On 01/03/22 15:24, tip-bot2 for Valentin Schneider wrote:
> The following commit has been merged into the sched/core branch of tip:
>
> Commit-ID: fa2c3254d7cfff5f7a916ab928a562d1165f17bb
> Gitweb: https://git.kernel.org/tip/fa2c3254d7cfff5f7a916ab928a562d1165f17bb
> Author: Valentin Schneider <valentin.schneider@xxxxxxx>
> AuthorDate: Thu, 20 Jan 2022 16:25:19
> Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CommitterDate: Tue, 01 Mar 2022 16:18:39 +01:00
>
> sched/tracing: Don't re-read p->state when emitting sched_switch event
>
> As of commit
>
> c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
>
> the following sequence becomes possible:
>
> p->__state = TASK_INTERRUPTIBLE;
> __schedule()
> deactivate_task(p);
> ttwu()
> READ !p->on_rq
> p->__state=TASK_WAKING
> trace_sched_switch()
> __trace_sched_switch_state()
> task_state_index()
> return 0;
>
> TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
> the trace event.
>
> Prevent this by pushing the value read from __schedule() down the trace
> event.
>
> Reported-by: Abhijeet Dharmapurikar <adharmap@xxxxxxxxxxx>
> Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
> Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@xxxxxxx
So I wasn't sure if that would be considered a "bug", but folks are asking
for this to be backported; do we want to slap
Fixes: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
to it?
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