linux-kernel - Re: [possible deadlock][3.1.0-g138c4ae] possible circular locking dependency detected

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Date:	Fri, 28 Oct 2011 13:49:23 +0800
From:	Wanlong Gao <gaowanlong@...fujitsu.com>
To:	Bob Liu <lliubbo@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [possible deadlock][3.1.0-g138c4ae] possible circular locking
 dependency detected

On 10/28/2011 01:44 PM, Bob Liu wrote:

> On Fri, Oct 28, 2011 at 11:42 AM, Wanlong Gao <gaowanlong@...fujitsu.com> wrote:
>> Hi folks:
>>
>> My dmesg said that:
>>
>> ======================================================
>> [ INFO: possible circular locking dependency detected ]
>> 3.1.0-138c4ae #2
>> -------------------------------------------------------
>> hugemmap05/18198 is trying to acquire lock:
>>  (&mm->mmap_sem){++++++}, at: [<ffffffff8114d85c>] might_fault+0x5c/0xb0
>>
>> but task is already holding lock:
>>  (&sb->s_type->i_mutex_key#21){+.+.+.}, at: [<ffffffff811a10f6>] vfs_readdir+0x86/0xe0
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #1 (&sb->s_type->i_mutex_key#21){+.+.+.}:
>>       [<ffffffff810afd34>] validate_chain+0x704/0x860
>>       [<ffffffff810b018c>] __lock_acquire+0x2fc/0x500
>>       [<ffffffff810b0b01>] lock_acquire+0xb1/0x1a0
>>       [<ffffffff815464f2>] __mutex_lock_common+0x62/0x420
>>       [<ffffffff81546a1a>] mutex_lock_nested+0x4a/0x60
>>       [<ffffffff8120b4ba>] hugetlbfs_file_mmap+0xaa/0x160
>>       [<ffffffff81158071>] mmap_region+0x3e1/0x590
>>       [<ffffffff81158584>] do_mmap_pgoff+0x364/0x3b0
>>       [<ffffffff811587d9>] sys_mmap_pgoff+0x209/0x240
>>       [<ffffffff8101aac9>] sys_mmap+0x29/0x30
>>       [<ffffffff81551542>] system_call_fastpath+0x16/0x1b
>>
>> -> #0 (&mm->mmap_sem){++++++}:
>>       [<ffffffff810af607>] check_prev_add+0x537/0x560
>>       [<ffffffff810afd34>] validate_chain+0x704/0x860
>>       [<ffffffff810b018c>] __lock_acquire+0x2fc/0x500
>>       [<ffffffff810b0b01>] lock_acquire+0xb1/0x1a0
>>       [<ffffffff8114d889>] might_fault+0x89/0xb0
>>       [<ffffffff811a0f2e>] filldir+0x7e/0xe0
>>       [<ffffffff811b445e>] dcache_readdir+0x5e/0x230
>>       [<ffffffff811a1130>] vfs_readdir+0xc0/0xe0
>>       [<ffffffff811a12c9>] sys_getdents+0x89/0x100
>>       [<ffffffff81551542>] system_call_fastpath+0x16/0x1b
>>
>> other info that might help us debug this:
>>
>>  Possible unsafe locking scenario:
>>
>>       CPU0                    CPU1
>>       ----                    ----
>>  lock(&sb->s_type->i_mutex_key);
>>                               lock(&mm->mmap_sem);
>>                               lock(&sb->s_type->i_mutex_key);
>>  lock(&mm->mmap_sem);
>>
>>  *** DEADLOCK ***
>>
>> 1 lock held by hugemmap05/18198:
>>  #0:  (&sb->s_type->i_mutex_key#21){+.+.+.}, at: [<ffffffff811a10f6>] vfs_readdir+0x86/0xe0
>>
>> stack backtrace:
>> Pid: 18198, comm: hugemmap05 Not tainted 3.1.0-138c4ae #2
>> Call Trace:
>>  [<ffffffff810ad469>] print_circular_bug+0x109/0x110
>>  [<ffffffff810af607>] check_prev_add+0x537/0x560
>>  [<ffffffff8114e112>] ? do_anonymous_page+0xf2/0x2d0
>>  [<ffffffff810afd34>] validate_chain+0x704/0x860
>>  [<ffffffff810b018c>] __lock_acquire+0x2fc/0x500
>>  [<ffffffff810b0b01>] lock_acquire+0xb1/0x1a0
>>  [<ffffffff8114d85c>] ? might_fault+0x5c/0xb0
>>  [<ffffffff8114d889>] might_fault+0x89/0xb0
>>  [<ffffffff8114d85c>] ? might_fault+0x5c/0xb0
>>  [<ffffffff81546763>] ? __mutex_lock_common+0x2d3/0x420
>>  [<ffffffff811a10f6>] ? vfs_readdir+0x86/0xe0
>>  [<ffffffff811a0f2e>] filldir+0x7e/0xe0
>>  [<ffffffff811b445e>] dcache_readdir+0x5e/0x230
>>  [<ffffffff811a0eb0>] ? filldir64+0xf0/0xf0
>>  [<ffffffff811a0eb0>] ? filldir64+0xf0/0xf0
>>  [<ffffffff811a0eb0>] ? filldir64+0xf0/0xf0
>>  [<ffffffff811a1130>] vfs_readdir+0xc0/0xe0
>>  [<ffffffff8118e9be>] ? fget+0xee/0x220
>>  [<ffffffff8118e8d0>] ? fget_raw+0x220/0x220
>>  [<ffffffff811a12c9>] sys_getdents+0x89/0x100
>>  [<ffffffff81551542>] system_call_fastpath+0x16/0x1b
>>
> 
> Please try this patch "lockdep: Add helper function for dir vs file
> i_mutex annotation" by josh.
> http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=commitdiff;h=e096d0c7e2e4e5893792db865dd065ac73cf1f00
> 


Oh, it looks like can fix this bug, but I also can't reproduce it whether with or without this patch.

Thanks
-Wanlong Gao
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