/**
* The <code>waitForNeighbors()</code> method is called from within the execution of a node when
* that node needs to wait for its neighbors to catch up to it in execution time. The node will be
* blocked until the other nodes in other threads catch up in global time.
*/
public void waitForNeighbors(long time) {
// get the current simulator thread
SimulatorThread thread = (SimulatorThread) Thread.currentThread();
SynchEvent event = (SynchEvent) threadMap.get(thread);
// if the current thread is not in the synchronizer, do nothing
if (event == null) return;
WaitSlot w;
synchronized (condition) {
// allocate a wait slot for this thread
w = insertWaiter(event, time);
// check for other waiters and wake them if necessary
WaitSlot h = checkWaiters();
// if we were at the head and just woken up, we can just return
if (w == h) return;
}
// falling through means that we are either not at the head
// or that not all threads have performed a meet or a wait
try {
// we must grab the lock for this wait slot
synchronized (w) {
// check for intervening wakeup between dropping global lock and taking local lock
if (w.shouldWait) w.wait();
}
} catch (InterruptedException e) {
throw Util.unexpected(e);
}
}
private WaitSlot insertAfter(WaitSlot prev, WaitSlot w) {
if (prev != null) {
w.next = prev.next;
prev.next = w;
} else {
waitSlotList = w;
}
return w;
}
protected WaitSlot checkWaiters() {
// have all threads reached either a meet or a wait?
if (wait_count + meet_count < goal) return null;
// are there any waiters at all?
if (waitSlotList == null) return null;
// there is a ready wait slot, wake those threads waiting on it
WaitSlot h = waitSlotList;
// move the wait list ahead to the next link
waitSlotList = h.next;
synchronized (h) {
// notify the threads waiting on this wait slot
h.shouldWait = false;
h.notifyAll();
}
// reduce the wait count by the number of waiters in this slot
wait_count -= h.numWaiters;
return h;
}
