s390/debug: Fix deadlock during unregister

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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.

Fixes: 9372a82892 ("s390/debug: fix debug area life cycle")
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

...

This commit is contained in:

Peter Oberparleiter 2026-08-12 09:53:19 +02:00 • committed by Vasily Gorbik

parent 337bd95507

commit 445c31ac63

1 changed files with 8 additions and 2 deletions

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arch/s390/kernel/debug.c

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