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