linux-kernel - [tip:perfcounters/urgent] perf

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Date:	Thu, 13 Aug 2009 11:00:54 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org, hpa@...or.com,
	mingo@...hat.com, eranian@...glemail.com, cjashfor@...ibm.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:perfcounters/urgent] perf_counter: Fix an ipi-deadlock

Commit-ID:  970892a9031a5dc7217bd394fb9d89fa75a4a7bc
Gitweb:     http://git.kernel.org/tip/970892a9031a5dc7217bd394fb9d89fa75a4a7bc
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Thu, 13 Aug 2009 11:47:54 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 13 Aug 2009 12:58:05 +0200

perf_counter: Fix an ipi-deadlock

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@...llo.nl>
Cc: Corey J Ashford <cjashfor@...ibm.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: stephane eranian <eranian@...glemail.com>
LKML-Reference: <20090813103655.244097721@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/perf_counter.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index b8c6b97..3f841be 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -307,6 +307,10 @@ counter_sched_out(struct perf_counter *counter,
 		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;
@@ -2343,7 +2347,7 @@ static void perf_pending_counter(struct perf_pending_entry *entry)
 
 	if (counter->pending_disable) {
 		counter->pending_disable = 0;
-		perf_counter_disable(counter);
+		__perf_counter_disable(counter);
 	}
 
 	if (counter->pending_wakeup) {
--
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