From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756309Ab3BXSi2 (ORCPT ); Sun, 24 Feb 2013 13:38:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6984 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751085Ab3BXSi1 (ORCPT ); Sun, 24 Feb 2013 13:38:27 -0500 Date: Sun, 24 Feb 2013 19:36:56 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Mandeep Singh Baines , Neil Horman , "Rafael J. Wysocki" , Tejun Heo , linux-kernel@vger.kernel.org Subject: [PATCH v2 2/3] freezer: do not send a fake signal to a PF_DUMPCORE thread Message-ID: <20130224183656.GA8903@redhat.com> References: <20130224173144.GA32179@redhat.com> <20130224173206.GA32206@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130224173206.GA32206@redhat.com> 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 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 --- 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); -- 1.5.5.1