enqueued:	10	c : 1	[from _p:=0]
	10	c : 1	[by _p:=0]
time: 10
enqueued:	20	c : 0	[from a:=1]
time: 10
queue:	20	c : 0	[from a:=1]
queue:	20	c : 0	[from a:=1]
a high should mask instability of b 
queue:	20	c : 0	[from a:=1]
	20	c : 0	[by a:=1]
