From: Peter Zijlstra <[email protected]>
[ Upstream commit 4d839dd9e4356bbacf3eb0ab13a549b83b008c21 ]
We must use {READ,WRITE}_ONCE() on rb->user_page data such that
concurrent usage will see whole values. A few key sites were missing
this.
Suggested-by: Yabin Cui <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Fixes: 7b732a750477 ("perf_counter: new output ABI - part 1")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
kernel/events/ring_buffer.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 4b5f8d932400..7a0c73e4b3eb 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -100,7 +100,7 @@ again:
* See perf_output_begin().
*/
smp_wmb(); /* B, matches C */
- rb->user_page->data_head = head;
+ WRITE_ONCE(rb->user_page->data_head, head);
/*
* We must publish the head before decrementing the nest count,
@@ -496,7 +496,7 @@ void perf_aux_output_end(struct perf_output_handle *handle,
unsigned long size)
perf_event_aux_event(handle->event, aux_head, size,
handle->aux_flags);
- rb->user_page->aux_head = rb->aux_head;
+ WRITE_ONCE(rb->user_page->aux_head, rb->aux_head);
if (rb_need_aux_wakeup(rb))
wakeup = true;
@@ -528,7 +528,7 @@ int perf_aux_output_skip(struct perf_output_handle *handle,
unsigned long size)
rb->aux_head += size;
- rb->user_page->aux_head = rb->aux_head;
+ WRITE_ONCE(rb->user_page->aux_head, rb->aux_head);
if (rb_need_aux_wakeup(rb)) {
perf_output_wakeup(handle);
handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
--
2.20.1
