From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f48.google.com (mail-pb0-f48.google.com [209.85.160.48]) by kanga.kvack.org (Postfix) with ESMTP id 08A006B00B2 for ; Fri, 6 Jun 2014 19:28:13 -0400 (EDT) Received: by mail-pb0-f48.google.com with SMTP id rr13so3068787pbb.35 for ; Fri, 06 Jun 2014 16:28:13 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id cc2si22069105pbc.255.2014.06.06.16.28.12 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 06 Jun 2014 16:28:13 -0700 (PDT) Message-ID: <53924D10.4050305@oracle.com> Date: Fri, 06 Jun 2014 19:21:52 -0400 From: Sasha Levin MIME-Version: 1.0 Subject: Re: 3.15-rc8 mm/filemap.c:202 BUG References: <20140603042121.GA27177@redhat.com> <538F121E.9020100@oracle.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds , Hugh Dickins Cc: Andrew Morton , "Kirill A. Shutemov" , Konstantin Khlebnikov , Dave Jones , "linux-mm@kvack.org" , Linux Kernel On 06/06/2014 07:16 PM, Linus Torvalds wrote: >> I have no evidence that its lack is responsible for the mm/filemap.c:202 >> > BUG_ON(page_mapped(page)) in __delete_from_page_cache() found by trinity, >> > and I am not optimistic that it will fix it. But I have found no other >> > explanation, and ACCESS_ONCE() here will surely not hurt. > The patch looks obviously correct to me, although like you, I have no > real reason to believe it really fixes anything. But we definitely > should just load it once, since it's very much an optimistic load done > before we take the real lock and re-compare. > > I'm somewhat dubious whether it actually would change code generation > - it doesn't change anything with the test-configuration I tried with > - but it's unquestionably a good patch. And hey, maybe some > configurations have sufficiently different code generation that gcc > actually _can_ sometimes do reloads, perhaps explaining why some > people see problems. So it's certainly worth testing even if it > doesn't make any change to code generation with *my* compiler and > config.. I'm seeing the same code generated here as well. I won't carry the patch unless Andrew/Linus take it so it won't hide possible bugs that trinity might stumble on. Thanks, Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org