central: Avoid getting workspace writeLock in getWorkspace

We move the code needing the writeLock into another thread.
getWorkspace is called from many places including places holding
the workspace readLock. So we move the code needing the writeLock
out of the caller's thread.

Fixes #5110

Signed-off-by: BJ Hargrave <bj@hargrave.dev>

bndtools.core/src/bndtools/central/Central.java

@@ -224,54 +224,76 @@ public static Workspace getWorkspace() throws Exception {
 			throw new IllegalStateException("Central is not initialised");
 		}
 		final Workspace ws;
-		java.util.function.Consumer<Workspace> resolve = null;
+		Consumer<Workspace> afterLock = null;
 		synchronized (workspace) {
 			if (workspace.peek() == null) { // No workspace has been created
 				ws = workspace.get();
 				// Resolve with new workspace
-				resolve = tryResolve(anyWorkspaceDeferred);
+				afterLock = tryResolve(anyWorkspaceDeferred);
 				if (!ws.isDefaultWorkspace()) {
-					resolve = resolve.andThen(tryResolve(cnfWorkspaceDeferred));
+					afterLock = afterLock.andThen(tryResolve(cnfWorkspaceDeferred));
 				}
 			} else {
 				ws = workspace.get();
 				// get the parent directory of the "cnf" project, if there is
 				// one
 				File workspaceDirectory = getWorkspaceDirectory();
-				// Check to see if we need to convert it...
+				// Check to see if we need to adjust it...
 				if (workspaceDirectory != null && !workspaceDirectory.equals(ws.getBase())) {
 					// There is a "cnf" project and the current workspace is
 					// not the same as the directory the cnf project is in,
 					// so switch the workspace to the directory
-					ws.writeLocked(() -> {
-						ws.setFileSystem(workspaceDirectory, Workspace.CNFDIR);
-						ws.forceRefresh();
-						ws.refresh();
-						ws.refreshProjects();
-						return null;
-					});
-					resolve = tryResolve(cnfWorkspaceDeferred);
+					afterLock = Central::adjustWorkspace;
 				} else if (workspaceDirectory == null && !ws.isDefaultWorkspace()) {
 					// There is no "cnf" project and the current workspace is
 					// not the default, so switch the workspace to the default
-					cnfWorkspaceDeferred = promiseFactory().deferred();
-					ws.writeLocked(() -> {
-						ws.setFileSystem(Workspace.BND_DEFAULT_WS, Workspace.CNFDIR);
-						ws.forceRefresh();
-						ws.refresh();
-						ws.refreshProjects();
-						return null;
-					});
+					afterLock = Central::adjustWorkspace;
 				}
 			}
 		}
-		if (resolve != null) { // resolve deferred if requested
-			resolve.accept(ws);
+		if (afterLock != null) { // perform after lock action
+			afterLock.accept(ws);
 		}
 		return ws;
 	}
 
-	private static <T> java.util.function.Consumer<T> tryResolve(Deferred<T> deferred) {
+	private static void adjustWorkspace(Workspace ws) throws Exception {
+		// Get write lock on another thread
+		promiseFactory().submit(() -> {
+			Consumer<Workspace> afterLock = ws.writeLocked(() -> {
+				// get the parent directory of the "cnf" project, if there is
+				// one
+				File workspaceDirectory = getWorkspaceDirectory();
+				// Check to see if we need to convert it...
+				if (workspaceDirectory != null && !workspaceDirectory.equals(ws.getBase())) {
+					// There is a "cnf" project and the current workspace is
+					// not the same as the directory the cnf project is in,
+					// so switch the workspace to the directory
+					ws.setFileSystem(workspaceDirectory, Workspace.CNFDIR);
+					ws.forceRefresh();
+					ws.refresh();
+					ws.refreshProjects();
+					return tryResolve(cnfWorkspaceDeferred);
+				} else if (workspaceDirectory == null && !ws.isDefaultWorkspace()) {
+					// There is no "cnf" project and the current workspace is
+					// not the default, so switch the workspace to the default
+					cnfWorkspaceDeferred = promiseFactory().deferred();
+					ws.setFileSystem(Workspace.BND_DEFAULT_WS, Workspace.CNFDIR);
+					ws.forceRefresh();
+					ws.refresh();
+					ws.refreshProjects();
+					return null;
+				}
+				return null;
+			});
+			if (afterLock != null) { // perform after lock action
+				afterLock.accept(ws);
+			}
+			return ws;
+		});
+	}
+
+	private static <T> Consumer<T> tryResolve(Deferred<T> deferred) {
 		return value -> {
 			try {
 				deferred.resolve(value);