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[2620:137:e000::1:20]) by mx.google.com with ESMTP id w18-20020a50fa92000000b00461d5afea01si8286588edr.165.2022.11.07.06.19.16; Mon, 07 Nov 2022 06:19:40 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=kgfOV8TY; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b=vWS9R1RB; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231689AbiKGORK (ORCPT + 99 others); Mon, 7 Nov 2022 09:17:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232099AbiKGOQq (ORCPT ); Mon, 7 Nov 2022 09:16:46 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0DC151CFF1 for ; Mon, 7 Nov 2022 06:16:45 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1667830603; 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=6/paKzOHPdL7LtYxjVc5vEnqdv9ZQ5lgTtMtTQHWNnQ=; b=kgfOV8TY/LzEY5UzgRdT3BlvUS4J1DgI43rtqiBP9Hat6fe0tbknUSa2d0RAAIOO+gTscI 9gmZ/Oe5VTwP6nr6aI5cirDD8ru3D4TaVVzQzcKFr/nXfUWAbIm76g0tG7oACi1zAypM21 wSACcAaMqT+08PtymJMHqyyKDvN6rE0eGaya9a2kYmWdI+WL8S/v3bS5NYBqugmdS4eUgw 2PBFr7mml7AoQQIqx6L9iXf/WfFvtkQbEyOJtpgmt4m1tvzCh+5Ks6dDOcremWNzfpqzKp 9uTWvROhtIUwlxLIz7tHhRdcrNZtybOB6R8xqouGyYP+HcGLH3dnVTezBOcTHQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1667830603; 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=6/paKzOHPdL7LtYxjVc5vEnqdv9ZQ5lgTtMtTQHWNnQ=; b=vWS9R1RBOLVJYj2nIE+UOu47k28bDRXb6conZQphvOjHz1Y9ErtSJTCEnA7Fn3BAEIUYkJ oQTGziecwCDdfmAQ== 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 v3 06/40] um: kmsg_dump: only dump when no output console available Date: Mon, 7 Nov 2022 15:22:04 +0106 Message-Id: <20221107141638.3790965-7-john.ogness@linutronix.de> In-Reply-To: <20221107141638.3790965-1-john.ogness@linutronix.de> References: <20221107141638.3790965-1-john.ogness@linutronix.de> MIME-Version: 1.0 X-Spam-Status: No, score=-3.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,INVALID_DATE_TZ_ABSURD, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1748847328428193040?= X-GMAIL-MSGID: =?utf-8?q?1748847328428193040?= 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 *dumper, unsigned long flags; size_t len = 0; - /* 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; for_each_console(con) { - if(strcmp(con->name, "tty") == 0 && - (con->flags & (CON_ENABLED | CON_CONSDEV)) != 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") != 0 && + (con->flags & CON_ENABLED)) { break; } }