From nobody Mon Apr 13 17:13:47 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8964FC4332F for ; Mon, 14 Nov 2022 16:30:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237584AbiKNQ37 (ORCPT ); Mon, 14 Nov 2022 11:29:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237519AbiKNQ3j (ORCPT ); Mon, 14 Nov 2022 11:29:39 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D3BC26B for ; Mon, 14 Nov 2022 08:29:39 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1668443377; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eUV7NYFJOYRPWEVh0G/EU6zT1t7HGJ6qLPZoOxwFJX0=; b=hXrAuUk0veFL2Qfb6GL5q62iv8qbDJs1l0+JFrxmW/AwVib9zp2qJNhFunHfBfU9Zqg88+ JTlaYWS7koTSowUankx8ymKJVaHyRcKqL0FQPxX2kJ3jy87p7JCO3vqBZ1Xg6IdsGqC/oT lfU3BO3xPx8wKUf74di2LOduzLl9D0hKHBnVEf1DeVGsqjTcFOWF1MSo2/PAMnLQL8uQN3 VAD8oc3lspCaTS0b/swtjZpIdl7aAj3KT1/bn7t0kTKgCnK346lG/0P7emVoeyvNCFXDuy ffxx3KsbLdFJj2Cm/sFn07Hv/82wgyTbEOfHV2EOrBLqmpQmhXGCKMWHi2JSkQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1668443377; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eUV7NYFJOYRPWEVh0G/EU6zT1t7HGJ6qLPZoOxwFJX0=; b=QxyEvyxZCYa8n5ddhd4y/3oG8Ik1RqNDjid21OVOW9aSygXYvipEI3nPBP20kFecVjgnoJ PQ89LtwsJTOe6+DQ== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org Subject: [PATCH printk v4 06/39] um: kmsg_dump: only dump when no output console available Date: Mon, 14 Nov 2022 17:34:59 +0106 Message-Id: <20221114162932.141883-7-john.ogness@linutronix.de> In-Reply-To: <20221114162932.141883-1-john.ogness@linutronix.de> References: <20221114162932.141883-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The initial intention of the UML kmsg_dumper is to dump the kernel buffers to stdout if there is no console available to perform the regular crash output. However, if ttynull was registered as a console, no crash output was seen. Commit e23fe90dec28 ("um: kmsg_dumper: always dump when not tty console") tried to fix this by performing the kmsg_dump unless the stdio console was behind /dev/console or enabled. But this allowed kmsg dumping to occur even if other non-stdio consoles will output the crash output. Also, a console being the driver behind /dev/console has nothing to do with a crash scenario. Restore the initial intention by dumping the kernel buffers to stdout only if a non-ttynull console is registered and enabled. Also add detailed comments so that it is clear why these rules are applied. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- arch/um/kernel/kmsg_dump.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 0224fcb36e22..40abf1e9ccb1 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -17,13 +17,22 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dump= er, unsigned long flags; size_t len =3D 0; =20 - /* only dump kmsg when no console is available */ + /* + * If no consoles are available to output crash information, dump + * the kmsg buffer to stdout. + */ + if (!console_trylock()) return; =20 for_each_console(con) { - if(strcmp(con->name, "tty") =3D=3D 0 && - (con->flags & (CON_ENABLED | CON_CONSDEV)) !=3D 0) { + /* + * The ttynull console and disabled consoles are ignored + * since they cannot output. All other consoles are + * expected to output the crash information. + */ + if (strcmp(con->name, "ttynull") !=3D 0 && + (con->flags & CON_ENABLED)) { break; } } --=20 2.30.2