Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424660AbWKPVdz (ORCPT ); Thu, 16 Nov 2006 16:33:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1424661AbWKPVdz (ORCPT ); Thu, 16 Nov 2006 16:33:55 -0500 Received: from mail.timesys.com ([65.117.135.102]:6614 "EHLO postfix.timesys.com") by vger.kernel.org with ESMTP id S1424660AbWKPVdy (ORCPT ); Thu, 16 Nov 2006 16:33:54 -0500 Subject: Re: BUG: cpufreq notification broken From: Thomas Gleixner Reply-To: tglx@timesys.com To: Alan Stern Cc: LKML , Linus Torvalds , john stultz , Ingo Molnar , David Miller , Arjan van de Ven , Andrew Morton , Andi Kleen In-Reply-To: References: Content-Type: text/plain Date: Thu, 16 Nov 2006 22:36:34 +0100 Message-Id: <1163712994.10333.49.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 978 Lines: 26 On Thu, 2006-11-16 at 16:26 -0500, Alan Stern wrote: > On Thu, 16 Nov 2006, Thomas Gleixner wrote: > > > There is another issue with this SRCU change: > > > > The notification comes actually after the real change, which is bad. We > > try to make the TSC usable by backing it with pm_timer accross such > > states, but this behaviour breaks the safety code. > > I don't understand. Sending notifications is completely separate from > setting up the notifier chain's head. The patch you mentioned didn't > touch the code that sends the notifications. Yeah, my bad. It just uses rcu based locking, but its still synchronous. I have to dig deeper, why the change of the frequency happens _before_ the notifier arrives. tglx - 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/