* Fixed race conditions in the server's bitmap/picture handling: the objects

are now removed from the maps as soon as the client deletes them. This also
  makes the "client reference" mechanism superfluous I introduced earlier.
* ServerApp::SetCurrentCursor() must always call Desktop::SetCursor(), since it
  is also called whenever the current application changes. This fixes the cursor
  almost never changing.
* Renamed ServerPicture::Usurp()/StepDown() to PushPicture(), and PopPicture().
* Also, they now acquire a reference to the picture in question (ie. the picture
  you get from PopPicture() also owns a reference you need to free).
* ServerApp::CreatePicture() may fail, too. This case is now handled in the code
  that calls it.
* Previously, the ServerWindow tried to process up to 70 messages in one go.
  That obviously caused bug #4709. Now, we have the additional requirement to
  not hold the desktop lock for longer than 25 ms. I haven't tested it with
  Kaleidoscope yet, though.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@35472 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/app/ServerApp.cpp

@@ -191,19 +191,11 @@ ServerApp::~ServerApp()
 
 	fMapLocker.Lock();
 
-	while (!fBitmapMap.empty()) {
-		ServerBitmap* bitmap = fBitmapMap.begin()->second;
+	while (!fBitmapMap.empty())
+		_DeleteBitmap(fBitmapMap.begin()->second);
 
-		fBitmapMap.erase(fBitmapMap.begin());
-		bitmap->ReleaseReference();
-	}
-
-	while (!fPictureMap.empty()) {
-		ServerPicture* picture = fPictureMap.begin()->second;
-
-		fPictureMap.erase(fPictureMap.begin());
-		picture->ReleaseReference();
-	}
+	while (!fPictureMap.empty())
+		RemovePicture(fPictureMap.begin()->second);
 
 	fDesktop->GetCursorManager().DeleteCursors(fClientTeam);
 
@@ -298,16 +290,15 @@ ServerApp::SendMessageToClient(BMessage* message) const
 void
 ServerApp::SetCurrentCursor(ServerCursor* cursor)
 {
-	if (fViewCursor == cursor)
-		return;
+	if (fViewCursor != cursor) {
+		if (fViewCursor)
+			fViewCursor->ReleaseReference();
 
-	if (fViewCursor)
-		fViewCursor->ReleaseReference();
+		fViewCursor = cursor;
 
-	fViewCursor = cursor;
-
-	if (fViewCursor)
-		fViewCursor->AcquireReference();
+		if (fViewCursor)
+			fViewCursor->AcquireReference();
+	}
 
 	fDesktop->SetCursor(CurrentCursor());
 }
@@ -419,29 +410,6 @@ ServerApp::GetBitmap(int32 token) const
 }
 
 
-bool
-ServerApp::BitmapAdded(ServerBitmap* bitmap)
-{
-	BAutolock _(fMapLocker);
-
-	try {
-		fBitmapMap.insert(std::make_pair(bitmap->Token(), bitmap));
-	} catch (std::bad_alloc& exception) {
-		return false;
-	}
-
-	return true;
-}
-
-
-void
-ServerApp::BitmapRemoved(ServerBitmap* bitmap)
-{
-	BAutolock _(fMapLocker);
-	fBitmapMap.erase(bitmap->Token());
-}
-
-
 ServerPicture*
 ServerApp::CreatePicture(const ServerPicture* original)
 {
@@ -477,7 +445,7 @@ ServerApp::GetPicture(int32 token) const
 
 
 bool
-ServerApp::PictureAdded(ServerPicture* picture)
+ServerApp::AddPicture(ServerPicture* picture)
 {
 	BAutolock _(fMapLocker);
 
@@ -492,10 +460,12 @@ ServerApp::PictureAdded(ServerPicture* picture)
 
 
 void
-ServerApp::PictureRemoved(ServerPicture* picture)
+ServerApp::RemovePicture(ServerPicture* picture)
 {
 	BAutolock _(fMapLocker);
+
 	fPictureMap.erase(picture->Token());
+	picture->ReleaseReference();
 }
 
 
@@ -743,7 +713,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			STRACE(("ServerApp %s: Create Bitmap (%.1fx%.1f)\n",
 				Signature(), frame.Width() + 1, frame.Height() + 1));
 
