[170910] Fix AbstractTerminalShell#waitFor() implementation

rse/plugins/org.eclipse.rse.services/src/org/eclipse/rse/internal/services/terminals/AbstractTerminalShell.java

@@ -58,18 +58,49 @@ public abstract class AbstractTerminalShell extends PlatformObject implements IT
 	public int exitValue() {
 		// exit values are not supported by default, but we need to observe the
 		// API by throwing IllegalThreadStateException
-		if (isActive())
+		if (isActive()) {
 			throw new IllegalThreadStateException();
+		}
 		return 0;
 	}
 
+	/**
+	 * Return the interval (in milliseconds) for polling the {@ink #isActive()}
+	 * method during the {@link #waitFor(long)} method. Subclasses may override
+	 * to return different poll intervals.
+	 *
+	 * The interval may be changed dynamically as appropriate for the current
+	 * state of this shell. That way, wait polling mechanisms such as
+	 * exponential backoff can be implemented.
+	 *
+	 * Or, a concrete implementation that supports a notification mechanism for
+	 * knowing when the shell terminates, can use this to tweak the waitFor()
+	 * method by returning Long.MAX_VALUE here (wait forever), but calling
+	 * {@link #notifyAll()} when the shell is dead.
+	 *
+	 * @return interval (in milliseconds) for polling active state
+	 */
+	protected long getWaitForPollInterval() {
+		return 500L;
+	}
+
+	/**
+	 * Wait for the shell to terminate. This uses a polling mechanism by
+	 * default, which can be tweaked by overriding
+	 * {@link #getWaitForPollInterval()}.
+	 *
+	 * @see IBaseShell#waitFor(long)
+	 */
 	public boolean waitFor(long timeout) throws InterruptedException {
 		boolean active = isActive();
 		if (active) {
-			synchronized (this) {
+			long endTime = (timeout <= 0) ? Long.MAX_VALUE : System.currentTimeMillis() + timeout - getWaitForPollInterval();
-				wait(timeout);
+			do {
-			}
+				synchronized (this) {
-			active = isActive();
+					wait(getWaitForPollInterval());
+				}
+				active = isActive();
+			} while (active && (timeout <= 0 || System.currentTimeMillis() < endTime));
 		}
 		return active;
 	}

rse/plugins/org.eclipse.rse.services/src/org/eclipse/rse/internal/services/terminals/ProcessBaseShell.java

@@ -125,6 +125,8 @@ public class ProcessBaseShell extends PlatformObject implements IBaseShell {
 		if (active) {
 			Thread watchdog = null;
 			if (timeout > 0) {
+				// TODO Check if using java.util.Timer would be more efficient
+				// than our own Watchdog
 				watchdog = new Watchdog(Thread.currentThread(), timeout) {
 					protected boolean conditionDone() {
 						return !isActive();