Re: perf/tracepoint: another fuzzer generated lockup

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Nov 08, 2013 at 11:36:58PM +0100, Frederic Weisbecker wrote:
> [  237.359091]  [<ffffffff8101a4d1>] perf_callchain_kernel+0x51/0x70
> [  237.365155]  [<ffffffff8111fec6>] perf_callchain+0x256/0x2c0
> [  237.370783]  [<ffffffff8111bb5b>] perf_prepare_sample+0x27b/0x300
> [  237.376849]  [<ffffffff810bc1ea>] ? __rcu_is_watching+0x1a/0x30
> [  237.382736]  [<ffffffff8111bd2c>] __perf_event_overflow+0x14c/0x310
> [  237.388973]  [<ffffffff8111bcd9>] ? __perf_event_overflow+0xf9/0x310
> [  237.395291]  [<ffffffff8109aa6d>] ? trace_hardirqs_off+0xd/0x10
> [  237.401186]  [<ffffffff815c8753>] ? _raw_spin_unlock_irqrestore+0x53/0x90
> [  237.407941]  [<ffffffff81061b46>] ? do_send_sig_info+0x66/0x90
> [  237.413744]  [<ffffffff8111c0f9>] perf_swevent_overflow+0xa9/0xc0
> [  237.419808]  [<ffffffff8111c16f>] perf_swevent_event+0x5f/0x80
> [  237.425610]  [<ffffffff8111c2b8>] perf_tp_event+0x128/0x420
> [  237.431154]  [<ffffffff81008108>] ? smp_trace_irq_work_interrupt+0x98/0x2a0
> [  237.438085]  [<ffffffff815c83b5>] ? _raw_read_unlock+0x35/0x60
> [  237.443887]  [<ffffffff81003fe7>] perf_trace_x86_irq_vector+0xc7/0xe0
> [  237.450295]  [<ffffffff81008108>] ? smp_trace_irq_work_interrupt+0x98/0x2a0
> [  237.457226]  [<ffffffff81008108>] smp_trace_irq_work_interrupt+0x98/0x2a0
> [  237.463983]  [<ffffffff815cb132>] trace_irq_work_interrupt+0x72/0x80
> [  237.470303]  [<ffffffff815c8fb7>] ? retint_restore_args+0x13/0x13
> [  237.476366]  [<ffffffff815c877a>] ? _raw_spin_unlock_irqrestore+0x7a/0x90
> [  237.483117]  [<ffffffff810c101b>] rcu_process_callbacks+0x1db/0x530
> [  237.489360]  [<ffffffff8105381d>] __do_softirq+0xdd/0x490
> [  237.494728]  [<ffffffff81053fe6>] irq_exit+0x96/0xc0
> [  237.499668]  [<ffffffff815cbc3a>] smp_trace_apic_timer_interrupt+0x5a/0x2b4
> [  237.506596]  [<ffffffff815ca7b2>] trace_apic_timer_interrupt+0x72/0x80

Cute.. so what appears to happen is that:

1) we trace irq_work_exit
2) we generate event
3) event needs to deliver signal
4) we queue irq_work to send signal
5) goto 1

Does something like this solve it?

---
 kernel/events/core.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4dc078d18929..a3ad40f347c4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5289,6 +5289,16 @@ static void perf_log_throttle(struct perf_event *event, int enable)
 	perf_output_end(&handle);
 }
 
+static inline void perf_pending(struct perf_event *event)
+{
+	if (in_nmi()) {
+		irq_work_pending(&event->pending);
+		return;
+	}
+
+	perf_pending_event(&event->pending);
+}
+
 /*
  * Generic event overflow handling, sampling.
  */
@@ -5345,7 +5355,7 @@ static int __perf_event_overflow(struct perf_event *event,
 		ret = 1;
 		event->pending_kill = POLL_HUP;
 		event->pending_disable = 1;
-		irq_work_queue(&event->pending);
+		perf_pending(event);
 	}
 
 	if (event->overflow_handler)
@@ -5355,7 +5365,7 @@ static int __perf_event_overflow(struct perf_event *event,
 
 	if (event->fasync && event->pending_kill) {
 		event->pending_wakeup = 1;
-		irq_work_queue(&event->pending);
+		perf_pending(event);
 	}
 
 	return ret;