From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed, 3 Aug 2011 11:49:31 +0000 (+0200)
Subject: perf: overflow/perf_count_sw_cpu_clock crashes recent kernels
X-Git-Tag: v2.6.32.44~2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=bb30b1915be745fa2ef499580ac5a74e8e50e7b9;p=thirdparty%2Fkernel%2Fstable.git

perf: overflow/perf_count_sw_cpu_clock crashes recent kernels

The below patch is for -stable only, upstream has a much larger patch
that contains the below hunk in commit a8b0ca17b80e92faab46ee7179ba9e99ccb61233

Vince found that under certain circumstances software event overflows
go wrong and deadlock. Avoid trying to delete a timer from the timer
callback.

Reported-by: Vince Weaver <vweaver1@eecs.utk.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index fc5ab8e444f03..37ebc14c9ce48 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3694,12 +3694,8 @@ static int __perf_event_overflow(struct perf_event *event, int nmi,
 	if (events && atomic_dec_and_test(&event->event_limit)) {
 		ret = 1;
 		event->pending_kill = POLL_HUP;
-		if (nmi) {
-			event->pending_disable = 1;
-			perf_pending_queue(&event->pending,
-					   perf_pending_event);
-		} else
-			perf_event_disable(event);
+		event->pending_disable = 1;
+		perf_pending_queue(&event->pending, perf_pending_event);
 	}
 
 	perf_event_output(event, nmi, data, regs);