From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758823Ab1IKBhv (ORCPT ); Sat, 10 Sep 2011 21:37:51 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:47118 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755036Ab1IKBhu (ORCPT ); Sat, 10 Sep 2011 21:37:50 -0400 Date: Sun, 11 Sep 2011 10:37:42 +0900 From: Tejun Heo To: Matt Helsley Cc: Oleg Nesterov , rjw@sisk.pl, paul@paulmenage.org, containers@lists.linux-foundation.org, linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 6/6] freezer: kill unused set_freezable_with_signal() Message-ID: <20110911013742.GJ29319@htj.dyndns.org> References: <1314988070-12244-1-git-send-email-tj@kernel.org> <1314988070-12244-7-git-send-email-tj@kernel.org> <20110904184626.GA30101@redhat.com> <20110905023315.GB9807@htj.dyndns.org> <20110905162012.GA4445@redhat.com> <20110906032846.GA18425@mtj.dyndns.org> <20110908180159.GA4197@count0.beaverton.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110908180159.GA4197@count0.beaverton.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Matt. On Thu, Sep 08, 2011 at 11:01:59AM -0700, Matt Helsley wrote: > Looking at the code and docs I realize I didn't explicitly mention that > kthreads could not be frozen by the cgroup freezer. However, the code did > not allow it. When freezing tasks the cgroup freezer always did: > > freeze_task(task, true) > > which would only freeze tasks without PF_FREEZER_NOSIG due to the second > "sig_only" parameter. I believe this means it could not be used to > freeze kthreads. > > My feeling is kthreads should not be "managed" directly by userspace. > Especially if that includes the ability to arbitrarily stop or freeze them. > So it seems more appropriate to explicitly disallow freezing of kthreads > via the cgroup freezer. Oh yeah, that's what we should do and maybe that's what the current code intends to achieve too but currently it ends up triggering BUG_ON(). Thanks. -- tejun