perf/x86/intel: Fix handling of wakeup_events for multi-entry PEBS

When an event is programmed with attr.wakeup_events=N (N>0), it means
the caller is interested in getting a user level notification after
N samples have been recorded in the kernel sampling buffer.

With precise events on Intel processors, the kernel uses PEBS.
The kernel tries minimize sampling overhead by verifying
if the event configuration is compatible with multi-entry PEBS mode.
If so, the kernel is notified only when the buffer has reached its threshold.
Other PEBS operates in single-entry mode, the kenrel is notified for each
PEBS sample.

The problem is that the current implementation look at frequency
mode and event sample_type but ignores the wakeup_events field. Thus,
it may not be possible to receive a notification after each precise event.

This patch fixes this problem by disabling multi-entry PEBS if wakeup_events
is non-zero.

Signed-off-by: Stephane Eranian <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 8baa441d8000..1539647ea39d 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3185,7 +3185,7 @@ static int intel_pmu_hw_config(struct perf_event *event)
 		return ret;
 
 	if (event->attr.precise_ip) {
-		if (!event->attr.freq) {
+		if (!(event->attr.freq || event->attr.wakeup_events)) {
 			event->hw.flags |= PERF_X86_EVENT_AUTO_RELOAD;
 			if (!(event->attr.sample_type &
 			      ~intel_pmu_large_pebs_flags(event)))