From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f182.google.com (mail-we0-f182.google.com [74.125.82.182]) by kanga.kvack.org (Postfix) with ESMTP id AD6E86B0031 for ; Wed, 9 Jul 2014 05:50:14 -0400 (EDT) Received: by mail-we0-f182.google.com with SMTP id q59so7197106wes.13 for ; Wed, 09 Jul 2014 02:50:13 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id cb12si7143670wib.106.2014.07.09.02.50.13 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 09 Jul 2014 02:50:13 -0700 (PDT) Message-ID: <53BD1053.5020401@suse.cz> Date: Wed, 09 Jul 2014 11:50:11 +0200 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree References: <53b45c9b.2rlA0uGYBLzlXEeS%akpm@linux-foundation.org> <53BCBF1F.1000506@oracle.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins , Sasha Levin Cc: akpm@linux-foundation.org, davej@redhat.com, koct9i@gmail.com, lczerner@redhat.com, stable@vger.kernel.org, "linux-mm@kvack.org" , LKML On 07/09/2014 08:35 AM, Hugh Dickins wrote: > On Wed, 9 Jul 2014, Sasha Levin wrote: >> On 07/02/2014 03:25 PM, akpm@linux-foundation.org wrote: >>> From: Hugh Dickins >>> Subject: shmem: fix faulting into a hole while it's punched, take 2 >> >> I suspect there's something off with this patch, as the shmem_fallocate >> hangs are back... Pretty much same as before: > > Thank you for reporting, but that is depressing news. > > I don't see what's wrong with this (take 2) patch, > and I don't see that it's been garbled in any way in next-20140708. > >> >> [ 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? I wonder, why wouldn't lockdep fire here if it was a double lock? I assume lockdep is enabled. It seems to me that the lock #1 is being printed because it's being acquired, not because it already is acquired. __mutex_lock_common() calls mutex_acquire_nest() *before* it actually tries to acquire the mutex. So the output is just confusing. So it would again help to see stacks of other tasks, to see who holds the i_mutex and where it's stuck... Vlastimil > In my source for next-20140708, the only return from shmem_fallocate() > which omits to mutex_unlock(&inode->i_mutex) is the "return -EOPNOTSUPP" > at the top, just before the mutex_lock(&inode->i_mutex). And inode > doesn't get reassigned in the middle. > > Does 3.16.0-rc4-next-20140708-sasha-00022-g94c7290-dirty look different? > > Hugh > -- 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