From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755606AbaHEQtS (ORCPT ); Tue, 5 Aug 2014 12:49:18 -0400 Received: from mail-vc0-f179.google.com ([209.85.220.179]:53740 "EHLO mail-vc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753983AbaHEQtQ (ORCPT ); Tue, 5 Aug 2014 12:49:16 -0400 MIME-Version: 1.0 In-Reply-To: References: <20140730014827.565626091@linuxfoundation.org> <20140730014829.344302554@linuxfoundation.org> <20140730065312.GA1652@laptop.redhat.com> Date: Tue, 5 Aug 2014 09:49:15 -0700 X-Google-Sender-Auth: RsCsiFkJqEkSl4apnQCAiu2ytZ0 Message-ID: Subject: Re: [PATCH 3.15 33/37] Fix gcc-4.9.0 miscompilation of load_balance() in scheduler From: Linus Torvalds To: Josh Boyer Cc: Jakub Jelinek , Greg Kroah-Hartman , Linux Kernel Mailing List , stable , =?UTF-8?Q?Michel_D=C3=A4nzer?= , Markus Trippelsdorf Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 5, 2014 at 4:31 AM, Josh Boyer wrote: > > Sorry to bring this back up after the fact, but it's important for a > number of things in various distros You said that before, and I ignored you before, because you didn't actually give any examples. >. I don't disagree it should be > disabled by default, but making it unconditional is going to force the > distributions that care about perf, systemtap, and debuggers to > manually revert this. Bah. I bet I use 'perf' more than most, and it doesn't care about debug info. Sure, if you want the annotated source code, or put probes in place, you want the line number information, but the amount of debug information it needs is miniscule, and not impacted bu this at all afaik. And systemtap people have more problems than this. Debuggers? Again, people who actually use kgdb have bigger issues than some slightly worse local variable tracking. People care about the frame pointer information and type information, but if you use kgdb on the kernel you can damn well look at the assembly code and source code annotation for local variable information. So I call bullshit. Give a real example of real-world use, not some random handwaving of cases that happen to use debug info but - at least for the kernel - don't actually care about the variable tracking. The variable tracking is absolutely the *least* important part of the debug info. By a huge margin. To the point of being entirely irrelevant for the kernel. You make it sound like you lose all debug information, when in reality that's not the case at all. Trust me, you lose *way* more debug information because the kernel uses "-O2" rather than "-O". Linus