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>

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 4b5f8d9..7a0c73e 100644 (file)
--- 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;