callee : before create A
A : before `reply; P(global_s1)'
callee : after create A ... about to V(global_s1) and then P(global_s2)
A : after `reply; P(global_s1)'
A : doing V(global_s2)
callee : after P(global_s2)
callee : before sending to no_server_op
callee : after sending to no_server_op
