linux-kernel - [tip:perf/pebs] perf, x86: Fix LBR enable/disable vs cpuc->enabled

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Date:	Wed, 10 Mar 2010 13:22:52 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, hpa@...or.com, mingo@...hat.com,
	acme@...radead.org, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:perf/pebs] perf, x86: Fix LBR enable/disable vs cpuc->enabled

Commit-ID:  2df202bf7520eaffcbfb07e45dfa3cfb0aeee2c0
Gitweb:     http://git.kernel.org/tip/2df202bf7520eaffcbfb07e45dfa3cfb0aeee2c0
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Sat, 6 Mar 2010 13:48:54 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 10 Mar 2010 13:23:37 +0100

perf, x86: Fix LBR enable/disable vs cpuc->enabled

We should never call ->enable with the pmu enabled, and we _can_ have
->disable called with the pmu enabled.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Arnaldo Carvalho de Melo <acme@...radead.org>
Cc: paulus@...ba.org
Cc: eranian@...gle.com
Cc: robert.richter@....com
Cc: fweisbec@...il.com
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/kernel/cpu/perf_event_intel_lbr.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index dcec765..0145f99 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -69,7 +69,7 @@ static void intel_pmu_lbr_enable(struct perf_event *event)
 	if (!x86_pmu.lbr_nr)
 		return;
 
-	WARN_ON(cpuc->enabled);
+	WARN_ON_ONCE(cpuc->enabled);
 
 	/*
 	 * Reset the LBR stack if this is the first LBR user or
@@ -93,9 +93,10 @@ static void intel_pmu_lbr_disable(struct perf_event *event)
 		return;
 
 	cpuc->lbr_users--;
-
 	BUG_ON(cpuc->lbr_users < 0);
-	WARN_ON(cpuc->enabled);
+
+	if (cpuc->enabled && !cpuc->lbr_users)
+		__intel_pmu_lbr_disable();
 }
 
 static void intel_pmu_lbr_enable_all(void)
--
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