From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f174.google.com (mail-wi0-f174.google.com [209.85.212.174]) by kanga.kvack.org (Postfix) with ESMTP id 287C9900002 for ; Fri, 11 Jul 2014 04:39:14 -0400 (EDT) Received: by mail-wi0-f174.google.com with SMTP id d1so3564794wiv.13 for ; Fri, 11 Jul 2014 01:39:11 -0700 (PDT) Received: from casper.infradead.org (casper.infradead.org. [2001:770:15f::2]) by mx.google.com with ESMTPS id cp2si2500470wib.107.2014.07.11.01.39.04 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Jul 2014 01:39:04 -0700 (PDT) Date: Fri, 11 Jul 2014 10:38:50 +0200 From: Peter Zijlstra Subject: Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree Message-ID: <20140711083850.GE20603@laptop.programming.kicks-ass.net> References: <53BD67DC.9040700@oracle.com> <53BE8B1B.3000808@oracle.com> <53BECBA4.3010508@oracle.com> <53BED7F6.4090502@oracle.com> <53BEE345.4090203@oracle.com> <20140711082500.GB20603@laptop.programming.kicks-ass.net> <53BFA14B.4010203@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53BFA14B.4010203@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Sasha Levin , Hugh Dickins , Heiko Carstens , akpm@linux-foundation.org, davej@redhat.com, koct9i@gmail.com, lczerner@redhat.com, stable@vger.kernel.org, "linux-mm@kvack.org" , LKML On Fri, Jul 11, 2014 at 10:33:15AM +0200, Vlastimil Babka wrote: > Quoting Hugh from previous mail in this thread: > > >>> > >>> [ 363.600969] INFO: task trinity-c327:9203 blocked for more than 120 seconds. > >>> [ 363.605359] Not tainted 3.16.0-rc4-next-20140708-sasha-00022-g94c7290-dirty #772 > >>> [ 363.609730] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > >>> [ 363.615861] trinity-c327 D 000000000000000b 13496 9203 8559 0x10000004 > >>> [ 363.620284] ffff8800b857bce8 0000000000000002 ffffffff9dc11b10 0000000000000001 > >>> [ 363.624468] ffff880104860000 ffff8800b857bfd8 00000000001d7740 00000000001d7740 > >>> [ 363.629118] ffff880104863000 ffff880104860000 ffff8800b857bcd8 ffff8801eaed8868 > >>> [ 363.633879] Call Trace: > >>> [ 363.635442] [] schedule+0x65/0x70 > >>> [ 363.638638] [] schedule_preempt_disabled+0x18/0x30 > >>> [ 363.642833] [] mutex_lock_nested+0x2e5/0x550 > >>> [ 363.646599] [] ? shmem_fallocate+0x6c/0x350 > >>> [ 363.651319] [] ? get_parent_ip+0x11/0x50 > >>> [ 363.654683] [] ? shmem_fallocate+0x6c/0x350 > >>> [ 363.658264] [] shmem_fallocate+0x6c/0x350 > > > >So it's trying to acquire i_mutex at shmem_fallocate+0x6c... > > > >>> [ 363.662010] [] ? put_lock_stats.isra.12+0xe/0x30 > >>> [ 363.665866] [] do_fallocate+0x153/0x1d0 > >>> [ 363.669381] [] SyS_madvise+0x33f/0x970 > >>> [ 363.672906] [] tracesys+0xe1/0xe6 > >>> [ 363.682900] 2 locks held by trinity-c327/9203: > >>> [ 363.684928] #0: (sb_writers#12){.+.+.+}, at: [] do_fallocate+0x13d/0x1d0 > >>> [ 363.715102] #1: (&sb->s_type->i_mutex_key#16){+.+.+.}, at: [] shmem_fallocate+0x6c/0x350 > > > >...but it already holds i_mutex, acquired at shmem_fallocate+0x6c. > >Am I reading that correctly? > > The output looks like mutex #1 is already taken, but actually the process is > sleeping when trying to take it. It appears that the output has taken > mutex_acquire_nest() action into account, but doesn't distinguish if > lock_acquired() already happened or not. The call trace is very clear on it that its not. I've never found this to be a problem in practise. You need to engage your brain anyhow, this little bit extra isn't going to make a difference or not. -- 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