-			if (bitmap != NULL && bitmap->SetOwner(this)) {
+			if (bitmap != NULL && _AddBitmap(bitmap)) {
 				fLink.StartMessage(B_OK);
 				fLink.Attach<int32>(bitmap->Token());
 				fLink.Attach<uint8>(allocationFlags);
@@ -770,8 +740,6 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			STRACE(("ServerApp %s: received BBitmap delete request\n",
 				Signature()));
 
-			// Delete a bitmap's allocated memory
-
 			// Attached Data:
 			// 1) int32 token
 			int32 token;
@@ -784,7 +752,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 				STRACE(("ServerApp %s: Deleting Bitmap %ld\n", Signature(),
 					token));
 
-				bitmap->ReleaseClientReference();
+				_DeleteBitmap(bitmap);
 			}
 
 			fMapLocker.Unlock();
@@ -833,6 +801,8 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 			break;
 		}
 
+		// Picture ops
+
 		case AS_CREATE_PICTURE:
 		{
 			// TODO: Maybe rename this to AS_UPLOAD_PICTURE ?
@@ -872,7 +842,7 @@ ServerApp::_DispatchMessage(int32 code, BPrivate::LinkReceiver& link)
 
 				ServerPicture* picture = _FindPicture(token);
 				if (picture != NULL)
-					picture->ReleaseClientReference();
+					RemovePicture(picture);
 			}
 			break;
 		}
@@ -3199,6 +3169,34 @@ ServerApp::_HasWindowUnderMouse()
 }
 
 
+bool
+ServerApp::_AddBitmap(ServerBitmap* bitmap)
+{
+	BAutolock _(fMapLocker);
+
+	try {
+		fBitmapMap.insert(std::make_pair(bitmap->Token(), bitmap));
+	} catch (std::bad_alloc& exception) {
+		return false;
+	}
+
+	bitmap->SetOwner(this);
+	return true;
+}
+
+
+void
+ServerApp::_DeleteBitmap(ServerBitmap* bitmap)
+{
+	ASSERT(fMapLock.IsLocked());
+
+	gBitmapManager->BitmapRemoved(bitmap);
+	fBitmapMap.erase(bitmap->Token());
+
+	bitmap->ReleaseReference();
+}
+
+
 ServerBitmap*
 ServerApp::_FindBitmap(int32 token) const
 {

src/servers/app/ServerApp.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2009, Haiku.
+ * Copyright 2001-2010, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -79,14 +79,12 @@ public:
 									{ return fInitialWorkspace; }
 
 			ServerBitmap*		GetBitmap(int32 token) const;
-			bool				BitmapAdded(ServerBitmap* bitmap);
-			void				BitmapRemoved(ServerBitmap* bitmap);
 
 			ServerPicture*		CreatePicture(
 									const ServerPicture* original = NULL);
 			ServerPicture*		GetPicture(int32 token) const;
-			bool				PictureAdded(ServerPicture* picture);
-			void				PictureRemoved(ServerPicture* picture);
+			bool				AddPicture(ServerPicture* picture);
+			void				RemovePicture(ServerPicture* picture);
 
 			Desktop*			GetDesktop() const { return fDesktop; }
 
@@ -105,7 +103,10 @@ private:
 
 			bool				_HasWindowUnderMouse();
 
+			bool				_AddBitmap(ServerBitmap* bitmap);
+			void				_DeleteBitmap(ServerBitmap* bitmap);
 			ServerBitmap*		_FindBitmap(int32 token) const;
+
 			ServerPicture*		_FindPicture(int32 token) const;
 
 private:

src/servers/app/ServerBitmap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2009, Haiku.
+ * Copyright 2001-2010, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -28,8 +28,7 @@ using std::nothrow;
 using namespace BPrivate;
 
 
-/*!
-	A word about memory housekeeping and why it's implemented this way:
+/*!	A word about memory housekeeping and why it's implemented this way:
 
 	The reason why this looks so complicated is to optimize the most common
 	path (bitmap creation from the application), and don't cause any further
@@ -47,8 +46,7 @@ using namespace BPrivate;
 */
 
