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perf: Fix exit() vs PERF_FORMAT_GROUP

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Both Stephane and Corey reported that PERF_FORMAT_GROUP didn't work
as expected if the task the counters were attached to quit before
the read() call.

The cause is that we unconditionally destroy the grouping when we
remove counters from their context. Fix this by only doing this when
we free the counter itself.

Reported-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1273160566.5605.404.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-05-06 17:31:38 +02:00 committed by Ingo Molnar
parent 722154e4ca
commit 4fd38e4595
2 changed files with 6 additions and 0 deletions
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1
include/linux/perf_event.h
View File

@ -522,6 +522,7 @@ struct pmu {
* enum perf_event_active_state - the states of a event
*/
enum perf_event_active_state {
PERF_EVENT_STATE_FREE = -3,
PERF_EVENT_STATE_ERROR = -2,
PERF_EVENT_STATE_OFF = -1,
PERF_EVENT_STATE_INACTIVE = 0,

5
kernel/perf_event.c
View File

@ -341,6 +341,9 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
if (event->state > PERF_EVENT_STATE_OFF)
event->state = PERF_EVENT_STATE_OFF;
if (event->state > PERF_EVENT_STATE_FREE)
return;
/*
* If this was a group event with sibling events then
* upgrade the siblings to singleton events by adding them
@ -1856,6 +1859,8 @@ int perf_event_release_kernel(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
event->state = PERF_EVENT_STATE_FREE;
WARN_ON_ONCE(ctx->parent_ctx);
mutex_lock(&ctx->mutex);
perf_event_remove_from_context(event);