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>
Orig-LKML-Reference: <20090319194233.195392657@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 219748d00262e8ac37a863495dee9a5d80c362f2..ca226a91abeeadeb2e66da5497c226daee4b031a 100644 (file)
--- 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 b39456ad74a1450b7f2c66bccbb18c8e5e1a60ca..4c4e9eb37ab0c0ee1937f6c00da5334c00ea3250 100644 (file)
--- 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();