Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757296Ab0GDJIK (ORCPT ); Sun, 4 Jul 2010 05:08:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33575 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757160Ab0GDJII (ORCPT ); Sun, 4 Jul 2010 05:08:08 -0400 Date: Sun, 4 Jul 2010 12:00:05 +0300 From: "Michael S. Tsirkin" To: Oleg Nesterov Cc: Peter Zijlstra , Sridhar Samudrala , Tejun Heo , Ingo Molnar , netdev , lkml , "kvm@vger.kernel.org" , Andrew Morton , Dmitri Vorobiev , Jiri Kosina , Thomas Gleixner , Andi Kleen Subject: Re: [PATCH repost] sched: export sched_set/getaffinity to modules Message-ID: <20100704090005.GA8078@redhat.com> References: <20100701130816.GB32223@redhat.com> <1277991024.1917.108.camel@laptop> <20100701133956.GD32223@redhat.com> <4C2CA5C5.4040402@kernel.org> <20100701144624.GA11171@redhat.com> <4C2CABF2.2020801@kernel.org> <1277996135.1917.198.camel@laptop> <4C2E2987.9040702@us.ibm.com> <1278094270.1917.288.camel@laptop> <20100702210637.GA12433@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100702210637.GA12433@redhat.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1499 Lines: 39 On Fri, Jul 02, 2010 at 11:06:37PM +0200, Oleg Nesterov wrote: > On 07/02, Peter Zijlstra wrote: > > > > On Fri, 2010-07-02 at 11:01 -0700, Sridhar Samudrala wrote: > > > > > > Does it (Tejun's kthread_clone() patch) also inherit the > > > cgroup of the caller? > > > > Of course, its a simple do_fork() which inherits everything just as you > > would expect from a similar sys_clone()/sys_fork() call. > > Yes. And I'm afraid it can inherit more than we want. IIUC, this is called > from ioctl(), right? > > Then the new thread becomes the natural child of the caller, and it shares > ->mm with the parent. And files, dup_fd() without CLONE_FS. > > Signals. Say, if you send SIGKILL to this new thread, it can't sleep in > TASK_INTERRUPTIBLE or KILLABLE after that. And this SIGKILL can be sent > just because the parent gets SIGQUIT or abother coredumpable signal. > Or the new thread can recieve SIGSTOP via ^Z. > > Perhaps this is OK, I do not know. Just to remind that kernel_thread() > is merely clone(CLONE_VM). > > Oleg. Right. Doing this might break things like flush. The signal and exit behaviour needs to be examined carefully. I am also unsure whether using such threads might be more expensive than inheriting kthreadd. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/