All consoles found on for_each_console are registered, meaning that all of
them are CON_ENABLED. The code tries to find an active console, so check if the
console is not suspended instead.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
 arch/um/kernel/kmsg_dump.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index 4190211752726593dd2847f66efd9d3a61cea982..f3025b2a813453f479d720618c630bee135d4e08 100644
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -31,7 +31,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 		 * expected to output the crash information.
 		 */
 		if (strcmp(con->name, "ttynull") != 0 &&
-		    (console_srcu_read_flags(con) & CON_ENABLED)) {
+		    (console_srcu_read_flags(con) & CON_SUSPENDED) == 0) {
 			break;
 		}
 	}

-- 
2.49.0

On Fri 2025-06-06 23:53:47, Marcos Paulo de Souza wrote:
> All consoles found on for_each_console are registered, meaning that all of
> them are CON_ENABLED. The code tries to find an active console, so check if the
> console is not suspended instead.
> 
> Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
> ---
>  arch/um/kernel/kmsg_dump.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
> index 4190211752726593dd2847f66efd9d3a61cea982..f3025b2a813453f479d720618c630bee135d4e08 100644
> --- a/arch/um/kernel/kmsg_dump.c
> +++ b/arch/um/kernel/kmsg_dump.c
> @@ -31,7 +31,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
>  		 * expected to output the crash information.
>  		 */
>  		if (strcmp(con->name, "ttynull") != 0 &&
> -		    (console_srcu_read_flags(con) & CON_ENABLED)) {
> +		    (console_srcu_read_flags(con) & CON_SUSPENDED) == 0) {
>  			break;

I think that we should actually replace the check of the
CON_ENABLE/CON_SUSPENDED flag with

		is_console_usable(con, console_srcu_read_flags(con), true)

And it should be done at the beginning of the patchset before
changing the semantic of the flags.

Motivation:

There is the following comment at the beginning of the function:

	/*
	 * If no consoles are available to output crash information, dump
	 * the kmsg buffer to stdout.
	 */

The if-condition checks for:

  + "ttynull" because this special console does not show any messages
    by definition

  + disabled/suspended consoles; note that this patchset is replacing
    CON_ENABLED with CON_SUSPENDED flag because it the state is
    changed during suspend.

But it should check also for:

  + whether the console is NBCON_console and does not have con->write_atomic
    because such a console would not be able to show the messages
    in panic().

And it should also check the global "consoles_suspended" flag. Because
consoles won't show anything when it is set.

And all these is already done by "is_console_usable()" except for
the check of "ttynull" which is very special.

How does the sound, please?

Best Regards,
Petr

>  		}
>  	}
> 
> -- 
> 2.49.0

On 2025-06-16, Petr Mladek <pmladek@suse.com> wrote:
> On Fri 2025-06-06 23:53:47, Marcos Paulo de Souza wrote:
>> All consoles found on for_each_console are registered, meaning that all of
>> them are CON_ENABLED. The code tries to find an active console, so check if the
>> console is not suspended instead.
>> 
>> Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
>> ---
>>  arch/um/kernel/kmsg_dump.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
>> index 4190211752726593dd2847f66efd9d3a61cea982..f3025b2a813453f479d720618c630bee135d4e08 100644
>> --- a/arch/um/kernel/kmsg_dump.c
>> +++ b/arch/um/kernel/kmsg_dump.c
>> @@ -31,7 +31,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
>>  		 * expected to output the crash information.
>>  		 */
>>  		if (strcmp(con->name, "ttynull") != 0 &&
>> -		    (console_srcu_read_flags(con) & CON_ENABLED)) {
>> +		    (console_srcu_read_flags(con) & CON_SUSPENDED) == 0) {
>>  			break;
>
> I think that we should actually replace the check of the
> CON_ENABLE/CON_SUSPENDED flag with
>
> 		is_console_usable(con, console_srcu_read_flags(con), true)
>
> And it should be done at the beginning of the patchset before
> changing the semantic of the flags.
>
> Motivation:
>
> There is the following comment at the beginning of the function:
>
> 	/*
> 	 * If no consoles are available to output crash information, dump
> 	 * the kmsg buffer to stdout.
> 	 */
>
> The if-condition checks for:
>
>   + "ttynull" because this special console does not show any messages
>     by definition
>
>   + disabled/suspended consoles; note that this patchset is replacing
>     CON_ENABLED with CON_SUSPENDED flag because it the state is
>     changed during suspend.
>
> But it should check also for:
>
>   + whether the console is NBCON_console and does not have con->write_atomic
>     because such a console would not be able to show the messages
>     in panic().
>
> And it should also check the global "consoles_suspended" flag. Because
> consoles won't show anything when it is set.
>
> And all these is already done by "is_console_usable()" except for
> the check of "ttynull" which is very special.
>
> How does the sound, please?

FWIW, I agree with all these points.

John