support force-able gomark marking

gmi/gmi.go

@@ -5,9 +5,14 @@ import "net/textproto"
 
 // Marker is an interface to provide variable marking.
 type Marker interface {
+	// ForceMark allows caller to set up a force flag, if force is false, the mark could be abandon,
+	// otherwise gomark should mark it as possible as it could
+	// return value indicates if mark is abandoned
+	ForceMark(n int32, force bool) bool
 	// Mark a number, the number definition is bound to marker itself.
-	Mark(n int32)
-	// Stop this marking.
+	// return value indicates if mark is abandoned
+	Mark(n int32) bool
+	// Cancel stops this marking.
 	Cancel()
 }
 type Route string

internal/gm/server.go

@@ -339,10 +339,12 @@ func ServerEnabled() bool {
 	return srv.disabled
 }
 
-func PushStub(s stub) {
-	if !srv.disabled && len(srv.stubc) < sizeOfQ-1 {
+func PushStub(s stub, force bool) bool {
+	if !srv.disabled && (force || len(srv.stubc) < sizeOfQ-1) {
 		srv.stubc <- s
+		return true
 	}
+	return false
 }
 
 func AddSampler(s sampler) disposer {

internal/gm/stub.go

@@ -2,11 +2,16 @@ package gm
 
 type Identity uint32
 
-func (i Identity) Mark(n int32) {
+func (i Identity) ForceMark(n int32, force bool) bool {
 	if i != 0 {
 		s := makeStub(i, Mark(n))
-		PushStub(s)
+		return PushStub(s, force)
 	}
+	return false
+
+}
+func (i Identity) Mark(n int32) bool {
+	return i.ForceMark(n, false)
 }
 
 func (i Identity) Cancel() {

internal/gm/variable.go

@@ -54,11 +54,15 @@ func (vb *VarBase) EnablePerf() {
 func (vb *VarBase) Marker() gmi.Marker {
 	return vb.id
 }
-func (vb *VarBase) Mark(n int32) {
+func (vb *VarBase) ForceMark(n int32, force bool) bool {
 	if vb != nil && vb.Valid() {
 		s := makeStub(vb.ID(), Mark(n))
-		PushStub(s)
+		return PushStub(s, force)
 	}
+	return false
+}
+func (vb *VarBase) Mark(n int32) bool {
+	return vb.ForceMark(n, false)
 }
 
 func (vb *VarBase) Cancel() {