sched/debug: Change SCHED_WARN_ON() to WARN_ON_ONCE()

The scheduler has this special SCHED_WARN() facility that
depends on CONFIG_SCHED_DEBUG.

Since CONFIG_SCHED_DEBUG is getting removed, convert
SCHED_WARN() to WARN_ON_ONCE().

Note that the warning output isn't 100% equivalent:

   #define SCHED_WARN_ON(x)      WARN_ONCE(x, #x)

Because SCHED_WARN_ON() would output the 'x' condition
as well, while WARN_ONCE() will only show a backtrace.

Hopefully these are rare enough to not really matter.

If it does, we should probably introduce a new WARN_ON()
variant that outputs the condition in stringified form,
or improve WARN_ON() itself.

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

Author: Ingo Molnar

kernel/sched/core.c

@@ -801,7 +801,7 @@ void update_rq_clock(struct rq *rq)
 
 #ifdef CONFIG_SCHED_DEBUG
 	if (sched_feat(WARN_DOUBLE_CLOCK))
-		SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
+		WARN_ON_ONCE(rq->clock_update_flags & RQCF_UPDATED);
 	rq->clock_update_flags |= RQCF_UPDATED;
 #endif
 	clock = sched_clock_cpu(cpu_of(rq));
@@ -1719,7 +1719,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
 
 	bucket = &uc_rq->bucket[uc_se->bucket_id];
 
-	SCHED_WARN_ON(!bucket->tasks);
+	WARN_ON_ONCE(!bucket->tasks);
 	if (likely(bucket->tasks))
 		bucket->tasks--;
 
@@ -1739,7 +1739,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
 	 * Defensive programming: this should never happen. If it happens,
 	 * e.g. due to future modification, warn and fix up the expected value.
 	 */
-	SCHED_WARN_ON(bucket->value > rq_clamp);
+	WARN_ON_ONCE(bucket->value > rq_clamp);
 	if (bucket->value >= rq_clamp) {
 		bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
 		uclamp_rq_set(rq, clamp_id, bkt_clamp);
@@ -2121,7 +2121,7 @@ void activate_task(struct rq *rq, struct task_struct *p, int flags)
 
 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
 {
-	SCHED_WARN_ON(flags & DEQUEUE_SLEEP);
+	WARN_ON_ONCE(flags & DEQUEUE_SLEEP);
 
 	WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING);
 	ASSERT_EXCLUSIVE_WRITER(p->on_rq);
@@ -2726,7 +2726,7 @@ __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
 	 * XXX do further audits, this smells like something putrid.
 	 */
 	if (ctx->flags & SCA_MIGRATE_DISABLE)
-		SCHED_WARN_ON(!p->on_cpu);
+		WARN_ON_ONCE(!p->on_cpu);
 	else
 		lockdep_assert_held(&p->pi_lock);
 
@@ -4195,7 +4195,7 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		 *  - we're serialized against set_special_state() by virtue of
 		 *    it disabling IRQs (this allows not taking ->pi_lock).
 		 */
-		SCHED_WARN_ON(p->se.sched_delayed);
+		WARN_ON_ONCE(p->se.sched_delayed);
 		if (!ttwu_state_match(p, state, &success))
 			goto out;
 
@@ -4489,7 +4489,7 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 	INIT_LIST_HEAD(&p->se.group_node);
 
 	/* A delayed task cannot be in clone(). */
-	SCHED_WARN_ON(p->se.sched_delayed);
+	WARN_ON_ONCE(p->se.sched_delayed);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	p->se.cfs_rq			= NULL;
@@ -5745,7 +5745,7 @@ static void sched_tick_remote(struct work_struct *work)
 			 * we are always sure that there is no proxy (only a
 			 * single task is running).
 			 */
-			SCHED_WARN_ON(rq->curr != rq->donor);
+			WARN_ON_ONCE(rq->curr != rq->donor);
 			update_rq_clock(rq);
 
 			if (!is_idle_task(curr)) {
@@ -5965,7 +5965,7 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
 		preempt_count_set(PREEMPT_DISABLED);
 	}
 	rcu_sleep_check();
-	SCHED_WARN_ON(ct_state() == CT_STATE_USER);
+	WARN_ON_ONCE(ct_state() == CT_STATE_USER);
 
 	profile_hit(SCHED_PROFILING, __builtin_return_address(0));
 
