From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755093Ab1IFPkB (ORCPT ); Tue, 6 Sep 2011 11:40:01 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:59390 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755029Ab1IFPj4 (ORCPT ); Tue, 6 Sep 2011 11:39:56 -0400 Subject: Re: [PATCH 4/4] posix-timers: turn it_signal into it_valid flag From: Eric Dumazet To: Oleg Nesterov Cc: Andi Kleen , Thomas Gleixner , Andi Kleen , LKML , Andrew Morton In-Reply-To: <20110906145124.GA15390@redhat.com> References: <1314661157-22173-1-git-send-email-andi@firstfloor.org> <1314661157-22173-4-git-send-email-andi@firstfloor.org> <20110904165658.GA23948@redhat.com> <20110904202907.GA3404@redhat.com> <20110906031411.GA24024@alboin.amr.corp.intel.com> <20110906145124.GA15390@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 06 Sep 2011 17:39:56 +0200 Message-ID: <1315323596.2899.6.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le mardi 06 septembre 2011 à 16:51 +0200, Oleg Nesterov a écrit : > On 09/05, Andi Kleen wrote: > > > > > I forgot everything I knew about ->it_requeue_pending logic, but it > > > seems to me that do_schedule_next_timer()->lock_timer() can find and > > > lock successfully the wrong timer. Another thread can do timer_delete() > > > and then re-create the timer with the same id. > > > > Do you mean after my patches or even before? > > Ah, sorry for confusion. > > Before. And after. IOW, I think this has nothing to do with your patches. > Hmm, you mean following patch is needed ? Before release of timer id to idr pool, we should make sure do_schedule_next_timer() wont be called, or it could find another timer reusing the just released id. diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c index 4556182..4369747 100644 --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -502,14 +502,14 @@ static void k_itimer_rcu_free(struct rcu_head *head) #define IT_ID_NOT_SET 0 static void release_posix_timer(struct k_itimer *tmr, int it_id_set) { + put_pid(tmr->it_pid); + sigqueue_free(tmr->sigq); if (it_id_set) { unsigned long flags; spin_lock_irqsave(&idr_lock, flags); idr_remove(&posix_timers_id, tmr->it_id); spin_unlock_irqrestore(&idr_lock, flags); } - put_pid(tmr->it_pid); - sigqueue_free(tmr->sigq); call_rcu(&tmr->it.rcu, k_itimer_rcu_free); }