linux-kernel - [PATCH 2/5] perf: Support disable() after stop() on software events

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Date:	Sat, 12 Jun 2010 09:34:55 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 2/5] perf: Support disable() after stop() on software events

If we call perf_event_stop() on a software event and then the
disable() pmu callback on them after that, we'll call twice
hlist_del_rcu() on the same hlist node and then bring a crash
by dereferencing LIST_POISON2.

Just use hlist_del_init_rcu() instead to fix this problem.

This preparates for new context exclusions.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Cyrill Gorcunov <gorcunov@...il.com>
Cc: Zhang Yanmin <yanmin_zhang@...ux.intel.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/perf_event.c             |    2 +-
 kernel/trace/trace_event_perf.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 95a56ed..c5f2306 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4292,7 +4292,7 @@ static int perf_swevent_enable(struct perf_event *event)
 
 static void perf_swevent_disable(struct perf_event *event)
 {
-	hlist_del_rcu(&event->hlist_entry);
+	hlist_del_init_rcu(&event->hlist_entry);
 }
 
 static void perf_swevent_void(struct perf_event *event)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 4799d70..7bc1f26 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -122,7 +122,7 @@ int perf_trace_enable(struct perf_event *p_event)
 
 void perf_trace_disable(struct perf_event *p_event)
 {
-	hlist_del_rcu(&p_event->hlist_entry);
+	hlist_del_init_rcu(&p_event->hlist_entry);
 }
 
 void perf_trace_destroy(struct perf_event *p_event)
-- 
1.6.2.3

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