Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964976AbWIIWUR (ORCPT ); Sat, 9 Sep 2006 18:20:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964975AbWIIWUQ (ORCPT ); Sat, 9 Sep 2006 18:20:16 -0400 Received: from taganka54-host.corbina.net ([213.234.233.54]:18900 "EHLO mail.screens.ru") by vger.kernel.org with ESMTP id S964973AbWIIWUO (ORCPT ); Sat, 9 Sep 2006 18:20:14 -0400 Date: Sun, 10 Sep 2006 02:20:02 +0400 From: Oleg Nesterov To: Andrew Morton , "Paul E. McKenney" Cc: "Eric W. Biederman" , Jean Delvare , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org Subject: [PATCH 3/3] proc: drop tasklist lock in task_state() Message-ID: <20060909222002.GA152@oleg> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1748 Lines: 51 task_state() needs tasklist_lock to protect ->parent/->real_parent. However task->parent points to nowhere only when the actions below happen in order 1) release_task(task) 2) release_task(task->parent) 3) a grace period passed But 3) implies that the memory ops from 1) should be finished, so pid_alive() can't be true in such a case. Otherwise, we don't care if ->parent/->real_parent changes under us. Signed-off-by: Oleg Nesterov --- rc6-mm1/fs/proc/array.c~3_tstate 2006-09-09 22:48:30.000000000 +0400 +++ rc6-mm1/fs/proc/array.c 2006-09-10 01:15:10.000000000 +0400 @@ -162,7 +162,7 @@ static inline char * task_state(struct t int g; struct fdtable *fdt = NULL; - read_lock(&tasklist_lock); + rcu_read_lock(); buffer += sprintf(buffer, "State:\t%s\n" "SleepAVG:\t%lu%%\n" @@ -174,14 +174,13 @@ static inline char * task_state(struct t "Gid:\t%d\t%d\t%d\t%d\n", get_task_state(p), (p->sleep_avg/1024)*100/(1020000000/1024), - p->tgid, - p->pid, pid_alive(p) ? p->group_leader->real_parent->tgid : 0, - pid_alive(p) && p->ptrace ? p->parent->pid : 0, + p->tgid, p->pid, + pid_alive(p) ? rcu_dereference(p->real_parent)->tgid : 0, + pid_alive(p) && p->ptrace ? rcu_dereference(p->parent)->pid : 0, p->uid, p->euid, p->suid, p->fsuid, p->gid, p->egid, p->sgid, p->fsgid); - read_unlock(&tasklist_lock); + task_lock(p); - rcu_read_lock(); if (p->files) fdt = files_fdtable(p->files); buffer += sprintf(buffer, - 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/