From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755886Ab0CQTac (ORCPT ); Wed, 17 Mar 2010 15:30:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2756 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755748Ab0CQTaZ (ORCPT ); Wed, 17 Mar 2010 15:30:25 -0400 Date: Wed, 17 Mar 2010 20:29:01 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Roland McGrath , Veaceslav Falico , linux-kernel@vger.kernel.org Subject: [PATCH 4/4] exit: avoid sig->count in __exit_signal() to detect the group-dead case Message-ID: <20100317192901.GA2109@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Change __exit_signal() to check thread_group_leader() instead of atomic_dec_and_test(&sig->count). This must be equivalent, the group leader must be released only after all other threads have exited and passed __exit_signal(). >>From now sig->count is not actually used, except in fs/proc for get_nr_threads/etc. Signed-off-by: Oleg Nesterov --- --- 34-rc1/kernel/exit.c~4_EXIT_SIGNAL 2010-03-17 19:37:18.000000000 +0100 +++ 34-rc1/kernel/exit.c 2010-03-17 20:05:38.000000000 +0100 @@ -89,11 +89,12 @@ static void __exit_signal(struct task_st rcu_read_lock_held() || lockdep_is_held(&tasklist_lock)); spin_lock(&sighand->siglock); + atomic_dec(&sig->count); posix_cpu_timers_exit(tsk); - if (atomic_dec_and_test(&sig->count)) + if (thread_group_leader(tsk)) { posix_cpu_timers_exit_group(tsk); - else { + } else { /* * If there is any task waiting for the group exit * then notify it: