Fix rtt_target blocking panic handler.

[reitermarkus]

In release mode, the panic_persist::report_panic_info was never reached because the panic handler would block when writing to the RTT target (since none is connected).

Only set BlockIfFull in debug mode, and replace unsafe UpChannel::conjure with with_terminal_channel while we're at it.

[jordens]

Why would this only be triggered in release?

IIRC the unsafe conjure is there to avoid deadlock/borrow failure. with_terminal_channel looks like it would panic when nested.

[jordens]

And a hang on panic doesn't sound too bad here. IIRC the watchdog should kick in.
I can see the peristent panic stuff being moved earlier though.

[reitermarkus]

Why would this only be triggered in release?

Right, it isn't. It's triggered when no debug probe is connected. However there is already an assumption in the panic_handler that when debug_assertions are disabled, the device should reset rather than loop.

And a hang on panic doesn't sound too bad here. IIRC the watchdog should kick in.

The watchdog does indeed kick in, but I'd like the device to immediately reset without delay rather than wait for 4 seconds for the watchdog.

Maybe adding an rtt-target feature that can be disabled is the better option?

[jordens]

Ack the rtt feature.

• Ensure that with rtt we don't enable the watchdog. It makes debugging difficult
• Early panic persist
• Blocking panic dump over rtt with unsafe conjure (or argue that there is no deadlock).

The reboot on panic never actually solves any problem or bug. I'm fine with keeping it as is. It seems slightly better than the alternative. But I won't spend time on "optimizing the panic experience". Rather fix the cause of the panic.

[reitermarkus]

Is this, combined with watchdog.stop_on_debug(...), enough, or do you additionally want to completely disable the watchdog when the rtt feature is enabled?

[jordens]

Ah. Just watchdog.stop_on_debug is fine. Good find.

[reitermarkus]

@jordens, anything still missing here?

[jordens]

The review request was.

[jordens]

Linker script needs fixing AFAICT

[reitermarkus]

Seems like rust-lld got more strict about whitespace. Should be fixed now.

[jordens]

+ probe-rs download --chip STM32F407ZGTx --log-file /dev/null --probe 0483:3754:003C002F5632500A20313236 target/thumbv7em-none-eabihf/release/booster
     Finished in 49.05s
+ probe-rs reset --chip STM32F407ZGTx --log-file /dev/null --probe 0483:3754:003C002F5632500A20313236 --connect-under-reset
 WARN probe_rs::architecture::arm::core::armv7m: Core is running, but we expected it to be halted
+ sleep 30
+ ping -c 5 -w 20 booster-hitl
+ python3 -m miniconf --broker mqtt.ber.quartiq.de --discover dt/sinara/booster/+ /telemetry_period=5
+ python3 hitl/basic.py --broker mqtt.ber.quartiq.de --prefix dt/sinara/booster/+
Traceback (most recent call last):
  File "/home/runner/actions-runner/_work/hitl/hitl/hitl/basic.py", line 45, in channel_on
    await booster.miniconf.set(f'/channel/{channel}/state', initial_state)
  File "/home/runner/actions-runner/_work/hitl/hitl/vpy/lib/python3.9/site-packages/miniconf/miniconf.py", line 144, in set
    ret = await self._do(
  File "/home/runner/actions-runner/_work/hitl/hitl/vpy/lib/python3.9/site-packages/miniconf/miniconf.py", line 134, in _do
    return await fut
miniconf.miniconf.MiniconfException: ('Error', 'Variant absent (depth: 2)')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/runner/actions-runner/_work/hitl/hitl/hitl/basic.py", line 162, in <module>
    main()
  File "/home/runner/actions-runner/_work/hitl/hitl/hitl/basic.py", line 151, in main
    sys.exit(loop.run_until_complete(test()))
  File "/usr/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete
    return future.result()
  File "/home/runner/actions-runner/_work/hitl/hitl/hitl/basic.py", line 147, in test
    await test_channel(booster, channel, tele.messages)
  File "/home/runner/actions-runner/_work/hitl/hitl/hitl/basic.py", line 63, in test_channel
    async with channel_on(booster, channel, 'Powered'):
  File "/usr/lib/python3.9/contextlib.py", line 175, in __aenter__
    return await self.gen.__anext__()
  File "/home/runner/actions-runner/_work/hitl/hitl/hitl/basic.py", line 49, in channel_on
    await booster.miniconf.set(f'/channel/{channel}/state', 'Off')
miniconf.miniconf.MiniconfException: ('Error', 'Variant absent (depth: 2)')
+ finish
+ mosquitto_pub -h mqtt.ber.quartiq.de -t cmnd/tasmota_4F64D0/POWER -m OFF
Error: Process completed with exit code 1.