.

wcfs/vendor/lab.nexedi.com/kirr/neo/go/zodb/internal/weak/weak.go

@@ -25,14 +25,17 @@
 package weak
 
 import (
+	"fmt"
 	"runtime"
 	"sync"
+	"time"
 	"unsafe"
 )
 
 // iface is how Go runtime represents an interface.
 //
 // NOTE layout must be synchronized to Go runtime representation.
+// NOTE depends on non-moving property of Go GC.
 type iface struct {
 	typ  uintptr // type
 	data uintptr // data
@@ -77,6 +80,11 @@ func NewRef(obj interface{}) *Ref {
 
 	var release func(interface{})
 	release = func(obj interface{}) {
+		ifobj := *(*iface)(unsafe.Pointer(&obj))
+		if w.iface != ifobj {
+			panic(fmt.Sprintf("weak: release: w.iface != obj;  w.iface=%x  obj=%x", w.iface, ifobj))
+		}
+
 		// GC decided that the object is no longer reachable and
 		// scheduled us to run as finalizer. During the time till we
 		// actually run, Ref.Get might have been come to run and
@@ -102,15 +110,21 @@ func NewRef(obj interface{}) *Ref {
 // If original object is still alive - it is returned.
 // If not - nil is returned.
 func (w *Ref) Get() (obj interface{}) {
+	get := false
 	w.mu.Lock()
 	if w.state != objReleased {
 		w.state = objGot
+		get = true
+	}
+	w.mu.Unlock()
 
+	if get {
+		time.Sleep(100*time.Nanosecond)
 		// recreate interface{} from saved words.
 		// XXX do writes as pointers so that compiler emits write barriers to notify GC?
 		i := (*iface)(unsafe.Pointer(&obj))
 		*i = w.iface
 	}
-	w.mu.Unlock()
+
 	return obj
 }