Problem/Bug Frequent Crashes: Does anyone know whats going on?

I have been experiencing frequent crashes, only starting recently, on my 1.8.3 craftbukkit server:

My plugins are:
AutoSaveWorld
boosCooldowns
Clearlag
Color_Signs_Text
CoreProtect_2.12.0
dynmap-2.4
EasySetSpawn
Essentials-2.x
HolographicDisplays
iDisguise-5.1.1
Multiverse-Core-2.5
PermissionsEx-1.23.4
perworldinventory
RandomTP
ServerSigns
SilkSpawners
WorldBorder
Worldedit-6.1
Worldguard-6.1

The most recent crash report is below:
If you know what is up, please let me know!

 

That's the server watchdog. It kills the server when a single tick takes longer than 60 (!!!) seconds. Usually there is about 20 ticks per second (0.05 seconds per tick).
So something is really going wrong on your server...

The method that is being executed and (in the end) causes the server to hang is

Code:

public synchronized void sendPacket(Packet object)

The 'synchronized' only allows one thread at a time to execute this method. And for whatever reason this method has the hiccups, never finishes to execute and thus blocks any further threads of executing this method.

Code:

"Server thread" Id=17 BLOCKED on de.robingrether.idisguise.management.impl.v1_8_R2.ChannelRegisterImpl$PlayerConnectionInjected@2e50c6ad owned by "Netty Server IO #8" Id=31
    at de.robingrether.idisguise.management.impl.v1_8_R2.ChannelRegisterImpl$PlayerConnectionInjected.sendPacket(ChannelRegisterImpl.java:167)
    -  blocked on de.robingrether.idisguise.management.impl.v1_8_R2.ChannelRegisterImpl$PlayerConnectionInjected@2e50c6ad
    at net.minecraft.server.v1_8_R2.EntityTrackerEntry.broadcast(EntityTrackerEntry.java:280)
    at net.minecraft.server.v1_8_R2.EntityTracker.a(EntityTracker.java:214)

Code:

"Netty Server IO #8" Id=31 BLOCKED on java.util.ArrayDeque@17c0764a owned by "Server thread" Id=17
    at net.minecraft.server.v1_8_R2.MinecraftServer.a(MinecraftServer.java:1418)
    -  blocked on java.util.ArrayDeque@17c0764a
    at net.minecraft.server.v1_8_R2.MinecraftServer.postToMainThread(MinecraftServer.java:1433)
    at net.minecraft.server.v1_8_R2.WorldServer.postToMainThread(WorldServer.java:1155)
    at net.minecraft.server.v1_8_R2.PlayerConnectionUtils.ensureMainThread(SourceFile:10)
    at net.minecraft.server.v1_8_R2.PlayerConnection.a(PlayerConnection.java:1198)
    at de.robingrether.idisguise.management.impl.v1_8_R2.ChannelRegisterImpl$PlayerConnectionInjected.a(ChannelRegisterImpl.java:152)
    -  locked de.robingrether.idisguise.management.impl.v1_8_R2.ChannelRegisterImpl$PlayerConnectionInjected@2e50c6ad
    at net.minecraft.server.v1_8_R2.PacketPlayInUseEntity.a(SourceFile:52)

When you take a look at the first lines of these two crash report excerpts:

Code:

Id=17 BLOCKED on ... Id=31
Id=31 BLOCKED on ... Id=17

A classic dead lock: Two threads are waiting on each other.

To get further information the related logfile (in <yourServerFolder/logs/) is required.