Re: [PATCH] s390/debug: Fix deadlock during unregister

> Unregistering an s390dbf debug area while one of the associated debugfs
> files is being written to can cause a deadlock:
> 
> $ echo >.../vmur/level    $ rmmod vmur
> ===================================================
> debugfs write
> debugfs_file_get()
>                           debug_unregister()
>                           mutex_lock(debug_mutex)
>                           debugfs_remove()
>                           wait for debugfs_file_put()
> debug_file_ops.write()
> debug_input()
> mutex_lock(debug_mutex) ==> DEADLOCK
> 
> Fix this by splitting debug_unregister() into an s390dbf and debugfs
> part, and running only the s390dbf part with debug_mutex locked.
> 
> Signed-off-by: Peter Oberparleiter <[email protected]>

Sashiko has reviewed this patch and found no issues. It looks great!

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