From 8a84c69460f82172196e5679316360b53b740c23 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu, 20 May 2010 14:35:15 +0200
Subject: [PATCH] --- yaml --- r: 199121 b: refs/heads/master c:
 0f139300c9057c16b5833a4636b715b104fe0baa h: refs/heads/master i:   199119:
 eaae6ef0379e2f2c8d403006d0d8197b5d21f57e v: v3

---
 [refs]                    |  2 +-
 trunk/kernel/perf_event.c | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 129eab04470f..ea0c985deb14 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1c024eca51fdc965290acf342ae16a476c2189d0
+refs/heads/master: 0f139300c9057c16b5833a4636b715b104fe0baa
diff --git a/trunk/kernel/perf_event.c b/trunk/kernel/perf_event.c
index 3f2cc313ee25..7a932526946f 100644
--- a/trunk/kernel/perf_event.c
+++ b/trunk/kernel/perf_event.c
@@ -4920,6 +4920,13 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
 	int fput_needed = 0;
 	int ret = -EINVAL;
 
+	/*
+	 * Don't allow output of inherited per-task events. This would
+	 * create performance issues due to cross cpu access.
+	 */
+	if (event->cpu == -1 && event->attr.inherit)
+		return -EINVAL;
+
 	if (!output_fd)
 		goto set;
 
@@ -4940,6 +4947,18 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
 	if (event->data)
 		goto out;
 
+	/*
+	 * Don't allow cross-cpu buffers
+	 */
+	if (output_event->cpu != event->cpu)
+		goto out;
+
+	/*
+	 * If its not a per-cpu buffer, it must be the same task.
+	 */
+	if (output_event->cpu == -1 && output_event->ctx != event->ctx)
+		goto out;
+
 	atomic_long_inc(&output_file->f_count);
 
 set: