Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753772AbYHCRqE (ORCPT ); Sun, 3 Aug 2008 13:46:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756858AbYHCRpq (ORCPT ); Sun, 3 Aug 2008 13:45:46 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:33166 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756682AbYHCRpp (ORCPT ); Sun, 3 Aug 2008 13:45:45 -0400 Date: Sun, 3 Aug 2008 21:49:10 +0400 From: Oleg Nesterov To: Andrew Morton Cc: Mark McLoughlin , Michael Kerrisk , Roland McGrath , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH 1/3] posix-timers: don't switch to ->group_leader if ->it_process dies Message-ID: <20080803174910.GA4913@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 Content-Length: 2108 Lines: 58 (textually depends on posix-timers-fix-posix_timer_event-vs-dequeue_signal-race.patch) posix_timer_event() drops SIGEV_THREAD_ID and switches to ->group_leader if send_sigqueue() fails. This is not very useful and doesn't work reliably. send_sigqueue() can only fail if ->it_process is dead. But it can die before it dequeues the SI_TIMER signal, in that case the timer stops anyway. Remove this code. I guess it was needed a long ago to ensure that the timer is not destroyed when when its creator thread dies. Q: perhaps it makes sense to change sys_timer_settime() to return an error if ->it_process is dead? Signed-off-by: Oleg Nesterov --- 26-rc2/kernel/posix-timers.c~1_DONT_RESEND 2008-07-23 20:24:05.000000000 +0400 +++ 26-rc2/kernel/posix-timers.c 2008-08-03 20:25:41.000000000 +0400 @@ -298,6 +298,7 @@ void do_schedule_next_timer(struct sigin int posix_timer_event(struct k_itimer *timr, int si_private) { + int shared, ret; /* * FIXME: if ->sigq is queued we can race with * dequeue_signal()->do_schedule_next_timer(). @@ -316,20 +317,10 @@ int posix_timer_event(struct k_itimer *t timr->sigq->info.si_tid = timr->it_id; timr->sigq->info.si_value = timr->it_sigev_value; - if (timr->it_sigev_notify & SIGEV_THREAD_ID) { - struct task_struct *leader; - int ret = send_sigqueue(timr->sigq, timr->it_process, 0); - - if (likely(ret >= 0)) - return ret; - - timr->it_sigev_notify = SIGEV_SIGNAL; - leader = timr->it_process->group_leader; - put_task_struct(timr->it_process); - timr->it_process = leader; - } - - return send_sigqueue(timr->sigq, timr->it_process, 1); + shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID); + ret = send_sigqueue(timr->sigq, timr->it_process, shared); + /* If we failed to send the signal the timer stops. */ + return ret > 0; } EXPORT_SYMBOL_GPL(posix_timer_event); -- 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/