From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f50.google.com (mail-pb0-f50.google.com [209.85.160.50]) by kanga.kvack.org (Postfix) with ESMTP id ECA1F6B0036 for ; Thu, 15 May 2014 13:36:33 -0400 (EDT) Received: by mail-pb0-f50.google.com with SMTP id ma3so1375293pbc.23 for ; Thu, 15 May 2014 10:36:33 -0700 (PDT) Received: from userp1040.oracle.com (userp1040.oracle.com. [156.151.31.81]) by mx.google.com with ESMTPS id wh4si3020024pbc.262.2014.05.15.10.36.32 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 15 May 2014 10:36:33 -0700 (PDT) Message-ID: <5374FA04.5@oracle.com> Date: Thu, 15 May 2014 13:31:48 -0400 From: Sasha Levin MIME-Version: 1.0 Subject: Re: mm: BUG in do_huge_pmd_wp_page References: <51559150.3040407@oracle.com> <515D882E.6040001@oracle.com> <533F09F0.1050206@oracle.com> <20140407144835.GA17774@node.dhcp.inet.fi> <5342FF3E.6030306@oracle.com> <20140407201106.GA21633@node.dhcp.inet.fi> In-Reply-To: <20140407201106.GA21633@node.dhcp.inet.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Hugh Dickins , "Kirill A. Shutemov" , Andrew Morton , David Rientjes , Andrea Arcangeli , "H. Peter Anvin" , Mel Gorman , Dave Jones , linux-mm , "linux-kernel@vger.kernel.org" , Josh Boyer On 04/07/2014 04:11 PM, Kirill A. Shutemov wrote: > On Mon, Apr 07, 2014 at 03:40:46PM -0400, Sasha Levin wrote: >> > It also breaks fairly quickly under testing because: >> > >> > On 04/07/2014 10:48 AM, Kirill A. Shutemov wrote: >>> > > + if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { >>> > > + spin_lock(ptl); >> > >> > ^ We go into atomic >> > >>> > > + if (unlikely(!pmd_same(*pmd, orig_pmd))) >>> > > + goto out_race; >>> > > + } >>> > > + >>> > > if (!page) >>> > > clear_huge_page(new_page, haddr, HPAGE_PMD_NR); >>> > > else >>> > > copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); >> > >> > copy_user_huge_page() doesn't like running in atomic state, >> > and asserts might_sleep(). > Okay, I'll try something else. I've Cc'ed Josh Boyer to this since it just occurred to me that Fedora is running with CONFIG_DEBUG_VM set, where this bug is rather easy to trigger. This issue was neglected because it triggers only on CONFIG_DEBUG_VM builds, but with Fedora running that, maybe it shouldn't be? 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