On 2/8/21 12:38, Donald Buczek wrote:

quoted

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