From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B89BC47254 for ; Fri, 1 May 2020 01:45:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E464D2074A for ; Fri, 1 May 2020 01:44:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Tcshg76Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728088AbgEABo6 (ORCPT ); Thu, 30 Apr 2020 21:44:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1727114AbgEABo5 (ORCPT ); Thu, 30 Apr 2020 21:44:57 -0400 Received: from mail-pl1-x643.google.com (mail-pl1-x643.google.com [IPv6:2607:f8b0:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF7B6C035494; Thu, 30 Apr 2020 18:44:57 -0700 (PDT) Received: by mail-pl1-x643.google.com with SMTP id n24so3120957plp.13; Thu, 30 Apr 2020 18:44:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=BJDB9lPyIL7yqfOmHsy2HCj6CJV5Y/ygJ4a/Yt4ueRw=; b=Tcshg76Y97lKweEKu4Gzgm583bqlkziZ4JStrZoKgao6MtHeAoodWQhMVO/lXjIY2G FvsHOLLcC0UIstahZaZG+KZ1bEgNSTltcuxq5krvhF6cOgx9Rh62+aJTs5Ho+2hC1v/i V/0Q+bgjzZQqIT5kvZzSa/8UWZi1+rWuqj3VP1iNWOL43pzieMbHk4n/WkLOh3uiq6sn VA4Y6GIn4cKd1U2WqH8DlczT3VzTPWI2DaO+ZuGk93UcqyB3SQ/rCq9jOTYNSXV1GJk2 I/N01tnibHm6+a7oRtKOCa1vkElQ/Nxn5qwvm7yJQmzRGlMHW3zA8RMgLEfDq0HeWpOh v2UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=BJDB9lPyIL7yqfOmHsy2HCj6CJV5Y/ygJ4a/Yt4ueRw=; b=nin/uEBjSoD4c/5FEt0TEzvRMtHRD55QWEahE4F6fFHL9zc7BpUdDdXdxLOh5jmxEI E/yWGmXvvtUYFhLHvT6GQzabuokc0uiXgx9c522DhxabeI3ulkirVdQWMD4uhA2GDKNV OASbvmnAnNiOWMMvm7t0FvBl716Z8rLwGY9wJN0aTrNXCOB4tOOPY0B3Ho6+Jt/9M8+e AaCTJuO6XtbsGcqOfrbhQ/oa+B1k26HmndzPcq++EithKgm/hj4fc/OLM6o/KzVl3czt wGgWtBZo7094XXFoF4/9CihIsymztzxx1oN1dGOMuPCknhzuow0k9PErgaXnrKQ/gR8k 1h4Q== X-Gm-Message-State: AGi0Pub5KrAfzvy+PzKq7DYvcqfEOnOFn9b+d/H3SDRS87Kys48B+4UY ZA9Pv0w7pHUREBLSMZOYDxA= X-Google-Smtp-Source: APiQypLCLfp3rK10yUdbPAE4Edv32G102rWA36hKIIpdEzEYeJyZFhsbGJpCwWMJe+hOipaDHzEbbg== X-Received: by 2002:a17:90a:2606:: with SMTP id l6mr1770330pje.188.1588297497099; Thu, 30 Apr 2020 18:44:57 -0700 (PDT) Received: from localhost (146.85.30.125.dy.iij4u.or.jp. [125.30.85.146]) by smtp.gmail.com with ESMTPSA id d18sm850855pfq.177.2020.04.30.18.44.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2020 18:44:56 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Fri, 1 May 2020 10:44:54 +0900 To: Alper Nebi Yasak Cc: Greg Kroah-Hartman , Jiri Slaby , Petr Mladek , Sergey Senozhatsky , linux-serial@vger.kernel.org, Steven Rostedt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Andrew Morton , Andy Shevchenko , Arvind Sankar , Benjamin Herrenschmidt , "David S. Miller" , Feng Tang Subject: Re: [RFC PATCH v2 1/3] printk: Add function to set console to preferred console's driver Message-ID: <20200501014454.GB288759@jagdpanzerIV.localdomain> References: <20200430161438.17640-1-alpernebiyasak@gmail.com> <20200430161438.17640-2-alpernebiyasak@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200430161438.17640-2-alpernebiyasak@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/04/30 19:14), Alper Nebi Yasak wrote: > Currently, add_preferred_console sets a preferred console, but doesn't > actually change /dev/console to match it. That part is handled within > register_device, where a newly registered console driver will be set as > /dev/console if it matches the preferred console. > > However, if the relevant driver is already registered, the only way to > set it as /dev/console is by un-registering and re-registering it. Hmm. Preferred console selection is very fragile, there are too many setups and workarounds that even