expect to see only one event in queue at a time, b/c blocking 
event queue:
check queue:
	time	eid	pid	event
	0	0	1	null
	0	0	1	null
event queue:
check queue:
	time	eid	pid	event
	10	1	0	
	10	1	0	
event queue:
check queue:
	time	eid	pid	event
	20	2	0	x := true
	20	3	0	B?(x)
	20	2	0	x := true
event queue:
check queue:
	time	eid	pid	event
	20	3	0	B?(x)
	30	4	0	B!(~x)
	30	4	0	B!(~x)
event queue:
	time	eid	pid	event
	30	3	0	B?(x)
check queue:
	40	4	0	B!(~x)
	30	3	0	B?(x)
event queue:
check queue:
	time	eid	pid	event
	40	4	0	B!(~x)
	40	3	0	B?(x)
	40	3	0	B?(x)
event queue:
	time	eid	pid	event
	40	4	0	B!(~x)
check queue:
	50	3	0	B?(x)
	40	4	0	B!(~x)
event queue:
check queue:
	time	eid	pid	event
	50	3	0	B?(x)
	50	4	0	B!(~x)
	50	4	0	B!(~x)
event queue:
	time	eid	pid	event
	50	3	0	B?(x)
check queue:
	60	4	0	B!(~x)
