sched/debug: Make CONFIG_SCHED_DEBUG functionality unconditional

All the big Linux distros enable CONFIG_SCHED_DEBUG, because
the various features it provides help not just with kernel
development, but with system administration and user-space
software development as well.

Reflect this reality and enable this functionality
unconditionally.

Signed-off-by: Ingo Molnar <[e-mail]>
Tested-by: Shrikanth Hegde <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Juri Lelli <[e-mail]>
Cc: Vincent Guittot <[e-mail]>
Cc: Dietmar Eggemann <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: Ben Segall <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Valentin Schneider <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

fs/proc/base.c

···
 #endif
 
 
-#ifdef CONFIG_SCHED_DEBUG
 /*
  * Print out various scheduling related per-task fields:
  */
···
 	.llseek		= seq_lseek,
 	.release	= single_release,
 };
-
-#endif
 
 #ifdef CONFIG_SCHED_AUTOGROUP
 /*
···
 	ONE("status",     S_IRUGO, proc_pid_status),
 	ONE("personality", S_IRUSR, proc_pid_personality),
 	ONE("limits",	  S_IRUGO, proc_pid_limits),
-#ifdef CONFIG_SCHED_DEBUG
 	REG("sched",      S_IRUGO|S_IWUSR, proc_pid_sched_operations),
-#endif
 #ifdef CONFIG_SCHED_AUTOGROUP
 	REG("autogroup",  S_IRUGO|S_IWUSR, proc_pid_sched_autogroup_operations),
 #endif
···
 	ONE("status",    S_IRUGO, proc_pid_status),
 	ONE("personality", S_IRUSR, proc_pid_personality),
 	ONE("limits",	 S_IRUGO, proc_pid_limits),
-#ifdef CONFIG_SCHED_DEBUG
 	REG("sched",     S_IRUGO|S_IWUSR, proc_pid_sched_operations),
-#endif
 	NOD("comm",      S_IFREG|S_IRUGO|S_IWUSR,
 			 &proc_tid_comm_inode_operations,
 			 &proc_pid_set_comm_operations, {}),

include/linux/energy_model.h

···
 	struct em_perf_state *ps;
 	int i;
 
-#ifdef CONFIG_SCHED_DEBUG
 	WARN_ONCE(!rcu_read_lock_held(), "EM: rcu read lock needed\n");
-#endif
 
 	if (!sum_util)
 		return 0;

include/linux/sched/debug.h

···
 
 extern void sched_show_task(struct task_struct *p);
 
-#ifdef CONFIG_SCHED_DEBUG
 struct seq_file;
 extern void proc_sched_show_task(struct task_struct *p,
 				 struct pid_namespace *ns, struct seq_file *m);
 extern void proc_sched_set_task(struct task_struct *p);
-#endif
 
 /* Attach to any functions which should be ignored in wchan output. */
 #define __sched		__section(".sched.text")

include/linux/sched/topology.h

···
 };
 #undef SD_FLAG
 
-#ifdef CONFIG_SCHED_DEBUG
-
 struct sd_flag_debug {
 	unsigned int meta_flags;
 	char *name;
 };
 extern const struct sd_flag_debug sd_flag_debug[];
-
-#endif
 
 #ifdef CONFIG_SCHED_SMT
 static inline int cpu_smt_flags(void)

include/trace/events/sched.h

···
 {
 	unsigned int state;
 
-#ifdef CONFIG_SCHED_DEBUG
 	BUG_ON(p != current);
-#endif /* CONFIG_SCHED_DEBUG */
 
 	/*
 	 * Preemption ignores task state, therefore preempted tasks are always

kernel/sched/build_utility.c

···
 # include "cpufreq_schedutil.c"
 #endif
 
-#ifdef CONFIG_SCHED_DEBUG
-# include "debug.c"
-#endif
+#include "debug.c"
 
 #ifdef CONFIG_SCHEDSTATS
 # include "stats.c"

kernel/sched/core.c

···
 
 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 
-#ifdef CONFIG_SCHED_DEBUG
 /*
  * Debugging: various feature bits
  *
···
  */
 __read_mostly int sysctl_resched_latency_warn_ms = 100;
 __read_mostly int sysctl_resched_latency_warn_once = 1;
-#endif /* CONFIG_SCHED_DEBUG */
 
 /*
  * Number of tasks to iterate in a single balance run.
···
 	if (rq->clock_update_flags & RQCF_ACT_SKIP)
 		return;
 
-#ifdef CONFIG_SCHED_DEBUG
 	if (sched_feat(WARN_DOUBLE_CLOCK))
 		WARN_ON_ONCE(rq->clock_update_flags & RQCF_UPDATED);
 	rq->clock_update_flags |= RQCF_UPDATED;
-#endif
+
 	clock = sched_clock_cpu(cpu_of(rq));
 	scx_rq_clock_update(rq, clock);
 
···
 
 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 {
-#ifdef CONFIG_SCHED_DEBUG
 	unsigned int state = READ_ONCE(p->__state);
 
 	/*
···
 	WARN_ON_ONCE(!cpu_online(new_cpu));
 
