Commit 90c91dfb authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

perf/core: Fix endless multiplex timer 



Kan and Andi reported that we fail to kill rotation when the flexible
events go empty, but the context does not. XXX moar

Fixes: fd7d5517 ("perf/cgroups: Don't rotate events for cgroups unnecessarily")
Reported-by: default avatarAndi Kleen <ak@linux.intel.com>
Reported-by: default avatarKan Liang <kan.liang@linux.intel.com>
Tested-by: default avatarKan Liang <kan.liang@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200305123851.GX2596@hirez.programming.kicks-ass.net
parent d8a73868

kernel/events/core.c

+14 −6
Original line number Diff line number Diff line
@@ -2291,6 +2291,7 @@ __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;
@@ -3188,12 +3189,6 @@ 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)
@@ -3203,6 +3198,13 @@ 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);

}
@@ -3985,6 +3987,12 @@ 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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