On Wed 2017-04-05 23:20:00, 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.
>
> Reported-by: Sudeep Holla <sudeep.ho...@arm.com>
> Signed-off-by: Aleksey Makarov <aleksey.maka...@linaro.org>
This version looks fine to me. Just a small nitpick below.
Anyway:
Reviewed-by: Petr Mladek <pmla...@suse.com>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index fd752f0c8ef1..be657af45758 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -269,6 +269,7 @@ 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;
> @@ -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;
> +
This extra new line is non-standard and looks slightly weird to me.
I just point it out. I personally do not mind ;-)
> + 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;
> }
> }
> @@ -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--) {
> +
Same here.
> + c = console_cmdline + i;
> +
> if (!newcon->match ||
> newcon->match(newcon, c->name, c->index, c->options) != 0) {
> /* default matching */
Best Regards,
Petr