minor tweaks introduce regressions oftentimes. We have, by the way, a pending patchset which changes the same are - preferred console selection. git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git for-5.7-preferred-console [..] > An example is the xenfb_make_preferred_console() function: > > console_lock(); > for_each_console(c) { > if (!strcmp(c->name, "tty") && c->index == 0) > break; > } > console_unlock(); > if (c) { > unregister_console(c); > c->flags |= CON_CONSDEV; > c->flags &= ~CON_PRINTBUFFER; /* don't print again */ > register_console(c); > } I didn't know about this code. > The code above was introduced in commit 9e124fe16ff2 ("xen: Enable > console tty by default in domU if it's not a dummy"). In short, it's aim > is to set VT as the preferred console only after a working framebuffer > is registered and thus VT is not the dummy device. > > This patch introduces an update_console_to_preferred function that > handles the necessary /dev/console change. With this change, the example > above can be replaced with: > > console_lock(); > add_preferred_console("tty", 0, NULL); > update_console_to_preferred(); > console_unlock(); > > More importantly, these two calls can be moved to vt.c in order to bump > its priority when a non-dummy backend for it is introduced, solving that > problem in general. Let me take a look over the weekend. -ss From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A40FC4724C for ; Fri, 1 May 2020 01:45:06 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1D3AA2074A for ; Fri, 1 May 2020 01:45:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="SzSq6S7i"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Tcshg76Y" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1D3AA2074A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:Date:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=GcHXE3h+0FDaADhMfLifrEMw5m6XU9IlDSoariPV65k=; b=SzSq6S7iUIf8dZ FzxzyQVa1CT8b7kUtTKAdLqfme10JupfIi7fB/1wSwBxJ2X6p7AVeM1RE9KCVsBV34urrY79hO5s6 gVoMKHIISgRhvz6Tznlsp+NMY78zNPlNC6XLTUi3NuyhDAE+01+wkucd2fj5HctKSiap0Z7hWXmES buD0+hJPNRRufRX089HpvrhG0GFsGyqmG1d4UD2IaLtHs4GyTZt63Cw0RW79Md4CF5JiG9ONtASdQ YBVXKXryhGM9DKn1RDOFUF2OJ/hlAubJvs+12ivxVI+2wmt72tl543jqvC/j52x3vaRP1DoQuXiCm WwWZlrjecCVwuHLDFK/Q==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jUKjc-0000qu-Rj; Fri, 01 May 2020 01:45:00 +0000 Received: from mail-pj1-x1044.google.com ([2607:f8b0:4864:20::1044]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jUKja-0000qC-6Z for linux-arm-kernel@lists.infradead.org; Fri, 01 May 2020 01:44:59 +0000 Received: by mail-pj1-x1044.google.com with SMTP id t40so1800132pjb.3 for ; Thu, 30 Apr 2020 18:44:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=BJDB9lPyIL7yqfOmHsy2HCj6CJV5Y/ygJ4a/Yt4ueRw=; b=Tcshg76Y97lKweEKu4Gzgm583bqlkziZ4JStrZoKgao6MtHeAoodWQhMVO/lXjIY2G FvsHOLLcC0UIstahZaZG+KZ1bEgNSTltcuxq5krvhF6cOgx9Rh62+aJTs5Ho+2hC1v/i V/0Q+bgjzZQqIT5kvZzSa/8UWZi1+rWuqj3VP1iNWOL43pzieMbHk4n/WkLOh3uiq6sn VA4Y6GIn4cKd1U2WqH8DlczT3VzTPWI2DaO+ZuGk93UcqyB3SQ/rCq9jOTYNSXV1GJk2 I/N01tnibHm6+a7oRtKOCa1vkElQ/Nxn5qwvm7yJQmzRGlMHW3zA8RMgLEfDq0HeWpOh v2UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=BJDB9lPyIL7yqfOmHsy2HCj6CJV5Y/ygJ4a/Yt4ueRw=; b=rAcZElMfaZvNlJG7oIzlpnB6Tu/kwa3vA9W2SYlfWw06LHnCjOKIEU85h17mmwJGnV chWiDQSiEtADWHURyMtmo08YWE+IQ953w7Tb376zRvCXbxGDZft+WirwHB/DQZUOR1OE LjIFyp7K/yFq5DKf3ozAfFPddHJsKZV/VTIM4GD43v83gkbGbAGOEmA2EiMfiKUhByCW wUY7S/S7YuQqrSAZ+BxcC3sArBA59k2yImmFIeTEoV0I4wVmLOKPtUn3Dm3JUYpV06Bw 