From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752843AbaFYSo5 (ORCPT ); Wed, 25 Jun 2014 14:44:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18951 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752483AbaFYSoy (ORCPT ); Wed, 25 Jun 2014 14:44:54 -0400 From: Jiri Olsa To: linux-kernel@vger.kernel.org Cc: Jiri Olsa , Arnaldo Carvalho de Melo , Corey Ashford , Frederic Weisbecker , Ingo Molnar , Paul Mackerras , Peter Zijlstra , Jiri Olsa Subject: [PATCH 1/1] perf: Prevent race in PERF_SAMPLE_READ group format sample output Date: Wed, 25 Jun 2014 20:44:35 +0200 Message-Id: <1403721875-15669-2-git-send-email-jolsa@kernel.org> In-Reply-To: <1403721875-15669-1-git-send-email-jolsa@kernel.org> References: <1403721875-15669-1-git-send-email-jolsa@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiri Olsa While iterating siblings in perf_output_read_group we could race with addition and removal of sibling in perf_group_attach and perf_group_detach respective. While in perf_output_read_group we are under active context, so the only sibling_list modification could come via IPI in: perf_install_in_context or perf_remove_from_context Disable interrupts before iterating siblings to prevent this race. Cc: Arnaldo Carvalho de Melo Cc: Corey Ashford Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Paul Mackerras Cc: Peter Zijlstra Signed-off-by: Jiri Olsa --- kernel/events/core.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index a33d9a2b..66649d3 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4509,6 +4509,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, { struct perf_event *leader = event->group_leader, *sub; u64 read_format = event->attr.read_format; + unsigned long flags; u64 values[5]; int n = 0; @@ -4529,6 +4530,15 @@ static void perf_output_read_group(struct perf_output_handle *handle, __output_copy(handle, values, n * sizeof(u64)); + /* + * We are now under active context, so the only sibling_list + * modification could come via IPI in: + * perf_install_in_context and perf_remove_from_context + * + * Disable interrupts to prevent this race. + */ + local_irq_save(flags); + list_for_each_entry(sub, &leader->sibling_list, group_entry) { n = 0; @@ -4542,6 +4552,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, __output_copy(handle, values, n * sizeof(u64)); } + local_irq_restore(flags); } #define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\ -- 1.8.3.1