proc: Exclude dead goroutines from results.

Some of the goroutines stored in runtime.allg are in the dead state and
should not be displayed. The state is determined by the 'g.atomicstatus'
member.

proc/variables.go

@@ -37,6 +37,19 @@ type M struct {
 	curg     uintptr // Current G running on this thread.
 }
 
+const (
+	// G status, from: src/runtime/runtime2.go
+	Gidle            uint64 = iota // 0
+	Grunnable                      // 1 runnable and on a run queue
+	Grunning                       // 2
+	Gsyscall                       // 3
+	Gwaiting                       // 4
+	Gmoribund_unused               // 5 currently unused, but hardcoded in gdb scripts
+	Gdead                          // 6
+	Genqueue                       // 7 Only the Gscanenqueue is used.
+	Gcopystack                     // 8 in this state when newstack is moving the stack
+)
+
 // Represents a runtime G (goroutine) structure (at least the
 // fields that Delve is interested in).
 type G struct {
@@ -45,6 +58,7 @@ type G struct {
 	SP         uint64 // SP of goroutine when it was parked.
 	GoPC       uint64 // PC of 'go' statement that created this goroutine.
 	WaitReason string // Reason for goroutine being parked.
+	Status     uint64
 
 	// Information on goroutine location.
 	File string
@@ -176,6 +190,12 @@ func parseG(thread *Thread, gaddr uint64, deref bool) (*G, error) {
 	if err != nil {
 		return nil, err
 	}
+	// Parse atomicstatus
+	atomicStatusAddr, err := rdr.AddrForMember("atomicstatus", initialInstructions)
+	if err != nil {
+		return nil, err
+	}
+	atomicStatus, err := thread.readUintRaw(uintptr(atomicStatusAddr), 4)
 	// Parse goid
 	goidAddr, err := rdr.AddrForMember("goid", initialInstructions)
 	if err != nil {
@@ -215,6 +235,7 @@ func parseG(thread *Thread, gaddr uint64, deref bool) (*G, error) {
 		Func:       fn,
 		WaitReason: waitreason,
 		DeferPC:    deferPC,
+		Status:     atomicStatus,
 	}
 	return g, nil
 }