[PATCH 2/2] perf_counter: Fix an ipi-deadlock

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: perf-fix-pending.patch --]
[-- Type: text/plain, Size: 1369 bytes --]

perf_pending_counter() is called from IRQ context and will call
perf_counter_disable(), however perf_counter_disable() uses
smp_call_function_single() which doesn't fancy being used with IRQs
disabled due to IPI deadlocks.

Fix this by making it use the local __perf_counter_disable() call and
teaching the counter_sched_out() code about pending disables as well.

This should cover the case where a counter migrates before the pending
queue gets processed.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 kernel/perf_counter.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -307,6 +307,10 @@ counter_sched_out(struct perf_counter *c
 		return;
 
 	counter->state = PERF_COUNTER_STATE_INACTIVE;
+	if (counter->pending_disable) {
+		counter->pending_disable = 0;
+		counter->state = PERF_COUNTER_STATE_OFF;
+	}
 	counter->tstamp_stopped = ctx->time;
 	counter->pmu->disable(counter);
 	counter->oncpu = -1;
@@ -2315,7 +2319,7 @@ static void perf_pending_counter(struct 
 
 	if (counter->pending_disable) {
 		counter->pending_disable = 0;
-		perf_counter_disable(counter);
+		__perf_counter_disable(counter);
 	}
 
 	if (counter->pending_wakeup) {

--