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SubjectRe: [PATCH v4 17/19] sched: Add migrate_disable() tracepoints
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On 23/10/20 11:12, Peter Zijlstra wrote:
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1732,6 +1732,8 @@ void migrate_disable(void)
> return;
> }
>
> + trace_sched_migrate_disable_tp(p);
> +
> preempt_disable();
> this_rq()->nr_pinned++;
> p->migration_disabled = 1;
> @@ -1764,6 +1766,8 @@ void migrate_enable(void)
> p->migration_disabled = 0;
> this_rq()->nr_pinned--;
> preempt_enable();
> +
> + trace_sched_migrate_enable_tp(p);

Don't you want those directly after the ->migration_disabled write?
esp. for migrate_enable(), if that preempt_enable() leads to a context
switch then the disable->enable deltas won't reflect the kernel view.

That delta may indeed include the time it took to run the stopper and
fix the task's affinity on migrate_enable(), but it could include all
sorts of other higher-priority tasks.

> }
> EXPORT_SYMBOL_GPL(migrate_enable);

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