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From: tip-bot for Peter Zijlstra <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: alexander.shishkin@linux.intel.com, eranian@google.com,
	tglx@linutronix.de, torvalds@linux-foundation.org,
	linux-kernel@vger.kernel.org, jolsa@redhat.com,
	vincent.weaver@maine.edu, yabinc@google.com, acme@redhat.com,
	mingo@kernel.org, hpa@zytor.com, peterz@infradead.org
Subject: [tip:perf/urgent] perf/ring-buffer: Always use {READ,WRITE}_ONCE() for rb->user_page data
Date: Fri, 24 May 2019 01:09:36 -0700	[thread overview]
Message-ID: <tip-4d839dd9e4356bbacf3eb0ab13a549b83b008c21@git.kernel.org> (raw)
In-Reply-To: <20190517115418.394192145@infradead.org>

Commit-ID:  4d839dd9e4356bbacf3eb0ab13a549b83b008c21
Gitweb:     https://git.kernel.org/tip/4d839dd9e4356bbacf3eb0ab13a549b83b008c21
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 17 May 2019 13:52:33 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 24 May 2019 09:00:11 +0200

perf/ring-buffer: Always use {READ,WRITE}_ONCE() for rb->user_page data

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 <yabinc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.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>
Cc: acme@kernel.org
Cc: mark.rutland@arm.com
Cc: namhyung@kernel.org
Fixes: 7b732a750477 ("perf_counter: new output ABI - part 1")
Link: http://lkml.kernel.org/r/20190517115418.394192145@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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;

  reply	other threads:[~2019-05-24  8:10 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-17 11:52 [PATCH 0/4] perf ring-buffer fixes Peter Zijlstra
2019-05-17 11:52 ` [PATCH 1/4] perf/ring_buffer: Fix exposing a temporarily decreased data_head Peter Zijlstra
2019-05-17 13:05   ` Ingo Molnar
2019-05-17 14:26     ` Peter Zijlstra
2019-05-24  7:01       ` Ingo Molnar
2019-05-24  8:08   ` [tip:perf/urgent] " tip-bot for Yabin Cui
2019-05-17 11:52 ` [PATCH 2/4] perf/ring_buffer: Add ordering to rb->nest increment Peter Zijlstra
2019-05-24  8:08   ` [tip:perf/urgent] " tip-bot for Peter Zijlstra
2019-05-17 11:52 ` [PATCH 3/4] perf/ring-buffer: Always use {READ,WRITE}_ONCE() for rb->user_page data Peter Zijlstra
2019-05-24  8:09   ` tip-bot for Peter Zijlstra [this message]
2019-05-17 11:52 ` [PATCH 4/4] perf/ring-buffer: Use regular variables for nesting Peter Zijlstra
2019-05-24  8:10   ` [tip:perf/urgent] " tip-bot for Peter Zijlstra

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