arduino firmware: random crashes/freezes on RP2040 when running MCP23X17 task on 2nd core

[juergenpabel]

The arduino firmware crashes/freezes randomly (only) when run on RP2040 with the MCP23X17 running as a task on the 2nd core (works without issues on ESP32). I have already analyzed for potential causes but didn't come up with a reasonable explanation, so for now I am assuming some issue in the arduino-pico runtime; until I can identify the cause this issue is meant to document the process (and if it does indeed turn out to be an issue in arduino-pico, I will open an issue there and link here).

As a workaround I disabled task creation for RP2040 firmwares (see Microcontroller::task_create() in enclosure/firmware/arduino/src/device/microcontroller/rp2040.cpp) and regular checking of MCP23X17 states is invoked from loop()).

[juergenpabel]

OK, so the issue seems to be that (for RP2040 only):

• 1) I had only implemented recursive mutexes
• 2) the owner id of recursive mutexes (which should be the cpu core of the given execution context) doesn't seem be set and/or validated correctly (I haven't investigated further)

So a working workaround is (for RP2040) to switch over to (non-recursive) mutex - due to code changes recursiveness isn't relevant anymore anyhow, so I might just remove recursiveness alltogether.

[juergenpabel]

support for recursive mutexes removed

[juergenpabel]

Reopened as crashes/freezes still occur...randomly