Allows Delve clients to stop a recording midway by sending a
Command('halt')
request.
This is implemented by changing debugger.New to start recording the
process on a separate goroutine while holding the processMutex locked.
By locking the processMutex we ensure that almost all RPC requests will
block until the recording is done, since we can not respond correctly
to any of them.
API calls that do not require manipulating or examining the target
process, such as "IsMulticlient", "SetApiVersion" and
"GetState(nowait=true)" will work while we are recording the process.
Two other internal changes are made to the API: both GetState and
Restart become asynchronous requests, like Command. Restart because
this way it can be interrupted by a StopRecording request if the
rerecord option is passed.
GetState because clients need a call that will block until the
recording is compelted and can also be interrupted with a
StopRecording.
Clients that are uninterested in allowing the user to stop a recording
can ignore this change, since eventually they will make a request to
Delve that will block until the recording is completed.
Clients that wish to support this feature must:
1. call GetState(nowait=false) after connecting to Delve, before any
call that would need to manipulate the target process
2. allow the user to send a StopRecording request during the initial
GetState call
3. allow the user to send a StopRecording request during any subsequent
Restart(rerecord=true) request (if supported).
Implements #1747
8bb93e9ae1