From c97f473643a9d3e618c0f0426b926bc3a3e23944 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 14 Jan 2016 10:51:03 +0100
Subject: [PATCH] perf: Add more assertions

Try to trigger warnings before races do damage.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6620432491f6..3eaf91b104e9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -263,6 +263,15 @@ static void event_function_call(struct perf_event *event, event_f func, void *da
 		.data = data,
 	};
 
+	if (!event->parent) {
+		/*
+		 * If this is a !child event, we must hold ctx::mutex to
+		 * stabilize the the event->ctx relation. See
+		 * perf_event_ctx_lock().
+		 */
+		lockdep_assert_held(&ctx->mutex);
+	}
+
 	if (!task) {
 		cpu_function_call(event->cpu, event_function, &efs);
 		return;
-- 
2.20.1