enqueued:	10	t : 0	[from bl:=0]
queue:	10	t : 0	[from bl:=0]
WARNING: unstable `t'-
rule: [after 10]	wl:1 & ~bl:1<0><0> -> t-:X
>> cause: `bl' (val: 1)
queue:	10	t : 1	[from bl:=0]	(weak)
	10	t : 1	[by bl:=1]
