Runtime Filtering of Log Levels Not Working Properly

[satheeshkola]

Bug Found: Issue with Runtime Log Level Filtering in Zephyr

Description: I've encountered an issue regarding the runtime filtering of log levels in Zephyr. Despite configuring the project with
LOG_MODULE_REGISTER(MONITOR)

and attempting to set the log filter using api:
log_filter_set(NULL, 0, log_source_id_get(STRINGIFY(MONITOR)), LOG_LEVEL_WRN),

I've noticed that the filtering doesn't apply as expected when the backend parameter is set to null for the module.

Project Configuration Summary:
• 12 frontends and 1 backend are utilized.
• Runtime filtering is enabled with CONFIG_LOG_RUNTIME_FILTERING=y.
• UART backend is disabled with CONFIG_LOG_BACKEND_UART=n.

Expected Behavior: Setting the log level filter using log_filter_set at runtime should effectively control the log output for the specified module.

Actual Behavior: Despite configuring the requested log level here in above eg: LOG_LEVEL_WRN using log_filter_set, the filtering doesn't function as anticipated when the backend parameter is set to null.

Steps to Reproduce:
1. Configure the project as described above.
2. Attempt to set log filtering using log_filter_set at runtime.
3. Observe that the filtering does not behave as expected when the backend parameter is null.

Environment:
Linux,
zephyr-sdk(zephyr 0.16.5)

I kindly request assistance in resolving this issue. Thank you.

[github-actions]

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[nordic-krch]

Thanks for submitting the issue. Can you clarify few things?

12 frontends and 1 backend are utilized.

What do you mean by 12 frontends? Logging support only one user frontend (log_frontend.h API implementation).
What kind of backend do you use? When is it started (from the beginning or later during runtime?). What is the unexpected behavior (INF level logs are still present vs no logs)? We are using this in samples/subsys/logging/logger and it works correctly there.

[satheeshkola]

1.I have registered modules, I have registered 12 LOG modules.
2. Custom backend using UART.
3. Custom backed is start from the beginning and trying to change Log level at runtime.
4. Even though i change the log level to WARN still i am getting INF logs.