[PATCH 4.2.y-ckt 144/305] perf: Fix PERF_EVENT_IOC_PERIOD deadlock

From: Kamal Mostafa
Date: Fri Jan 15 2016 - 19:50:05 EST


4.2.8-ckt2 -stable review patch. If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

commit 642c2d671ceff40e9453203ea0c66e991e11e249 upstream.

Dmitry reported a fairly silly recursive lock deadlock for
PERF_EVENT_IOC_PERIOD, fix this by explicitly doing the inactive part of
__perf_event_period() instead of calling that function.

Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kostya Serebryany <kcc@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Fixes: c7999c6f3fed ("perf: Fix PERF_EVENT_IOC_PERIOD migration race")
Link: http://lkml.kernel.org/r/20151130115615.GJ17308@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
kernel/events/core.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c06fa66..d86859f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4034,7 +4034,14 @@ retry:
goto retry;
}

- __perf_event_period(&pe);
+ if (event->attr.freq) {
+ event->attr.sample_freq = value;
+ } else {
+ event->attr.sample_period = value;
+ event->hw.sample_period = value;
+ }
+
+ local64_set(&event->hw.period_left, 0);
raw_spin_unlock_irq(&ctx->lock);

return 0;
--
1.9.1