From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751374AbXB0EKc (ORCPT ); Mon, 26 Feb 2007 23:10:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751472AbXB0EKc (ORCPT ); Mon, 26 Feb 2007 23:10:32 -0500 Received: from ausmtp04.au.ibm.com ([202.81.18.152]:44309 "EHLO ausmtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751374AbXB0EKa (ORCPT ); Mon, 26 Feb 2007 23:10:30 -0500 Date: Sat, 24 Feb 2007 00:33:34 +0530 From: Gautham R Shenoy To: Srivatsa Vaddagiri Cc: "Rafael J. Wysocki" , Aneesh Kumar , oleg@tv-sign.ru, linux-kernel@vger.kernel.org Subject: Re: freezer problems Message-ID: <20070223190334.GA23599@in.ibm.com> Reply-To: ego@in.ibm.com References: <20070214144031.GA15257@in.ibm.com> <200702231041.17136.rjw@sisk.pl> <20070223100817.GA10973@in.ibm.com> <200702231115.00718.rjw@sisk.pl> <20070223104723.GB10973@in.ibm.com> <20070223110201.GC10973@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070223110201.GC10973@in.ibm.com> User-Agent: Mutt/1.5.12-2006-07-14 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 23, 2007 at 04:32:01PM +0530, Srivatsa Vaddagiri wrote: > On Fri, Feb 23, 2007 at 04:17:23PM +0530, Srivatsa Vaddagiri wrote: > > Ok that was my point of concern. For hotplug we would ideally like > > everyone to be frozen. If we are not freezing some (like vfork parents), > > (rather if we dont -wait- for them to get frozen) before offlining a > > cpu, then it may expose some hotplug unsafe code in the caller of vfork > > in kernel - hopefully that is not a issue practically speaking. > > I notice that __call_usermodehelper() work function calls kernel_thread with > CLONE_VFORK set. __call_usermodehelper() is usualled called in the > context of a worker thread (kevent). But I see __call_usermodehelper being called from the context of khelper_wq which is a singlethreaded workqueue. I thought we were not planning to freeze singlethreaded workqueue's for hotplug, since we are not kthread_stopping them anywhere. So this kthread_stop waiting for parent(khelper_wq) which is blocked on wait_for_complete(child->vfork_done) shouldn't occur. No? Thanks and Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!"