diff mbox series

[v2] sched: Add trace_sched_waking() tracepoint to sched_ttwu_pending()

Message ID 20240301032637.2117250-1-jstultz@google.com
State New
Headers
Series [v2] sched: Add trace_sched_waking() tracepoint to sched_ttwu_pending() |

Commit Message

John Stultz March 1, 2024, 3:26 a.m. UTC 
  Zimuzo reported seeing occasional cases in perfetto traces where
tasks went from sleeping directly to trace_sched_wakeup()
without always seeing a trace_sched_waking().

Looking at the code, trace_sched_wakeup() is only called in
ttwu_do_wakeup()

The call paths that get you to ttwu_do_wakeup() are:
try_to_wake_up() -> ttwu_do_wakeup()
try_to_wake_up() -> ttwu_runnable() -> ttwu_do_wakeup()
try_to_wake_up() -> ttwu_queue() -> ttwu_do_activate() -> ttwu_do_wakeup()
sched_ttwu_pending() -> ttwu_do_activate() -> ttwu_do_wakeup()

where trace_sched_waking() is currently called only in
try_to_wake_up().

So add a trace_sched_waking() call to sched_ttwu_pending(), so
we see the same state machine transitions.

With this change, the number of unexpected state transitions in
perfetto was greatly reduced.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: kernel-team@android.com
Reviewed-by: Phil Auld <pauld@redhat.com>
Reported-by: Zimuzo Ezeozue <zezeozue@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
v2:
* Minor commit message fix suggested by Phil Auld
---
 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9116bcc90346..233f06360d6a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3894,6 +3894,7 @@  void sched_ttwu_pending(void *arg)
 		if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
 			set_task_cpu(p, cpu_of(rq));
 
+		trace_sched_waking(p);
 		ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
 	}