Callback into mJS from another thread: is it safe?

General
1

I have a C API which takes a callback from the mJS world (including the userdata void * parameter) and calls that callback some time later from another RTOS thread (this is ESP32, so FreeRTOS). The thread that is doing the calling-back is allocated 8 kbytes of stack.

If I do something simple, like print("Hello.\n"), in the mJS callback then all works fine but when I do anything more adventurous: perform some processing on received data, access other mJS global, variables, I get random errors, e.g. mJS complains that the global variable is not defined or even that print is not defined.

My question is: is it safe to call back into mJS from another RTOS thread? If so then I guess I must just be suffering from stack overflow or a waggly pointer.

2

Yeah, mjs is expecting to be executed by the mongoose os thread.

You might try this:

3

Ah, unfortunately I don’t seem to have such a function, I’m using standalone mJS rather than Mongoose OS as a whole.

4

Ah I see.
Then, make your own!
The idea is: mjs VM should execute by only one task / thread. Thus, is another thread should execute the callback, do not execute it but instead signal the mjs task to do it. Use whatever IPC API is available in your environment.

5

Understood, will do.