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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@chello.nl>
AuthorDate: Thu, 19 Mar 2009 20:26:11 +0100
Committer: Ingo Molnar <mingo@elte.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@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20090319194233.195392657@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.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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