linux-kernel - Re: md_raid: mdX_raid6 looping after sync

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Date:   Mon, 8 Feb 2021 15:53:40 +0100
From:   Guoqing Jiang <guoqing.jiang@...ud.ionos.com>
To:     Donald Buczek <buczek@...gen.mpg.de>, Song Liu <song@...nel.org>,
        linux-raid@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        it+raid@...gen.mpg.de
Subject: Re: md_raid: mdX_raid6 looping after sync_action "check" to "idle"
 transition



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.

Thanks,
Guoqing