Messages in this thread | | | Subject | Re: [PATCH] perf/core: Fix endless multiplex timer | From | "Liang, Kan" <> | Date | Thu, 5 Mar 2020 12:56:49 -0500 |
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On 3/5/2020 7:38 AM, Peter Zijlstra wrote: > On Wed, Mar 04, 2020 at 09:20:42AM -0500, Liang, Kan wrote: >> >> NMI watchdog is pinned event. >> ctx_event_to_rotate() will only pick an event from the flexible_groups. >> So the cpu_ctx_sched_out() in perf_rotate_context() will never be called. > > Surely that's fixable; same principle. >
Yes, after applying this patch, the issue has gone.
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Thanks, Kan > --- > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 3f1f77de7247..595fb3decd43 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -2182,6 +2182,7 @@ __perf_remove_from_context(struct perf_event *event, > > if (!ctx->nr_events && ctx->is_active) { > ctx->is_active = 0; > + ctx->rotate_necessary = 0; > if (ctx->task) { > WARN_ON_ONCE(cpuctx->task_ctx != ctx); > cpuctx->task_ctx = NULL; > @@ -3077,12 +3078,6 @@ static void ctx_sched_out(struct perf_event_context *ctx, > if (!ctx->nr_active || !(is_active & EVENT_ALL)) > return; > > - /* > - * If we had been multiplexing, no rotations are necessary, now no events > - * are active. > - */ > - ctx->rotate_necessary = 0; > - > perf_pmu_disable(ctx->pmu); > if (is_active & EVENT_PINNED) { > list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list) > @@ -3092,6 +3087,13 @@ static void ctx_sched_out(struct perf_event_context *ctx, > if (is_active & EVENT_FLEXIBLE) { > list_for_each_entry_safe(event, tmp, &ctx->flexible_active, active_list) > group_sched_out(event, cpuctx, ctx); > + > + /* > + * Since we cleared EVENT_FLEXIBLE, also clear > + * rotate_necessary, is will be reset by > + * ctx_flexible_sched_in() when needed. > + */ > + ctx->rotate_necessary = 0; > } > perf_pmu_enable(ctx->pmu); > } > @@ -3841,6 +3843,12 @@ ctx_event_to_rotate(struct perf_event_context *ctx) > typeof(*event), group_node); > } > > + /* > + * Unconditionally clear rotate_necessary; if ctx_flexible_sched_in() > + * finds there are unschedulable events, it will set it again. > + */ > + ctx->rotate_necessary = 0; > + > return event; > } > >
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