int wait){ preempt_disable(); smp_call_function_many(cpu_online_mask, func, info, wait); preempt_enable();}EXPORT_SYMBOL(smp_call_function);
/* Setup configured maximum number of CPUs to activate */unsigned int setup_max_cpus = NR_CPUS;EXPORT_SYMBOL(setup_max_cpus);
/* * Setup routine for controlling SMP activation * * Command-line option of "nosmp" or "maxcpus=0" will disable SMP * activation entirely (the MPS table probe still happens, though). * * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer * greater than 0, limits the maximum number of CPUs activated in * SMP mode to <NUM>. */
void __weak __init arch_disable_smp_support(void) { }
static int __init nosmp(char *str){ setup_max_cpus = 0; arch_disable_smp_support();
return 0;}
early_param("nosmp", nosmp);
/* this is hard limit */static int __init nrcpus(char *str){ int nr_cpus;
if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) set_nr_cpu_ids(nr_cpus);
return 0;}
early_param("nr_cpus", nrcpus);
static int __init maxcpus(char *str){ get_option(&str, &setup_max_cpus); if (setup_max_cpus == 0) arch_disable_smp_support();
return 0;}
early_param("maxcpus", maxcpus);
#if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS)/* Setup number of possible processor ids */unsigned int nr_cpu_ids __read_mostly = NR_CPUS;EXPORT_SYMBOL(nr_cpu_ids);#endif
/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */void __init setup_nr_cpu_ids(void){ set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1);}
/* Called by boot processor to activate the rest. */void __init smp_init(void){ int num_nodes, num_cpus;
idle_threads_init(); cpuhp_threads_init();
pr_info("Bringing up secondary CPUs ...\n");
bringup_nonboot_cpus(setup_max_cpus);
num_nodes = num_online_nodes(); num_cpus = num_online_cpus(); pr_info("Brought up %d node%s, %d CPU%s\n", num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus));
/* Any cleanup work */ smp_cpus_done(setup_max_cpus);}
/** * on_each_cpu_cond_mask() - Call a function on each processor for which * the supplied function cond_func returns true, optionally waiting * for all the required CPUs to finish. This may include the local * processor. * @cond_func: A callback function that is passed a cpu id and * the info parameter. The function is called * with preemption disabled. The function should * return a boolean value indicating whether to IPI * the specified CPU. * @func: The function to run on all applicable CPUs. * This must be fast and non-blocking. * @info: An arbitrary pointer to pass to both functions. * @wait: If true, wait (atomically) until function has * completed on other CPUs. * @mask: The set of cpus to run on (only runs on online subset). * * Preemption is disabled to protect against CPUs going offline but not online. * CPUs going online during the call will not be seen or sent an IPI. * * You must not call this function with disabled interrupts or * from a hardware interrupt handler or from a bottom half handler. */void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, void *info, bool wait, const struct cpumask *mask){ unsigned int scf_flags = SCF_RUN_LOCAL;
if (wait) scf_flags |= SCF_WAIT;
preempt_disable(); smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); preempt_enable();}EXPORT_SYMBOL(on_each_cpu_cond_mask);
static void do_nothing(void *unused){}
/** * kick_all_cpus_sync - Force all cpus out of idle * * Used to synchronize the update of pm_idle function pointer. It's * called after the pointer is updated and returns after the dummy * callback function has been executed on all cpus. The execution of * the function can only happen on the remote cpus after they have * left the idle function which had been called via pm_idle function * pointer. So it's guaranteed that nothing uses the previous pointer * anymore. */void kick_all_cpus_sync(void){ /* Make sure the change is visible before we kick the cpus */ smp_mb(); smp_call_function(do_nothing, NULL, 1);}EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
/** * wake_up_all_idle_cpus - break all cpus out of idle * wake_up_all_idle_cpus try to break all cpus which is in idle state even * including idle polling cpus, for non-idle cpus, we will do nothing * for them. */void wake_up_all_idle_cpus(void){ int cpu;
for_each_possible_cpu(cpu) { preempt_disable(); if (cpu != smp_processor_id() && cpu_online(cpu)) wake_up_if_idle(cpu); preempt_enable(); }}EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
/** * cpus_peek_for_pending_ipi - Check for pending IPI for CPUs * @mask: The CPU mask for the CPUs to check. * * This function walks through the @mask to check if there are any pending IPIs * scheduled, for any of the CPUs in the @mask. It does not guarantee * correctness as it only provides a racy snapshot. * * Returns: true if there is a pending IPI scheduled and false otherwise. */bool cpus_peek_for_pending_ipi(const struct cpumask *mask){ unsigned int cpu;
for_each_cpu(cpu, mask) { if (!llist_empty(per_cpu_ptr(&call_single_queue, cpu))) return true; }
return false;}
/** * struct smp_call_on_cpu_struct - Call a function on a specific CPU * @work: &work_struct * @done: &completion to signal * @func: function to call * @data: function's data argument * @ret: return value from @func * @cpu: target CPU (%-1 for any CPU) * * Used to call a function on a specific cpu and wait for it to return. * Optionally make sure the call is done on a specified physical cpu via vcpu * pinning in order to support virtualized environments. */struct smp_call_on_cpu_struct { struct work_struct work; struct completion done; int (*func)(void *); void *data; int ret; int cpu;};
static void smp_call_on_cpu_callback(struct work_struct *work){ struct smp_call_on_cpu_struct *sscs;
sscs = container_of(work, struct smp_call_on_cpu_struct, work); if (sscs->cpu >= 0) hypervisor_pin_vcpu(sscs->cpu); sscs->ret = sscs->func(sscs->data); if (sscs->cpu >= 0) hypervisor_pin_vcpu(-1);
complete(&sscs->done);}
/** * smp_call_on_cpu() - Call a function on a specific CPU and wait * for it to return. * @cpu: The CPU to run on. * @func: The function to run * @par: An arbitrary pointer parameter for @func. * @phys: If @true, force to run on physical @cpu. See * &struct smp_call_on_cpu_struct for more info. * * Returns: %-ENXIO if the @cpu is invalid; otherwise the return value * from @func. */int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys){ struct smp_call_on_cpu_struct sscs = { .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), .func = func, .data = par, .cpu = phys ? cpu : -1, };
INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
if (cpu >= nr_cpu_ids || !cpu_online(cpu)) return -ENXIO;
queue_work_on(cpu, system_percpu_wq, &sscs.work); wait_for_completion(&sscs.done); destroy_work_on_stack(&sscs.work);
return sscs.ret;}EXPORT_SYMBOL_GPL(smp_call_on_cpu);