From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752884AbdCOKda (ORCPT ); Wed, 15 Mar 2017 06:33:30 -0400 Received: from mail-lf0-f48.google.com ([209.85.215.48]:36122 "EHLO mail-lf0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752501AbdCOKdZ (ORCPT ); Wed, 15 Mar 2017 06:33:25 -0400 From: Aleksey Makarov To: linux-serial@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Aleksey Makarov , Sudeep Holla , Greg Kroah-Hartman , Peter Hurley , Jiri Slaby , Robin Murphy , Steven Rostedt , "Nair, Jayachandran" , Sergey Senozhatsky , Petr Mladek Subject: [PATCH v5 3/3] printk: fix double printing with earlycon Date: Wed, 15 Mar 2017 13:28:52 +0300 Message-Id: <20170315102854.1763-4-aleksey.makarov@linaro.org> X-Mailer: git-send-email 2.12.0 In-Reply-To: <20170315102854.1763-1-aleksey.makarov@linaro.org> References: <20170315102854.1763-1-aleksey.makarov@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a console was specified by ACPI SPCR table _and_ command line parameters like "console=ttyAMA0" _and_ "earlycon" were specified, then log messages appear twice. The root cause is that the code traverses the list of specified consoles (the `console_cmdline` array) and stops at the first match. But it may happen that the same console is referred by the elements of this array twice: pl011,mmio,0x87e024000000,115200 -- from SPCR ttyAMA0 -- from command line but in this case `preferred_console` points to the second entry and the flag CON_CONSDEV is not set, so bootconsole is not deregistered. To fix that, introduce an invariant "The last non-braille console is always the preferred one" on the entries of the console_cmdline array and don't try to check for double entries. Then traverse it in reverse order to be sure that if the console is preferred then it will be the first matching entry. Reported-by: Sudeep Holla Signed-off-by: Aleksey Makarov --- kernel/printk/printk.c | 45 +++++++++++++++++++++++++++++---------------- 1 file changed, 29 insertions(+), 16 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fd752f0c8ef1..7dc53b2831fb 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1902,20 +1902,25 @@ static int __add_preferred_console(char *name, int idx, char *options, int i; /* - * See if this tty is not yet registered, and - * if we have a slot free. + * Don't check if the console has already been registered, because it is + * pointless. After all, we can not check if two entries refer to + * the same console if one is matched with console->match(), and another + * by name/index: + * + * pl011,mmio,0x87e024000000,115200 -- added from SPCR + * ttyAMA0 -- added from command line + * + * Also this allows to maintain an invariant that will help to find if + * the matching console is preferred, see register_console(): + * + * The last non-braille console is always the preferred one. */ - for (i = 0, c = console_cmdline; - i < MAX_CMDLINECONSOLES && c->name[0]; - i++, c++) { - if (strcmp(c->name, name) == 0 && c->index == idx) { - if (!brl_options) - preferred_console = i; - return 0; - } - } + for (i = 0; i < MAX_CMDLINECONSOLES; i++) + if (!console_cmdline[i].name[0]) + break; if (i == MAX_CMDLINECONSOLES) return -E2BIG; + c = console_cmdline + i; if (!brl_options) preferred_console = i; strlcpy(c->name, name, sizeof(c->name)); @@ -2457,12 +2462,20 @@ void register_console(struct console *newcon) } /* - * See if this console matches one we selected on - * the command line. + * See if this console matches one we selected on the command line. + * + * The console_cmdline array is traversed in the reverse order because + * we want to be sure that if this console is preferred then it will be + * the first matching entry. We use the invariant that is maintained in + * __add_preferred_console(). */ - for (i = 0, c = console_cmdline; - i < MAX_CMDLINECONSOLES && c->name[0]; - i++, c++) { + for (i = MAX_CMDLINECONSOLES - 1; i >= 0; i--) { + + if (!console_cmdline[i].name[0]) + continue; + + c = console_cmdline + i; + if (!newcon->match || newcon->match(newcon, c->name, c->index, c->options) != 0) { /* default matching */ -- 2.12.0