Weird server crash. Something to do with zombie horses?

Here's the error log:
http://pastebin.com/xAh5gjCs

This has happened two times today. The error reports are almost exactly the same. Both times it's zombie horse, but not the same horse.

The only part that really makes sense is the following:

Code:java

java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:926)
        at java.util.HashMap$KeyIterator.next(HashMap.java:960)
        at net.minecraft.server.v1_7_R1.EntityLiving.removeAllEffects(EntityLiving.java:440)
        at net.minecraft.server.v1_7_R1.EntityLiving.C(EntityLiving.java:232)
        at net.minecraft.server.v1_7_R1.EntityInsentient.C(EntityInsentient.java:111)
        at net.minecraft.server.v1_7_R1.Entity.h(Entity.java:238)
        at net.minecraft.server.v1_7_R1.EntityLiving.h(EntityLiving.java:1265)
        at net.minecraft.server.v1_7_R1.EntityInsentient.h(EntityInsentient.java:150)
        at net.minecraft.server.v1_7_R1.EntityHorse.h(EntityHorse.java:748)
        at net.minecraft.server.v1_7_R1.World.entityJoinedWorld(World.java:1338)
        at net.minecraft.server.v1_7_R1.World.playerJoinedWorld(World.java:1319)
        at net.minecraft.server.v1_7_R1.World.tickEntities(World.java:1207)
        at net.minecraft.server.v1_7_R1.WorldServer.tickEntities(WorldServer.java:480)
        at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:637)
        at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250)
        at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545)
        at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457)
        at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617)

I guess that means the entities potion effects were modified while being accessed from another thread?

One of my plugins allows players to create zombie horses by poisoning normal horses, so could this be a problem? I can post the code for this if you think it's the problem.

 

thok13
Yes, to me it seems that way too. What exactly is the name of the plugin that you're using? Is it up to date? Have you tried asking this on their forums?

 

It's a plugin that I wrote.

 

thok13
In that case, I think this thread should be moved to Plugin Developments. I've reported it so please wait for an administrator to move the thread.

 

Moved to correct section.
Please provide code of plugin.

 

Here's the horse part:

Code:java

    @EventHandler
    public void OnEntityDamageEvent(EntityDamageEvent e)
    {
        if(e.getEntityType() == EntityType.HORSE)
        {
            Horse h = (Horse)e.getEntity();
            if(e.getCause() == DamageCause.POISON)
            {
                h.removePotionEffect(PotionEffectType.POISON);
                h.setHealth(h.getMaxHealth());
                h.setVariant(Variant.UNDEAD_HORSE);
                e.setCancelled(true);
            }
        }
    }

 

thok13
I can't see any large problems with that code. Are there any other codes affecting the horses and the undead ones?