perf: Do not send exit event twice (4e93ad60) · Commits · 戴 / test

In case we monitor events system wide, we get EXIT event (when configured) twice for each task that exited. Note doubled lines with same pid/tid in following example: $ sudo ./perf record -a ^C[ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.480 MB perf.data (2518 samples) ] $ sudo ./perf report -D | grep EXIT 0 60290687567581 0x59910 [0x38]: PERF_RECORD_EXIT(1250:1250):(1250:1250) 0 60290687568354 0x59948 [0x38]: PERF_RECORD_EXIT(1250:1250):(1250:1250) 0 60290687988744 0x59ad8 [0x38]: PERF_RECORD_EXIT(1250:1250):(1250:1250) 0 60290687989198 0x59b10 [0x38]: PERF_RECORD_EXIT(1250:1250):(1250:1250) 1 60290692567895 0x62af0 [0x38]: PERF_RECORD_EXIT(1253:1253):(1253:1253) 1 60290692568322 0x62b28 [0x38]: PERF_RECORD_EXIT(1253:1253):(1253:1253) 2 60290692739276 0x69a18 [0x38]: PERF_RECORD_EXIT(1252:1252):(1252:1252) 2 60290692739910 0x69a50 [0x38]: PERF_RECORD_EXIT(1252:1252):(1252:1252) The reason is that the cpu contexts are processes each time we call perf_event_task. I'm changing the perf_event_aux logic to serve task_ctx and cpu contexts separately, which ensure we don't get EXIT event generated twice on same cpu context. This does not affect other auxiliary events, as they don't use task_ctx at all. Signed-off-by:

Jiri Olsa <jolsa@kernel.org> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: http://lkml.kernel.org/r/1446649205-5822-1-git-send-email-jolsa@kernel.org Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/events/core.c

+31 −11

Original line number	Diff line number	Diff line
		@@ -5682,6 +5682,17 @@ perf_event_aux_ctx(struct perf_event_context *ctx,
		}
		}

		static void
		perf_event_aux_task_ctx(perf_event_aux_output_cb output, void *data,
		struct perf_event_context *task_ctx)
		{
		rcu_read_lock();
		preempt_disable();
		perf_event_aux_ctx(task_ctx, output, data);
		preempt_enable();
		rcu_read_unlock();
		}

		static void
		perf_event_aux(perf_event_aux_output_cb output, void *data,
		struct perf_event_context *task_ctx)
		@@ -5691,14 +5702,23 @@ perf_event_aux(perf_event_aux_output_cb output, void *data,
		struct pmu *pmu;
		int ctxn;

		/*
		* If we have task_ctx != NULL we only notify
		* the task context itself. The task_ctx is set
		* only for EXIT events before releasing task
		* context.
		*/
		if (task_ctx) {
		perf_event_aux_task_ctx(output, data, task_ctx);
		return;
		}

		rcu_read_lock();
		list_for_each_entry_rcu(pmu, &pmus, entry) {
		cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
		if (cpuctx->unique_pmu != pmu)
		goto next;
		perf_event_aux_ctx(&cpuctx->ctx, output, data);
		if (task_ctx)
		goto next;
		ctxn = pmu->task_ctx_nr;
		if (ctxn < 0)
		goto next;
		@@ -5708,12 +5728,6 @@ perf_event_aux(perf_event_aux_output_cb output, void *data,
		next:
		put_cpu_ptr(pmu->pmu_cpu_context);
		}

		if (task_ctx) {
		preempt_disable();
		perf_event_aux_ctx(task_ctx, output, data);
		preempt_enable();
		}
		rcu_read_unlock();
		}

		@@ -8803,10 +8817,8 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
		struct perf_event_context child_ctx, clone_ctx = NULL;
		unsigned long flags;

		if (likely(!child->perf_event_ctxp[ctxn])) {
		perf_event_task(child, NULL, 0);
		if (likely(!child->perf_event_ctxp[ctxn]))
		return;
		}

		local_irq_save(flags);
		/*
		@@ -8890,6 +8902,14 @@ void perf_event_exit_task(struct task_struct *child)

		for_each_task_context_nr(ctxn)
		perf_event_exit_task_context(child, ctxn);

		/*
		* The perf_event_exit_task_context calls perf_event_task
		* with child's task_ctx, which generates EXIT events for
		* child contexts and sets child->perf_event_ctxp[] to NULL.
		* At this point we need to send EXIT events to cpu contexts.
		*/
		perf_event_task(child, NULL, 0);
		}

		static void perf_free_event(struct perf_event *event,

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