From cf39bf58afdaabc0b86f141630fb3fd18190294e Mon Sep 17 00:00:00 2001 From: Aleksey Makarov Date: Wed, 5 Apr 2017 23:20:00 +0300 Subject: [PATCH] printk: fix double printing with earlycon 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. Link: http://lkml.kernel.org/r/20170405202006.18234-1-aleksey.makarov@linaro.org Cc: Steven Rostedt Cc: Greg Kroah-Hartman Cc: Peter Hurley Cc: Jiri Slaby Cc: Robin Murphy Cc: "Nair, Jayachandran" Cc: linux-serial@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Aleksey Makarov Reported-by: Sudeep Holla Acked-by: Sergey Senozhatsky Signed-off-by: Petr Mladek --- kernel/printk/printk.c | 46 +++++++++++++++++++++++++++++++++--------- 1 file changed, 36 insertions(+), 10 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 82927ca04849..06051926dfde 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -266,6 +266,7 @@ static struct console *exclusive_console; #define MAX_CMDLINECONSOLES 8 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; +static int console_cmdline_cnt; static int preferred_console = -1; int console_set_on_cmdline; @@ -1902,12 +1903,25 @@ 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; + + /* + * 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]); + + preferred_console = console_cmdline_cnt - 1; + return 0; } } @@ -1920,6 +1934,7 @@ 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; } /* @@ -2459,12 +2474,23 @@ 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 */