[PATCH 3.13 112/259] perf: Do not allow optimized switch for non-cloned events

[Kamal Mostafa]

3.13.11.6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Olsa <jolsa at redhat.com>

commit 1f9a7268c67f0290837aada443d28fd953ddca90 upstream.

The context check in perf_event_context_sched_out allows
non-cloned context to be part of the optimized schedule
out switch.

This could move non-cloned context into another workload
child. Once this child exits, the context is closed and
leaves all original (parent) events in closed state.

Any other new cloned event will have closed state and not
measure anything. And probably causing other odd bugs.

Signed-off-by: Jiri Olsa <jolsa at kernel.org>
Signed-off-by: Peter Zijlstra <peterz at infradead.org>
Cc: Arnaldo Carvalho de Melo <acme at kernel.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Frederic Weisbecker <fweisbec at gmail.com>
Cc: Namhyung Kim <namhyung at kernel.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Corey Ashford <cjashfor at linux.vnet.ibm.com>
Cc: David Ahern <dsahern at gmail.com>
Cc: Jiri Olsa <jolsa at redhat.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Link: http://lkml.kernel.org/r/1403598026-2310-2-git-send-email-jolsa@kernel.org
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f0a8ac7..f8519d6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2296,7 +2296,7 @@ static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
 	next_parent = rcu_dereference(next_ctx->parent_ctx);
 
 	/* If neither context have a parent context; they cannot be clones. */
-	if (!parent && !next_parent)
+	if (!parent || !next_parent)
 		goto unlock;
 
 	if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
-- 
1.9.1