From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755090Ab2HNMqh (ORCPT ); Tue, 14 Aug 2012 08:46:37 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:26446 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753437Ab2HNMqg (ORCPT ); Tue, 14 Aug 2012 08:46:36 -0400 X-Authority-Analysis: v=2.0 cv=Hun06jvS c=1 sm=0 a=s5Htg7xnQOKvHEu9STBOug==:17 a=OpT9cpI26MMA:10 a=Ae7MPIGovj8A:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=ayC55rCoAAAA:8 a=tYNMMJoXDhy72iSMQagA:9 a=PUjeQqilurYA:10 a=s5Htg7xnQOKvHEu9STBOug==:117 X-Cloudmark-Score: 0 X-Originating-IP: 72.230.195.127 Message-ID: <1344948394.6724.3.camel@gandalf.stny.rr.com> Subject: Re: [PATCH] preempt/hardirq.h: Clarify PREEMPT_ACTIVE bit location From: Steven Rostedt To: Thomas Gleixner Cc: "Srivatsa S. Bhat" , mingo@kernel.org, paulmck@linux.vnet.ibm.com, josh@joshtriplett.org, linux-kernel@vger.kernel.org Date: Tue, 14 Aug 2012 08:46:34 -0400 In-Reply-To: References: <20120720192459.6149.14821.stgit@srivatsabhat.in.ibm.com> <1343706583.27983.28.camel@gandalf.stny.rr.com> <502A0C19.6010007@linux.vnet.ibm.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-08-14 at 12:18 +0200, Thomas Gleixner wrote: > On Tue, 14 Aug 2012, Srivatsa S. Bhat wrote: > > > > > By default, the PREEMPT_ACTIVE flag is bit 27, but different > > architectures can override that. Update the comment to reflect > > this fact. > > Is there any sensible reason why architectures need to override that? > I can't find one. > > If there is none, then we should just remove all the overrides from > the arch code instead. If there is a reason, then it should be > documented. IIRC, when I added the NMI bits to implement 'in_nmi()' I tried to make this work across archs. But I found that bits in the preempt count have been hard coded in assembly all over the place, and to clean it up looked to be a nightmare. It probably should be done, but I didn't have the time to do it then. Perhaps we can revisit it. In fact, looking at all the archs, I believe all archs override the PREEMPT_ACTIVE bit, and not one of them uses the default (bit 27). -- Steve