Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755212AbZAJJfi (ORCPT ); Sat, 10 Jan 2009 04:35:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752668AbZAJJfX (ORCPT ); Sat, 10 Jan 2009 04:35:23 -0500 Received: from mail-bw0-f21.google.com ([209.85.218.21]:64475 "EHLO mail-bw0-f21.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752578AbZAJJfU (ORCPT ); Sat, 10 Jan 2009 04:35:20 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=TtsP9HQmp3j937iR/Ss/IZxxLDw0lTBQfunLkOkvaOKlGOQ+XIotoajq6S5nB6nHOo np3pO7TVWfY1hGq1WxZSQdlC1PXb6BX8wWxsyTB6EQ9WLW62ToRW5truzexFtSz/4qdm dCiTyTCBGnS7PQCuNDBOZNl0Oq3WilJQ4FHZc= Message-ID: Date: Sat, 10 Jan 2009 12:35:18 +0300 From: "Alexey Zaytsev" To: "Harvey Harrison" Subject: Re: [PATCH] Disable branch profiling macros when sparsed. Cc: "David Miller" , linux-kernel@vger.kernel.org, mingo@elte.hu, rostedt@goodmis.org In-Reply-To: <1231571906.5714.30.camel@brick> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20090110052727.5471.3654.stgit@zaytsev.su> <20090109.221348.166902734.davem@davemloft.net> <1231571906.5714.30.camel@brick> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1882 Lines: 44 On Sat, Jan 10, 2009 at 10:18, Harvey Harrison wrote: > On Fri, 2009-01-09 at 22:13 -0800, David Miller wrote: >> From: Alexey Zaytsev >> Date: Sat, 10 Jan 2009 08:57:28 +0300 >> >> > The macros produce lots of unneeded warnings when >> > recursive if(({ .. if() {..} ..})) {..} and such >> > are substituted. And there is no point in sparsing >> > them anyway. This is useful if someone decides to >> > sparse an allyesconfig kernel. >> > >> > Signed-off-by: Alexey Zaytsev >> >> If even sparse can't handle these things, it's no surprise >> how many gcc bogus warning problems we've run into because >> of this hairy if() macro. > > It's not that sparse can't handle it, the warning is valid, > _____r and ______f are shadowed when these get nested. It > gets even worse when interacting with likely/unlikely tracing > as that chose the same identifiers too. So there the noise > could be drastically reduced changing the different identifiers > for the if () and __branch_check macros, but nesting will always > warn. > > I've just been setting this to no in my allyesconfig sparse > runs....just wait until kmemtrace gets to mainline, then it > gets really bad :( > I don't really understand what is bad here. The 'unlikely' and 'if' trace implementation looks quite elegant to me. Yes, they generate 10kbyte spaghetti monsters (in C) for a simple WARN_ON_ONCE(), but probably we should just remove a few unlekely() from the WARN_* code, and I'm not sure it's even worth it. There would be no direct speedup. And it took only one line to disable. -- 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/