Consider adding a lock to RTree

[asinghvi17]

Libspatialindex is not threadsafe, so all operations (even queries as I understand) need to be done under a lock.

The way you would do this is by adding a lock field to the struct, providing it a ReentrantLock on construction, and then calling the C-API only under a

lock(index.lock)
try
	# call CAPI here
finally
	unlock(index.lock)
end

[rafaqz]

Right even queries use a shared memory pool:
libspatialindex/libspatialindex#189