[MC-23105] Exception in Server when exiting

When exiting a freshly created minecraft Server with Ctrl+C on the linux console, I got a lot of console spam. The messages all were

java.util.ConcurrentModificationException
        at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1115)
        at java.util.TreeMap$KeyIterator.next(TreeMap.java:1169)
        at jr.a(SourceFile:454)
        at aed.a(SourceFile:217)
        at aed.a(SourceFile:91)
        at jq.b(SourceFile:154)
        at jq.a(SourceFile:183)
        at jr.a(SourceFile:602)
        at net.minecraft.server.MinecraftServer.a(SourceFile:263)
        at net.minecraft.server.MinecraftServer.m(SourceFile:283)
        at hg.run(SourceFile:566)

Being able to code a little bit in Java, this seems to be a severe bug (race condition or missing synchronization or something).

After restarting the server some chunks looked as if they were not saved correctly.

This is reproducible.

Can attach additional files like server.properties if necessary.

Linked issues

relates to 1

MC-509 Exception in server tick loop :: ConcurrentModificationException Resolved

Comments 12

Anon Ymus 2013-07-06T17:29:27Z

Are you using any plugins?

Jonathan Haas 2013-07-06T17:40:29Z

No, just a fresh vanilla server.

Jonathan Haas 2013-09-22T09:45:52Z

I guess this is caused by generating the chunks at the same time as saving them.

Jonathan Haas 2013-11-19T20:22:33Z

Note that this bug only occurs when you exit a server you just created/started a few seconds ago with a fresh world. As I said, it's probably happening because the initial chunk generation is still happening while the server is already exiting.

CubeTheThird 2014-01-05T17:18:11Z

What version of java do you have installed?
Also, is this a problem for server 1.7.4?

2 more comments

kumasasa 2014-07-28T18:10:31Z

@@unknown: That's something different.

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification

vs.

java.util.ConcurrentModificationException
        at java.util.TreeMap$PrivateEntryIterator.nextEntry

ConcurrentModificationException means that one thread cannot get a lock on a resource because some other thread has it already (If I do interpret that correctly), but the causes for both exceptions are different.

Anthony Martin 2014-07-28T20:45:53Z

It's usually a race condition. This report mentions race conditions. So, rather than risk a duplicate report, I just commented here.

Anthony Martin 2014-08-07T03:55:47Z

I believe this situation now triggers the watchdog thread, by default: MC-63590

galaxy_2alex 2014-10-25T18:12:39Z

Is this still a concern in the current Minecraft version 1.8.1 Prerelease 3 / Launcher version 1.5.3 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

user-f2760 2016-03-18T16:29:20Z

No response for over a year.