From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 143DF2192F9; Fri, 15 Aug 2025 05:56:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755237366; cv=none; b=PZkGyyksgeXTNVVsc2DX4XX2snZLSIYtRw457uUsvgHcdnwDNRThXdxvHn/4+8QjH4ihKXf9mxYHL5qYAn24QWhVy4wptHVC9UO4D2B8xEAW0cm8inDD36H/3agkb0t+x3yU2r/Eenvt1eMTNdzVyfEdyxc16m60WeTWyM+r2iQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755237366; c=relaxed/simple; bh=bfKrrkTfyrpACOTNr5WVmWTWKBqGGumeVY6yYEwqPq4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HFNKZ/eez7aHIC/d4cY5LuuEe3brgV2mbYNczCzY1Sel/Q2WUfCoI2IFHxSx8ijzL9FmFdmVxpQgmWJsMr1j7feJFRcs/PnV2KoaDnHmaiWoAdXL1OB+hd3uM3oScbdNK7AomZJPxnD/NyzavpsRnW92vh1e6OsNbSs9XEc6RHc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mdAE6JbU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mdAE6JbU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56AB9C4CEEB; Fri, 15 Aug 2025 05:56:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755237365; bh=bfKrrkTfyrpACOTNr5WVmWTWKBqGGumeVY6yYEwqPq4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mdAE6JbUY7lLx9LHAyTfYwbSAkRe0rPYMOe/xDJyb2RTNZhxbE2qjanljm8/cuS0P WkDPpk7+uxT5BXifCcQ5f/zOa2xB1Dvm34tU9reas/eYMub1GKu/ZqBNejOVe6Z5EU zCabyP+4P+Pc3ZsNUwmV0kk38FLk+K+EvaN1sUCzwLZj+mOHAkfPuX+kukSje7v/XY hSjo9GNL6Z/ejQ6LuFE4NEtTCqLWsHce2cxaQu74z51keathXC2+5MsaXpduIfs1yX iq9aSNjFVWZHZq98ifEe8vl6BRqTWCapEmboxcUvLSFLZqu9gOXzlEB/8uaNa1ttQ1 atZWPnctRd5uA== Message-ID: Date: Fri, 15 Aug 2025 07:55:59 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net/nfc: Fix A-B/B-A deadlock between nfc_unregister_device and rfkill_fop_write To: Yunseong Kim , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Taehee Yoo , Byungchul Park , max.byungchul.park@gmail.com, yeoreum.yun@arm.com, ppbuk5246@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250814173142.632749-2-ysk@kzalloc.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; keydata= xsFNBFVDQq4BEAC6KeLOfFsAvFMBsrCrJ2bCalhPv5+KQF2PS2+iwZI8BpRZoV+Bd5kWvN79 cFgcqTTuNHjAvxtUG8pQgGTHAObYs6xeYJtjUH0ZX6ndJ33FJYf5V3yXqqjcZ30FgHzJCFUu JMp7PSyMPzpUXfU12yfcRYVEMQrmplNZssmYhiTeVicuOOypWugZKVLGNm0IweVCaZ/DJDIH gNbpvVwjcKYrx85m9cBVEBUGaQP6AT7qlVCkrf50v8bofSIyVa2xmubbAwwFA1oxoOusjPIE J3iadrwpFvsZjF5uHAKS+7wHLoW9hVzOnLbX6ajk5Hf8Pb1m+VH/E8bPBNNYKkfTtypTDUCj NYcd27tjnXfG+SDs/EXNUAIRefCyvaRG7oRYF3Ec+2RgQDRnmmjCjoQNbFrJvJkFHlPeHaeS BosGY+XWKydnmsfY7SSnjAzLUGAFhLd/XDVpb1Een2XucPpKvt9ORF+48gy12FA5GduRLhQU vK4tU7ojoem/G23PcowM1CwPurC8sAVsQb9KmwTGh7rVz3ks3w/zfGBy3+WmLg++C2Wct6nM Pd8/6CBVjEWqD06/RjI2AnjIq5fSEH/BIfXXfC68nMp9BZoy3So4ZsbOlBmtAPvMYX6U8VwD