From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751345AbWECVBy (ORCPT ); Wed, 3 May 2006 17:01:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751355AbWECVBy (ORCPT ); Wed, 3 May 2006 17:01:54 -0400 Received: from gateway-1237.mvista.com ([63.81.120.158]:29160 "EHLO gateway-1237.mvista.com") by vger.kernel.org with ESMTP id S1751345AbWECVBx (ORCPT ); Wed, 3 May 2006 17:01:53 -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: <20060503210125.GB16696@elte.hu> References: <200604221505.k3MF5mql022083@dwalker1.mvista.com> <20060503204747.GC15965@elte.hu> <1146689257.3363.13.camel@localhost.localdomain> <20060503210125.GB16696@elte.hu> Content-Type: text/plain Date: Wed, 03 May 2006 14:01:51 -0700 Message-Id: <1146690111.3363.14.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 23:01 +0200, Ingo Molnar wrote: > * Daniel Walker wrote: > > > > 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 ? > > hm, you are right - that code can be in a preempt-off section. I've > applied your patch. We could switch it to locked types if it's a latency concern.. Daniel