Program: 161699
Project: 161699
Buggy source:
protected TaskWrapper getNextTask() throws InterruptedException {
  while (runningThread != null) {
    TaskWrapper nextScheduledTask=scheduleQueue.peekFirst();
    TaskWrapper nextExecuteTask=executeQueue.peek();
    if (nextExecuteTask != null) {
      if (nextScheduledTask != null) {
        long scheduleDelay;
        long executeDelay;
        ClockWrapper.stopForcingUpdate();
        try {
          scheduleDelay=nextScheduledTask.getDelay(TimeUnit.MILLISECONDS);
          executeDelay=nextExecuteTask.getDelay(TimeUnit.MILLISECONDS);
        }
  finally {
          ClockWrapper.resumeForcingUpdate();
        }
        if (scheduleDelay < executeDelay) {
synchronized (scheduleQueue.getModificationLock()) {
            if (scheduleQueue.remove(nextScheduledTask)) {
              nextScheduledTask.executing();
              return nextScheduledTask;
            }
          }
        }
 else         if (executeQueue.remove(nextExecuteTask)) {
          nextExecuteTask.executing();
          return nextExecuteTask;
        }
      }
 else       if (executeQueue.remove(nextExecuteTask)) {
        nextExecuteTask.executing();
        return nextExecuteTask;
      }
    }
 else     if (nextScheduledTask != null) {
      if (nextScheduledTask.getDelay(TimeUnit.MILLISECONDS) <= 0) {
synchronized (scheduleQueue.getModificationLock()) {
          if (scheduleQueue.remove(nextScheduledTask)) {
            nextScheduledTask.executing();
            return nextScheduledTask;
          }
        }
      }
 else {
        LockSupport.parkNanos(Clock.NANOS_IN_MILLISECOND * nextScheduledTask.getDelay(TimeUnit.MILLISECONDS));
      }
    }
 else {
      LockSupport.park();
    }
    if (Thread.currentThread().isInterrupted()) {
      throw new InterruptedException();
    }
  }
  return null;
}

Fixed version (ground truth):
protected TaskWrapper getNextTask() throws InterruptedException {
  while (runningThread != null) {
    TaskWrapper nextScheduledTask=scheduleQueue.peekFirst();
    TaskWrapper nextExecuteTask=executeQueue.peek();
    if (nextExecuteTask != null) {
      if (nextScheduledTask != null) {
        long scheduleDelay;
        long executeDelay;
        ClockWrapper.stopForcingUpdate();
        try {
          scheduleDelay=nextScheduledTask.getDelay(TimeUnit.MILLISECONDS);
          executeDelay=nextExecuteTask.getDelay(TimeUnit.MILLISECONDS);
        }
  finally {
          ClockWrapper.resumeForcingUpdate();
        }
        if (scheduleDelay < executeDelay) {
synchronized (scheduleQueue.getModificationLock()) {
            if (scheduleQueue.remove(nextScheduledTask)) {
              nextScheduledTask.executing();
              return nextScheduledTask;
            }
          }
        }
 else         if (executeQueue.remove(nextExecuteTask)) {
          nextExecuteTask.executing();
          return nextExecuteTask;
        }
      }
 else       if (executeQueue.remove(nextExecuteTask)) {
        nextExecuteTask.executing();
        return nextExecuteTask;
      }
    }
 else     if (nextScheduledTask != null) {
      if (nextScheduledTask.getDelay(TimeUnit.MILLISECONDS) <= 0) {
synchronized (scheduleQueue.getModificationLock()) {
          if (scheduleQueue.remove(nextScheduledTask)) {
            nextScheduledTask.executing();
            return nextScheduledTask;
          }
        }
      }
 else {
        if (queuePriority == TaskPriority.High) {
          workerPool.handleEstimatedTimeTillNextHighPriority(nextScheduledTask.getDelayEstimateInMs());
        }
        LockSupport.parkNanos(Clock.NANOS_IN_MILLISECOND * nextScheduledTask.getDelay(TimeUnit.MILLISECONDS));
      }
    }
 else {
      if (queuePriority == TaskPriority.High) {
        workerPool.handleEstimatedTimeTillNextHighPriority(Long.MAX_VALUE);
      }
      LockSupport.park();
    }
    if (Thread.currentThread().isInterrupted()) {
      throw new InterruptedException();
    }
  }
  return null;
}