From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EA42F3D76; Mon, 1 Jun 2026 07:27:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780298852; cv=none; b=Z5BglWGegr9mj7CH+WfnNXoscUCDABg8TtPvyFf8jTSUPVTPJhubGL8lq8AK/UeP9rRHmTmZ0N1aa5bQNYnIHOMC/2f8u5+emhM4ZAg65x31FjJcKMDAmkqcgnWLbjcqtFjdKQywvGWG5ZKo1UIFOInqmN7zlZA2t4pl4mvVxQU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780298852; c=relaxed/simple; bh=wMbTWGjuic+ST4Ffoux/6Etu/zn8n6qCExrO5zXlApU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=p6NcXb1KqZufz/yJiPP4MzGxLsVHghj0xA4YZZU0SouiHSJReBfppWUu0Tn5WvmqdnJ3xobQVubW4pS8SREf5myT+LIp3RGxBG9Q2Y0RVm0lb/xbrHsT8SWzneZX9CXj+SU3fOiGr83VL/AYIQ5qroX5Sd1iRIj6I98MyZxZwWY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nh5A+/2+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nh5A+/2+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1B2C91F00893; Mon, 1 Jun 2026 07:27:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780298851; bh=7snzxVSxi3ygpRfS5YXqVDVEjeMpSEmeXDAlj457stQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=nh5A+/2+SKdjoxjd86GM0PCvAAeKdRkq/p3dDhUACVQd6trP2iinS0Syj3YdTIWSn Oui2ZipEIJYLhXkJfaHiTQfRgfcmaAXyK2Lutu2w/zHLSAHjdYXcQE6k2U7EZ0Se1C gDqQa2HIyhRF3OO3L4YIbOCyGSMWsw9JiW3HFAPAJCziBb7TULD5piMuw/w1/WZNwS STjZ5DbyCyIKqaH1ZdKv+PDwEdoqanVb9TBdYK1tFeckoGALkOlSJ1m4v6VxhEhywd QeDrTbKlUYLZvvZoie4GBQ4lHeMmAh28EQzmYMLrGkKpR+j+jXv9y0JGbUXl7ZayTd 4f3XC1igsx/vQ== Message-ID: <1e11dea6-a9a4-425e-a31b-ab5f8561f3b8@kernel.org> Date: Mon, 1 Jun 2026 17:27:21 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net 09/10] mptcp: pm: avoid sleeping while holding rcu_read_lock Content-Language: fr To: Sebastian Andrzej Siewior Cc: Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Florian Westphal , netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, stable@vger.kernel.org, Clark Williams , Steven Rostedt , Hannes Reinecke , linux-rt-devel@lists.linux.dev References: <20260601-net-mptcp-misc-fixes-7-1-rc7-v1-0-a5ae7791754b@kernel.org> <20260601-net-mptcp-misc-fixes-7-1-rc7-v1-9-a5ae7791754b@kernel.org> <20260601065813.Z8V8Tb6d@linutronix.de> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU c7SPFMpMesgpcu1xFt0F6bcxE+0ojRtSCZ5HDElKlHJNYtD1uwY4UYVGWUGCF/+cY1YLmtfb WdNb/SFo+Mp0HItfBC12qtDIXYvbfNUGVnA5jXeWMEyYhSNktLnpDL2gBUCsdbkov5VjiOX7 CRTkX0UgNWRjyFZwThaZADEvAOo12M5uSBk7h07yJ97gqvBtcx45IsJwfUJE4hy8qZqsA62A nTRflBvp647IXAiCcwWsEgE5AXKwA3aL6dcpVR17JXJ6nwHHnslVi8WesiqzUI9sbO/hXeXw TDSB+YhErbNOxvHqCzZEnGAAFf6ges26fRVyuU119AzO40sjdLV0l6LE7GshddyazWZf0iac nEhX9NKxGnuhMu5SXmo2poIQttJuYAvTVUNwQVEx/0yY5xmiuyqvXa+XT7NKJkOZSiAPlNt6 VffjgOP62S7M9wDShUghN3F7CPOrrRsOHWO/l6I/qJdUMW+MHSFYPfYiFXoLUZyPvNVCYSgs 3oQaFhHapq1f345XBtfG3fOYp1K2wTXd4ThFraTLl8PHxCn4ywARAQABzSRNYXR0aGlldSBC YWVydHMgPG1hdHR0YmVAa2VybmVsLm9yZz7CwZEEEwEIADsCGwMFCwkIBwIGFQoJCAsCBBYC AwECHgECF4AWIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZUDpDAIZAQAKCRD2t4JPQmmgcz33 EACjROM3nj9FGclR5AlyPUbAq/txEX7E0EFQCDtdLPrjBcLAoaYJIQUV8IDCcPjZMJy2ADp7 /zSwYba2rE2C9vRgjXZJNt21mySvKnnkPbNQGkNRl3TZAinO1Ddq3fp2c/GmYaW1NWFSfOmw MvB5CJaN0UK5l0/drnaA6Hxsu62V5UnpvxWgexqDuo0wfpEeP1PEqMNzyiVPvJ8bJxgM8qoC cpXLp1Rq/jq7pbUycY8GeYw2j+FVZJHlhL0w0Zm9CFHThHxRAm1tsIPc+oTorx7haXP+nN0J