Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751235AbdCQNtJ (ORCPT ); Fri, 17 Mar 2017 09:49:09 -0400 Received: from mail-lf0-f46.google.com ([209.85.215.46]:35655 "EHLO mail-lf0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751092AbdCQNsm (ORCPT ); Fri, 17 Mar 2017 09:48:42 -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 v7 3/3] printk: fix double printing with earlycon Date: Fri, 17 Mar 2017 16:43:45 +0300 Message-Id: <20170317134352.5725-1-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 Content-Length: 3701 Lines: 117 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. Reported-by: Sudeep Holla Signed-off-by: Aleksey Makarov --- v6 -> v7: - return back to v5 :) - leave the check for already registered entries and add a function that maintains the invariant. v5 -> v6: - drop v5 and continue to work on v4: - introduce _braille_is_braille_console(). It helps to split original loop into three parts: 1) search for braille console, 2) check for preferred_console, 3) match other entries so that these three parts do not intersect. - introduce for_each_console_cmdline() macros to traverse console_cmdline (Petr Mladek) kernel/printk/printk.c | 48 ++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 42 insertions(+), 6 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fd752f0c8ef1..88f86fb23bc4 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1895,6 +1895,34 @@ asmlinkage __visible void early_printk(const char *fmt, ...) } #endif +/* + * This function maintains 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. + */ +static void ensure_preferred_is_last(int i) +{ + int last; + + for (last = MAX_CMDLINECONSOLES - 1; + last >= 0 && !console_cmdline[last].name[0]; + last--) + ; + + BUG_ON(last < 0); + + if (i != last) { + struct console_cmdline t; + + t = console_cmdline[i]; + console_cmdline[i] = console_cmdline[last]; + console_cmdline[last] = t; + } + + preferred_console = last; +} + static int __add_preferred_console(char *name, int idx, char *options, char *brl_options) { @@ -1910,7 +1938,7 @@ static int __add_preferred_console(char *name, int idx, char *options, i++, c++) { if (strcmp(c->name, name) == 0 && c->index == idx) { if (!brl_options) - preferred_console = i; + ensure_preferred_is_last(i); return 0; } } @@ -2457,12 +2485,20 @@ 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