Commit 09348d75 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched/all: Change all BUG_ON() instances in the scheduler to WARN_ON_ONCE() 



There's no good reason to crash a user's system with a BUG_ON(),
chances are high that they'll never even see the crash message on
Xorg, and it won't make it into the syslog either.

By using a WARN_ON_ONCE() we at least give the user a chance to report
any bugs triggered here - instead of getting silent hangs.

None of these WARN_ON_ONCE()s are supposed to trigger, ever - so we ignore
cases where a NULL check is done via a BUG_ON() and we let a NULL
pointer through after a WARN_ON_ONCE().

There's one exception: WARN_ON_ONCE() arguments with side-effects,
such as locking - in this case we use the return value of the
WARN_ON_ONCE(), such as in:

 -       BUG_ON(!lock_task_sighand(p, &flags));
 +       if (WARN_ON_ONCE(!lock_task_sighand(p, &flags)))
 +               return;

Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/YvSsKcAXISmshtHo@gmail.com
parent ffcf9c57

kernel/sched/autogroup.c

+2 −1
Original line number Diff line number Diff line
@@ -161,7 +161,8 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag) 
	struct task_struct *t;

	unsigned long flags;



	BUG_ON(!lock_task_sighand(p, &flags));

	if (WARN_ON_ONCE(!lock_task_sighand(p, &flags)))

		return;



	prev = p->signal->autogroup;

	if (prev == ag) {

kernel/sched/core.c

+1 −1
Original line number Diff line number Diff line
@@ -2328,7 +2328,7 @@ static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, 
	rq = cpu_rq(new_cpu);



	rq_lock(rq, rf);

	BUG_ON(task_cpu(p) != new_cpu);

	WARN_ON_ONCE(task_cpu(p) != new_cpu);

	activate_task(rq, p, 0);

	check_preempt_curr(rq, p, 0);

kernel/sched/cpupri.c

+1 −1
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ int cpupri_find_fitness(struct cpupri *cp, struct task_struct *p, 
	int task_pri = convert_prio(p->prio);

	int idx, cpu;



	BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);

	WARN_ON_ONCE(task_pri >= CPUPRI_NR_PRIORITIES);



	for (idx = 0; idx < task_pri; idx++) {

kernel/sched/deadline.c

+13 −13
Original line number Diff line number Diff line
@@ -310,7 +310,7 @@ static void dl_change_utilization(struct task_struct *p, u64 new_bw) 
{

	struct rq *rq;



	BUG_ON(p->dl.flags & SCHED_FLAG_SUGOV);

	WARN_ON_ONCE(p->dl.flags & SCHED_FLAG_SUGOV);



	if (task_on_rq_queued(p))

		return;
@@ -607,7 +607,7 @@ static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p) 
{

	struct rb_node *leftmost;



	BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));

	WARN_ON_ONCE(!RB_EMPTY_NODE(&p->pushable_dl_tasks));



	leftmost = rb_add_cached(&p->pushable_dl_tasks,

				 &rq->dl.pushable_dl_tasks_root,
@@ -684,7 +684,7 @@ static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p 
			 * Failed to find any suitable CPU.

			 * The task will never come back!

			 */

			BUG_ON(dl_bandwidth_enabled());

			WARN_ON_ONCE(dl_bandwidth_enabled());



			/*

			 * If admission control is disabled we
@@ -830,7 +830,7 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se) 
	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);

	struct rq *rq = rq_of_dl_rq(dl_rq);



	BUG_ON(pi_of(dl_se)->dl_runtime <= 0);

	WARN_ON_ONCE(pi_of(dl_se)->dl_runtime <= 0);



	/*

	 * This could be the case for a !-dl task that is boosted.
@@ -1616,7 +1616,7 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se) 
{

	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);



	BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));

	WARN_ON_ONCE(!RB_EMPTY_NODE(&dl_se->rb_node));



	rb_add_cached(&dl_se->rb_node, &dl_rq->root, __dl_less);
@@ -1640,7 +1640,7 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se) 
static void

enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)

{

	BUG_ON(on_dl_rq(dl_se));

	WARN_ON_ONCE(on_dl_rq(dl_se));



	update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags);
@@ -2017,7 +2017,7 @@ static struct task_struct *pick_task_dl(struct rq *rq) 
		return NULL;



	dl_se = pick_next_dl_entity(dl_rq);

	BUG_ON(!dl_se);

	WARN_ON_ONCE(!dl_se);

	p = dl_task_of(dl_se);



	return p;
@@ -2277,12 +2277,12 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq) 


	p = __node_2_pdl(rb_first_cached(&rq->dl.pushable_dl_tasks_root));



	BUG_ON(rq->cpu != task_cpu(p));

	BUG_ON(task_current(rq, p));

	BUG_ON(p->nr_cpus_allowed <= 1);

	WARN_ON_ONCE(rq->cpu != task_cpu(p));

	WARN_ON_ONCE(task_current(rq, p));

	WARN_ON_ONCE(p->nr_cpus_allowed <= 1);



	BUG_ON(!task_on_rq_queued(p));

	BUG_ON(!dl_task(p));

	WARN_ON_ONCE(!task_on_rq_queued(p));

	WARN_ON_ONCE(!dl_task(p));



	return p;

}
@@ -2492,7 +2492,7 @@ static void set_cpus_allowed_dl(struct task_struct *p, 
	struct root_domain *src_rd;

	struct rq *rq;



	BUG_ON(!dl_task(p));

	WARN_ON_ONCE(!dl_task(p));



	rq = task_rq(p);

	src_rd = rq->rd;

kernel/sched/fair.c

+5 −5
Original line number Diff line number Diff line
@@ -2600,7 +2600,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags, 
	if (!join)

		return;



	BUG_ON(irqs_disabled());

	WARN_ON_ONCE(irqs_disabled());

	double_lock_irq(&my_grp->lock, &grp->lock);



	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
@@ -7279,7 +7279,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ 
		return;



	find_matching_se(&se, &pse);

	BUG_ON(!pse);

	WARN_ON_ONCE(!pse);



	cse_is_idle = se_is_idle(se);

	pse_is_idle = se_is_idle(pse);
@@ -8159,7 +8159,7 @@ static void attach_task(struct rq *rq, struct task_struct *p) 
{

	lockdep_assert_rq_held(rq);



	BUG_ON(task_rq(p) != rq);

	WARN_ON_ONCE(task_rq(p) != rq);

	activate_task(rq, p, ENQUEUE_NOCLOCK);

	check_preempt_curr(rq, p, 0);

}
@@ -10134,7 +10134,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, 
		goto out_balanced;

	}



	BUG_ON(busiest == env.dst_rq);

	WARN_ON_ONCE(busiest == env.dst_rq);



	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
@@ -10430,7 +10430,7 @@ static int active_load_balance_cpu_stop(void *data) 
	 * we need to fix it. Originally reported by

	 * Bjorn Helgaas on a 128-CPU setup.

	 */

	BUG_ON(busiest_rq == target_rq);

	WARN_ON_ONCE(busiest_rq == target_rq);



	/* Search for an sd spanning us and the target CPU. */

	rcu_read_lock();