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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-02-15 22:26:07 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-02-24 14:54:40 -0800
commite922e3380b4b02babff5feade9b1428945429a69 (patch)
tree9841d7e295a6c5f7cea3a8f3031f70b79ff47147 /kernel
parentd68e33163fe5801ce882824968fd4ec261d47af0 (diff)
perf: Fix throttle logic
commit 4fe757dd48a9e95e1a071291f15dda5421dacb66 upstream. 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> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/perf_event.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 64668bd5d81b..785c66a2088a 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -652,6 +652,10 @@ retry:
raw_spin_unlock_irq(&ctx->lock);
}
+#define MAX_INTERRUPTS (~0ULL)
+
+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,
@@ -662,6 +666,17 @@ event_sched_in(struct perf_event *event,
event->state = PERF_EVENT_STATE_ACTIVE;
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:
*/
@@ -1469,10 +1484,6 @@ void __perf_event_task_sched_in(struct task_struct *task)
}
}
-#define MAX_INTERRUPTS (~0ULL)
-
-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;