From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754307Ab1AUWNU (ORCPT ); Fri, 21 Jan 2011 17:13:20 -0500 Received: from hera.kernel.org ([140.211.167.34]:58409 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752861Ab1AUWNT (ORCPT ); Fri, 21 Jan 2011 17:13:19 -0500 Date: Fri, 21 Jan 2011 22:12:43 GMT From: tip-bot for Oleg Nesterov Cc: linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, hpa@zytor.com, mingo@redhat.com, oleg@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, oleg@redhat.com, mingo@elte.hu In-Reply-To: <20110121174547.GA8796@redhat.com> References: <20110121174547.GA8796@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] perf: perf_event_exit_task_context: s/rcu_dereference/rcu_dereference_raw/ Message-ID: Git-Commit-ID: 806839b22cbda90176d7f8d421889bddd7826e93 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Fri, 21 Jan 2011 22:12:45 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 806839b22cbda90176d7f8d421889bddd7826e93 Gitweb: http://git.kernel.org/tip/806839b22cbda90176d7f8d421889bddd7826e93 Author: Oleg Nesterov AuthorDate: Fri, 21 Jan 2011 18:45:47 +0100 Committer: Ingo Molnar CommitDate: Fri, 21 Jan 2011 22:08:16 +0100 perf: perf_event_exit_task_context: s/rcu_dereference/rcu_dereference_raw/ In theory, almost every user of task->child->perf_event_ctxp[] is wrong. find_get_context() can install the new context at any moment, we need read_barrier_depends(). dbe08d82ce3967ccdf459f7951d02589cf967300 "perf: Fix find_get_context() vs perf_event_exit_task() race" added rcu_dereference() into perf_event_exit_task_context() to make the precedent, but this makes __rcu_dereference_check() unhappy. Use rcu_dereference_raw() to shut up the warning. Reported-by: Ingo Molnar Signed-off-by: Oleg Nesterov Cc: acme@redhat.com Cc: paulus@samba.org Cc: stern@rowland.harvard.edu Cc: a.p.zijlstra@chello.nl Cc: fweisbec@gmail.com Cc: roland@redhat.com Cc: prasad@linux.vnet.ibm.com Cc: Paul E. McKenney LKML-Reference: <20110121174547.GA8796@redhat.com> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index c5fa717..126a302 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -6136,7 +6136,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) * scheduled, so we are now safe from rescheduling changing * our context. */ - child_ctx = rcu_dereference(child->perf_event_ctxp[ctxn]); + child_ctx = rcu_dereference_raw(child->perf_event_ctxp[ctxn]); task_ctx_sched_out(child_ctx, EVENT_ALL); /*