 
-/*!
-	\brief Constructor called by the BitmapManager (only).
+/*!	\brief Constructor called by the BitmapManager (only).
 	\param rect Size of the bitmap.
 	\param space Color space of the bitmap
 	\param flags Various bitmap flags to tweak the bitmap as defined in Bitmap.h
@@ -65,7 +63,6 @@ ServerBitmap::ServerBitmap(BRect rect, color_space space, uint32 flags,
 	fAllocationCookie(NULL),
 	fOverlay(NULL),
 	fBuffer(NULL),
-	fReferenceCount(1),
 	// WARNING: '1' is added to the width and height.
 	// Same is done in FBBitmap subclass, so if you
 	// modify here make sure to do the same under
@@ -75,8 +72,7 @@ ServerBitmap::ServerBitmap(BRect rect, color_space space, uint32 flags,
 	fBytesPerRow(0),
 	fSpace(space),
 	fFlags(flags),
-	fOwner(NULL),
-	fHasClientReference(true)
+	fOwner(NULL)
 	// fToken is initialized (if used) by the BitmapManager
 {
 	int32 minBytesPerRow = get_bytes_per_row(space, fWidth);
@@ -92,8 +88,7 @@ ServerBitmap::ServerBitmap(const ServerBitmap* bitmap)
 	fAllocationCookie(NULL),
 	fOverlay(NULL),
 	fBuffer(NULL),
-	fReferenceCount(1),
-	fHasClientReference(false)
+	fOwner(NULL)
 {
 	if (bitmap) {
 		fWidth = bitmap->fWidth;
@@ -101,14 +96,12 @@ ServerBitmap::ServerBitmap(const ServerBitmap* bitmap)
 		fBytesPerRow = bitmap->fBytesPerRow;
 		fSpace = bitmap->fSpace;
 		fFlags = bitmap->fFlags;
-		fOwner = bitmap->fOwner;
 	} else {
 		fWidth = 0;
 		fHeight = 0;
 		fBytesPerRow = 0;
 		fSpace = B_NO_COLOR_SPACE;
 		fFlags = 0;
-		fOwner = NULL;
 	}
 }
 
@@ -200,18 +193,10 @@ ServerBitmap::Overlay() const
 }
 
 
-bool
+void
 ServerBitmap::SetOwner(ServerApp* owner)
 {
-	if (fOwner != NULL)
-		fOwner->BitmapRemoved(this);
-
-	if (owner != NULL && owner->BitmapAdded(this)) {
-		fOwner = owner;
-		return true;
-	}
-
-	return false;
+	fOwner = owner;
 }
 
 
@@ -222,18 +207,6 @@ ServerBitmap::Owner() const
 }
 
 
-bool
-ServerBitmap::ReleaseClientReference()
-{
-	if (!fHasClientReference)
-		return false;
-
-	fHasClientReference = false;
-	ReleaseReference();
-	return true;
-}
-
-
 void
 ServerBitmap::PrintToStream()
 {
@@ -242,30 +215,21 @@ ServerBitmap::PrintToStream()
 }
 
 
-void
-ServerBitmap::LastReferenceReleased()
-{
-	if (fOwner != NULL)
-		fOwner->BitmapRemoved(this);
-
-	gBitmapManager->BitmapRemoved(this);
-	delete this;
-}
-
-
 //	#pragma mark -
 
 
 UtilityBitmap::UtilityBitmap(BRect rect, color_space space, uint32 flags,
-		int32 bytesperline, screen_id screen)
-	: ServerBitmap(rect, space, flags, bytesperline, screen)
+		int32 bytesPerRow, screen_id screen)
+	:
+	ServerBitmap(rect, space, flags, bytesPerRow, screen)
 {
 	AllocateBuffer();
 }
 
 
 UtilityBitmap::UtilityBitmap(const ServerBitmap* bitmap)
-	: ServerBitmap(bitmap)
+	:
+	ServerBitmap(bitmap)
 {
 	AllocateBuffer();
 
@@ -276,7 +240,8 @@ UtilityBitmap::UtilityBitmap(const ServerBitmap* bitmap)
 
