From nobody Thu Dec 18 11:25:50 2025 Received: from NAM11-DM6-obe.outbound.protection.outlook.com (mail-dm6nam11on2068.outbound.protection.outlook.com [40.107.223.68]) (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 2846B3A1BB; Thu, 1 Feb 2024 10:33:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.223.68 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706783596; cv=fail; b=d3OvepfqCwEi4cQsLXBG9z1ACY+9hawZrW9kZegIr5vqfMaojeiIYf2JLyuWcNOWbgR9+gweF2CsOcSCGBeoIP4fkVS5FqJBrqGATOSwhQsrfk2poVememcK3ani6kiaf8OIeofG/6/axNX1p+QrXwNderlwn/ETN7oxqqYjLhc= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706783596; c=relaxed/simple; bh=G7cRbRPxs8CUJ1VViTGx72ig0XolbIz4vieMwZ6ZtUc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HQZJHWb0lpLDaw8u+7S4yuk3f73FKEpolvG70/R9TnxV8735aR2ZxXTGSuk+kvNLvT+jLZRqIgn84z2eYbygyTnm0BeNLpSJSUmU3ynOvdwsXf5u2EAPna0nKtroQr20YPnJz/lITv725pg080YdtGeswCzcb1na6PNFLoh5lXg= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sony.com; spf=pass smtp.mailfrom=sony.com; dkim=pass (1024-bit key) header.d=Sony.onmicrosoft.com header.i=@Sony.onmicrosoft.com header.b=FVoRHlHb; arc=fail smtp.client-ip=40.107.223.68 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sony.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sony.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=Sony.onmicrosoft.com header.i=@Sony.onmicrosoft.com header.b="FVoRHlHb" ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=F/mdVVJu2qP5yNPefKI0U+ZCBdC/urlu7vNMnylv4JXDD9EbkTVfH/C584qymmzw1xwFeMglpx2Fioqy010oYOKYYPyK0bQ0H8Y4fNsXMXYSypBsQKDw0RMPBimm2tnxKOAMcndRmSCPWqD+14i7QPqmWG+xOceX0J62eni8pBLZ72awOA6rtkJszhB+sQuakh5UiFHRU2lNQvEy+2TKYwAaDYYv5lgUK4K7oMbHhkm5JebcTCRbT8khB9q+TwL1Uo5TIUnRxcrLT1BeAZN1ZX9K2Slh2zqQxWqa4FvrhuTHrUBp7V21AWGRv+WVPD3AYnBq+7HAzv6IiPtghTFtoA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=yLs2P3s49bjsbevW4T9Hhuh5aR5rSGmElejR7NCZc/g=; b=RGO9ahAv+oQwhbA5i71wNTyWEdYW9LpRPTs7b68lTbRjqevknhnVS+M+mK/fdQHHIOPHeh2ThgZnvu+murkDGXF3kk18kb+8RhOTRm1r8NFCq/8n2+KmBB+noIySzZCcpMHPkMYqOlZ0PbcEHcqy0Pk6v0rPtyGT02eg085432hSlaCQMgEebox6UDg6ljTN2GQ3NeHTlxMEPZ59dYt7SDnywSiROk/6VzhUIkfVA/uXav8L2WwsLj2aoilQSY8Q/awiYn7drW8su6YkE/+lCxQHHaZxnNpK7Bx6J2kpyfOExM8335P/OevmZKEm5H13JsXFPiBtB0HZ02tZkITtgw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=fail (sender ip is 121.100.38.196) smtp.rcpttodomain=vger.kernel.org smtp.mailfrom=sony.com; dmarc=fail (p=none sp=none pct=100) action=none header.from=sony.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Sony.onmicrosoft.com; s=selector2-Sony-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=yLs2P3s49bjsbevW4T9Hhuh5aR5rSGmElejR7NCZc/g=; b=FVoRHlHbTDGN/IVgACwfgNTvddVkZshiaU/hWpY1FB30ZskaSyEZRkWVPy/WXbaEmFAO8PmPeBj1iS5OrOQTONfSRnVmfZ7319LqCV6LghNkI+LJ6i/sQ/91n0JejXC2r8wVDQ55k7qJMHPI3rNJ4yVrFneq/l0AnJSVwTrAOWE= Received: from CH0PR03CA0243.namprd03.prod.outlook.com (2603:10b6:610:e5::8) by SJ0PR13MB5983.namprd13.prod.outlook.com (2603:10b6:a03:43f::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7228.34; Thu, 1 Feb 2024 10:33:12 +0000 Received: from DS2PEPF00003443.namprd04.prod.outlook.com (2603:10b6:610:e5:cafe::56) by CH0PR03CA0243.outlook.office365.com (2603:10b6:610:e5::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7249.24 via Frontend Transport; Thu, 1 Feb 2024 10:33:12 +0000 X-MS-Exchange-Authentication-Results: spf=fail (sender IP is 121.100.38.196) smtp.mailfrom=sony.com; dkim=none (message not signed) header.d=none;dmarc=fail action=none header.from=sony.com; Received-SPF: Fail (protection.outlook.com: domain of sony.com does not designate 121.100.38.196 as permitted sender) receiver=protection.outlook.com; client-ip=121.100.38.196; helo=gepdcl07.sg.gdce.sony.com.sg; Received: from gepdcl07.sg.gdce.sony.com.sg (121.100.38.196) by DS2PEPF00003443.mail.protection.outlook.com (10.167.17.70) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7249.19 via Frontend Transport; Thu, 1 Feb 2024 10:33:11 +0000 Received: from gepdcl04.s.gdce.sony.com.sg (SGGDCSE1NS08.sony.com.sg [146.215.123.198]) by gepdcl07.sg.gdce.sony.com.sg (8.14.7/8.14.4) with ESMTP id 411AVlS0022120 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 1 Feb 2024 18:32:52 +0800 Received: