From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f170.google.com (mail-ob0-f170.google.com [209.85.214.170]) by kanga.kvack.org (Postfix) with ESMTP id 4F0906B0038 for ; Wed, 9 Sep 2015 21:05:34 -0400 (EDT) Received: by obbbh8 with SMTP id bh8so22677398obb.0 for ; Wed, 09 Sep 2015 18:05:34 -0700 (PDT) Received: from userp1040.oracle.com (userp1040.oracle.com. [156.151.31.81]) by mx.google.com with ESMTPS id ar6si6044359obc.104.2015.09.09.18.05.32 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Sep 2015 18:05:33 -0700 (PDT) Message-ID: <55F0D5B2.2090205@oracle.com> Date: Wed, 09 Sep 2015 20:58:26 -0400 From: Sasha Levin MIME-Version: 1.0 Subject: Re: Multiple potential races on vma->vm_flags References: <55EC9221.4040603@oracle.com> <20150907114048.GA5016@node.dhcp.inet.fi> In-Reply-To: <20150907114048.GA5016@node.dhcp.inet.fi> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" , Rik van Riel , Andrew Morton Cc: Andrey Konovalov , Dmitry Vyukov , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 09/07/2015 07:40 AM, Kirill A. Shutemov wrote: > On Sun, Sep 06, 2015 at 03:21:05PM -0400, Sasha Levin wrote: >> > ================================================================== >> > ThreadSanitizer: data-race in munlock_vma_pages_range >> > >> > Write of size 8 by thread T378 (K2633, CPU3): >> > [] munlock_vma_pages_range+0x59/0x3e0 mm/mlock.c:425 >> > [] mlock_fixup+0x1c9/0x280 mm/mlock.c:549 >> > [] do_mlock+0x14c/0x180 mm/mlock.c:589 >> > [< inlined >] SyS_munlock+0x74/0xb0 SYSC_munlock mm/mlock.c:651 >> > [] SyS_munlock+0x74/0xb0 mm/mlock.c:643 >> > [] entry_SYSCALL_64_fastpath+0x12/0x71 >> > arch/x86/entry/entry_64.S:186 > ... > >> > Previous read of size 8 by thread T398 (K2623, CPU2): >> > [] try_to_unmap_one+0x78/0x4f0 mm/rmap.c:1208 >> > [< inlined >] rmap_walk+0x147/0x450 rmap_walk_file mm/rmap.c:1540 >> > [] rmap_walk+0x147/0x450 mm/rmap.c:1559 >> > [] try_to_munlock+0xa2/0xc0 mm/rmap.c:1423 >> > [] __munlock_isolated_page+0x30/0x60 mm/mlock.c:129 >> > [] __munlock_pagevec+0x236/0x3f0 mm/mlock.c:331 >> > [] munlock_vma_pages_range+0x380/0x3e0 mm/mlock.c:476 >> > [] mlock_fixup+0x1c9/0x280 mm/mlock.c:549 >> > [] do_mlock+0x14c/0x180 mm/mlock.c:589 >> > [< inlined >] SyS_munlock+0x74/0xb0 SYSC_munlock mm/mlock.c:651 >> > [] SyS_munlock+0x74/0xb0 mm/mlock.c:643 >> > [] entry_SYSCALL_64_fastpath+0x12/0x71 >> > arch/x86/entry/entry_64.S:186 > Okay, the detected race is mlock/munlock vs. rmap. > > On rmap side we check vma->vm_flags in few places without taking > vma->vm_mm->mmap_sem. The vma cannot be freed since we hold i_mmap_rwsem > or anon_vma_lock, but nothing prevent vma->vm_flags from changing under > us. > > In this particular case, speculative check in beginning of > try_to_unmap_one() is fine, since we re-check it under mmap_sem later in > the function. So you're suggesting that this isn't the cause of the bad page flags error observed by Andrey and myself? 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