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Remove synchronisation on "Device.class", because it is deadlock prone. #344

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Remove synchronisation on "Device.class", because it is deadlock prone. #344

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30 changes: 19 additions & 11 deletions bundles/org.eclipse.rap.rwt/src/org/eclipse/swt/internal/widgets/DisplaysHolder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -12,23 +12,31 @@
package org.eclipse.swt.internal.widgets;

import java.lang.ref.WeakReference;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;

import org.eclipse.swt.widgets.Display;


public class DisplaysHolder {
private WeakReference<Display>[] displays;

@SuppressWarnings("unchecked")
public final class DisplaysHolder {

private final Map<Thread, WeakReference<Display>> displays;

public DisplaysHolder() {
displays = new WeakReference[ 4 ];
displays = Collections.synchronizedMap( new WeakHashMap<>() );
}
public WeakReference<Display>[] getDisplays() {
return displays;

public void addDisplay( Thread tread, Display display ) {
displays.put( tread, new WeakReference<>( display ) );
}

public void setDisplays( WeakReference<Display>[] displays ) {
this.displays = displays;

public Display getDisplay( Thread thread ) {
WeakReference<Display> wr = displays.get( thread );
if ( wr != null ) {
return wr.get();
}
return null;
}

}
62 changes: 9 additions & 53 deletions bundles/org.eclipse.rap.rwt/src/org/eclipse/swt/widgets/Display.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,6 @@
import static org.eclipse.rap.rwt.remote.JsonMapping.readRectangle;

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
Expand Down Expand Up @@ -939,17 +938,11 @@ private void detachThread() {
* @return the display for the given thread
*/
public static Display findDisplay( Thread thread ) {
synchronized( Device.class ) {
for( WeakReference<Display> displayRef : getDisplays() ) {
if( displayRef != null ) {
Display display = displayRef.get();
if( display != null && !display.isDisposed() && display.thread == thread ) {
return display;
}
}
}
Display display = getDisplay( thread );
if (display == null || display.thread != thread || display.isDisposed()) {
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@ifurnadjiev ifurnadjiev Oct 28, 2025

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Please fix the code formatting here: if( display == ... )

return null;
}
return display;
}

/**
Expand Down Expand Up @@ -2217,57 +2210,20 @@ public boolean getTouchEnabled() {
return false;
}

@SuppressWarnings("unchecked")
private void register() {
synchronized( Device.class ) {
boolean registered = false;
WeakReference<Display>[] displays = getDisplays();
for( int i = 0; !registered && i < displays.length; i++ ) {
if( canDisplayRefBeReplaced( displays[ i ] ) ) {
displays[ i ] = new WeakReference<>( this );
registered = true;
}
}
if( !registered ) {
WeakReference<Display>[] newDisplays = new WeakReference[ displays.length + 4 ];
System.arraycopy( displays, 0, newDisplays, 0, displays.length );
newDisplays[ displays.length ] = new WeakReference<>( this );
setDisplays( newDisplays );
}
}
}

private boolean canDisplayRefBeReplaced( WeakReference<Display> displayRef ) {
boolean result = false;
if( displayRef == null ) {
result = true;
} else {
Display display = displayRef.get();
if( display == null || display.thread == thread ) {
result = true;
}
}
return result;
addDisplay( this );
}

private void deregister() {
synchronized( Device.class ) {
WeakReference<Display>[] displays = getDisplays();
for( int i = 0; i < displays.length; i++ ) {
WeakReference<Display> current = displays[ i ];
if( current != null && this == current.get() ) {
displays[ i ] = null;
}
}
}

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@ifurnadjiev ifurnadjiev Oct 28, 2025

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Do you need to remove the display from the holder here?

}

private static WeakReference<Display>[] getDisplays() {
return ContextProvider.getApplicationContext().getDisplaysHolder().getDisplays();
private static Display getDisplay( Thread thread ) {
return ContextProvider.getApplicationContext().getDisplaysHolder().getDisplay( thread );
}

private void setDisplays( WeakReference<Display>[] displays ) {
getApplicationContext().getDisplaysHolder().setDisplays( displays );
private void addDisplay( Display display ) {
getApplicationContext().getDisplaysHolder().addDisplay( thread, display );
}

/////////////////////
Expand Down