Messages in this thread Patch in this message | | | Date | Mon, 30 Nov 2015 12:56:15 +0100 | From | Peter Zijlstra <> | Subject | Re: deadlock in perf_ioctl |
| |
On Mon, Nov 30, 2015 at 10:20:49AM +0100, Dmitry Vyukov wrote: > ============================================= > [ INFO: possible recursive locking detected ] > 4.4.0-rc1+ #129 Not tainted > --------------------------------------------- > a.out/6283 is trying to acquire lock: > (&ctx->lock){-.....}, at: [<ffffffff815072ce>] > __perf_event_period+0x8e/0x4b0 kernel/events/core.c:4156 > > but task is already holding lock: > (&ctx->lock){-.....}, at: [< inline >] perf_event_period > kernel/events/core.c:4212 > (&ctx->lock){-.....}, at: [< inline >] _perf_ioctl > kernel/events/core.c:4266 > (&ctx->lock){-.....}, at: [<ffffffff8152331c>] perf_ioctl+0x7bc/0xcc0 > kernel/events/core.c:4320 >
Indeed so. I suppose the below should fix this, I'll go try in a bit.
--- Subject: perf: Fix PERF_EVENT_IOC_PERIOD deadlock
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> Fixes: c7999c6f3fed ("perf: Fix PERF_EVENT_IOC_PERIOD migration race") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.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 36babfd20648..a991e12e4d0d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4216,7 +4216,14 @@ 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;
| |