path: root/kernel
diff options
authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-02-15 22:26:07 +0100
committerIngo Molnar <mingo@elte.hu>2011-02-16 13:25:29 +0100
commit4fe757dd48a9e95e1a071291f15dda5421dacb66 (patch)
tree9981eaf986d477d096cdb0388e0f95a80eeb2c38 /kernel
parent7d44ec193d95416d1342cdd86392a1eeb7461186 (diff)
perf: Fix throttle logic
It was possible to call pmu::start() on an already running event. In particular this lead so some wreckage as the hrtimer events would re-initialize active timers. This was due to throttled events being activated again by scheduling. Scheduling in a context would add and force start events, resulting in running events with a possible throttle status. The next tick to hit that task will then try to unthrottle the event and call ->start() on an already running event. Reported-by: Jeff Moyer <jmoyer@redhat.com> Cc: <stable@kernel.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
1 files changed, 15 insertions, 4 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 999835b6112b..656222fcf767 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -782,6 +782,10 @@ retry:
+static void perf_log_throttle(struct perf_event *event, int enable);
static int
event_sched_in(struct perf_event *event,
struct perf_cpu_context *cpuctx,
@@ -794,6 +798,17 @@ event_sched_in(struct perf_event *event,
event->oncpu = smp_processor_id();
+ /*
+ * Unthrottle events, since we scheduled we might have missed several
+ * ticks already, also for a heavily scheduling task there is little
+ * guarantee it'll get a tick in a timely manner.
+ */
+ if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
+ perf_log_throttle(event, 1);
+ event->hw.interrupts = 0;
+ }
* The new state must be visible before we turn it on in the hardware:
@@ -1596,10 +1611,6 @@ void __perf_event_task_sched_in(struct task_struct *task)
-static void perf_log_throttle(struct perf_event *event, int enable);
static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
u64 frequency = event->attr.sample_freq;