Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751131AbWCNS32 (ORCPT ); Tue, 14 Mar 2006 13:29:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751608AbWCNS32 (ORCPT ); Tue, 14 Mar 2006 13:29:28 -0500 Received: from mail.tv-sign.ru ([213.234.233.51]:29369 "EHLO several.ru") by vger.kernel.org with ESMTP id S1750937AbWCNS31 (ORCPT ); Tue, 14 Mar 2006 13:29:27 -0500 Message-ID: <44170AD3.35031A67@tv-sign.ru> Date: Tue, 14 Mar 2006 21:26:27 +0300 From: Oleg Nesterov X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.2.20 i686) X-Accept-Language: en MIME-Version: 1.0 To: "Eric W. Biederman" Cc: Andrew Morton , linux-kernel@vger.kernel.org, "Paul E. McKenney" , Ingo Molnar , William Irwin , Roland McGrath Subject: Re: [PATCH] task: Make task list manipulations RCU safe. References: <4416FF1F.5DA06CFB@tv-sign.ru> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 800 Lines: 25 "Eric W. Biederman" wrote: > > Oleg Nesterov writes: > > > Some questions. > > > > first_tgid: > > ... > > for (; pos && pid_alive(pos); pos = next_task(pos)) > > > > I think this patch makes this 'pid_alive(pos)' unneeded? > > Close. The problem is that we could have slept with the > count elevated on start before we do rcu_read_lock(). Yes, we could have slept. But (unlike next_tgid) this loop starts from pos=init_task or from pos=find_task_by_pid() and we are doing find_task_by_pid under rcu_read_lock() ? Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/