releases/4.19.54/perf-ring-buffer-always-use-read-write-_once-for-rb-.patch

   1 From c9aaa2b9874868e372a8e3b1ede9140e00cdf4fb 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
   5  data
   6
   7 [ Upstream commit 4d839dd9e4356bbacf3eb0ab13a549b83b008c21 ]
   8
   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
  11 this.
  12
  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>
  23 Cc: acme@kernel.org
  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>
  30 ---
  31  kernel/events/ring_buffer.c | 6 +++---
  32  1 file changed, 3 insertions(+), 3 deletions(-)
  33
  34 diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
  35 index d32b9375ec0e..12f351b253bb 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().
  40          */
  41         smp_wmb(); /* B, matches C */
  42 -       rb->user_page->data_head = head;
  43 +       WRITE_ONCE(rb->user_page->data_head, head);
  44
  45         /*
  46          * We must publish the head before decrementing the nest count,
  47 @@ -490,7 +490,7 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
  48                                      handle->aux_flags);
  49         }
  50
  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))
  54                 wakeup = true;
  55
  56 @@ -522,7 +522,7 @@ int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)
  57
  58         rb->aux_head += size;
  59
  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;
  65 --
  66 2.20.1
  67