[Ocfs2-devel] Ocfs2-devel Digest, Vol 167, Issue 20
Gang He
ghe at suse.com
Sun Jan 14 19:03:29 PST 2018
Hi Zhonghua,
>From you describe, the issue is reproducible.
I suggest you to trigger a core dump when you find the threads meet a dead lock, the crash dump is most convincing.
Then, you can use crash command to list the related threads/backtraces/lock variables in the patch description.
it is easy to let the people know where we meet this dead-lock when code review,
and it is easy to let the users find your patch to fix this bug in the future.
Thanks
Gang
>>>
> Hi Guozhonghua,
>
> It seems that deadlock could be reproduced easily, right? Sharing the
> lock with VFS-layer probably is risky, and introducing a new lock for
> "quota_recovery" sounds good. Could you post a patch to fix this
> problem?
>
> thanks,
> Jun
>
> On 2018/1/13 11:04, Guozhonghua wrote:
>>
>>> Message: 1
>>> Date: Fri, 12 Jan 2018 06:15:01 +0000
>>> From: Shichangkuo <shi.changkuo at h3c.com>
>>> Subject: Re: [Ocfs2-devel] [Ocfs2-dev] BUG: deadlock with umount and
>>> ocfs2 workqueue triggered by ocfs2rec thread
>>> To: Joseph Qi <jiangqi903 at gmail.com>, "zren at suse.com" <zren at suse.com>,
>>> "jack at suse.cz" <jack at suse.cz>
>>> Cc: "ocfs2-devel at oss.oracle.com" <ocfs2-devel at oss.oracle.com>
>>> Message-ID:
>>> <D1E4D02760513D4B90DC3B40FF32AF35E22EC513 at H3CMLB14-EX.srv.huawe
>>> i-3com.com>
>>>
>>> Content-Type: text/plain; charset="gb2312"
>>>
>>> Hi Joseph
>>> Thanks for replying.
>>> Umount will flush the ocfs2 workqueue in function
>>> ocfs2_truncate_log_shutdown and journal recovery is one work of ocfs2 wq.
>>>
>>> Thanks
>>> Changkuo
>>>
>>
>> Umount
>> mngput
>> cleanup_mnt
>> deactivate_super: down_write the rw_semaphore: down_write(&s->s_umount)
>> deactivate_locked_super
>> kill_sb: kill_block_super
>> generic_shutdown_super
>> put_super : ocfs2_put_supe
>> ocfs2_dismount_volume
>> ocfs2_truncate_log_shutdown
>> flush_workqueue(osb->ocfs2_wq);
>> ocfs2_finish_quota_recovery
>> down_read(&sb->s_umount);
>> Here retry down_read rw_semaphore; down read while holding write? Try
> rw_semaphore twice, dead lock ?
>> The flush work queue of ocfs2_wq will be
> blocked, so as the umount ops.
>>
>> Thanks.
>>
>>
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>
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