From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754870AbZBCVvi (ORCPT ); Tue, 3 Feb 2009 16:51:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751699AbZBCVva (ORCPT ); Tue, 3 Feb 2009 16:51:30 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:38859 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751050AbZBCVv3 (ORCPT ); Tue, 3 Feb 2009 16:51:29 -0500 Date: Tue, 3 Feb 2009 22:51:23 +0100 From: Ingo Molnar To: Oleg Nesterov Cc: Steven Rostedt , "Eric W. Biederman" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] ftrace: do_each_pid_task() needs rcu lock Message-ID: <20090203215123.GA12123@elte.hu> References: <20090203193904.GA23695@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090203193904.GA23695@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Oleg Nesterov wrote: > "ftrace: use struct pid" commit 978f3a45d9499c7a447ca7615455cefb63d44165 > converted ftrace_pid_trace to "struct pid*". But we can't use > do_each_pid_task() without rcu_read_lock() even if we know the pid > itself can't go away (it was pinned in ftrace_pid_write). The exiting > task can detach itself from this pid at any moment. > > Signed-off-by: Oleg Nesterov Applied to tip/tracing/urgent (for v2.6.29), thanks Oleg! Ingo