linux-kernel - [54/55] perf: overflow/perf_count_sw_cpu

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Date:	Fri, 05 Aug 2011 17:02:24 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Greg KH <greg@...ah.com>
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Vince Weaver <vweaver1@...s.utk.edu>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [54/55] perf: overflow/perf_count_sw_cpu_clock crashes recent kernels

2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Peter Zijlstra <a.p.zijlstra@...llo.nl>

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@...s.utk.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/perf_event.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3694,12 +3694,8 @@ static int __perf_event_overflow(struct
 	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);


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