From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753923Ab2FMOM6 (ORCPT ); Wed, 13 Jun 2012 10:12:58 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:62244 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751540Ab2FMOM4 (ORCPT ); Wed, 13 Jun 2012 10:12:56 -0400 Date: Wed, 13 Jun 2012 16:12:52 +0200 From: Stephane Eranian To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@elte.hu, jolsa@redhat.com Subject: [PATCH] perf: fix ordering in perf_output_sample() Message-ID: <20120613141252.GA1417@quad> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It seems like the merge of commits a7ac67ea and bce38cd5 caused an ordering problem in perf_output_sample(). The watermark check must be done at the very end of the function and not in the middle of writing data to the buffer. Signed-off-by: Stephane Eranian --- diff --git a/kernel/events/core.c b/kernel/events/core.c index f85c015..721ba28 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3979,20 +3979,6 @@ void perf_output_sample(struct perf_output_handle *handle, } } - if (!event->attr.watermark) { - int wakeup_events = event->attr.wakeup_events; - - if (wakeup_events) { - struct ring_buffer *rb = handle->rb; - int events = local_inc_return(&rb->events); - - if (events >= wakeup_events) { - local_sub(wakeup_events, &rb->events); - local_inc(&rb->wakeup); - } - } - } - if (sample_type & PERF_SAMPLE_BRANCH_STACK) { if (data->br_stack) { size_t size; @@ -4010,6 +3996,20 @@ void perf_output_sample(struct perf_output_handle *handle, perf_output_put(handle, nr); } } + + if (!event->attr.watermark) { + int wakeup_events = event->attr.wakeup_events; + + if (wakeup_events) { + struct ring_buffer *rb = handle->rb; + int events = local_inc_return(&rb->events); + + if (events >= wakeup_events) { + local_sub(wakeup_events, &rb->events); + local_inc(&rb->wakeup); + } + } + } } void perf_prepare_sample(struct perf_event_header *header,