Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752496AbaJKOQ5 (ORCPT ); Sat, 11 Oct 2014 10:16:57 -0400 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:60551 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752390AbaJKOQ4 (ORCPT ); Sat, 11 Oct 2014 10:16:56 -0400 Date: Sat, 11 Oct 2014 15:16:38 +0100 From: Russell King - ARM Linux To: Peter Chen Cc: Nathan Lynch , Felipe Balbi , Rik van Riel , "Paul E. McKenney" , Tony Lindgren , Linux USB Mailing List , Linux Kernel Mailing List , josh@joshtriplett.org, Rabin Vincent , Alan Stern , Johannes Weiner , Sasha Levin , Andrew Morton , Linux OMAP Mailing List , Linus Torvalds , Linux ARM Kernel Mailing List Subject: Re: RCU bug with v3.17-rc3 ? Message-ID: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141011035431.GK3756@peterchendt> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- 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/