Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751351AbXAFPMF (ORCPT ); Sat, 6 Jan 2007 10:12:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751353AbXAFPMF (ORCPT ); Sat, 6 Jan 2007 10:12:05 -0500 Received: from e5.ny.us.ibm.com ([32.97.182.145]:45047 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751351AbXAFPMC (ORCPT ); Sat, 6 Jan 2007 10:12:02 -0500 Date: Sat, 6 Jan 2007 20:41:53 +0530 From: Srivatsa Vaddagiri To: Oleg Nesterov Cc: Andrew Morton , David Howells , Christoph Hellwig , Ingo Molnar , Linus Torvalds , linux-kernel@vger.kernel.org, Gautham shenoy Subject: Re: [PATCH, RFC] reimplement flush_workqueue() Message-ID: <20070106151153.GA24274@in.ibm.com> Reply-To: vatsa@in.ibm.com References: <20061217223416.GA6872@tv-sign.ru> <20061218162701.a3b5bfda.akpm@osdl.org> <20061219004319.GA821@tv-sign.ru> <20070104113214.GA30377@in.ibm.com> <20070104142936.GA179@tv-sign.ru> <20070104091850.c1feee76.akpm@osdl.org> <20070105085634.GB18088@in.ibm.com> <20070105124246.GA83@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070105124246.GA83@tv-sign.ru> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1267 Lines: 31 On Fri, Jan 05, 2007 at 03:42:46PM +0300, Oleg Nesterov wrote: > preempt_disable() can't prevent cpu_up, but flush_workqueue() doesn't care > _unless_ cpu_down also happened meantime (and hence a fresh CPU may have > pending work_structs which were moved from a dead CPU). Yes, that was what I had in mind. > So you are right, we still need the patch above, but I think we don't have > new problems with preempt_disable(). Right, preempt_disable() hasn't added any new problem. Its just revealing the same problem as earlier, by opening up window for cpu hotplug events to happen in the middle of flush_workqueue(). Ideally I would have liked a lock_cpu_hotplug() equivalent which blocks all cpu hotplug events during the entire flush_workqueue(). In its absence, I guess we just need to deal with all these ugly races .. In summary, I think we need to go ahead with the preemp_disable() patch in flush_workqueue() from Andrew and the race fix you posted here: http://lkml.org/lkml/2006/12/30/37 -- Regards, vatsa - 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/