[tip:perf/core] perf: Fix perf_event_init_context()

[tip-bot for Peter Zijlstra <tipbot@zytor.com>]

Commit-ID:  ffb4ef21ac4308c2e738e6f83b6741bbc9b4fa3b
Gitweb:     http://git.kernel.org/tip/ffb4ef21ac4308c2e738e6f83b6741bbc9b4fa3b
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 5 May 2014 19:12:20 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 7 May 2014 11:33:15 +0200

perf: Fix perf_event_init_context()

perf_pin_task_context() can return NULL but perf_event_init_context()
assumes it will not, correct this.

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Link: http://lkml.kernel.org/r/20140505171428.GU26782@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index ea899e2..7123284 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7729,6 +7729,8 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
 	 * swapped under us.
 	 */
 	parent_ctx = perf_pin_task_context(parent, ctxn);
+	if (!parent_ctx)
+		return 0;
 
 	/*
 	 * No need to check if parent_ctx != NULL here; since we saw