Should the kernel be using K_LOWEST_APPLICATION_THREAD_PRIO?

[jmgao]

My project has some extremely low-priority work that needs to get done at some point eventually, but I want everything else to be able to preempt it. Unfortunately, the kernel uses the K_LOWEST_APPLICATION_THREAD_PRIO for shell/logging, so any work done at that priority will block those until it's done.

I found one instance in the tests that adjusts the logging thread's priority, and it seems rather distasteful.

Should there be a global K_LOWEST_KERNEL_THREAD_PRIO, and/or individual options for each thread's priority?

[jukkar]

Could you use K_LOWEST_THREAD_PRIO instead?

[jmgao]

The scheduler asserts that Z_ASSERT_VALID_PRIO, and that requires that the caller must be the idle thread if it uses K_LOWEST_THREAD_PRIO.

(I'm not sure if there's a similar assertion for threads that begin existence with K_LOWEST_THREAD_PRIO, but I'm running this on the main thread after initial setup is complete, and configuring it to start with K_LOWEST_THREAD_PRIO seems like a bad idea? Either way, if there isn't an assertion, that itself seems like a bug: you shouldn't be able to start at a priority you can't return to.)