From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751836Ab1H1Ryr (ORCPT ); Sun, 28 Aug 2011 13:54:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41020 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750980Ab1H1Ryn (ORCPT ); Sun, 28 Aug 2011 13:54:43 -0400 Date: Sun, 28 Aug 2011 19:51:16 +0200 From: Oleg Nesterov To: Tejun Heo Cc: rjw@sisk.pl, paul@paulmenage.org, linux-kernel@vger.kernel.org, arnd@arndb.de Subject: Re: [PATCH 08/16] freezer: use dedicated lock instead of task_lock() + memory barrier Message-ID: <20110828175116.GA27032@redhat.com> References: <1313763382-12341-1-git-send-email-tj@kernel.org> <1313763382-12341-9-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1313763382-12341-9-git-send-email-tj@kernel.org> 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 On 08/19, Tejun Heo wrote: > > it's by no means a > hot path and the priority is staying unintrusive and safe. This patch > makes it simply use a dedicated lock Agreed. but could you explain why it should be irq-safe? This is not clear from the changelog. > + if (!(current->flags & PF_NOFREEZE)) > + current->flags |= PF_FROZEN; it is not clear why do we check PF_NOFREEZE... but OK, iiuc you remove this check later anyway. Off-topic, but fake_signal_wake_up() is not safe if the caller try_to_freeze_cgroup(). Unlike try_to_freeze_tasks() (which holds tasklist) we can race with the exiting thread, ->sighand can be NULL. Oleg.