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Message-ID: <c7454021-5559-6556-e9ec-de856e00f1fb@suse.de>
Date: Wed, 23 Aug 2023 08:04:10 +0200
From: Hannes Reinecke <hare@...e.de>
To: Yu Kuai <yukuai1@...weicloud.com>,
Carlos Carvalho <carlos@...ica.ufpr.br>,
Song Liu <song@...nel.org>
Cc: Bagas Sanjaya <bagasdotme@...il.com>,
Christoph Hellwig <hch@....de>, AceLan Kao <acelan@...il.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux Regressions <regressions@...ts.linux.dev>,
Linux RAID <linux-raid@...r.kernel.org>,
"yukuai (C)" <yukuai3@...wei.com>,
"yangerkun@...wei.com" <yangerkun@...wei.com>
Subject: Re: Infiniate systemd loop when power off the machine with multiple
MD RAIDs
On 8/23/23 03:28, Yu Kuai wrote:
> Hi,
>
> 在 2023/08/23 3:13, Carlos Carvalho 写道:
>> Song Liu (song@...nel.org) wrote on Tue, Aug 22, 2023 at 03:56:04PM -03:
>>> >From systemd code, i.e. function delete_md(), this error:
>>>
>>> [ 205.957004] systemd-shutdown[1]: Stopping MD /dev/md124p1 (259:6).
>>> [ 205.964177] systemd-shutdown[1]: Could not stop MD /dev/md124p1:
>>> Device or resource busy
>>>
>>> is most likely triggered by ioctl(STOP_ARRAY).
>>>
>>> And based on the code, I think the ioctl fails here:
>>>
>>> if (cmd == STOP_ARRAY || cmd == STOP_ARRAY_RO) {
>>> /* Need to flush page cache, and ensure no-one else
>>> opens
>>> * and writes
>>> */
>>> mutex_lock(&mddev->open_mutex);
>>> if (mddev->pers && atomic_read(&mddev->openers) > 1) {
>>> mutex_unlock(&mddev->open_mutex);
>>> err = -EBUSY;
>>> goto out; ////////////////////// HERE
>
> Yes, I suspect here as well, but I do some test with error injection to
> gurantee that ioctl(STOP_ARRAY) always return -EBUSY, but I found that
> system reboot didn't hang, it'll try a few times but eventually reboot
> finished.
>
>>> }
>>> if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
>>> mutex_unlock(&mddev->open_mutex);
>>> err = -EBUSY;
>>> goto out;
>>> }
>>> did_set_md_closing = true;
>>> mutex_unlock(&mddev->open_mutex);
>>> sync_blockdev(bdev);
>>> }
>>
>> Probably. The problem is why doesn't it manage to flush the page
>> cache? I find
>> strange that the problem appears only when trying to stop the array, I
>> get it
>> when trying to umount the filesystem, where it also hangs because of
>> the same
>> reason. The kworker thread runs continuously using 100% cpu of only 1
>> core.
>
> The kworker do you mean the daemon thread or the sync thread? runs
> continuously using 100% cpu doen't sounds correct to me.
>
That sounds more like kworker waiting on a mutex to be released.
Can you trigger a kdump while in that state?
Or do a sysrq-T to get a stack trace of all running processes?
That should tell you where exactly the 100% cpu time is being
wasted.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@...e.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman
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