Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756677AbWK0Eha (ORCPT ); Sun, 26 Nov 2006 23:37:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756681AbWK0Eha (ORCPT ); Sun, 26 Nov 2006 23:37:30 -0500 Received: from pool-71-111-72-250.ptldor.dsl-w.verizon.net ([71.111.72.250]:13655 "EHLO IBM-8EC8B5596CA.beaverton.ibm.com") by vger.kernel.org with ESMTP id S1756677AbWK0Eh3 (ORCPT ); Sun, 26 Nov 2006 23:37:29 -0500 Date: Sun, 26 Nov 2006 20:33:23 -0800 From: "Paul E. McKenney" To: Oleg Nesterov Cc: Alan Stern , linux-kernel@vger.kernel.org Subject: Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall_sync Message-ID: <20061127043323.GB5021@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <20061117065128.GA5452@us.ibm.com> <20061117092925.GT7164@kernel.dk> <20061119190027.GA3676@oleg> <20061123145910.GA145@oleg> <20061123204054.GA4533@us.ibm.com> <20061123214908.GB106@oleg> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061123214908.GB106@oleg> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1276 Lines: 34 On Fri, Nov 24, 2006 at 12:49:08AM +0300, Oleg Nesterov wrote: > On 11/23, Paul E. McKenney wrote: > > > > For general use, I believe that this has > > difficulties with the sequence of events I sent out on November 20th, see: > > > > http://marc.theaimsgroup.com/?l=linux-kernel&m=116397154808901&w=2 > > > > ... > > > > I don't understand why an unlucky sequence of events mightn't be able > > to hang this __wait_event(). Suppose we did the atomic_dec_and_test(), > > then some other CPU executed xxx_read_unlock(), finding no one to awaken, > > then we execute the __wait_event()? > > Please note how ->ctr[] is initialized, > > atomic_set(sp->ctr + 0, 1); <---- 1, not 0 > atomic_set(sp->ctr + 1, 0); > > atomic_read(sp->ctr + idx) == 0 means that this counter is inactive, > nobody use it. I definitely should have slept before commenting on the earlier version, it would appear. ;-) Please accept my apologies for my confusion! I will take a look at your later patch. Thanx, Paul - 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/