From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 642c2d671ceff40e9453203ea0c66e991e11e249 ]
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@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Cc: Alexander Potapenko glider@google.com Cc: Arnaldo Carvalho de Melo acme@kernel.org Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Eric Dumazet edumazet@google.com Cc: Jiri Olsa jolsa@redhat.com Cc: Kostya Serebryany kcc@google.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Sasha Levin sasha.levin@oracle.com Cc: Stephane Eranian eranian@google.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Vince Weaver vincent.weaver@maine.edu Fixes: c7999c6f3fed ("perf: Fix PERF_EVENT_IOC_PERIOD migration race") Link: http://lkml.kernel.org/r/20151130115615.GJ17308@twins.programming.kicks-ass.... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 1f08f691de59..7b2f9d432fe7 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3929,7 +3929,14 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg) 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;