From: Heiko Carstens <hca@linux.ibm.com>
To: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
linux-s390@vger.kernel.org, Ilya Leoshkevich <iii@linux.ibm.com>
Subject: Re: [PATCH] s390/debug: Fix deadlock during unregister
Date: Wed, 12 Aug 2026 12:11:14 +0200 [thread overview]
Message-ID: <20260812101114.18999A06-hca@linux.ibm.com> (raw)
In-Reply-To: <20260812075319.2007940-1-oberpar@linux.ibm.com>
On Wed, Aug 12, 2026 at 09:53:19AM +0200, Peter Oberparleiter wrote:
> 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 <oberpar@linux.ibm.com>
> ---
> arch/s390/kernel/debug.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
next prev parent reply other threads:[~2026-08-12 10:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-12 7:53 [PATCH] s390/debug: Fix deadlock during unregister Peter Oberparleiter
2026-08-12 8:02 ` sashiko-bot
2026-08-12 10:11 ` Heiko Carstens [this message]
2026-08-12 14:28 ` Vasily Gorbik
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