Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762556AbXJQFiZ (ORCPT ); Wed, 17 Oct 2007 01:38:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750830AbXJQFiR (ORCPT ); Wed, 17 Oct 2007 01:38:17 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:43303 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750769AbXJQFiQ (ORCPT ); Wed, 17 Oct 2007 01:38:16 -0400 Date: Wed, 17 Oct 2007 11:07:54 +0530 From: Gautham R Shenoy To: Rusty Russell Cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Srivatsa Vaddagiri , Dipankar Sarma , Oleg Nesterov , Ingo Molnar , Paul E McKenney Subject: Re: [RFC PATCH 1/4] Refcount Based Cpu-Hotplug Implementation Message-ID: <20071017053754.GB9940@in.ibm.com> Reply-To: ego@in.ibm.com References: <20071016103308.GA9907@in.ibm.com> <20071016103417.GA16570@in.ibm.com> <200710171047.42693.rusty@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200710171047.42693.rusty@rustcorp.com.au> User-Agent: Mutt/1.5.12-2006-07-14 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1449 Lines: 51 On Wed, Oct 17, 2007 at 10:47:41AM +1000, Rusty Russell wrote: > On Tuesday 16 October 2007 20:34:17 Gautham R Shenoy wrote: > > This patch implements a Refcount + Waitqueue based model for > > cpu-hotplug. > > Hi Gautham, Hi Rusty, > > I can't see where you re-initialize the completion. The cpu_hotplug.readers_done is a global variable which has been initialized in cpu_hotplug_init. So I am wondering is the re-initialization required ? > > > +static void cpu_hotplug_begin(void) > > +{ > > + mutex_lock(&cpu_hotplug.lock); > > + cpu_hotplug.active_writer = current; > > + while (cpu_hotplug.refcount) { > > + mutex_unlock(&cpu_hotplug.lock); > > + wait_for_completion(&cpu_hotplug.readers_done); > > + mutex_lock(&cpu_hotplug.lock); > > + } > > AFAICT this will busy-wait on the second CPU hotplug. > Well when the first cpu_hotplug comes out of wait_for_completion, it would have decremented the ->done count, so it's as good as new for the second CPU hotplug, no? > Cheers, > Rusty. 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!" - 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/