2SArudu5Yipksyp9wUjywjbeQwgDcfvHKTmn+b5+DO5JRTIhTExmddIBc2eCxjKpnTBJ bAQQ== X-Gm-Message-State: AGi0PuZKKgQ+rsad9uki7oCwYNRVaejIlzGJrytJiuR3q6biWfO9bXvB a4J1FeIoQF2jHNOq4WP8IBo= X-Google-Smtp-Source: APiQypLCLfp3rK10yUdbPAE4Edv32G102rWA36hKIIpdEzEYeJyZFhsbGJpCwWMJe+hOipaDHzEbbg== X-Received: by 2002:a17:90a:2606:: with SMTP id l6mr1770330pje.188.1588297497099; Thu, 30 Apr 2020 18:44:57 -0700 (PDT) Received: from localhost (146.85.30.125.dy.iij4u.or.jp. [125.30.85.146]) by smtp.gmail.com with ESMTPSA id d18sm850855pfq.177.2020.04.30.18.44.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2020 18:44:56 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Fri, 1 May 2020 10:44:54 +0900 To: Alper Nebi Yasak Subject: Re: [RFC PATCH v2 1/3] printk: Add function to set console to preferred console's driver Message-ID: <20200501014454.GB288759@jagdpanzerIV.localdomain> References: <20200430161438.17640-1-alpernebiyasak@gmail.com> <20200430161438.17640-2-alpernebiyasak@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200430161438.17640-2-alpernebiyasak@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200430_184458_260662_9650C35B X-CRM114-Status: GOOD ( 17.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Petr Mladek , Feng Tang , Benjamin Herrenschmidt , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Steven Rostedt , Sergey Senozhatsky , Arvind Sankar , linux-serial@vger.kernel.org, Jiri Slaby , Andrew Morton , Andy Shevchenko , "David S. Miller" , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On (20/04/30 19:14), Alper Nebi Yasak wrote: > Currently, add_preferred_console sets a preferred console, but doesn't > actually change /dev/console to match it. That part is handled within > register_device, where a newly registered console driver will be set as > /dev/console if it matches the preferred console. > > However, if the relevant driver is already registered, the only way to > set it as /dev/console is by un-registering and re-registering it. Hmm. Preferred console selection is very fragile, there are too many setups and workarounds that even minor tweaks introduce regressions oftentimes. We have, by the way, a pending patchset which changes the same are - preferred console selection. git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git for-5.7-preferred-console [..] > An example is the xenfb_make_preferred_console() function: > > console_lock(); > for_each_console(c) { > if (!strcmp(c->name, "tty") && c->index == 0) > break; > } > console_unlock(); > if (c) { > unregister_console(c); > c->flags |= CON_CONSDEV; > c->flags &= ~CON_PRINTBUFFER; /* don't print again */ > register_console(c); > } I didn't know about this code. > The code above was introduced in commit 9e124fe16ff2 ("xen: Enable > console tty by default in domU if it's not a dummy"). In short, it's aim > is to set VT as the preferred console only after a working framebuffer > is registered and thus VT is not the dummy device. > > This patch introduces an update_console_to_preferred function that > handles the necessary /dev/console change. With this change, the example > above can be replaced with: > > console_lock(); > add_preferred_console("tty", 0, NULL); > update_console_to_preferred(); > console_unlock(); > > More importantly, these two calls can be moved to vt.c in order to bump > its priority when a non-dummy backend for it is introduced, solving that > problem in general. Let me take a look over the weekend. -ss _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel