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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E110C433EF for ; Thu, 2 Jun 2022 08:52:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232282AbiFBIwg (ORCPT ); Thu, 2 Jun 2022 04:52:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231966AbiFBIwf (ORCPT ); Thu, 2 Jun 2022 04:52:35 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7075F45ADC; Thu, 2 Jun 2022 01:52:31 -0700 (PDT) Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id EE8752223E; Thu, 2 Jun 2022 10:52:28 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1654159949; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jwNt2A64Uimiyvogwxk15XDFZT8JagE7v8+a7BtJjLg=; b=fe22pOYV8FB4xcx1IleSAX6hTBhzhsIUT297iQf1Ox7Ux/zm3CJsGSl/fIHkD7VovutxPg 4yYFBEaTP5mKwdjrgd6lVmhROpgnm+dWeHZSK7znQqB7q7vrJ+fFDrt9kzM8SD1LRC/d25 7xh1P8z3T5mAtZ/07M8OjjptM7HzggU= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 02 Jun 2022 10:52:28 +0200 From: Michael Walle To: Rob Herring Cc: Frank Rowand , Greg Kroah-Hartman , Jiri Slaby , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, "open list:SERIAL DRIVERS" Subject: Re: [PATCH] earlycon: prevent multiple register_console() In-Reply-To: References: <20220601135528.3176471-1-michael@walle.cc> User-Agent: Roundcube Webmail/1.4.13 Message-ID: X-Sender: michael@walle.cc Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi, Am 2022-06-01 18:39, schrieb Rob Herring: > On Wed, Jun 1, 2022 at 8:55 AM Michael Walle wrote: >> >> If the earlycon parameter is given twice, the kernel will spit out a >> WARN() in register_console() because it was already registered. The >> non-dt variant setup_earlycon() already handles that gracefully. The >> dt >> variant of_setup_earlycon() doesn't. Add the check there and propagate >> it through early_init_dt_scan_chosen_stdout(). >> >> FWIW, this doesn't happen if CONFIG_ACPI_SPCR_TABLE is set. In that >> case >> the registration is delayed until after earlycon parameter(s) are >> parsed. >> >> Signed-off-by: Michael Walle >> --- Scrap this version. Somehow I missed to add the actual check in of_setup_earlycon() to this patch. >> I'm not sure if this should have a Fixes tag or not. If so I guess it >> should be the very first commit which introduced the support (commit >> fb11ffe74c79 ("of/fdt: add FDT serial scanning for earlycon")). > > Considering no one noticed or cared in 8 years and that earlycon is > supposed to be a debug option, I'd say no. > >> For the curious, here is the backtrace: >> >> [ 0.000000] ------------[ cut here ]------------ >> [ 0.000000] WARNING: CPU: 0 PID: 0 at kernel/printk/printk.c:3328 >> register_console+0x2b4/0x364 >> [ 0.000000] console 'atmel_serial0' already registered >> [ 0.000000] Modules linked in: >> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted >> 5.18.0-next-20220601+ #652 >> [ 0.000000] Hardware name: Generic DT based system >> [ 0.000000] Backtrace: >> [ 0.000000] dump_backtrace from show_stack+0x18/0x1c >> [ 0.000000] show_stack from dump_stack_lvl+0x48/0x54 >> [ 0.000000] dump_stack_lvl from dump_stack+0x18/0x1c >> [ 0.000000] dump_stack from __warn+0xd0/0x148 >> [ 0.000000] __warn from warn_slowpath_fmt+0x9c/0xc4 >> [ 0.000000] warn_slowpath_fmt from register_console+0x2b4/0x364 >> [ 0.000000] register_console from of_setup_earlycon+0x29c/0x2ac >> [ 0.000000] of_setup_earlycon from >> early_init_dt_scan_chosen_stdout+0x154/0x18c >> [ 0.000000] early_init_dt_scan_chosen_stdout from >> param_setup_earlycon+0x40/0x48 >> [ 0.000000] param_setup_earlycon from do_early_param+0x88/0xc4 >> [ 0.000000] do_early_param from parse_args+0x1a4/0x404 >> [ 0.000000] parse_args from parse_early_options+0x40/0x48 >> [ 0.000000] parse_early_options from parse_early_param+0x38/0x48 >> [ 0.000000] parse_early_param from setup_arch+0x114/0x7a4 >> [ 0.000000] setup_arch from start_kernel+0x74/0x6dc >> [ 0.000000] start_kernel from 0x0 >> [ 0.000000] ---[ end trace 0000000000000000 ]--- >> >> drivers/of/fdt.c | 6 ++++-- >> drivers/tty/serial/earlycon.c | 5 ++++- >> 2 files changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c >> index a8f5b6532165..7f3524213b43 100644 >> --- a/drivers/of/fdt.c >> +++ b/drivers/of/fdt.c >> @@ -1025,6 +1025,7 @@ int __init >> early_init_dt_scan_chosen_stdout(void) >> int l; >> const struct earlycon_id *match; >> const void *fdt = initial_boot_params; >> + int ret; >> >> offset = fdt_path_offset(fdt, "/chosen"); >> if (offset < 0) >> @@ -1057,8 +1058,9 @@ int __init >> early_init_dt_scan_chosen_stdout(void) >> if (fdt_node_check_compatible(fdt, offset, >> match->compatible)) >> continue; >> >> - if (of_setup_earlycon(match, offset, options) == 0) >> - return 0; >> + ret = of_setup_earlycon(match, offset, options); >> + if (!ret || ret == -EALREADY) >> + return ret; > > Wouldn't just doing a 'return 0' here be simpler? The only other > caller of this function doesn't check the error. Ok. -michael