boards: posix: native_posix: Handle SDL events in zephyr thread

[pdgendt]

This commit introduces a zephyr thread for SDL events. This allows to use zephyr mutex locking with SDL callbacks.

Relates to #50080; as this calls gpio_emul_input_set which locks a mutex, and asserts if called from an idle thread (which apparently is the case for the posix main thread).

[aescolar]

(which apparently is the case for the posix main thread).

Just for info: The native_posix main thread is a separate thread than the Zephyr SW threads. If you call Zephyr APIs from it, you confuse the Zephyr kernel :)

[pdgendt]

If you call Zephyr APIs from it, you confuse the Zephyr kernel :)

That is exactly the problem :)

[aescolar]

You can still define a kconfig option for the delay :), just not a too tiny amount

[pdgendt]

@aescolar FYI when enabling CONFIG_STACK_SENTINEL the CONFIG_ARCH_POSIX_RECOMMENDED_STACK_SIZE should be set to 44 instead of 40 in case of 64 bit, to prevent a stack overflow. Not sure for 32 bit though.

[aescolar]

@aescolar FYI when enabling CONFIG_STACK_SENTINEL the CONFIG_ARCH_POSIX_RECOMMENDED_STACK_SIZE should be set to 44 instead of 40 in case of 64 bit, to prevent a stack overflow. Not sure for 32 bit though.

Would you so kind as to send a PR to fix it?

[pdgendt]

Would you so kind as to send a PR to fix it?

Done #50416