from mail.sony.com ([43.88.80.246]) by gepdcl04.s.gdce.sony.com.sg (8.14.7/8.14.4) with ESMTP id 411AVFXd012375; Thu, 1 Feb 2024 18:31:15 +0800 Received: by mail.sony.com (Postfix, from userid 1000) id 70FBB20C1C4D; Thu, 1 Feb 2024 15:59:42 +0530 (IST) Date: Thu, 1 Feb 2024 15:59:42 +0530 From: Sreenath Vijayan To: john.ogness@linutronix.de, corbet@lwn.net, gregkh@linuxfoundation.org, jirislaby@kernel.org, pmladek@suse.com Cc: rdunlap@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, taichi.shimoyashiki@sony.com, daniel.palmer@sony.com, anandakumar.balasubramaniam@sony.com, sreenath.vijayan@sony.com Subject: [PATCH v4 2/2] tty/sysrq: Dump printk ring buffer messages via sysrq Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS2PEPF00003443:EE_|SJ0PR13MB5983:EE_ X-MS-Office365-Filtering-Correlation-Id: 2a94104c-5cf2-4bcd-ecba-08dc231130c4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:121.100.38.196;CTRY:SG;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:gepdcl07.sg.gdce.sony.com.sg;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230031)(4636009)(346002)(376002)(396003)(39860400002)(136003)(230922051799003)(451199024)(1800799012)(64100799003)(82310400011)(186009)(40470700004)(36840700001)(46966006)(41300700001)(47076005)(83380400001)(107886003)(6266002)(426003)(336012)(26005)(8676002)(356005)(36860700001)(4326008)(44832011)(450100002)(15650500001)(5660300002)(82740400003)(8936002)(2906002)(478600001)(81166007)(42186006)(316002)(2616005)(70206006)(36756003)(82960400001)(86362001)(40480700001)(40460700003)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: sony.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Feb 2024 10:33:11.2208 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2a94104c-5cf2-4bcd-ecba-08dc231130c4 X-MS-Exchange-CrossTenant-Id: 66c65d8a-9158-4521-a2d8-664963db48e4 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=66c65d8a-9158-4521-a2d8-664963db48e4;Ip=[121.100.38.196];Helo=[gepdcl07.sg.gdce.sony.com.sg] X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: TreatMessagesAsInternal-DS2PEPF00003443.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR13MB5983 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When terminal is unresponsive, one cannot use dmesg to view printk ring buffer messages. Also, syslog services may be disabled, to check the messages after a reboot, especially on embedded systems. In this scenario, dump the printk ring buffer messages via sysrq by pressing sysrq+D. Signed-off-by: Sreenath Vijayan Signed-off-by: Shimoyashiki Taichi Reviewed-by: John Ogness --- Documentation/admin-guide/sysrq.rst | 2 ++ drivers/tty/sysrq.c | 20 +++++++++++++++++++- 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guid= e/sysrq.rst index 2f2e5bd440f9..c634e8b4cea2 100644 --- a/Documentation/admin-guide/sysrq.rst +++ b/Documentation/admin-guide/sysrq.rst @@ -161,6 +161,8 @@ Command Function will be printed to your console. (``0``, for example would make it so that only emergency messages like PANICs or OOPSes would make it to your console.) + +``D`` Dump the printk ring buffer =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D =20 Okay, so what can I use them for? diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 02217e3c916b..365f7fa145f0 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -450,6 +450,24 @@ static const struct sysrq_key_op sysrq_unrt_op =3D { .enable_mask =3D SYSRQ_ENABLE_RTNICE, }; =20 +static void dmesg_dump_callback(struct work_struct *work) +{ + dump_printk_buffer(); +} + +static DECLARE_WORK(sysrq_dmesg_work, dmesg_dump_callback); + +static void sysrq_handle_dmesg_dump(u8 key) +{ + queue_work(system_unbound_wq, &sysrq_dmesg_work); +} +static struct sysrq_key_op sysrq_dmesg_dump_op =3D { + .handler =3D sysrq_handle_dmesg_dump, + .help_msg =3D "dump-dmesg(D)", + .action_msg =3D "Dump dmesg", + .enable_mask =3D SYSRQ_ENABLE_DUMP, +}; + /* Key Operations table and lock */ static DEFINE_SPINLOCK(sysrq_key_table_lock); =20 @@ -505,7 +523,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = =3D { NULL, /* A */ NULL, /* B */ NULL, /* C */ - NULL, /* D */ + &sysrq_dmesg_dump_op, /* D */ NULL, /* E */ NULL, /* F */ NULL, /* G */ --=20 2.43.0