linux-kernel - [PATCH] perf_events: fix validate

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Message-ID: <4b0bdf36.1818d00a.07cc.25ae@mx.google.com>
Date:	Tue, 24 Nov 2009 05:27:18 -0800 (PST)
From:	Stephane Eranian <eranian@...gle.com>
To:	linux-kernel@...r.kernel.org
Cc:	peterz@...radead.org, mingo@...e.hu, paulus@...ba.org,
	perfmon2-devel@...ts.sourceforge.net, eranian@...gle.com,
	eranian@...il.com
Subject: [PATCH] perf_events: fix validate_event bug

	The validate_event() was failing on valid event
	combinations. The function was assuming that if
	x86_schedule_event() returned 0, it meant error.
	But x86_schedule_event() returns the counter index
	and 0 is a perfectly valid value. An error is returned
	if the function returns a negative value.

	Furthermore, validate_event() was also failing for
	event groups because the event->pmu was not set until
	after hw_perf_event_init().
	
	Signed-off-by: Stephane Eranian <eranian@...gle.com>
--
 arch/x86/kernel/cpu/perf_event.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index bd87430..c1bbed1 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2229,10 +2229,10 @@ validate_event(struct cpu_hw_events *cpuc, struct perf_event *event)
 {
 	struct hw_perf_event fake_event = event->hw;
 
-	if (event->pmu != &pmu)
+	if (event->pmu && event->pmu != &pmu)
 		return 0;
 
-	return x86_schedule_event(cpuc, &fake_event);
+	return x86_schedule_event(cpuc, &fake_event) >= 0;
 }
 
 static int validate_group(struct perf_event *event)
--
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