[PATCH 8/9] sched/deadline: defer WARN console output under rq->lock

[Rik van Riel]

Convert the WARN*() calls that run under rq->lock or ->pi_lock to the
SCHED_WARN*() variants, so their console output is deferred to irq_work
instead of being emitted synchronously (which can deadlock via
console_unlock() -> up(&console_sem) -> try_to_wake_up() while the lock
is held).

This should prevent a deadlock if these warnings fire with a legacy
or boot console configured.

Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
Assisted-by: Claude:claude-opus-4-8
---
 kernel/sched/cpudeadline.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 0a2b7e30fd10..271f28b87a4e 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -149,7 +149,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	} else {
 		int best_cpu = cpudl_maximum(cp);
 
-		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
+		SCHED_WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
 
 		if (cpumask_test_cpu(best_cpu, &p->cpus_mask) &&
 		    dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
@@ -177,7 +177,7 @@ void cpudl_clear(struct cpudl *cp, int cpu, bool online)
 	int old_idx, new_cpu;
 	unsigned long flags;
 
-	WARN_ON(!cpu_present(cpu));
+	SCHED_WARN_ON(!cpu_present(cpu));
 
 	raw_spin_lock_irqsave(&cp->lock, flags);
 
@@ -220,7 +220,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
 	int old_idx;
 	unsigned long flags;
 
-	WARN_ON(!cpu_present(cpu));
+	SCHED_WARN_ON(!cpu_present(cpu));
 
 	raw_spin_lock_irqsave(&cp->lock, flags);
 
-- 
2.53.0-Meta