Merge "Call ProgressMonitor.update() from main thread"

1 files changed, 97 insertions, 23 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ThreadSafeProgressMonitor.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ThreadSafeProgressMonitor.java
index 9708bb2f92..9e8e256b01 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ThreadSafeProgressMonitor.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ThreadSafeProgressMonitor.java
@@ -43,16 +43,35 @@
 
 package org.eclipse.jgit.lib;
 
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * Wrapper around the general {@link ProgressMonitor} to make it thread safe.
+ *
+ * Updates to the underlying ProgressMonitor are made only from the thread that
+ * allocated this wrapper. Callers are responsible for ensuring the allocating
+ * thread uses {@link #pollForUpdates()} or {@link #waitForCompletion()} to
+ * update the underlying ProgressMonitor.
+ *
+ * Only {@link #update(int)}, {@link #isCancelled()}, and {@link #endWorker()}
+ * may be invoked from a worker thread. All other methods of the ProgressMonitor
+ * interface can only be called from the thread that allocates this wrapper.
  */
 public class ThreadSafeProgressMonitor implements ProgressMonitor {
 	private final ProgressMonitor pm;
 
 	private final ReentrantLock lock;
 
+	private final Thread mainThread;
+
+	private final AtomicInteger workers;
+
+	private final AtomicInteger pendingUpdates;
+
+	private final Semaphore process;
+
 	/**
 	 * Wrap a ProgressMonitor to be thread safe.
 	 *
@@ -62,33 +81,87 @@ public class ThreadSafeProgressMonitor implements ProgressMonitor {
 	public ThreadSafeProgressMonitor(ProgressMonitor pm) {
 		this.pm = pm;
 		this.lock = new ReentrantLock();
+		this.mainThread = Thread.currentThread();
+		this.workers = new AtomicInteger(0);
+		this.pendingUpdates = new AtomicInteger(0);
+		this.process = new Semaphore(0);
 	}
 
 	public void start(int totalTasks) {
-		lock.lock();
-		try {
-			pm.start(totalTasks);
-		} finally {
-			lock.unlock();
-		}
+		if (!isMainThread())
+			throw new IllegalStateException();
+		pm.start(totalTasks);
 	}
 
 	public void beginTask(String title, int totalWork) {
-		lock.lock();
-		try {
-			pm.beginTask(title, totalWork);
-		} finally {
-			lock.unlock();
+		if (!isMainThread())
+			throw new IllegalStateException();
+		pm.beginTask(title, totalWork);
+	}
+
+	/** Notify the monitor a worker is starting. */
+	public void startWorker() {
+		startWorkers(1);
+	}
+
+	/**
+	 * Notify the monitor of workers starting.
+	 *
+	 * @param count
+	 *            the number of worker threads that are starting.
+	 */
+	public void startWorkers(int count) {
+		workers.addAndGet(count);
+	}
+
+	/** Notify the monitor a worker is finished. */
+	public void endWorker() {
+		if (workers.decrementAndGet() == 0)
+			process.release();
+	}
+
+	/**
+	 * Non-blocking poll for pending updates.
+	 *
+	 * This method can only be invoked by the same thread that allocated this
+	 * ThreadSafeProgressMonior.
+	 */
+	public void pollForUpdates() {
+		assert isMainThread();
+		doUpdates();
+	}
+
+	/**
+	 * Process pending updates and wait for workers to finish.
+	 *
+	 * This method can only be invoked by the same thread that allocated this
+	 * ThreadSafeProgressMonior.
+	 *
+	 * @throws InterruptedException
+	 *             if the main thread is interrupted while waiting for
+	 *             completion of workers.
+	 */
+	public void waitForCompletion() throws InterruptedException {
+		assert isMainThread();
+		while (0 < workers.get()) {
+			doUpdates();
+			process.acquire();
 		}
+		doUpdates();
+	}
+
+	private void doUpdates() {
+		int cnt = pendingUpdates.getAndSet(0);
+		if (0 < cnt)
+			pm.update(cnt);
 	}
 
 	public void update(int completed) {
-		lock.lock();
-		try {
-			pm.update(completed);
-		} finally {
-			lock.unlock();
-		}
+		int old = pendingUpdates.getAndAdd(completed);
+		if (isMainThread())
+			doUpdates();
+		else if (old == 0)
+			process.release();
 	}
 
 	public boolean isCancelled() {
@@ -101,11 +174,12 @@ public class ThreadSafeProgressMonitor implements ProgressMonitor {
 	}
 
 	public void endTask() {
-		lock.lock();
-		try {
-			pm.endTask();
-		} finally {
-			lock.unlock();
-		}
+		if (!isMainThread())
+			throw new IllegalStateException();
+		pm.endTask();
+	}
+
+	private boolean isMainThread() {
+		return Thread.currentThread() == mainThread;
 	}
 }