TNeBxJu5Ex0Izf1NV9CzC3nNaFUYOY8KfN01X5SExAoVTr09ewARAQABzSVLcnp5c3p0b2Yg S296bG93c2tpIDxrcnprQGtlcm5lbC5vcmc+wsGVBBMBCgA/AhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgBYhBJvQfg4MUfjVlne3VBuTQ307QWKbBQJoF1BKBQkWlnSaAAoJEBuTQ307 QWKbHukP/3t4tRp/bvDnxJfmNdNVn0gv9ep3L39IntPalBFwRKytqeQkzAju0whYWg+R/rwp +r2I1Fzwt7+PTjsnMFlh1AZxGDmP5MFkzVsMnfX1lGiXhYSOMP97XL6R1QSXxaWOpGNCDaUl ajorB0lJDcC0q3xAdwzRConxYVhlgmTrRiD8oLlSCD5baEAt5Zw17UTNDnDGmZQKR0fqLpWy 786Lm5OScb7DjEgcA2PRm17st4UQ1kF0rQHokVaotxRM74PPDB8bCsunlghJl1DRK9s1aSuN hL1Pv9VD8b4dFNvCo7b4hfAANPU67W40AaaGZ3UAfmw+1MYyo4QuAZGKzaP2ukbdCD/DYnqi tJy88XqWtyb4UQWKNoQqGKzlYXdKsldYqrLHGoMvj1UN9XcRtXHST/IaLn72o7j7/h/Ac5EL 8lSUVIG4TYn59NyxxAXa07Wi6zjVL1U11fTnFmE29ALYQEXKBI3KUO1A3p4sQWzU7uRmbuxn naUmm8RbpMcOfa9JjlXCLmQ5IP7Rr5tYZUCkZz08LIfF8UMXwH7OOEX87Y++EkAB+pzKZNNd hwoXulTAgjSy+OiaLtuCys9VdXLZ3Zy314azaCU3BoWgaMV0eAW/+gprWMXQM1lrlzvwlD/k whyy9wGf0AEPpLssLVt9VVxNjo6BIkt6d1pMg6mHsUEVzsFNBFVDXDQBEADNkrQYSREUL4D3 Gws46JEoZ9HEQOKtkrwjrzlw/tCmqVzERRPvz2Xg8n7+HRCrgqnodIYoUh5WsU84N03KlLue MNsWLJBvBaubYN4JuJIdRr4dS4oyF1/fQAQPHh8Thpiz0SAZFx6iWKB7Qrz3OrGCjTPcW6ei OMheesVS5hxietSmlin+SilmIAPZHx7n242u6kdHOh+/SyLImKn/dh9RzatVpUKbv34eP1wA GldWsRxbf3WP9pFNObSzI/Bo3kA89Xx2rO2roC+Gq4LeHvo7ptzcLcrqaHUAcZ3CgFG88CnA 6z6lBZn0WyewEcPOPdcUB2Q7D/NiUY+HDiV99rAYPJztjeTrBSTnHeSBPb+qn5ZZGQwIdUW9 YegxWKvXXHTwB5eMzo/RB6vffwqcnHDoe0q7VgzRRZJwpi6aMIXLfeWZ5Wrwaw2zldFuO4Dt 91pFzBSOIpeMtfgb/Pfe/a1WJ/GgaIRIBE+NUqckM+3zJHGmVPqJP/h2Iwv6nw8U+7Yyl6gU BLHFTg2hYnLFJI4Xjg+AX1hHFVKmvl3VBHIsBv0oDcsQWXqY+NaFahT0lRPjYtrTa1v3tem/ JoFzZ4B0p27K+qQCF2R96hVvuEyjzBmdq2esyE6zIqftdo4MOJho8uctOiWbwNNq2U9pPWmu 4vXVFBYIGmpyNPYzRm0QPwARAQABwsF8BBgBCgAmAhsMFiEEm9B+DgxR+NWWd7dUG5NDfTtB YpsFAmgXUF8FCRaWWyoACgkQG5NDfTtBYptO0w//dlXJs5/42hAXKsk+PDg3wyEFb4NpyA1v qmx7SfAzk9Hf6lWwU1O6AbqNMbh6PjEwadKUk1m04S7EjdQLsj/MBSgoQtCT3MDmWUUtHZd5 RYIPnPq3WVB47GtuO6/u375tsxhtf7vt95QSYJwCB+ZUgo4T+FV4hquZ4AsRkbgavtIzQisg Dgv76tnEv3YHV8Jn9mi/Bu0FURF+5kpdMfgo1sq6RXNQ//TVf8yFgRtTUdXxW/qHjlYURrm2 H4kutobVEIxiyu6m05q3e9eZB/TaMMNVORx+1kM3j7f0rwtEYUFzY1ygQfpcMDPl7pRYoJjB dSsm0ZuzDaCwaxg2t8hqQJBzJCezTOIkjHUsWAK+tEbU4Z4SnNpCyM3fBqsgYdJxjyC/tWVT AQ18NRLtPw7tK1rdcwCl0GFQHwSwk5pDpz1NH40e6lU+NcXSeiqkDDRkHlftKPV/dV+lQXiu jWt87ecuHlpL3uuQ0ZZNWqHgZoQLXoqC2ZV5KrtKWb/jyiFX/sxSrodALf0zf+tfHv0FZWT2 zHjUqd0t4njD/UOsuIMOQn4Ig0SdivYPfZukb5cdasKJukG1NOpbW7yRNivaCnfZz6dTawXw XRIV/KDsHQiyVxKvN73bThKhONkcX2LWuD928tAR6XMM2G5ovxLe09vuOzzfTWQDsm++9UKF a/A= In-Reply-To: <20250814173142.632749-2-ysk@kzalloc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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