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SubjectRe: [PATCH v9 3/3] printk: fix double printing with earlycon
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On 04/10/2017 05:22 PM, Petr Mladek wrote:
> 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.holla@arm.com>
>> Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
>
> This version looks fine to me. Just a small nitpick below.
> Anyway:
>
> Reviewed-by: Petr Mladek <pmladek@suse.com>

Thank you for review. Can you (or anybody else) ACK it?
I am going to resend the whole series without those empty lines.
May I add your Acked-by:?

Thank you
Aleksey Makarov

>> 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
>

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