check that a task is valid before executing incase it was cancelled e…

…lsewhere

also set runners in the short circuit path so we know of the pending task incase its long running

Spigot-Server-Patches/0275-Improved-Async-Task-Scheduler.patch

@@ -1,4 +1,4 @@
-From 64c30d8a2caa9ff443e46f399839579d9b4517c2 Mon Sep 17 00:00:00 2001
+From 2b304a51b4e740aaab398d6bd31f54da4486ef81 Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Fri, 16 Mar 2018 22:59:43 -0400
 Subject: [PATCH] Improved Async Task Scheduler
@@ -38,10 +38,10 @@ queue if a plugin schedules lots of asynchronous tasks.
 
 diff --git a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftAsyncScheduler.java b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftAsyncScheduler.java
 new file mode 100644
-index 000000000..b1efbc3e7
+index 000000000..cf5aada2f
 --- /dev/null
 +++ b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftAsyncScheduler.java
-@@ -0,0 +1,151 @@
+@@ -0,0 +1,161 @@
 +/*
 + * Copyright (c) 2018 Daniel Ennis (Aikar) MIT License
 + *
@@ -82,6 +82,7 @@ index 000000000..b1efbc3e7
 +
 +    private final Executor management = Executors.newFixedThreadPool(1, new ThreadFactoryBuilder()
 +        .setNameFormat("Craft Scheduler Management Thread").build());
++    private final List<CraftTask> temp = new ArrayList<>();
 +    CraftAsyncScheduler() {
 +        super(true);
 +    }
@@ -108,41 +109,50 @@ index 000000000..b1efbc3e7
 +    }
 +
 +    private synchronized void runTasks(int currentTick) {
-+        final List<CraftTask> temp = new ArrayList<>();
 +        while (!this.pending.isEmpty() && this.pending.peek().getNextRun() <= currentTick) {
 +            CraftTask task = this.pending.remove();
-+            this.runners.put(task.getTaskId(), task);
-+            this.executor.execute(new ServerSchedulerReportingWrapper(task));
-+            final long period = task.getPeriod();
-+            if (period > 0) {
-+                task.setNextRun(currentTick + period);
-+                temp.add(task);
++            if (executeTask(task)) {
++                final long period = task.getPeriod();
++                if (period > 0) {
++                    task.setNextRun(currentTick + period);
++                    temp.add(task);
++                }
 +            }
 +        }
 +        this.pending.addAll(temp);
++        temp.clear();
 +    }
 +
 +    @Override
 +    protected CraftTask handle(CraftTask task, final long delay) {
 +        if (task.getPeriod() == -1L && delay == 0L) {
-+            this.executor.execute(task);
-+            return task;
++            executeTask(task);
++        } else {
++            task.setNextRun(this.currentTick + delay);
++            this.management.execute(() -> this.addTask(task));
 +        }
-+        task.setNextRun(this.currentTick + delay);
-+        this.management.execute(() -> this.addTask(task));
 +        return task;
 +    }
 +
++    private boolean executeTask(CraftTask task) {
++        if (isValid(task)) {
++            this.runners.put(task.getTaskId(), task);
++            this.executor.execute(new ServerSchedulerReportingWrapper(task));
++            return true;
++        }
++        return false;
++    }
++
 +    private synchronized void addTask(CraftTask task) {
 +        this.pending.add(task);
 +    }
 +
 +    @Override
 +    public synchronized void cancelTasks(Plugin plugin) {
 +        for (Iterator<CraftTask> iterator = this.pending.iterator(); iterator.hasNext(); ) {
-+            CraftTask taskPending = iterator.next();
-+            if (taskPending.getTaskId() != -1 && (plugin == null || taskPending.getOwner().equals(plugin))) {
-+                taskPending.cancel0();
++            CraftTask task = iterator.next();
++            if (task.getTaskId() != -1 && (plugin == null || task.getOwner().equals(plugin))) {
++                task.cancel0();
 +                iterator.remove();
 +            }
 +        }