CFG_TUSB_DEBUG=2 Serial1 deadlock on nRF52 about tinyusb HOT 4 OPEN

Hi, your issue involved Arduino which isn't covered by this repo. Please try to reproduce with stock examples:
https://github.com/hathach/tinyusb/tree/master/examples/device

from tinyusb.

You might be correct that it's limited to the Arduino library.

However, upon investigating a bit more, it seems that tusb_hal_nrf_power_event calls TU_LOG from inside an ISR.

Is the tu_printf logging function expected to be ISR-safe? If so, it doesn't seem to be documented as a requirement.

The nRF52 Arduino core seems to have some issues with Serial1 being used from within an ISR.

Examining the state of the FreeRTOS task list suggests that it has gotten corrupted by turning into a loop, possibly due to calling non-ISR synchronization primitives from within an ISR.

from tinyusb.

Confirmed that LOG=2 with examples/device/hid_boot_interface appears to function correctly, producing debug logs without deadlocking. I'll open an issue with the Arduino library.

I would still like some clarification about whether tu_printf is expected to be ISR-safe.

from tinyusb.

Is the tu_printf logging function expected to be ISR-safe? If so, it doesn't seem to be documented as a requirement.
The nRF52 Arduino core seems to have some issues with Serial1 being used from within an ISR.

Yes it should be ISR safe, while documentation is a bit lacking...

Meanwhile even for built-in logging interrupt lock is also missing:

from tinyusb.