Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934207AbdDEV5Y (ORCPT ); Wed, 5 Apr 2017 17:57:24 -0400 Received: from mail-qk0-f176.google.com ([209.85.220.176]:35872 "EHLO mail-qk0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934077AbdDEV5P (ORCPT ); Wed, 5 Apr 2017 17:57:15 -0400 MIME-Version: 1.0 In-Reply-To: <20170405202006.18234-1-aleksey.makarov@linaro.org> References: <20170315102854.1763-1-aleksey.makarov@linaro.org> <20170405202006.18234-1-aleksey.makarov@linaro.org> From: Andy Shevchenko Date: Thu, 6 Apr 2017 00:57:13 +0300 Message-ID: Subject: Re: [PATCH v9 3/3] printk: fix double printing with earlycon To: Aleksey Makarov Cc: "linux-serial@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Sudeep Holla , Greg Kroah-Hartman , Peter Hurley , Jiri Slaby , Robin Murphy , Steven Rostedt , "Nair, Jayachandran" , Sergey Senozhatsky , Petr Mladek Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4656 Lines: 125 On Wed, Apr 5, 2017 at 11:20 PM, Aleksey Makarov wrote: > 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. Then traverse it in reverse order to be sure that if > the console is preferred then it will be the first matching entry. > Introduce variable console_cmdline_cnt that keeps the number > of elements of the console_cmdline array (Petr Mladek). It helps > to get rid of the loop that searches for the end of this array. > #define MAX_CMDLINECONSOLES 8 > > static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; > +static int console_cmdline_cnt; This should be equal to -1 at the beginning, am I right? > static int preferred_console = -1; > int console_set_on_cmdline; > @@ -1905,12 +1906,26 @@ static int __add_preferred_console(char *name, int idx, char *options, > * See if this tty is not yet registered, and > * if we have a slot free. > */ > - for (i = 0, c = console_cmdline; > - i < MAX_CMDLINECONSOLES && c->name[0]; > - i++, c++) { > + for (i = 0, c = console_cmdline; i < console_cmdline_cnt; i++, c++) { > if (strcmp(c->name, name) == 0 && c->index == idx) { > - if (!brl_options) > - preferred_console = i; > + > + if (brl_options) > + return 0; Is it invariant or brl_options may appear while looping? > + > + /* > + * 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. > + */ > + if (i != console_cmdline_cnt - 1) > + swap(console_cmdline[i], > + console_cmdline[console_cmdline_cnt - 1]); i'm wondering if you can iterate from the end to beginning as you do below. It would simplify things. > + > + preferred_console = console_cmdline_cnt - 1; > + > return 0; > } > } > @@ -1923,6 +1938,7 @@ static int __add_preferred_console(char *name, int idx, char *options, > braille_set_options(c, brl_options); > > c->index = idx; > + console_cmdline_cnt++; > return 0; > } > /* > @@ -2457,12 +2473,24 @@ 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. > + * > + * There may be several entries in the console_cmdline array matching > + * with the same console, one with newcon->match(), another by > + * name/index: > + * > + * pl011,mmio,0x87e024000000,115200 -- added from SPCR > + * ttyAMA0 -- added from command line > + * > + * Traverse the console_cmdline array in reverse order 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 = console_cmdline_cnt - 1; i >= 0; i--) { > + > + c = console_cmdline + i; > + > if (!newcon->match || > newcon->match(newcon, c->name, c->index, c->options) != 0) { > /* default matching */ > -- > 2.12.1 > -- With Best Regards, Andy Shevchenko