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Commit 4e93ad60 authored by Jiri Olsa's avatar Jiri Olsa Committed by Ingo Molnar
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perf: Do not send exit event twice 



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: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 169b932a

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,