 UtilityBitmap::UtilityBitmap(const uint8* alreadyPaddedData, uint32 width,
 		uint32 height, color_space format)
-	: ServerBitmap(BRect(0, 0, width - 1, height - 1), format, 0)
+	:
+	ServerBitmap(BRect(0, 0, width - 1, height - 1), format, 0)
 {
 	AllocateBuffer();
 	if (Bits())

src/servers/app/ServerBitmap.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2009, Haiku.
+ * Copyright 2001-2010, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -69,11 +69,9 @@ public:
 			void			SetOverlay(::Overlay* overlay);
 			::Overlay*		Overlay() const;
 
-			bool			SetOwner(ServerApp* owner);
+			void			SetOwner(ServerApp* owner);
 			ServerApp*		Owner() const;
 
-			bool			ReleaseClientReference();
-
 	//! Does a shallow copy of the bitmap passed to it
 	inline	void			ShallowCopy(const ServerBitmap *from);
 
@@ -95,8 +93,6 @@ protected:
 							ServerBitmap(const ServerBitmap* bmp);
 	virtual					~ServerBitmap();
 
-	virtual	void			LastReferenceReleased();
-
 			void			AllocateBuffer();
 
 protected:
@@ -104,7 +100,6 @@ protected:
 			void*			fAllocationCookie;
 			::Overlay*		fOverlay;
 			uint8*			fBuffer;
-			int32			fReferenceCount;
 
 			int32			fWidth;
 			int32			fHeight;
@@ -114,7 +109,6 @@ protected:
 
 			ServerApp*		fOwner;
 			int32			fToken;
-			bool			fHasClientReference;
 };
 
 class UtilityBitmap : public ServerBitmap {

src/servers/app/ServerPicture.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2009, Haiku.
+ * Copyright 2001-2010, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -783,9 +783,8 @@ ServerPicture::ServerPicture()
 	:
 	fFile(NULL),
 	fPictures(NULL),
-	fUsurped(NULL),
-	fOwner(NULL),
-	fHasClientReference(true)
+	fPushed(NULL),
+	fOwner(NULL)
 {
 	fToken = gTokenSpace.NewToken(kPictureToken, this);
 	fData = new(std::nothrow) BMallocIO();
@@ -799,9 +798,8 @@ ServerPicture::ServerPicture(const ServerPicture& picture)
 	fFile(NULL),
 	fData(NULL),
 	fPictures(NULL),
-	fUsurped(NULL),
-	fOwner(NULL),
-	fHasClientReference(false)
+	fPushed(NULL),
+	fOwner(NULL)
 {
 	fToken = gTokenSpace.NewToken(kPictureToken, this);
 
@@ -827,9 +825,8 @@ ServerPicture::ServerPicture(const char* fileName, int32 offset)
 	fFile(NULL),
 	fData(NULL),
 	fPictures(NULL),
-	fUsurped(NULL),
-	fOwner(NULL),
-	fHasClientReference(true)
+	fPushed(NULL),
+	fOwner(NULL)
 {
 	fToken = gTokenSpace.NewToken(kPictureToken, this);
 
@@ -852,16 +849,26 @@ ServerPicture::ServerPicture(const char* fileName, int32 offset)
 
 ServerPicture::~ServerPicture()
 {
+	ASSERT(fOwner == NULL);
+
 	delete fData;
 	delete fFile;
 	gTokenSpace.RemoveToken(fToken);
 
 	if (fPictures != NULL) {
-		for (int32 i = fPictures->CountItems(); i-- > 0;)
-			fPictures->ItemAt(i)->ReleaseReference();
+		for (int32 i = fPictures->CountItems(); i-- > 0;) {
+			ServerPicture* picture = fPictures->ItemAt(i);
+			picture->SetOwner(NULL);
+			picture->ReleaseReference();
+		}
 
 		delete fPictures;
 	}
+	
+	if (fPushed != NULL) {
+		fPushed->SetOwner(NULL);
+		fPushed->ReleaseReference();
+	}
 }
 
 
@@ -869,29 +876,18 @@ bool
 ServerPicture::SetOwner(ServerApp* owner)
 {
 	if (fOwner != NULL)
-		fOwner->PictureRemoved(this);
+		fOwner->RemovePicture(this);
 
