vscode: remote-debug: Preventively kill gdbserver

[tksc]

An existing gdbserver process prevents the vscode debug session. So
kill all running gdbserver beforehand.

[michaelolbrich]

Hmm, so we have two somewhat related issues:

1. sometimes a gdbserver process is not stopped
2. two gdbserver try to use the same port

I assume, that the second is what's visible here right? The new gdbserver tries to bind to a port and that fails.
And calling kill here like this is racy: it asynchronous, so the new gdbserver may try to bind the port before it is release.

Maybe randomize the port for this:

LOCAL_PORT="$((($$%10000)+10000))"
...
 ssh -L"${GDBSERVER_TARGET_PORT}:localhost:${LOCAL_PORT}" "${GDBSERVER_USER_REMOTE}@${GDBSERVER_TARGET_HOST}" << EOF
...
 gdbserver --once :"${LOCAL_PORT}" "${GDBSERVER_EXECUTABLE}"

This also helps with other conflicting ports: and if one try fails, then the next one will succeed.

I'm not so sure about remaining gdbserver processes. Why do they stick around anyways? I assume the ssh connection was terminated? Or are you accidentally reusing the port forwarding from the old one?

[tksc]

IIUC (the error message), your assumption on the double port usage is right.

Failed to attach: Remote communication error. Target disconnected.: Connection reset by peer. (from target-select remote :14242)

Randomizing the port will be a good thing either way.

Or are you accidentally reusing the port forwarding from the old one?

I just use Start, Stop and Restart from VSCode.

I will investigate this behavior further. Right now I cannot reproduce it in a consistent way.

[michaelolbrich]

I think, the ssh process remains as well. We just start the task in the background, so if gdbserver sticks aground, then ssh will as well.

These is a "postDebugTask" that we could use, see for example:
microsoft/vscode#90786
https://stackoverflow.com/questions/54480792/terminate-another-task-from-within-a-postdebugtask-vs-code

That would probably mean stopping all tasks, but I think that's ok. I don't see an API that allows us to stop a specific task.

Then the ssh should be gone at least. I'm not so sure about the gdbserver.