Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760141AbXKTQe5 (ORCPT ); Tue, 20 Nov 2007 11:34:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752535AbXKTQeu (ORCPT ); Tue, 20 Nov 2007 11:34:50 -0500 Received: from x346.tv-sign.ru ([89.108.83.215]:34403 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750963AbXKTQet (ORCPT ); Tue, 20 Nov 2007 11:34:49 -0500 Date: Tue, 20 Nov 2007 19:34:57 +0300 From: Oleg Nesterov To: "Eric W. Biederman" Cc: Andrew Morton , Pavel Emelyanov , linux-kernel@vger.kernel.org Subject: [PATCH] proc-remove-races-from-proc_id_readdir-factor-out-tgid-increment Message-ID: <20071120163457.GA13021@tv-sign.ru> References: <20071117181549.GA1415@tv-sign.ru> <20071118142047.GA360@tv-sign.ru> <20071119182937.GA89@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1975 Lines: 57 On 11/19, Eric W. Biederman wrote: > > So to fix the problem this patch modifies next_tgid() to return > both a tgid and the task struct in question. > > A structure is introduced to return these values because it is > slightly cleaner and easier to optimize, and the resulting code > is a little shorter. Nice. Perhaps we can also factor out the incrementing of iter.tgid? Lessens the generated code, and (imho) cleanups the source a little bit. (untested, 2.6.24-rc2-mm1 doesn't boot on my machine) Signed-off-by: Oleg Nesterov --- PT/fs/proc/base.c~ 2007-11-20 19:00:05.000000000 +0300 +++ PT/fs/proc/base.c 2007-11-20 19:06:28.000000000 +0300 @@ -2378,6 +2378,7 @@ static struct tgid_iter next_tgid(struct rcu_read_lock(); retry: iter.task = NULL; + iter.tgid++; pid = find_ge_pid(iter.tgid, ns); if (pid) { iter.tgid = pid_nr_ns(pid, ns); @@ -2394,10 +2395,8 @@ retry: * found doesn't happen to be a thread group leader. * As we don't care in the case of readdir. */ - if (!iter.task || !has_group_leader_pid(iter.task)) { - iter.tgid += 1; + if (!iter.task || !has_group_leader_pid(iter.task)) goto retry; - } get_task_struct(iter.task); } rcu_read_unlock(); @@ -2434,10 +2433,8 @@ int proc_pid_readdir(struct file * filp, ns = filp->f_dentry->d_sb->s_fs_info; iter.task = NULL; - iter.tgid = filp->f_pos - TGID_OFFSET; - for (iter = next_tgid(ns, iter); - iter.task; - iter.tgid += 1, iter = next_tgid(ns, iter)) { + iter.tgid = filp->f_pos - TGID_OFFSET - 1; + while ((iter = next_tgid(ns, iter)).task) { filp->f_pos = iter.tgid + TGID_OFFSET; if (proc_pid_fill_cache(filp, dirent, filldir, iter) < 0) { put_task_struct(iter.task); - 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/