perf events: Fix swevent hrtimer sampling by keeping track of remaining time when enabling/disabling swevent hrtimers

Make the hrtimer based events work for sysprof.

Whenever a swevent is scheduled out, the hrtimer is canceled.
When it is scheduled back in, the timer is restarted. This
happens every scheduler tick, which means the timer never
expired because it was getting repeatedly restarted over and
over with the same period.

To fix that, save the remaining time when disabling; when
reenabling, use that saved time as the period instead of the
user-specified sampling period.

Also, move the starting and stopping of the hrtimers to helper
functions instead of duplicating the code.

Signed-off-by: Søren Sandmann Pedersen <sandmann@redhat.com>
LKML-Reference: <ye8vdi7mluz.fsf@camel16.daimi.au.dk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 2e6d95f97419..9e7012689a84 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -471,8 +471,8 @@ struct hw_perf_event {
                         unsigned long   event_base;
                         int             idx;
                 };
-                union { /* software */
-                        atomic64_t      count;
+                struct { /* software */
+                        s64             remaining;
                         struct hrtimer  hrtimer;
                 };
         };