From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751088AbWECUrk (ORCPT ); Wed, 3 May 2006 16:47:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751090AbWECUrk (ORCPT ); Wed, 3 May 2006 16:47:40 -0400 Received: from gateway-1237.mvista.com ([63.81.120.158]:15062 "EHLO gateway-1237.mvista.com") by vger.kernel.org with ESMTP id S1751088AbWECUrj (ORCPT ); Wed, 3 May 2006 16:47:39 -0400 Subject: Re: [PATCH -rt] revert bh_lru_lock() to preempt_disable() From: Daniel Walker To: Ingo Molnar Cc: linux-kernel@vger.kernel.org In-Reply-To: <20060503204747.GC15965@elte.hu> References: <200604221505.k3MF5mql022083@dwalker1.mvista.com> <20060503204747.GC15965@elte.hu> Content-Type: text/plain Date: Wed, 03 May 2006 13:47:37 -0700 Message-Id: <1146689257.3363.13.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2006-05-03 at 22:47 +0200, Ingo Molnar wrote: > * Daniel Walker wrote: > > > The bh_lru_lock() was set to disable interrupt to protect from > > IPI's, which are only on SMP . So I don't think it's needed in UP > > PREEMPT_RT configs. > > i agree that this is a problem, but the fix is incorrect. What would be > the right approach is to convert the PER_CPU bh_lrus to PER_CPU_LOCKED, > and to use the appropriate primitives to use them. That automatically > makes this code rt-safe. (it isnt right now) Hmm, in UP it should be safe to access per cpu data under either a preempt_disable or local_irq_disable . I'm not sure how RT changes that .. Is there some other part of the code that isn't rt-safe, which I've overlooked ? Daniel