1 From 8672d3d861e6ab5cc5a62b247391ca9f32a96ffe Mon Sep 17 00:00:00 2001
2 From: Peter Zijlstra <peterz@infradead.org>
3 Date: Fri, 17 May 2019 13:52:33 +0200
4 Subject: perf/ring-buffer: Always use {READ,WRITE}_ONCE() for rb->user_page
7 [ Upstream commit 4d839dd9e4356bbacf3eb0ab13a549b83b008c21 ]
9 We must use {READ,WRITE}_ONCE() on rb->user_page data such that
10 concurrent usage will see whole values. A few key sites were missing
13 Suggested-by: Yabin Cui <yabinc@google.com>
14 Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
15 Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
16 Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
17 Cc: Jiri Olsa <jolsa@redhat.com>
18 Cc: Linus Torvalds <torvalds@linux-foundation.org>
19 Cc: Peter Zijlstra <peterz@infradead.org>
20 Cc: Stephane Eranian <eranian@google.com>
21 Cc: Thomas Gleixner <tglx@linutronix.de>
22 Cc: Vince Weaver <vincent.weaver@maine.edu>
24 Cc: mark.rutland@arm.com
25 Cc: namhyung@kernel.org
26 Fixes: 7b732a750477 ("perf_counter: new output ABI - part 1")
27 Link: http://lkml.kernel.org/r/20190517115418.394192145@infradead.org
28 Signed-off-by: Ingo Molnar <mingo@kernel.org>
29 Signed-off-by: Sasha Levin <sashal@kernel.org>
31 kernel/events/ring_buffer.c | 6 +++---
32 1 file changed, 3 insertions(+), 3 deletions(-)
34 diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
35 index aef2af80a927..f3a69a4f0d57 100644
36 --- a/kernel/events/ring_buffer.c
37 +++ b/kernel/events/ring_buffer.c
38 @@ -101,7 +101,7 @@ static void perf_output_put_handle(struct perf_output_handle *handle)
39 * See perf_output_begin().
41 smp_wmb(); /* B, matches C */
42 - rb->user_page->data_head = head;
43 + WRITE_ONCE(rb->user_page->data_head, head);
46 * We must publish the head before decrementing the nest count,
47 @@ -489,7 +489,7 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
51 - rb->user_page->aux_head = rb->aux_head;
52 + WRITE_ONCE(rb->user_page->aux_head, rb->aux_head);
53 if (rb_need_aux_wakeup(rb))
56 @@ -520,7 +520,7 @@ int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)
60 - rb->user_page->aux_head = rb->aux_head;
61 + WRITE_ONCE(rb->user_page->aux_head, rb->aux_head);
62 if (rb_need_aux_wakeup(rb)) {
63 perf_output_wakeup(handle);
64 handle->wakeup = rb->aux_wakeup + rb->aux_watermark;