Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932579AbWLSBAx (ORCPT ); Mon, 18 Dec 2006 20:00:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932578AbWLSBAx (ORCPT ); Mon, 18 Dec 2006 20:00:53 -0500 Received: from smtp.osdl.org ([65.172.181.25]:37565 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932582AbWLSBAw (ORCPT ); Mon, 18 Dec 2006 20:00:52 -0500 Date: Mon, 18 Dec 2006 17:00:28 -0800 From: Andrew Morton To: Oleg Nesterov Cc: David Howells , Christoph Hellwig , Ingo Molnar , Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: [PATCH, RFC] reimplement flush_workqueue() Message-Id: <20061218170028.eaa1faf0.akpm@osdl.org> In-Reply-To: <20061219004319.GA821@tv-sign.ru> References: <20061217223416.GA6872@tv-sign.ru> <20061218162701.a3b5bfda.akpm@osdl.org> <20061219004319.GA821@tv-sign.ru> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1587 Lines: 45 On Tue, 19 Dec 2006 03:43:19 +0300 Oleg Nesterov wrote: > On 12/18, Andrew Morton wrote: > > > > On Mon, 18 Dec 2006 01:34:16 +0300 > > Oleg Nesterov wrote: > > > > > NOTE: I removed 'int cpu' parameter, flush_workqueue() locks/unlocks > > > workqueue_mutex unconditionally. It may be restored, but I think it > > > doesn't make much sense, we take the mutex for the very short time, > > > and the code becomes simpler. > > > > > > > Taking workqueue_mutex() unconditionally in flush_workqueue() means > > that we'll deadlock if a single-threaded workqueue callback handler calls > > flush_workqueue(). > > Well. But flush_workqueue() drops workqueue_mutex before going to sleep ? > > flush_workqueue(single_threaded_wq); > ... > mutex_lock(&workqueue_mutex); > ... > mutex_unlock(&workqueue_mutex); > wait_for_completition(); > handler runs, > calls flush_workqueue(), > workqueue_mutex is free Oh. OK. In that case we can switch to preempt_disable() for the cpu-hotplug holdoff. Sometime. > > It's an idiotic thing to do, but I think I spotted a site last week which > > does this. scsi? Not sure.. > > Ok, it is time to sleep. I'll look tomorrov and re-send if flush_cpu_workqueue() > really needs "bool workqueue_mutex_is_locked" parameter. Hopefully not. - 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/