[tip:perf/core] perf: Ensure we call add_event_to_ctx() with the right locks held

tip-bot for Peter Zijlstra
2010-09-10T14:33:12Z

Commit-ID: cee010ec5211b96f33c5c2208f5c14ebb04b634a
Gitweb: http://git.kernel.org/tip/cee010ec5211b96f33c5c2208f5c14ebb04b634a
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 10 Sep 2010 12:51:54 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 10 Sep 2010 16:24:33 +0200

perf: Ensure we call add_event_to_ctx() with the right locks held

Even though we call it from the inherit path, where the child is
not yet accessible, we need to hold ctx->lock, add_event_to_ctx()
assumes IRQs are disabled.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/perf_event.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index eaf1c5d..f395fb4 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5913,6 +5913,7 @@ inherit_event(struct perf_event *parent_event,
struct perf_event_context *child_ctx)
{
struct perf_event *child_event;
+ unsigned long flags;

/*
* Instead of creating recursive hierarchies of events,
@@ -5957,7 +5958,9 @@ inherit_event(struct perf_event *parent_event,
/*
* Link it up in the child's context:
*/
+ raw_spin_lock_irqsave(&child_ctx->lock, flags);
add_event_to_ctx(child_event, child_ctx);
+ raw_spin_unlock_irqrestore(&child_ctx->lock, flags);

/*
* Get a reference to the parent filp - we will fput it