Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751103AbaJKBon (ORCPT ); Fri, 10 Oct 2014 21:44:43 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:44406 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750706AbaJKBol (ORCPT ); Fri, 10 Oct 2014 21:44:41 -0400 Message-ID: <54388B81.5020306@mentor.com> Date: Fri, 10 Oct 2014 20:44:33 -0500 From: Nathan Lynch User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 MIME-Version: 1.0 To: Russell King - ARM Linux CC: Felipe Balbi , Rik van Riel , "Paul E. McKenney" , Tony Lindgren , Linux USB Mailing List , Linux Kernel Mailing List , , 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 ? References: <20140905213216.GD5001@linux.vnet.ibm.com> <20141008171322.GH22688@saruman> <20141008175707.GI22688@saruman> <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> In-Reply-To: <20141010162531.GL12379@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Hopefully nobody's still using gcc 4.8 from the Linaro 2013.11 toolchain release -- since it's a 4.8.3 prerelease from before the fix was committed you'll get GCC_VERSION == 40803 but still generate bad code. > However, I'm rather annoyed that there are people here who have known > for some time that GCC 4.8.1 and GCC 4.8.2 _can_ lead to filesystem > corruption, and have sat on their backsides doing nothing about getting > it blacklisted for something like a year. Mea culpa, although I hadn't drawn the connection to FS corruption reports until now. I have known about the issue for some time, but figured the prevalence of the fix in downstream projects largely mitigated the issue. -- 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/