linux-kernel - [tip:perfcounters/core] perf_counter: fix uninitialized usage of event

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Date:	Fri, 20 Mar 2009 10:24:50 GMT
From:	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, rostedt@...dmis.org, a.p.zijlstra@...llo.nl,
	tglx@...utronix.de, mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: fix uninitialized usage of event_list

Commit-ID:  50d8b58c48c7acb4f4ed80c24593ffe2a9c7d1ce
Gitweb:     http://git.kernel.org/tip/50d8b58c48c7acb4f4ed80c24593ffe2a9c7d1ce
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Thu, 19 Mar 2009 20:26:11 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Fri, 20 Mar 2009 11:15:11 +0100

perf_counter: fix uninitialized usage of event_list

Impact: fix boot crash

When doing the generic context switch event I ran into some early
boot hangs, which were caused by inf func recursion (event, fault,
event, fault).

I eventually tracked it down to event_list not being initialized
at the time of the first event. Fix this.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
LKML-Reference: <20090319194233.195392657@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 include/linux/init_task.h |    2 ++
 kernel/perf_counter.c     |    2 +-
 2 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 219748d..ca226a9 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -124,6 +124,8 @@ extern struct cred init_cred;
 # define INIT_PERF_COUNTERS(tsk)					\
 	.perf_counter_ctx.counter_list =				\
 		LIST_HEAD_INIT(tsk.perf_counter_ctx.counter_list),	\
+	.perf_counter_ctx.event_list =					\
+		LIST_HEAD_INIT(tsk.perf_counter_ctx.event_list),	\
 	.perf_counter_ctx.lock =					\
 		__SPIN_LOCK_UNLOCKED(tsk.perf_counter_ctx.lock),
 #else
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index b39456a..4c4e9eb 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1506,7 +1506,7 @@ static void perf_swcounter_ctx_event(struct perf_counter_context *ctx,
 {
 	struct perf_counter *counter;
 
-	if (list_empty(&ctx->event_list))
+	if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
 		return;
 
 	rcu_read_lock();
--
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