From: Yu Kuai <yukuai3@huawei.com>
To: Guoqing Jiang <guoqing.jiang@linux.dev>,
Marc Smith <msmith626@gmail.com>
Cc: Donald Buczek <buczek@molgen.mpg.de>, Song Liu <song@kernel.org>,
<linux-raid@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
<it+raid@molgen.mpg.de>, "yukuai (C)" <yukuai3@huawei.com>
Subject: Re: md_raid: mdX_raid6 looping after sync_action "check" to "idle" transition
Date: Wed, 15 Mar 2023 11:02:37 +0800 [thread overview]
Message-ID: <60829bc7-2eb9-f4ca-1a36-d2dbda5b0f3e@huawei.com> (raw)
In-Reply-To: <2af18cf7-05eb-f1d1-616a-2c5894d1ac43@linux.dev>
在 2023/03/14 21:55, Guoqing Jiang 写道:
>
>
> On 3/14/23 21:25, Marc Smith wrote:
>> On Mon, Feb 8, 2021 at 7:49 PM Guoqing Jiang
>> <guoqing.jiang@cloud.ionos.com> wrote:
>>> Hi Donald,
>>>
>>> On 2/8/21 19:41, Donald Buczek wrote:
>>>> Dear Guoqing,
>>>>
>>>> On 08.02.21 15:53, Guoqing Jiang wrote:
>>>>>
>>>>> On 2/8/21 12:38, Donald Buczek wrote:
>>>>>>> 5. maybe don't hold reconfig_mutex when try to unregister
>>>>>>> sync_thread, like this.
>>>>>>>
>>>>>>> /* resync has finished, collect result */
>>>>>>> mddev_unlock(mddev);
>>>>>>> md_unregister_thread(&mddev->sync_thread);
>>>>>>> mddev_lock(mddev);
>>>>>> As above: While we wait for the sync thread to terminate, wouldn't it
>>>>>> be a problem, if another user space operation takes the mutex?
>>>>> I don't think other places can be blocked while hold mutex, otherwise
>>>>> these places can cause potential deadlock. Please try above two lines
>>>>> change. And perhaps others have better idea.
>>>> Yes, this works. No deadlock after >11000 seconds,
>>>>
>>>> (Time till deadlock from previous runs/seconds: 1723, 37, 434, 1265,
>>>> 3500, 1136, 109, 1892, 1060, 664, 84, 315, 12, 820 )
>>> Great. I will send a formal patch with your reported-by and tested-by.
>>>
>>> Thanks,
>>> Guoqing
>> I'm still hitting this issue with Linux 5.4.229 -- it looks like 1/2
>> of the patches that supposedly resolve this were applied to the stable
>> kernels, however, one was omitted due to a regression:
>> md: don't unregister sync_thread with reconfig_mutex held (upstream
>> commit 8b48ec23cc51a4e7c8dbaef5f34ebe67e1a80934)
Hi, Guoqing,
Just borrow this thread to discuss, I think this commit might have
problem in some corner cases:
t1: t2:
action_store
mddev_lock
if (mddev->sync_thread)
mddev_unlock
md_unregister_thread
md_check_recovery
set_bit(MD_RECOVERY_RUNNING, &mddev->recovery)
queue_work(md_misc_wq, &mddev->del_work)
mddev_lock_nointr
md_reap_sync_thread
// clear running
mddev_lock
t3:
md_start_sync
// running is not set
Our test report a problem that can be cause by this in theory, by we
can't be sure for now...
We thought about how to fix this, instead of calling
md_register_thread() here to wait for sync_thread to be done
synchronisely, we do this asynchronously like what md_set_readonly() and
do_md_stop() does.
What do you think?
Thanks,
Kuai
>>
>> I don't see any follow-up on the thread from June 8th 2022 asking for
>> this patch to be dropped from all stable kernels since it caused a
>> regression.
>>
>> The patch doesn't appear to be present in the current mainline kernel
>> (6.3-rc2) either. So I assume this issue is still present there, or it
>> was resolved differently and I just can't find the commit/patch.
>
> It should be fixed by commit 9dfbdafda3b3"md: unlock mddev before reap
> sync_thread in action_store".
>
> Thanks,
> Guoqing
> .
>
next prev parent reply other threads:[~2023-03-15 3:02 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-28 12:25 md_raid: mdX_raid6 looping after sync_action "check" to "idle" transition Donald Buczek
2020-11-30 2:06 ` Guoqing Jiang
2020-12-01 9:29 ` Donald Buczek
2020-12-02 17:28 ` Donald Buczek
2020-12-03 1:55 ` Guoqing Jiang
2020-12-03 11:42 ` Donald Buczek
2020-12-21 12:33 ` Donald Buczek
2021-01-19 11:30 ` Donald Buczek
2021-01-20 16:33 ` Guoqing Jiang
2021-01-23 13:04 ` Donald Buczek
2021-01-25 8:54 ` Donald Buczek
2021-01-25 21:32 ` Donald Buczek
2021-01-26 0:44 ` Guoqing Jiang
2021-01-26 9:50 ` Donald Buczek
2021-01-26 11:14 ` Guoqing Jiang
2021-01-26 12:58 ` Donald Buczek
2021-01-26 14:06 ` Guoqing Jiang
2021-01-26 16:05 ` Donald Buczek
2021-02-02 15:42 ` Guoqing Jiang
2021-02-08 11:38 ` Donald Buczek
2021-02-08 14:53 ` Guoqing Jiang
2021-02-08 18:41 ` Donald Buczek
2021-02-09 0:46 ` Guoqing Jiang
2021-02-09 9:24 ` Donald Buczek
2023-03-14 13:25 ` Marc Smith
2023-03-14 13:55 ` Guoqing Jiang
2023-03-14 14:45 ` Marc Smith
2023-03-16 15:25 ` Marc Smith
2023-03-29 0:01 ` Song Liu
2023-08-22 21:16 ` Dragan Stancevic
2023-08-23 1:22 ` Yu Kuai
2023-08-23 15:33 ` Dragan Stancevic
2023-08-24 1:18 ` Yu Kuai
2023-08-28 20:32 ` Dragan Stancevic
2023-08-30 1:36 ` Yu Kuai
2023-09-05 3:50 ` Yu Kuai
2023-09-05 13:54 ` Dragan Stancevic
2023-09-13 9:08 ` Donald Buczek
2023-09-13 14:16 ` Dragan Stancevic
2023-09-14 6:03 ` Donald Buczek
2023-09-17 8:55 ` Donald Buczek
2023-09-24 14:35 ` Donald Buczek
2023-09-25 1:11 ` Yu Kuai
2023-09-25 9:11 ` Donald Buczek
2023-09-25 9:32 ` Yu Kuai
2023-03-15 3:02 ` Yu Kuai [this message]
2023-03-15 9:30 ` Guoqing Jiang
2023-03-15 9:53 ` Yu Kuai
2023-03-15 7:52 ` Donald Buczek
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