-	if (owner != NULL && owner->PictureAdded(this)) {
+	if (owner != NULL && owner->AddPicture(this)) {
 		fOwner = owner;
 		return true;
 	}
 
+	fOwner = NULL;
 	return false;
 }
 
 
-bool
-ServerPicture::ReleaseClientReference()
-{
-	if (!fHasClientReference)
-		return false;
-
-	fHasClientReference = false;
-	ReleaseReference();
-	return true;
-}
-
-
 void
 ServerPicture::EnterStateChange()
 {
@@ -1014,22 +1010,38 @@ ServerPicture::Play(View* view)
 }
 
 
+/*!	Acquires a reference to the pushed picture.
+*/
 void
-ServerPicture::Usurp(ServerPicture* picture)
+ServerPicture::PushPicture(ServerPicture* picture)
 {
-	fUsurped = picture;
+	if (fPushed != NULL)
+		debugger("already pushed a picture");
+
+	fPushed = picture;
+	fPushed->AcquireReference();
 }
 
 
+/*!	Returns a reference with the popped picture.
+*/
 ServerPicture*
-ServerPicture::StepDown()
+ServerPicture::PopPicture()
 {
-	ServerPicture* old = fUsurped;
-	fUsurped = NULL;
+	ServerPicture* old = fPushed;
+	fPushed = NULL;
 	return old;
 }
 
 
+void
+ServerPicture::AppendPicture(ServerPicture* picture)
+{
+	// A pushed picture is the same as an appended one
+	PushPicture(picture);
+}
+
+
 bool
 ServerPicture::NestPicture(ServerPicture* picture)
 {
@@ -1119,13 +1131,3 @@ ServerPicture::ExportData(BPrivate::PortLink& link)
 	fData->Seek(oldPosition, SEEK_SET);
 	return status;
 }
-
-
-void
-ServerPicture::LastReferenceReleased()
-{
-	if (fOwner != NULL)
-		fOwner->PictureRemoved(this);
-
-	delete this;
-}

src/servers/app/ServerPicture.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2009, Haiku.
+ * Copyright 2001-2010, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -49,9 +49,10 @@ public:
 
 			void				Play(View* view);
 
-			void 				Usurp(ServerPicture* newPicture);
-			ServerPicture*		StepDown();
+			void 				PushPicture(ServerPicture* picture);
+			ServerPicture*		PopPicture();
 
+			void				AppendPicture(ServerPicture* picture);
 			bool				NestPicture(ServerPicture* picture);
 
 			off_t				DataLength() const;
@@ -59,19 +60,16 @@ public:
 			status_t			ImportData(BPrivate::LinkReceiver& link);
 			status_t			ExportData(BPrivate::PortLink& link);
 
-protected:
-	virtual	void				LastReferenceReleased();
-
 private:
-	typedef BObjectList<ServerPicture> PictureList;
+			typedef BObjectList<ServerPicture> PictureList;
 
 			int32				fToken;
 			BFile*				fFile;
 			BPositionIO*		fData;
 			PictureList*		fPictures;
-			ServerPicture*		fUsurped;
+			ServerPicture*		fPushed;
 			ServerApp*			fOwner;
-			bool				fHasClientReference;
 };
 
+
 #endif	// SERVER_PICTURE_H

src/servers/app/ServerWindow.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2001-2009, Haiku.
+ * Copyright 2001-2010, Haiku.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -2066,8 +2066,10 @@ fDesktop->LockSingleWindow();
 			DTRACE(("ServerWindow %s: Message AS_VIEW_BEGIN_PICTURE\n",
 				Title()));
 			ServerPicture* picture = App()->CreatePicture();
-			picture->SyncState(fCurrentView);
-			fCurrentView->SetPicture(picture);
+			if (picture != NULL) {
+				picture->SyncState(fCurrentView);
+				fCurrentView->SetPicture(picture);
+			}
 			break;
 		}
 
@@ -2756,9 +2758,9 @@ ServerWindow::_DispatchViewDrawingMessage(int32 code,
 
 
 bool
-ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
+ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver& link)
 {
-	ServerPicture *picture = fCurrentView->Picture();
+	ServerPicture* picture = fCurrentView->Picture();
 	if (picture == NULL)
 		return false;
 