 	WARN_ON_ONCE(is_migration_disabled(p));
-#endif
 
 	trace_sched_migrate_task(p, new_cpu);
 
···
 	return ns;
 }
 
-#ifdef CONFIG_SCHED_DEBUG
 static u64 cpu_resched_latency(struct rq *rq)
 {
 	int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
···
 	return 1;
 }
 __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
-#else
-static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
-#endif /* CONFIG_SCHED_DEBUG */
 
 /*
  * This function gets called by the timer code, with HZ frequency.
···
 picked:
 	clear_tsk_need_resched(prev);
 	clear_preempt_need_resched();
-#ifdef CONFIG_SCHED_DEBUG
 	rq->last_seen_need_resched_ns = 0;
-#endif
 
 	if (likely(prev != next)) {
 		rq->nr_switches++;
···
 int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
 			  void *key)
 {
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~(WF_SYNC|WF_CURRENT_CPU));
+	WARN_ON_ONCE(wake_flags & ~(WF_SYNC|WF_CURRENT_CPU));
 	return try_to_wake_up(curr->private, mode, wake_flags);
 }
 EXPORT_SYMBOL(default_wake_function);
···
 			sched_show_task(p);
 	}
 
-#ifdef CONFIG_SCHED_DEBUG
 	if (!state_filter)
 		sysrq_sched_debug_show();
-#endif
+
 	rcu_read_unlock();
 	/*
 	 * Only show locks if all tasks are dumped:

kernel/sched/deadline.c

···
 }
 #endif
 
-#ifdef CONFIG_SCHED_DEBUG
 void print_dl_stats(struct seq_file *m, int cpu)
 {
 	print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
 }
-#endif /* CONFIG_SCHED_DEBUG */

kernel/sched/fair.c

···
 	return best;
 }
 
-#ifdef CONFIG_SCHED_DEBUG
 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
 	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
···
 
 	return 0;
 }
-#endif
 #endif
 
 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se);
···
 #endif
 };
 
-#ifdef CONFIG_SCHED_DEBUG
 void print_cfs_stats(struct seq_file *m, int cpu)
 {
 	struct cfs_rq *cfs_rq, *pos;
···
 	rcu_read_unlock();
 }
 #endif /* CONFIG_NUMA_BALANCING */
-#endif /* CONFIG_SCHED_DEBUG */
 
 __init void init_sched_fair_class(void)
 {

kernel/sched/rt.c

···
 
 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
 {
-#ifdef CONFIG_SCHED_DEBUG
 	WARN_ON_ONCE(!rt_entity_is_task(rt_se));
-#endif
+
 	return container_of(rt_se, struct task_struct, rt);
 }
 
···
 }
 #endif /* CONFIG_SYSCTL */
 
-#ifdef CONFIG_SCHED_DEBUG
 void print_rt_stats(struct seq_file *m, int cpu)
 {
 	rt_rq_iter_t iter;
···
 		print_rt_rq(m, cpu, rt_rq);
 	rcu_read_unlock();
 }
-#endif /* CONFIG_SCHED_DEBUG */

kernel/sched/sched.h

···
 
 	atomic_t		nr_iowait;
 
-#ifdef CONFIG_SCHED_DEBUG
 	u64 last_seen_need_resched_ns;
 	int ticks_without_resched;
-#endif
 
 #ifdef CONFIG_MEMBARRIER
 	int membarrier_state;
···
 struct rq_flags {
 	unsigned long flags;
 	struct pin_cookie cookie;
-#ifdef CONFIG_SCHED_DEBUG
 	/*
 	 * A copy of (rq::clock_update_flags & RQCF_UPDATED) for the
 	 * current pin context is stashed here in case it needs to be
 	 * restored in rq_repin_lock().
 	 */
 	unsigned int clock_update_flags;
-#endif
 };
 
 extern struct balance_callback balance_push_callback;
···
 {
 	rf->cookie = lockdep_pin_lock(__rq_lockp(rq));
 
-#ifdef CONFIG_SCHED_DEBUG
 	rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
 	rf->clock_update_flags = 0;
-# ifdef CONFIG_SMP
+#ifdef CONFIG_SMP
 	WARN_ON_ONCE(rq->balance_callback && rq->balance_callback != &balance_push_callback);
-# endif
 #endif
 }
 
 static inline void rq_unpin_lock(struct rq *rq, struct rq_flags *rf)
 {
-#ifdef CONFIG_SCHED_DEBUG
 	if (rq->clock_update_flags > RQCF_ACT_SKIP)
 		rf->clock_update_flags = RQCF_UPDATED;
-#endif
+
 	scx_rq_clock_invalidate(rq);
 	lockdep_unpin_lock(__rq_lockp(rq), rf->cookie);
 }
···
 {
 	lockdep_repin_lock(__rq_lockp(rq), rf->cookie);
 
-#ifdef CONFIG_SCHED_DEBUG
 	/*
 	 * Restore the value we stashed in @rf for this pin context.
 	 */
 	rq->clock_update_flags |= rf->clock_update_flags;
-#endif
 }
 
 extern
···
 	unsigned long		next_update;
 	int			imbalance;		/* XXX unrelated to capacity but shared group state */
 
