Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752576AbaJKOv1 (ORCPT ); Sat, 11 Oct 2014 10:51:27 -0400 Received: from mail-yk0-f177.google.com ([209.85.160.177]:36973 "EHLO mail-yk0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752393AbaJKOvY (ORCPT ); Sat, 11 Oct 2014 10:51:24 -0400 MIME-Version: 1.0 In-Reply-To: <20141011141638.GN12379@n2100.arm.linux.org.uk> References: <20141008212938.GP22688@saruman> <20141009160138.GA2396@cmpxchg.org> <20141009162656.GE16002@saruman> <20141009204101.GA25955@debian> <20141009204637.GE25729@saruman> <20141009210715.GH25729@saruman> <20141010135743.GB31348@saruman> <20141010162531.GL12379@n2100.arm.linux.org.uk> <54388B81.5020306@mentor.com> <20141011035431.GK3756@peterchendt> <20141011141638.GN12379@n2100.arm.linux.org.uk> Date: Sat, 11 Oct 2014 11:51:23 -0300 X-Google-Sender-Auth: _WC1PAEeO7zhQzrPa8wV-IUrcf8 Message-ID: Subject: Re: RCU bug with v3.17-rc3 ? From: Otavio Salvador To: Russell King - ARM Linux Cc: Peter Chen , Rik van Riel , Linux OMAP Mailing List , Tony Lindgren , Linux USB Mailing List , Nathan Lynch , Linux Kernel Mailing List , Felipe Balbi , Josh Triplett , Rabin Vincent , Alan Stern , Johannes Weiner , Sasha Levin , Andrew Morton , "Paul E. McKenney" , Linus Torvalds , Linux ARM Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Russell, On Sat, Oct 11, 2014 at 11:16 AM, Russell King - ARM Linux wrote: > On Sat, Oct 11, 2014 at 11:54:32AM +0800, Peter Chen wrote: >> On Fri, Oct 10, 2014 at 08:44:33PM -0500, Nathan Lynch wrote: >> > On 10/10/2014 11:25 AM, Russell King - ARM Linux wrote: >> > > >> > > Right, so GCC 4.8.{1,2} are totally unsuitable for kernel building (and >> > > it seems that this has been known about for some time.) >> > >> > Looking at http://gcc.gnu.org/PR58854 it seems that all 4.8.x for x < 3 >> > are affected, as well as 4.9.0. >> > >> > > We can blacklist these GCC versions quite easily. We already have GCC >> > > 3.3 blacklisted, and it's trivial to add others. I would want to include >> > > some proper details about the bug, just like the other existing entries >> > > we already have in asm-offsets.c, where we name the functions that the >> > > compiler is known to break where appropriate. >> > >> > Before blacklisting anything, it's worth considering that simple version >> > checks would break existing pre-4.8.3 compilers that have been patched >> > for PR58854. It looks like Yocto and Buildroot issued releases with >> > patched 4.8.2 compilers well before the (fixed) 4.8.3 release. I think >> > the most we can reasonably do without breaking some correctly-behaving >> > toolchains is to emit a warning. >> >> Yocto has PR58854 problem patch. >> >> http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/recipes-devtools/gcc/gcc-4.8/0048-PR58854_fix_arm_apcs_epilogue.patch?h=daisy > > Right, and we can provide links to these in the comments above the #error > so people have the right places to do a bit of research into whether their > compiler is safe. > > It is unfortunate that they are indistinguishable from the broken versions, > but that's really a distro problem for causing that issue themselves - > especially given how serious this bug is. What about checking if GCC_PR58854_FIXED is not defined for error? So build systems and people could easily define it if they know their GCC has the fix applied. -- Otavio Salvador O.S. Systems http://www.ossystems.com.br http://code.ossystems.com.br Mobile: +55 (53) 9981-7854 Mobile: +1 (347) 903-9750 -- 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/