[tip: sched/core] sched/debug: Change need_resched warnings to pr_err

[tip-bot2 for David Rientjes]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     8061b9f5e111a3012f8b691e5b75dd81eafbb793
Gitweb:        https://git.kernel.org/tip/8061b9f5e111a3012f8b691e5b75dd81eafbb793
Author:        David Rientjes <rientjes@xxxxxxxxxx>
AuthorDate:    Thu, 09 Jan 2025 16:24:33 -08:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 13 Jan 2025 14:10:23 +01:00

sched/debug: Change need_resched warnings to pr_err

need_resched warnings, if enabled, are treated as WARNINGs.  If
kernel.panic_on_warn is enabled, then this causes a kernel panic.

It's highly unlikely that a panic is desired for these warnings, only a
stack trace is normally required to debug and resolve.

Thus, switch need_resched warnings to simply be a printk with an
associated stack trace so they are no longer in scope for panic_on_warn.

Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Madadi Vineeth Reddy <vineethr@xxxxxxxxxxxxx>
Acked-by: Josh Don <joshdon@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/e8d52023-5291-26bd-5299-8bb9eb604929@xxxxxxxxxx
---
 kernel/sched/debug.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 5e8e84a..fd7e852 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1292,8 +1292,10 @@ void resched_latency_warn(int cpu, u64 latency)
 {
 	static DEFINE_RATELIMIT_STATE(latency_check_ratelimit, 60 * 60 * HZ, 1);
 
-	WARN(__ratelimit(&latency_check_ratelimit),
-	     "sched: CPU %d need_resched set for > %llu ns (%d ticks) "
-	     "without schedule\n",
-	     cpu, latency, cpu_rq(cpu)->ticks_without_resched);
+	if (likely(!__ratelimit(&latency_check_ratelimit)))
+		return;
+
+	pr_err("sched: CPU %d need_resched set for > %llu ns (%d ticks) without schedule\n",
+	       cpu, latency, cpu_rq(cpu)->ticks_without_resched);
+	dump_stack();
 }