Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261256AbUKBPLA (ORCPT ); Tue, 2 Nov 2004 10:11:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261817AbUKBO6m (ORCPT ); Tue, 2 Nov 2004 09:58:42 -0500 Received: from viper.oldcity.dca.net ([216.158.38.4]:24244 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S262137AbUKBOyY (ORCPT ); Tue, 2 Nov 2004 09:54:24 -0500 Subject: Re: [PATCH] [CPU-HOTPLUG] convert cpucontrol to be a rwsem From: Lee Revell To: Rusty Russell Cc: Zwane Mwaikambo , Dominik Brodowski , lkml - Kernel Mailing List In-Reply-To: <1099352903.20402.2.camel@localhost.localdomain> References: <20041101084337.GA7824@dominikbrodowski.de> <1099332277.3647.43.camel@krustophenia.net> <1099352903.20402.2.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 02 Nov 2004 09:54:22 -0500 Message-Id: <1099407263.1563.4.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1265 Lines: 29 On Tue, 2004-11-02 at 10:48 +1100, Rusty Russell wrote: > On Mon, 2004-11-01 at 13:04 -0500, Lee Revell wrote: > > On Mon, 2004-11-01 at 07:00 -0700, Zwane Mwaikambo wrote: > > > Agreed it makes a lot more sense, i think there could be some places where > > > we use preempt_disable to protect against cpu offline which could > > > converted, but that can come later. > > > > > > > You know I picked up Robert Love's book the other day and was surprised > > to read we are not supposed to be using preempt_disable, there is a > > per_cpu interface for exactly this kind of thing. Which is currently > > recommended? > > get_cpu() both ensures that this CPU won't go down, and ensures we won't > get scheduled off it. It returns the current processor ID, as well. > put_cpu() puts the CPU back. > > In my experience it's usually clearer than preempt_disable(). To answer Zwane's earlier question, Love's book covers this on page 136, then all of Appendix B. I also completely missed this the first time... Lee - 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/