From 4d839dd9e4356bbacf3eb0ab13a549b83b008c21 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 17 May 2019 13:52:33 +0200 Subject: 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver 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 --- kernel/events/ring_buffer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') 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; -- cgit v1.2.3-58-ga151