iqBXVAxLK2KxrHtMygim50xk2QpUotWYfZpRRv8dMygEPIB3f1Vi5JMwP4M47NZNdpqVkHrm jvcNuLfDgf/vqUvuXs2eA2/BkIHcOuAAbsvreX1WX1rTHmx5ud3OhsWQQRVL2rt+0p1DpROI 3Ob8F78W5rKr4HYvjX2Inpy3WahAm7FzUY184OyfPO/2zadKCqg8n01mWA9PXxs84bFEV2mP VzC5j6K8U3RNA6cb9bpE5bzXut6T2gxj6j+7TsgMQFhbyH/tZgpDjWvAiPZHb3sV29t8XaOF BwzqiI2AEkiWMySiHwCCMsIH9WUH7r7vpwROko89Tk+InpEbiphPjd7qAkyJ+tNIEWd1+MlX ZPtOaFLVHhLQ3PLFLkrU3+Yi3tXqpvLE3gO3LM7BTQRV4/npARAA5+u/Sx1n9anIqcgHpA7l 5SUCP1e/qF7n5DK8LiM10gYglgY0XHOBi0S7vHppH8hrtpizx+7t5DBdPJgVtR6SilyK0/mp 9nWHDhc9rwU3KmHYgFFsnX58eEmZxz2qsIY8juFor5r7kpcM5dRR9aB+HjlOOJJgyDxcJTwM 1ey4L/79P72wuXRhMibN14SX6TZzf+/XIOrM6TsULVJEIv1+NdczQbs6pBTpEK/G2apME7vf mjTsZU26Ezn+LDMX16lHTmIJi7Hlh7eifCGGM+g/AlDV6aWKFS+sBbwy+YoS0Zc3Yz8zrdbi Kzn3kbKd+99//mysSVsHaekQYyVvO0KD2KPKBs1S/ImrBb6XecqxGy/y/3HWHdngGEY2v2IP Qox7mAPznyKyXEfG+0rrVseZSEssKmY01IsgwwbmN9ZcqUKYNhjv67WMX7tNwiVbSrGLZoqf Xlgw4aAdnIMQyTW8nE6hH/Iwqay4S2str4HZtWwyWLitk7N+e+vxuK5qto4AxtB7VdimvKUs x6kQO5F3YWcC3vCXCgPwyV8133+fIR2L81R1L1q3swaEuh95vWj6iskxeNWSTyFAVKYYVskG V+OTtB71P1XCnb6AJCW9cKpC25+zxQqD2Zy0dK3u2RuKErajKBa/YWzuSaKAOkneFxG3LJIv Hl7iqPF+JDCjB5sAEQEAAcLBXwQYAQIACQUCVeP56QIbDAAKCRD2t4JPQmmgc5VnD/9YgbCr HR1FbMbm7td54UrYvZV/i7m3dIQNXK2e+Cbv5PXf19ce3XluaE+wA8D+vnIW5mbAAiojt3Mb 6p0WJS3QzbObzHNgAp3zy/L4lXwc6WW5vnpWAzqXFHP8D9PTpqvBALbXqL06smP47JqbyQxj Xf7D2rrPeIqbYmVY9da1KzMOVf3gReazYa89zZSdVkMojfWsbq05zwYU+SCWS3NiyF6QghbW voxbFwX1i/0xRwJiX9NNbRj1huVKQuS4W7rbWA87TrVQPXUAdkyd7FRYICNW+0gddysIwPoa KrLfx3Ba6Rpx0JznbrVOtXlihjl4KV8mtOPjYDY9u+8x412xXnlGl6AC4HLu2F3ECkamY4G6 UxejX+E6vW6Xe4n7H+rEX5UFgPRdYkS1TA/X3nMen9bouxNsvIJv7C6adZmMHqu/2azX7S7I vrxxySzOw9GxjoVTuzWMKWpDGP8n71IFeOot8JuPZtJ8omz+DZel+WCNZMVdVNLPOd5frqOv mpz0VhFAlNTjU1Vy0CnuxX3AM51J8dpdNyG0S8rADh6C8AKCDOfUstpq28/6oTaQv7QZdge0 JY6dglzGKnCi/zsmp2+1w559frz4+IC7j/igvJGX4KDDKUs0mlld8J2u2sBXv7CGxdzQoHaz lzVbFe7fduHbABmYz9cefQpO7wDE/Q== Organization: NGI0 Core In-Reply-To: <20260601065813.Z8V8Tb6d@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Sebastian, Thank you for the review! On 01/06/2026 16:58, Sebastian Andrzej Siewior wrote: > On 2026-06-01 13:10:05 [+1000], Matthieu Baerts (NGI0) wrote: >> sk_stop_timer_sync() calls del_timer_sync(), which spin-waits for the > There is no del_timer_sync() Indeed, not sure why I put that one. I wanted to say timer_delete_sync() >> timer callback to complete on non-RT kernels. But on PREEMPT_RT, it can >> sleep. Sleeping inside an RCU read-side critical section might trigger a >> lockdep splat. > > It can not sleep. timer_delete_sync() does not sleep. It can block on > spinlock_t and schedule but this is okay within a RCU read section. Sorry, I got confused by the comment in __timer_delete_sync(). > Do you have a report for this? No, sorry. I was exploring the code in timer.c after a related comment from Sashiko [1]. I noticed the comment in __timer_delete_sync() about being able to sleep on PREEMPT_RT, then saw that timer_delete_sync() was called inside a rcu_read_lock(), and I thought it was wrong. I should have tried to reproduce the warning on PREEMPT_RT, but I switched to the next bug instead :-/ Sorry for the noise, let's drop this patch if it is not needed then. [1] https://github.com/multipath-tcp/mptcp_net-next/issues/623 Cheers, Matt -- Sponsored by the NGI0 Core fund.