.

wcfs/zodb.go

@@ -18,7 +18,7 @@ import (
 	"context"
 	"fmt"
 	"sync"
-	"sync/atomic"
+//	"sync/atomic"
 
 	"lab.nexedi.com/kirr/neo/go/zodb"
 
@@ -109,7 +109,7 @@ const (
 	// no STICKY - we pin objects in RAM with PActivate
 )
 
-// object is common base for in-RAM implementations of ZODB objects.
+// object is common base implementation for in-RAM representation of ZODB objects.
 type object struct {
 	jar	*Connection
 	oid	zodb.Oid
@@ -124,30 +124,28 @@ func (obj *object) PJar() *Connection	{ return obj.jar	}
 func (obj *object) POid() zodb.Oid	{ return obj.oid	}
 func (obj *object) PSerial() zodb.Tid	{ return obj.serial	}
 
-// pyObject is common base for in-RAM implementations of ZODB Python objects.
+// pyObject is common base implementation for in-RAM representation of ZODB Python objects.
 type pyObject struct {
 	object
 	pyclass pickle.Class
 
 	// protected by object.mu
 	instance PyStateful
-	loaded   *loaded
-//	loaderr  error		// if there was error at state loading
-//	ready    chan struct{}	// activation complete
+	loading  *loadState
 }
 
 func (pyobj *pyObject) PyClass() pickle.Class	{ return pyobj.pyclass	}
 //func (pyobj *pyObject) PyState() interface{}	{ return pyobj.pystate	}
 
-// loaded indicates object's load state/result.
+// loadState indicates object's load state/result.
 //
 // when !ready the loading is in progress.
 // when ready the loading has been completed.
-type loaded struct {
+type loadState struct {
 	ready chan struct{} // closed when loading finishes
 
 	// error from the load.
-	// if there was no error loaded data goes to object state.
+	// if there was no error, loaded data goes to object state.
 	err   error
 }
 
@@ -426,6 +424,8 @@ func (d *dummyPyInstance) PySetState(pystate interface{}) error	{
 // activate increments object reference counter.
 //
 // it returns whether object data needs to be loaded.
+// the caller must adjust .state after loading is complete.
+//
 // must be called with .mu held.
 func (obj *object) activate() (load bool) {
 	obj.refcnt++
@@ -452,28 +452,40 @@ func (obj *object) deactivate() (drop bool) {
 		panic("deactivate: refcnt < 0")
 	}
 	if obj.refcnt > 0 {
-		return // users still left
+		return false // users still left
 	}
 
 	// no users left. Let's see whether we should transition this object to ghost.
-	drop = true
 	if obj.state >= CHANGED {
-		drop = false
+		return false
 	}
 
 	// XXX -> pyObject?
-	if drop {
-		if cc := obj.jar.cacheControl; cc != nil {
-			drop = cc.WantEvict(obj.instance)
+	if cc := obj.jar.cacheControl; cc != nil {
+		if !cc.WantEvict(obj.instance) {
+			return false
 		}
 	}
 
-	if drop {
-		obj.serial  = 0
-		obj.instance.DropState()
+	obj.serial = 0
+	obj.instance.DropState()
+	obj.state = GHOST
+
+	return true
+}
+
+// invalidate XXX
+//
+// must be called with .mu held.
+func (obj *object) invalidate() {
+	if obj.refcnt != 0 {
+		// object is currently in use
+		panic("invalidate: refcnt != 0")
 	}
 
-	return drop
+	obj.serial = 0
+	obj.instance.DropState()
+	obj.state = GHOST
 }
 
 
@@ -485,16 +497,17 @@ func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
 		if err != nil {
 			// no need to check for drop - the state is already
 			// dropped - we just need to decref here.
-			// XXX locking?
-			pyobj.deactivate()
+			//
+			// XXX locking
+			pyobj.deactivate()	// XXX -> drop?
 		}
 	}()
 	if !doload {
+		// someone else is already activated/activating the object.
+		// wait for its loading to complete and we are done.
 		loading := pyobj.loading
 		pyobj.mu.Unlock()
 
-		// someone else is already activated/activating the object.
-		// wait for its loading to complete and we are done.
 		select {
 		case <-ctx.Done():
 			return ctx.Err()	// XXX err ctx
@@ -504,10 +517,11 @@ func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
 	}
 
 	// we become responsible for loading the object
-	loading := &loading{ready: make(chan struct{})}
+	loading := &loadState{ready: make(chan struct{})}
 	pyobj.loading = loading	// XXX assert before it was = nil ?
 	pyobj.mu.Unlock()
 
+	// do the loading outside of pyobj lock
 	pyclass, pystate, serial, err := pyobj.jar.loadpy(ctx, pyobj.oid)
 	if err == nil && pyclass != pyobj.pyclass {
 		// complain pyclass changed
@@ -516,8 +530,12 @@ func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
 		pystate = nil
 	}
 
+	// relock the object
 	pyobj.mu.Lock()
 
+	// XXX assert pyobj.loading == loading
+	// XXX assert pyobj.state   == GHOST
+
 	pyobj.serial  = serial
 //	pyobj.pystate = pystate
 
@@ -525,36 +543,36 @@ func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
 		err = pyobj.instance.PySetState(pystate)	// XXX err ctx
 	}
 	if err != nil {
-		pyobj.instance.DropState()
+		pyobj.instance.DropState()	// XXX already in deactivate
+	} else {
+		pyobj.state = UPTODATE
 	}
 
-	// XXX unlock
-
 	loading.err = err
+
+	pyobj.mu.Unlock()
 	close(loading.ready)
+
 	return err	// XXX err ctx
 }
 
 
 // PDeactivate implements Object.
 func (pyobj *pyObject) PDeactivate() {
-	drop := pyobj.pdeactivate()
-	if !drop {
-		return
-	}
+	pyobj.mu.Lock()
+	defer pyobj.mu.Unlock()
 
-	// we have to drop pyobject state
-	// XXX locking?
-//	pyobj.pystate = nil
-	pyobj.instance.DropState()
-	pyobj.loaderr = nil
-	pyobj.ready   = make(chan struct{})
+	drop := pyobj.deactivate()
+	if drop {
+		pyobj.loading = nil
+	}
 }
 
-// XXX pyobj.PInvalidate()	= deactivate without checking if state != modified
+// PInvalidate() implements Object.
 func (pyobj *pyObject) PInvalidate() {
-	// XXX panic if refcnt != 0  (object being used)
-	pyobj.instance.DropState()
-	pyobj.loaderr = nil
-	pyobj.ready   = make(chan struct{})
+	pyobj.mu.Lock()
+	defer pyobj.mu.Unlock()
+
+	pyobj.invalidate()
+	pyobj.loading = nil
 }