[RFC][PATCH 01/11] perf_counter: fix uninitialized usage of event_list

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: perf_swcounter_fix-init.patch --]
[-- Type: text/plain, Size: 1346 bytes --]

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>
---
 kernel/perf_counter.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -1506,7 +1506,7 @@ static void perf_swcounter_ctx_event(str
 {
 	struct perf_counter *counter;
 
-	if (list_empty(&ctx->event_list))
+	if (!ctx->is_active || list_empty(&ctx->event_list))
 		return;
 
 	rcu_read_lock();
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

--