-#ifdef CONFIG_SCHED_DEBUG
 	int			id;
-#endif
 
 	unsigned long		cpumask[];		/* Balance mask */
 };
···
 
 extern int group_balance_cpu(struct sched_group *sg);
 
-#ifdef CONFIG_SCHED_DEBUG
 extern void update_sched_domain_debugfs(void);
 extern void dirty_sched_domain_sysctl(int cpu);
-#else
-static inline void update_sched_domain_debugfs(void) { }
-static inline void dirty_sched_domain_sysctl(int cpu) { }
-#endif
 
 extern int sched_update_scaling(void);
 
···
 
 #undef SCHED_FEAT
 
-#ifdef CONFIG_SCHED_DEBUG
-
 /*
  * To support run-time toggling of sched features, all the translation units
  * (but core.c) reference the sysctl_sched_features defined in core.c.
···
 #define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
 
 #endif /* !CONFIG_JUMP_LABEL */
-
-#else /* !SCHED_DEBUG: */
-
-/*
- * Each translation unit has its own copy of sysctl_sched_features to allow
- * constants propagation at compile time and compiler optimization based on
- * features default.
- */
-#define SCHED_FEAT(name, enabled)	\
-	(1UL << __SCHED_FEAT_##name) * enabled |
-static __read_mostly __maybe_unused unsigned int sysctl_sched_features =
-#include "features.h"
-	0;
-#undef SCHED_FEAT
-
-#define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
-
-#endif /* !SCHED_DEBUG */
 
 extern struct static_key_false sched_numa_balancing;
 extern struct static_key_false sched_schedstats;
···
 
 extern unsigned int sysctl_sched_base_slice;
 
-#ifdef CONFIG_SCHED_DEBUG
 extern int sysctl_resched_latency_warn_ms;
 extern int sysctl_resched_latency_warn_once;
 
···
 extern unsigned int sysctl_numa_balancing_scan_period_max;
 extern unsigned int sysctl_numa_balancing_scan_size;
 extern unsigned int sysctl_numa_balancing_hot_threshold;
-#endif
 
 #ifdef CONFIG_SCHED_HRTICK
 
···
 }
 #endif
 
-#ifdef CONFIG_SCHED_DEBUG
 /*
  * In double_lock_balance()/double_rq_lock(), we use raw_spin_rq_lock() to
  * acquire rq lock instead of rq_lock(). So at the end of these two functions
···
 	rq2->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
 #endif
 }
-#else
-static inline void double_rq_clock_clear_update(struct rq *rq1, struct rq *rq2) { }
-#endif
 
 #define DEFINE_LOCK_GUARD_2(name, type, _lock, _unlock, ...)				\
 __DEFINE_UNLOCK_GUARD(name, type, _unlock, type *lock2; __VA_ARGS__)			\
···
 extern struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq);
 extern struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq);
 
-#ifdef	CONFIG_SCHED_DEBUG
 extern bool sched_debug_verbose;
 
 extern void print_cfs_stats(struct seq_file *m, int cpu);
···
 extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);
 
 extern void resched_latency_warn(int cpu, u64 latency);
-# ifdef CONFIG_NUMA_BALANCING
+#ifdef CONFIG_NUMA_BALANCING
 extern void show_numa_stats(struct task_struct *p, struct seq_file *m);
 extern void
 print_numa_stats(struct seq_file *m, int node, unsigned long tsf,
 		 unsigned long tpf, unsigned long gsf, unsigned long gpf);
-# endif /* CONFIG_NUMA_BALANCING */
-#else /* !CONFIG_SCHED_DEBUG: */
-static inline void resched_latency_warn(int cpu, u64 latency) { }
-#endif /* !CONFIG_SCHED_DEBUG */
+#endif /* CONFIG_NUMA_BALANCING */
 
 extern void init_cfs_rq(struct cfs_rq *cfs_rq);
 extern void init_rt_rq(struct rt_rq *rt_rq);

kernel/sched/topology.c

···
 static cpumask_var_t sched_domains_tmpmask;
 static cpumask_var_t sched_domains_tmpmask2;
 
-#ifdef CONFIG_SCHED_DEBUG
-
 static int __init sched_debug_setup(char *str)
 {
 	sched_debug_verbose = true;
···
 			break;
 	}
 }
-#else /* !CONFIG_SCHED_DEBUG */
-
-# define sched_debug_verbose 0
-# define sched_domain_debug(sd, cpu) do { } while (0)
-static inline bool sched_debug(void)
-{
-	return false;
-}
-#endif /* CONFIG_SCHED_DEBUG */
 
 /* Generate a mask of SD flags with the SDF_NEEDS_GROUPS metaflag */
 #define SD_FLAG(name, mflags) (name * !!((mflags) & SDF_NEEDS_GROUPS)) |
···
 			if (!sgc)
 				return -ENOMEM;
 
-#ifdef CONFIG_SCHED_DEBUG
 			sgc->id = j;
-#endif
 
 			*per_cpu_ptr(sdd->sgc, j) = sgc;
 		}