@@ -2778,7 +2780,6 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
 			BRect rect;
 			link.Read<BRect>(&rect);
 			picture->WriteInvertRect(rect);
-
 			break;
 		}
 
@@ -3092,13 +3093,12 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
 			link.Read<int32>(&opCount);
 			link.Read<int32>(&ptCount);
 
-			uint32 *opList = new(nothrow) uint32[opCount];
-			BPoint *ptList = new(nothrow) BPoint[ptCount];
+			uint32* opList = new(std::nothrow) uint32[opCount];
+			BPoint* ptList = new(std::nothrow) BPoint[ptCount];
 			if (opList != NULL && ptList != NULL
 				&& link.Read(opList, opCount * sizeof(uint32)) >= B_OK
 				&& link.Read(ptList, ptCount * sizeof(BPoint)) >= B_OK) {
-
-				// This might seem a bit weird, but under R5, the shapes
+				// This might seem a bit weird, but under BeOS, the shapes
 				// are always offset by the current pen location
 				BPoint penLocation
 					= fCurrentView->CurrentState()->PenLocation();
@@ -3108,9 +3108,9 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
 				const bool fill = (code == AS_FILL_SHAPE);
 				picture->WriteDrawShape(opCount, opList, ptCount, ptList, fill);
 			}
+
 			delete[] opList;
 			delete[] ptList;
-
 			break;
 		}
 
@@ -3175,16 +3175,17 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
 				// we are supposed to clear the clipping region
 				picture->WriteClearClipping();
 			}
-
 			break;
 		}
+
 		case AS_VIEW_BEGIN_PICTURE:
 		{
-			ServerPicture *newPicture = App()->CreatePicture();
-			newPicture->Usurp(picture);
-			newPicture->SyncState(fCurrentView);
-			fCurrentView->SetPicture(newPicture);
-
+			ServerPicture* newPicture = App()->CreatePicture();
+			if (newPicture != NULL) {
+				newPicture->PushPicture(picture);
+				newPicture->SyncState(fCurrentView);
+				fCurrentView->SetPicture(newPicture);
+			}
 			break;
 		}
 
@@ -3196,7 +3197,7 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
 			ServerPicture* appendPicture = App()->GetPicture(token);
 			if (appendPicture != NULL) {
 				//picture->SyncState(fCurrentView);
-				appendPicture->Usurp(picture);
+				appendPicture->AppendPicture(picture);
 			}
 
 			fCurrentView->SetPicture(appendPicture);
@@ -3208,9 +3209,11 @@ ServerWindow::_DispatchPictureMessage(int32 code, BPrivate::LinkReceiver &link)
 
 		case AS_VIEW_END_PICTURE:
 		{
-			ServerPicture* steppedDown = picture->StepDown();
+			ServerPicture* poppedPicture = picture->PopPicture();
+			fCurrentView->SetPicture(poppedPicture);
+			if (poppedPicture != NULL)
+				poppedPicture->ReleaseReference();
 
-			fCurrentView->SetPicture(steppedDown);
 			fLink.StartMessage(B_OK);
 			fLink.Attach<int32>(picture->Token());
 			fLink.Flush();
@@ -3301,6 +3304,7 @@ ServerWindow::_MessageLooper()
 #endif
 
 		int32 messagesProcessed = 0;
+		bigtime_t processingStart = system_time();
 		bool lockedDesktop = false;
 		bool needsAllWindowsLocked = false;
 
@@ -3384,8 +3388,9 @@ ServerWindow::_MessageLooper()
 				fDesktop->UnlockAllWindows();
 
 			// Only process up to 70 waiting messages at once (we have the
-			// Desktop locked)
-			if (!receiver.HasMessages() || ++messagesProcessed > 70) {
+			// Desktop locked), but don't hold the lock longer than 25 ms
+			if (!receiver.HasMessages() || ++messagesProcessed > 70
+				|| system_time() - processingStart > 25000) {
 				if (lockedDesktop)
 					fDesktop->UnlockSingleWindow();
 				break;