Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756285Ab0D1WJT (ORCPT ); Wed, 28 Apr 2010 18:09:19 -0400 Received: from mail-pv0-f174.google.com ([74.125.83.174]:62864 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755970Ab0D1WJR convert rfc822-to-8bit (ORCPT ); Wed, 28 Apr 2010 18:09:17 -0400 MIME-Version: 1.0 In-Reply-To: <201004282309.42188.rjw@sisk.pl> References: <1272429119-12103-1-git-send-email-arve@android.com> <1272429119-12103-7-git-send-email-arve@android.com> <20100428194028.GA16389@redhat.com> <201004282309.42188.rjw@sisk.pl> Date: Wed, 28 Apr 2010 15:09:16 -0700 Message-ID: Subject: Re: [PATCH 6/8] PM: Add suspend blocking work. From: =?ISO-8859-1?Q?Arve_Hj=F8nnev=E5g?= To: "Rafael J. Wysocki" Cc: Oleg Nesterov , linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Alan Stern , Tejun Heo , Pavel Machek , Len Brown Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2586 Lines: 83 2010/4/28 Rafael J. Wysocki : > On Wednesday 28 April 2010, Oleg Nesterov wrote: >> On 04/27, Arve Hj?nnev?g wrote: >> > >> > Allow work to be queued that will block suspend while it is pending >> > or executing. To get the same functionality in the calling code often >> > requires a separate suspend_blocker for pending and executing work, or >> > additional state and locking. This implementation does add additional >> > state and locking, but this can be removed later if we add support for >> > suspend blocking work to the core workqueue code. >> >> I think this patch is fine. >> >> Just one silly question, >> >> > +int queue_suspend_blocking_work(struct workqueue_struct *wq, >> > + ? ? ? ? ? ? ? ? ? ? ? ? ? struct suspend_blocking_work *work) >> > +{ >> > + ? int ret; >> > + ? unsigned long flags; >> > + >> > + ? spin_lock_irqsave(&work->lock, flags); >> > + ? suspend_block(&work->suspend_blocker); >> > + ? ret = queue_work(wq, &work->work); >> > + ? if (ret) >> > + ? ? ? ? ? work->active++; >> >> why not >> >> ? ? ? ret = queue_work(wq, &work->work); >> ? ? ? if (ret) { >> ? ? ? ? ? ? ? suspend_block(&work->suspend_blocker); >> ? ? ? ? ? ? ? work->active++; >> ? ? ? } >> >> ? >> >> Afaics, we can't race with work->func() doing unblock, we hold work-lock. >> And this way the code looks more clear. > > Agreed. ?Arve, any objections to doing that? > I need to fix the race, but I can easily fix it in cancel_suspend_blocking_work_sync instead. If the suspend blocker is active for a long time, and DEBUG_SUSPEND_BLOCKER is enabled, we can tell if the work is constantly re-queued or if the workqueue is stuck. >> Sorry, I had no chance to read the previous patches. After the quick look >> at 1/8 I think it is OK to call suspend_block() twice, but still... > > It is. > >> Or I missed something? Just curious. >> >> >> Hmm... actually, queue_work() can also fail if we race with cancel_ which >> temporary sets WORK_STRUCT_PENDING. In that case suspend_block() won't >> be paired by unblock ? >> >> >> > +int schedule_suspend_blocking_work(struct suspend_blocking_work *work) >> > +{ >> > ... >> > + ? ret = schedule_work(&work->work); >> >> Off-topic. We should probably export keventd_wq to avoid the duplications >> like this. > > Please see my reply to Tejun. :-) > > Rafael > -- Arve Hj?nnev?g -- 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/