Using ZBus with ISRs

[saiff]

Hi,

I just started working with ZBus and even though Zephyr's documentation states that "Publishing, reading, claiming, and finishing are available in all RTOS thread contexts, including ISRs.", Nordic documentation claims the opposite "Publishing and reading are available in all RTOS contexts except inside an Interrupt Service Routine (ISR). " and in fact i wasn't able to add ZBus's operations inside an ISR.

Is there a problem with its emplementation on nordic's boards or did i get something wrong?

Thanks in advance,

Kind regards,

[Håkon Alseth]

Hi,

 

Not sure which version of ncs that holds this specific docs sentence, but we base our sdk-zephyr on upstream-zephyr, so the docs will be similar.

For example, here's the upstream zephyr v3.5.0 docs:

https://docs.zephyrproject.org/3.5.0/services/zbus/index.html#concepts

 

Is it this sentence you're wondering about? This sentence is removed from the docs in newer zephyr version(s) (v3.6.99 and newer)

However, it cannot run inside Interrupt Service Routines (ISR) because it uses mutexes to control channel access, and mutexes cannot work appropriately inside ISRs.

Mutex'es cannot be taken from ISR context, and the same goes for anything that has a timeout that is non-zero (ie. needs to be K_NO_WAIT).

This is also notified on the specific API's as well, for instance here:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/services/zbus/index.html#publishing-to-a-channel

  

Kind regards,

Håkon

[saiff]

Hi Hakon,

Thanks for your response, indeed apparently i was checking an older version of the documentation, thanks for clearing that up.

Kind regards,

[Håkon Alseth]

Hi,

 

Always happy to help out.

Hope you have a wonderful day!

 

Kind regards,

Håkon