Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753301AbaJMJNd (ORCPT ); Mon, 13 Oct 2014 05:13:33 -0400 Received: from mx0.aculab.com ([213.249.233.131]:50917 "HELO mx0.aculab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753173AbaJMJN0 convert rfc822-to-8bit (ORCPT ); Mon, 13 Oct 2014 05:13:26 -0400 From: David Laight To: "'Nathan Lynch'" , Russell King - ARM Linux CC: 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 ? Thread-Topic: RCU bug with v3.17-rc3 ? Thread-Index: AQHP5PUYyBwqwCOmRU6/T6T+Bfea1ZwtwNIg Date: Mon, 13 Oct 2014 09:11:34 +0000 Message-ID: <063D6719AE5E284EB5DD2968C1650D6D174C996E@AcuExch.aculab.com> 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> <54388B81.5020306@mentor.com> In-Reply-To: <54388B81.5020306@mentor.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.202.99.200] Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nathan Lynch > 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. Is it possible to compile a small code fragment and check the generated code for the bug? Possibly predicated on the broken version number to avoid false positives. David -- 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/