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SubjectRe: [PATCH v4 1/4] ftrace: Implement fs notification for tracing_max_latency
On Wed, May 22, 2019 at 02:30:14AM +0200, Viktor Rosendahl wrote:

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 874c427742a9..440cd1a62722 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3374,6 +3374,7 @@ static void __sched notrace __schedule(bool preempt)
> struct rq *rq;
> int cpu;
>
> + trace_disable_fsnotify();
> cpu = smp_processor_id();
> rq = cpu_rq(cpu);
> prev = rq->curr;
> @@ -3449,6 +3450,7 @@ static void __sched notrace __schedule(bool preempt)
> }
>
> balance_callback(rq);
> + trace_enable_fsnotify();
> }
>
> void __noreturn do_task_dead(void)
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 80940939b733..1a38bcdb3652 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -225,6 +225,7 @@ static void cpuidle_idle_call(void)
> static void do_idle(void)
> {
> int cpu = smp_processor_id();
> + trace_disable_fsnotify();
> /*
> * If the arch has a polling bit, we maintain an invariant:
> *
> @@ -284,6 +285,7 @@ static void do_idle(void)
> smp_mb__after_atomic();
>
> sched_ttwu_pending();
> + /* schedule_idle() will call trace_enable_fsnotify() */
> schedule_idle();
>
> if (unlikely(klp_patch_pending(current)))

I still hate this.. why are we doing this? We already have this
stop_critical_timings() nonsense and are now adding more gunk.



> +static DEFINE_PER_CPU(atomic_t, notify_disabled) = ATOMIC_INIT(0);

> + atomic_set(&per_cpu(notify_disabled, cpu), 1);

> + atomic_set(&per_cpu(notify_disabled, cpu), 0);

> + if (!atomic_read(&per_cpu(notify_disabled, cpu)))

That's just wrong on so many levels..

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