From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793976979; b=yxJsZmTkl4X1KjJqerXmInsVUG+o8/KQggNdTLYiCGB38ol+YNQl6gIGLnegAYrxvBku Bni6i7rhob9oJPx3X0rFqVfg85cEFjyJG1iN7S4zfZGX+CO+wTMfUsVmlq37MoSFhFN9U EDjCE1nSifBb45/uD9sR1UiBz3pcIA6bAANLBSLSFQfpVnnY5KABT2A20/afdbF4LgDzO eekNQN6DimRklCiaYZHAHbJFJqUyGOEeNzEm6qPatOgYYv/Xw9Ip4Xh7bsnZjAD5QtNpw zplvJN7q+4kK0WEJv5mZOFo/VtG35iBCjIGqaMy1u7mfE/yfFiZX8lv7K1NKVncvW3w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793976979; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=IEZWLk/AGoUYBUKudPzypu/X+xW0lzdHtoUypJviS28=; b=KtSsJNaqKO6Q5br+N120L6y+67S2HpVmOEV8HH2+umqCP7C+9uJJEA/GOjkmEI3ztS9e jnHELol+CvwsDoyqe9R1yDUnkFuUWyVR2/pZyHf1+cW9FyZYpUgp7Vsed1q64SUvbarCQ Ke2DfAwTBcFDqeCC5RPdn5GUvJofGdFNP/vflBqCfLGWzRzE8gu7AYkhckv41QdZmvpln 0vwVcsV+Hk8X8zSivnHFrnLyNGRVnDccbaO/3dCXcYE/4RQTDvb1+/WlVdHepxbCAwthR xXmbBWPTvl5FfjmD7O4yklXhyxVLgVrulSw1cmEd7ZH4EwPcr7j4NuON83iWYVMqboQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nIVEYIF+; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D290B606A32C for ; Fri, 6 Nov 2026 14:56:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nIVEYIF+ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 928D01F0089F; Fri, 6 Nov 2026 14:56:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793976978; bh=IEZWLk/AGoUYBUKudPzypu/X+xW0lzdHtoUypJviS28=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=nIVEYIF+wFWUFZisTcFzMZjuDAMI6I/EkB9RBsWAFTjnhnJSDngR6DwwlXwK6mZ3h BFHtPzvKvnZmDXG/11/GYiPxpvy+38KraQMj9GyhkiwzwX4mqme8ezsOgdoD+Rv9X2 LIZLIAV8L2acig8nHU6tSW20X2CnBwPystXGoBir8KIPRd8zrVvPSq3TVqLWKrmEoR P0kT/9TgB6lsm4ykjTzkE3CZdhX5mtw5aHUKr/oaQMrKf1Wig27BzaSjaPuQ3uiSwh C/jCMeglzDm2W7UiED7zs25Ry0HPfNct9VUJyUQKg9mXy70kj3IQUyW24J5IwQ8cEf y+TVTJ6R2CWuA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2] serial: amba-pl011: touch the watchdogs in write_atomic() Reply-To: sashiko-reviews@lists.linux.dev To: "Breno Leitao" Cc: linux-serial@vger.kernel.org In-Reply-To: <20261106-pl011_touch-v2-1-8f4996113320@debian.org> References: <20261106-pl011_touch-v2-1-8f4996113320@debian.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 06 Nov 2026 14:56:18 +0000 X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > In emergency context, such as WARN(), nbcon prints the pending records > through write_atomic() with preemption disabled. >=20 > On arm64, WARN() can run with IRQs masked, so the whole backlog is > printed with IRQs off as well. >=20 > Commit 9bd18e1262c0 ("printk/nbcon: Restore IRQ in atomic flush after > each emitted record") does not help here, as it only restores the > caller's IRQ state between records. >=20 > pl011_console_write_atomic() busy-waits on the UART for every > character, and at 115200 baud it prints about 11.5KB per second. > Flushing a few hundred kilobytes outlasts the hard lockup threshold > (10 seconds by default), so the printing CPU is reported, or the > machine panics with hardlockup_panic set. See [1]. >=20 > The 8250 driver avoids this by calling touch_nmi_watchdog() while it > polls the transmitter. Do the same in pl011_console_write_atomic(), > once per record. >=20 > Suggested-by: John Ogness > Link: https://lore.kernel.org/all/87wlqtxb14.fsf@jogness.linutronix.de/ [= 1] > Reviewed-by: John Ogness > Reviewed-by: Petr Mladek > Signed-off-by: Breno Leitao Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261106-pl011_touc= h-v2-1-8f4996113320@debian.org?part=3D1