Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756355AbXHBWF2 (ORCPT ); Thu, 2 Aug 2007 18:05:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753507AbXHBWFT (ORCPT ); Thu, 2 Aug 2007 18:05:19 -0400 Received: from mail.screens.ru ([213.234.233.54]:47180 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752372AbXHBWFR (ORCPT ); Thu, 2 Aug 2007 18:05:17 -0400 Date: Fri, 3 Aug 2007 02:05:41 +0400 From: Oleg Nesterov To: "Rafael J. Wysocki" Cc: Andrew Morton , LKML , Nigel Cunningham , Pavel Machek , pm list Subject: Re: [PATCH -mm 2/3] Freezer: Use wait queue instead of busy looping (updated) Message-ID: <20070802220541.GA572@tv-sign.ru> References: <200708012328.23939.rjw@sisk.pl> <200708022313.32944.rjw@sisk.pl> <20070802212307.GA521@tv-sign.ru> <200708022349.44778.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200708022349.44778.rjw@sisk.pl> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1741 Lines: 44 On 08/02, Rafael J. Wysocki wrote: > > On Thursday, 2 August 2007 23:23, Oleg Nesterov wrote: > > On 08/02, Rafael J. Wysocki wrote: > > > > > > On Thursday, 2 August 2007 20:40, Oleg Nesterov wrote: > > > > On 08/02, Rafael J. Wysocki wrote: > > > > > > > > > > @@ -171,6 +186,10 @@ static int try_to_freeze_tasks(int freez > > > > > > > > > > end_time = jiffies + TIMEOUT; > > > > > do { > > > > > + DEFINE_WAIT(wait); > > > > > + > > > > > + add_wait_queue(&refrigerator_waitq, &wait); > > > > > > > > Hmm. In that case I'd sugest to use prepare_to_wait(). This means that > > > > multiple wakeups from refrigerator() won't do unnecessary work, > > > > > > I'm not sure what you mean. > > > > > > Do you mean that if we are TASK_UNINTERRUPTIBLE, then the first wake up > > > should remove us from the queue? > > > > No, not because we are TASK_UNINTERRUPTIBLE, but yes, first wake up will > > remove us because DEFINE_WAIT() uses autoremove_wake_function(). > > Yes, it does, but the prepare_to_wait() version would only cause current to > become TASK_UNINTERRUPTIBLE before it sends freezing requests, the other > differences don't seem to matter. I'm trying to understand why it would change > the behavior in the way you have described. Ugh, this is not the first time when I didn't read your patch carefully, sorry! I missed that your patch already uses DEFINE_WAIT(), and I was confused by the add_wait_queue() which is usually used along with DECLARE_WAITQUEUE(). Oleg. - 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/