From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759026Ab2CFK6s (ORCPT ); Tue, 6 Mar 2012 05:58:48 -0500 Received: from casper.infradead.org ([85.118.1.10]:40276 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758931Ab2CFK6r convert rfc822-to-8bit (ORCPT ); Tue, 6 Mar 2012 05:58:47 -0500 Message-ID: <1331031498.11248.273.camel@twins> Subject: Re: [RFC PATCH 5/6] implement per-cpu&per-domain state machine call_srcu() From: Peter Zijlstra To: Lai Jiangshan Cc: "Paul E. McKenney" , linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org Date: Tue, 06 Mar 2012 11:58:18 +0100 In-Reply-To: <1331027858-7648-5-git-send-email-laijs@cn.fujitsu.com> References: <1331023359-6987-1-git-send-email-laijs@cn.fujitsu.com> <1331027858-7648-1-git-send-email-laijs@cn.fujitsu.com> <1331027858-7648-5-git-send-email-laijs@cn.fujitsu.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-03-06 at 17:57 +0800, Lai Jiangshan wrote: > /* > + * 'return left < right;' but handle the overflow issues. > + * The same as 'return (long)(right - left) > 0;' but it cares more. About what? And why? We do the (long)(a - b) thing all over the kernel, why would you care more? > + */ > +static inline > +bool safe_less_than(unsigned long left, unsigned long right, unsigned long max) > +{ > + unsigned long a = right - left; > + unsigned long b = max - left; > + > + return !!a && (a <= b); > +}