From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756213AbYCIRTp (ORCPT ); Sun, 9 Mar 2008 13:19:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752935AbYCIRTg (ORCPT ); Sun, 9 Mar 2008 13:19:36 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:34759 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752170AbYCIRTf (ORCPT ); Sun, 9 Mar 2008 13:19:35 -0400 Date: Sun, 9 Mar 2008 20:23:29 +0300 From: Oleg Nesterov To: Andrew Morton Cc: Ingo Molnar , Pavel Emelyanov , Roland McGrath , linux-kernel@vger.kernel.org Subject: [PATCH 7/6] signals: handle_stop_signal: don't worry about SIGKILL Message-ID: <20080309172329.GA1344@tv-sign.ru> 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org handle_stop_signal() clears SIGNAL_STOP_DEQUEUED when sig == SIGKILL. Remove this nasty special case. It was needed to prevent the race with group stop and exit caused by thread-specific SIGKILL. Now that we use complete_signal() for private signals too this is not needed, complete_signal() will notice SIGKILL and abort the soon-to-begin group stop. Except: the target thread is dead (has PF_EXITING). But in that case we should not just clear SIGNAL_STOP_DEQUEUED and nothing more. We should either kill the whole thread group, or silently ignore the signal. I suspect we are not right wrt zombie leaders, but this is another issue which and should be fixed separately. Note that this check can't abort the group stop if it was already started/finished, this check only adds a subtle side effect if we race with the thread which has already dequeued sig_kernel_stop() signal and temporary released ->siglock. Signed-off-by: Oleg Nesterov --- 25/kernel/signal.c~7_HSS_NO_KILL 2008-03-09 17:48:28.000000000 +0300 +++ 25/kernel/signal.c 2008-03-09 20:21:02.000000000 +0300 @@ -643,12 +643,6 @@ static void handle_stop_signal(int sig, */ signal->flags &= ~SIGNAL_STOP_DEQUEUED; } - } else if (sig == SIGKILL) { - /* - * Make sure that any pending stop signal already dequeued - * is undone by the wakeup for SIGKILL. - */ - signal->flags &= ~SIGNAL_STOP_DEQUEUED; } }