Mapgen double-generating mapblocks, destroying user-built structures

[fireglow]

Hi,

Did a clearobjects run, afterwards chunks that had buildings, etc in were regenerated.
I've noticed that problem before, but in a smaller scale. This time, a huge part of our spawn-area park got demolished.
So this is a serious issue where user-build structures get damaged, and /rollback can't do anything about.
According to PilzAdam, this is a known issue.

A fix would be most welcome.

[sapier]

Can someone post the parameters when this happens?

[davisonio]

Can someone post the parameters when this happens?

An error like this happens:

In thread 2a7c:
..\..\minetest\src\emerge.cpp:633: EmergeThread::Thread: Assertion '0' failed.
Debug stacks:
DEBUG STACK FOR THREAD 90:
#0  main
#1  Dedicated server branch
#2  dedicated_server_loop
(Leftover data: #3  Server::step)
DEBUG STACK FOR THREAD ef8:
#0  CurlFetchThread::Thread
DEBUG STACK FOR THREAD 29dc:
#0  ServerThread::Thread
#1  Server::Receive
(Leftover data: #2  ServerEnvironment::step)
(Leftover data: #3  RemoteClient::GetNextBlocks)
(Leftover data: #4  Server::SendAccessDenied)
(Leftover data: #5  ItemStack::deSerialize)
DEBUG STACK FOR THREAD 2a7c:
#0  EmergeThread::Thread
(Leftover data: #1  ServerMap::emergeBlock: p=(-2,3,3), create_blank=0)
(Leftover data: #2  ServerMap::loadBlock)
(Leftover data: #3  ServerMap::createSector: p2d=(-47,53))

[davisonio]

Also, another cause of this bug is when running 2 servers from one minetest installation.

[sapier]

minetest doesn't have locking, if your run two instances on same map that's a user error

Is this the only way to trigger the error? or is there another way to do?

[fireglow]

All I can say is that

1. it happens after or during a /clearobjects run, and
2. there was no other instance of mt running, the world/ is a ZFS file system.

[ShadowNinja]

I didn't find any assert(0);s in a recent emerge.cpp, so this bug would appear to be gone.

[paramat]

Can anyone reproduce or is this now fixed?

[paramat]

I think this can be closed then.