From: Krzysztof Kozlowski <krzk@kernel.org>
To: Yunseong Kim <ysk@kzalloc.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>, Taehee Yoo <ap420073@gmail.com>,
Byungchul Park <byungchul@sk.com>,
max.byungchul.park@gmail.com, yeoreum.yun@arm.com,
ppbuk5246@gmail.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net/nfc: Fix A-B/B-A deadlock between nfc_unregister_device and rfkill_fop_write
Date: Fri, 15 Aug 2025 07:55:59 +0200 [thread overview]
Message-ID: <e3cfdd98-6c51-479d-8d99-857316dcd64b@kernel.org> (raw)
In-Reply-To: <20250814173142.632749-2-ysk@kzalloc.com>
On 14/08/2025 19:31, Yunseong Kim wrote:
> A potential deadlock due to A-B/B-A deadlock exists between the NFC core
> and the RFKill subsystem, involving the NFC device lock and the
> rfkill_global_mutex.
>
> This issue is particularly visible on PREEMPT_RT kernels, which can
> report the following warning:
Why are not you crediting syzbot and its report?
there is clear INSTRUCTION in that email from Syzbot.
>
> | rtmutex deadlock detected
> | WARNING: CPU: 0 PID: 22729 at kernel/locking/rtmutex.c:1674 rt_mutex_handle_deadlock+0x68/0xec kernel/locking/rtmutex.c:-1
> | Modules linked in:
> | CPU: 0 UID: 0 PID: 22729 Comm: syz.7.2187 Kdump: loaded Not tainted 6.17.0-rc1-00001-g1149a5db27c8-dirty #55 PREEMPT_RT
> | Hardware name: QEMU KVM Virtual Machine, BIOS 2025.02-8ubuntu1 06/11/2025
> | pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> | pc : rt_mutex_handle_deadlock+0x68/0xec kernel/locking/rtmutex.c:-1
> | lr : rt_mutex_handle_deadlock+0x40/0xec kernel/locking/rtmutex.c:1674
> | sp : ffff8000967c7720
> | x29: ffff8000967c7720 x28: 1fffe0001946d182 x27: dfff800000000000
> | x26: 0000000000000001 x25: 0000000000000003 x24: 1fffe0001946d00b
> | x23: 1fffe0001946d182 x22: ffff80008aec8940 x21: dfff800000000000
> | x20: ffff0000ca368058 x19: ffff0000ca368c10 x18: ffff80008af6b6e0
> | x17: 1fffe000590b8088 x16: ffff80008046cc08 x15: 0000000000000001
> | x14: 1fffe000590ba990 x13: 0000000000000000 x12: 0000000000000000
> | x11: ffff6000590ba991 x10: 0000000000000002 x9 : 0fe446e029bcfe00
> | x8 : 0000000000000000 x7 : 0000000000000000 x6 : 000000000000003f
> | x5 : 0000000000000001 x4 : 0000000000001000 x3 : ffff800080503efc
> | x2 : 0000000000000001 x1 : 0000000000000001 x0 : 0000000000000001
This all is irrelevant, really. Trim the log.
> | Call trace:
> | rt_mutex_handle_deadlock+0x68/0xec kernel/locking/rtmutex.c:-1 (P)
> | __rt_mutex_slowlock+0x1cc/0x480 kernel/locking/rtmutex.c:1734
> | __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1760 [inline]
> | rt_mutex_slowlock+0x140/0x21c kernel/locking/rtmutex.c:1800
Best regards,
Krzysztof
next prev parent reply other threads:[~2025-08-15 5:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-14 17:31 [PATCH] net/nfc: Fix A-B/B-A deadlock between nfc_unregister_device and rfkill_fop_write Yunseong Kim
2025-08-15 5:55 ` Krzysztof Kozlowski [this message]
2025-08-15 8:23 ` Yunseong Kim
2025-08-17 5:45 ` Krzysztof Kozlowski
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