proc: add minor comments (go-delve#2228)

This patch adds some comments around RequestManualStop().

pkg/proc/interface.go

@@ -98,6 +98,7 @@ type ThreadInfo interface {
 
 // ProcessManipulation is an interface for changing the execution state of a process.
 type ProcessManipulation interface {
+	// RequestManualStop attempts to stop all the process' threads.
 	RequestManualStop() error
 	// CheckAndClearManualStopRequest returns true the first time it's called
 	// after a call to RequestManualStop.

pkg/proc/native/proc.go

@@ -27,11 +27,14 @@ type nativeProcess struct {
 
 	os                  *osProcessDetails
 	firstStart          bool
-	stopMu              sync.Mutex
 	resumeChan          chan<- struct{}
 	ptraceChan          chan func()
 	ptraceDoneChan      chan interface{}
 	childProcess        bool // this process was launched, not attached to
+	stopMu              sync.Mutex // protects manualStopRequested
+	// manualStopRequested is set if all the threads in the process were
+	// signalled to stop as a result of a Halt API call. Used to disambiguate
+	// why a thread is found to have stopped.
 	manualStopRequested bool
 
 	// Controlling terminal file descriptor for
@@ -176,7 +179,7 @@ func (dbp *nativeProcess) Breakpoints() *proc.BreakpointMap {
 	return &dbp.breakpoints
 }
 
-// RequestManualStop sets the `halt` flag and
+// RequestManualStop sets the `manualStopRequested` flag and
 // sends SIGSTOP to all threads.
 func (dbp *nativeProcess) RequestManualStop() error {
 	if dbp.exited {