Paging system crash when moving too fast about projectzombie HOT 3 CLOSED

Okay this is caused by "overwhelming" the system where you load a page, which 
generates a load page task (threading stuff), then immediately ask it to unload 
a page while the actual page has yet to be generated! 

Actually, this issue came up before, but we forgot about it. In the future we 
should immediately note a problem so we don't "rediscover" bugs again and again.

The fix is not that simple. Current idea is to do a reference count thing, so 
if after a thread finishes generation, it checks a variable (atomic?) to see if 
it has been unloaded. If so, then it unloads it.

It's fixed. Now the system does deferred unloading. The system now defers 
unloading to the response thread for pages that had unload called when still 
being processed for loading. 

This is fixed in r166

http://code.google.com/p/projectzombie/source/detail?r=166