[v2] perf/Power: PERF_EVENT_IOC_ENABLE does not reenable event

Submitted by Sukadev Bhattiprolu on Jan. 24, 2013, 11:25 p.m.


Message ID 20130124232523.GA12162@us.ibm.com
State Accepted, archived
Commit f53d168c025f27d64417a56bf129dbb39d2e1189
Headers show

Commit Message

Sukadev Bhattiprolu Jan. 24, 2013, 11:25 p.m.
perf/Power: PERF_EVENT_IOC_ENABLE does not reenable event

If we disable a perf event because we exceeded the specified ->event_limit,
power_pmu_stop() sets the PERF_HES_STOPPED flag on the event.

If the application then re-enables the event using PERF_EVENT_IOC_ENABLE
ioctl, we don't ever clear this STOPPED flag. Consequently, the user space
is never notified of the event.

Following message has more background and test case.


Used the following test cases to verify that this patch works on latest PAPI.

	$ papi.git/src/ctests/nonthread PAPI_TOT_CYC@5000000

	$ papi.git/src/ctests/overflow_single_event

	- [Paul Mackerras] Also clear PERF_HES_UPTODATE flag since we are
	  restarting the event; cleanup comments and patch description.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
 arch/powerpc/perf/core-book3s.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

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diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index aa2465e..4b1e584 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -880,8 +880,16 @@  static int power_pmu_add(struct perf_event *event, int ef_flags)
 	cpuhw->events[n0] = event->hw.config;
 	cpuhw->flags[n0] = event->hw.event_base;
+	/*
+	 * This event may have been disabled/stopped in record_and_restart()
+	 * because we exceeded the ->event_limit. If re-starting the event,
+	 * clear the ->hw.state (STOPPED and UPTODATE flags), so the user
+	 * notification is re-enabled.
+	 */
 	if (!(ef_flags & PERF_EF_START))
 		event->hw.state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
+	else
+		event->hw.state = 0;
 	 * If group events scheduling transaction was started,