From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759441Ab3BXXcX (ORCPT ); Sun, 24 Feb 2013 18:32:23 -0500 Received: from hydra.sisk.pl ([212.160.235.94]:43310 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758955Ab3BXXcW (ORCPT ); Sun, 24 Feb 2013 18:32:22 -0500 From: "Rafael J. Wysocki" To: Oleg Nesterov Cc: Andrew Morton , Mandeep Singh Baines , Neil Horman , Tejun Heo , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] freezer: do not send a fake signal to a PF_DUMPCORE thread Date: Mon, 25 Feb 2013 00:39:03 +0100 Message-ID: <45402727.PXDVBuj6zy@vostro.rjw.lan> User-Agent: KMail/4.9.5 (Linux/3.8.0; KDE/4.9.5; x86_64; ; ) In-Reply-To: <20130224183656.GA8903@redhat.com> References: <20130224173144.GA32179@redhat.com> <20130224173206.GA32206@redhat.com> <20130224183656.GA8903@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sunday, February 24, 2013 07:36:56 PM Oleg Nesterov wrote: > A coredumping thread can't be frozen anyway but the fake signal sent > by freeze_task() can confuse dump_write/wait_for_dump_helpers/etc > and interrupt the coredump. > > We are going to make the do_coredump() paths freezable but the fake > TIF_SIGPENDING doesn't help, it only makes sense when we assume that > the target can return to user-mode and call get_signal_to_deliver(). > > Change freeze_task() to check PF_DUMPCORE along with PF_KTHREAD. We > need to recheck PF_DUMPCORE under ->siglock to avoid the race with > zap_threads() which can set this flag right before we take the lock. > > Signed-off-by: Oleg Nesterov Acked-by: Rafael J. Wysocki > --- > kernel/freezer.c | 19 ++++++++++++------- > 1 files changed, 12 insertions(+), 7 deletions(-) > > diff --git a/kernel/freezer.c b/kernel/freezer.c > index c38893b..595afab 100644 > --- a/kernel/freezer.c > +++ b/kernel/freezer.c > @@ -85,14 +85,21 @@ bool __refrigerator(bool check_kthr_stop) > } > EXPORT_SYMBOL(__refrigerator); > > -static void fake_signal_wake_up(struct task_struct *p) > +static bool fake_signal_wake_up(struct task_struct *p) > { > unsigned long flags; > + bool ret = false; > + > + if (p->flags & (PF_KTHREAD | PF_DUMPCORE)) > + return ret; > > if (lock_task_sighand(p, &flags)) { > - signal_wake_up(p, 0); > + ret = !(p->flags & PF_DUMPCORE); > + if (ret) > + signal_wake_up(p, 0); > unlock_task_sighand(p, &flags); > } > + return ret; > } > > /** > @@ -100,8 +107,8 @@ static void fake_signal_wake_up(struct task_struct *p) > * @p: task to send the request to > * > * If @p is freezing, the freeze request is sent either by sending a fake > - * signal (if it's not a kernel thread) or waking it up (if it's a kernel > - * thread). > + * signal (if it's not a kernel thread or a coredumping thread) or waking > + * it up otherwise. > * > * RETURNS: > * %false, if @p is not freezing or already frozen; %true, otherwise > @@ -116,9 +123,7 @@ bool freeze_task(struct task_struct *p) > return false; > } > > - if (!(p->flags & PF_KTHREAD)) > - fake_signal_wake_up(p); > - else > + if (!fake_signal_wake_up(p)) > wake_up_state(p, TASK_INTERRUPTIBLE); > > spin_unlock_irqrestore(&freezer_lock, flags); > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.