@@ -6811,7 +6811,7 @@ static inline void sched_submit_work(struct task_struct *tsk)
 	 * deadlock if the callback attempts to acquire a lock which is
 	 * already acquired.
 	 */
-	SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT);
+	WARN_ON_ONCE(current->__state & TASK_RTLOCK_WAIT);
 
 	/*
 	 * If we are going to sleep and we have plugged IO queued,
@@ -9249,7 +9249,7 @@ static void cpu_util_update_eff(struct cgroup_subsys_state *css)
 	unsigned int clamps;
 
 	lockdep_assert_held(&uclamp_mutex);
-	SCHED_WARN_ON(!rcu_read_lock_held());
+	WARN_ON_ONCE(!rcu_read_lock_held());
 
 	css_for_each_descendant_pre(css, top_css) {
 		uc_parent = css_tg(css)->parent
@@ -10584,7 +10584,7 @@ static void task_mm_cid_work(struct callback_head *work)
 	struct mm_struct *mm;
 	int weight, cpu;
 
-	SCHED_WARN_ON(t != container_of(work, struct task_struct, cid_work));
+	WARN_ON_ONCE(t != container_of(work, struct task_struct, cid_work));
 
 	work->next = work;	/* Prevent double-add */
 	if (t->flags & PF_EXITING)

kernel/sched/core_sched.c

@@ -65,7 +65,7 @@ static unsigned long sched_core_update_cookie(struct task_struct *p,
 	 * a cookie until after we've removed it, we must have core scheduling
 	 * enabled here.
 	 */
-	SCHED_WARN_ON((p->core_cookie || cookie) && !sched_core_enabled(rq));
+	WARN_ON_ONCE((p->core_cookie || cookie) && !sched_core_enabled(rq));
 
 	if (sched_core_enqueued(p))
 		sched_core_dequeue(rq, p, DEQUEUE_SAVE);

kernel/sched/deadline.c

@@ -249,8 +249,8 @@ void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 
 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
 	dl_rq->running_bw += dl_bw;
-	SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
-	SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
+	WARN_ON_ONCE(dl_rq->running_bw < old); /* overflow */
+	WARN_ON_ONCE(dl_rq->running_bw > dl_rq->this_bw);
 	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
 	cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
 }
@@ -262,7 +262,7 @@ void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 
 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
 	dl_rq->running_bw -= dl_bw;
-	SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
+	WARN_ON_ONCE(dl_rq->running_bw > old); /* underflow */
 	if (dl_rq->running_bw > old)
 		dl_rq->running_bw = 0;
 	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
@@ -276,7 +276,7 @@ void __add_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
 
 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
 	dl_rq->this_bw += dl_bw;
-	SCHED_WARN_ON(dl_rq->this_bw < old); /* overflow */
+	WARN_ON_ONCE(dl_rq->this_bw < old); /* overflow */
 }
 
 static inline
@@ -286,10 +286,10 @@ void __sub_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
 
 	lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
 	dl_rq->this_bw -= dl_bw;
-	SCHED_WARN_ON(dl_rq->this_bw > old); /* underflow */
+	WARN_ON_ONCE(dl_rq->this_bw > old); /* underflow */
 	if (dl_rq->this_bw > old)
 		dl_rq->this_bw = 0;
-	SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
+	WARN_ON_ONCE(dl_rq->running_bw > dl_rq->this_bw);
 }
 
 static inline

kernel/sched/ext.c

@@ -2341,7 +2341,7 @@ static bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq,
 {
 	int cpu = cpu_of(rq);
 
-	SCHED_WARN_ON(task_cpu(p) == cpu);
+	WARN_ON_ONCE(task_cpu(p) == cpu);
 
 	/*
 	 * If @p has migration disabled, @p->cpus_ptr is updated to contain only