Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932179AbWCTHUm (ORCPT ); Mon, 20 Mar 2006 02:20:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932180AbWCTHUl (ORCPT ); Mon, 20 Mar 2006 02:20:41 -0500 Received: from willy.net1.nerim.net ([62.212.114.60]:32010 "EHLO willy.net1.nerim.net") by vger.kernel.org with ESMTP id S932179AbWCTHUl (ORCPT ); Mon, 20 Mar 2006 02:20:41 -0500 Date: Mon, 20 Mar 2006 08:18:46 +0100 From: Willy Tarreau To: Linus Torvalds Cc: Andrew Morton , kernel-stuff@comcast.net, linux-kernel@vger.kernel.org, alex-kernel@digriz.org.uk, jun.nakajima@intel.com, davej@redhat.com, viro@ftp.linux.org.uk Subject: Re: OOPS: 2.6.16-rc6 cpufreq_conservative Message-ID: <20060320071846.GA19642@w.ods.org> References: <200603181525.14127.kernel-stuff@comcast.net> <20060318165302.62851448.akpm@osdl.org> <20060320061212.GG21493@w.ods.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.10i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1958 Lines: 57 On Sun, Mar 19, 2006 at 10:26:30PM -0800, Linus Torvalds wrote: > > > On Mon, 20 Mar 2006, Willy Tarreau wrote: > > > > Now, does removing the macro completely change the output code ? > > I think that if something written like this produces the same > > code, it would be easier to read : > > > > #define for_each_cpu_mask(cpu, mask) \ > > for ((cpu) = 0; (cpu) < NR_CPUS; (cpu)++) { \ > > unsigned long __bits = (mask).bits[0] >> (cpu); \ > > if (!__bits) \ > > break; \ > > if (!__bits & 1) \ > > continue; \ > > else > > Absolutely, but now it has a dangling "{" that didn't get closed. So the > above would definitely be more readable, it just doesn't actually work. > > Unless you'd do the "end_for_each_cpu" define (to close the statement), > and update the 300+ places that use this. Which might well be worth it. > > So the subtle "break from the middle of a statement expression" was just a > rather hacky way to avoid having to change all the users of this macro. > > Linus Oh, you're right, now I understand your motivation in doing this. Then perhaps using your trick but applying it to the whole for loop would make it easier to read ? #define for_each_cpu_mask(cpu, mask) \ for ((cpu) = 0; (cpu) < NR_CPUS; (cpu)++) \ ({ unsigned long __bits = (mask).bits[0] >> (cpu); \ if (!__bits) \ break; \ if (!__bits & 1) \ continue; \ else \ ... \ }) Please note that I've not read the rest of the code, so there may be some problems left. However, if the above works, I find it easier to read. And in this case, yes, it's interesting to be able to break from within an expression. Cheers, Willy - 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/