4.2 互斥的实现方法
Program mutualexclusion
Const n=…(* number of process*)
Var
bolt:integer;
Procedure P(i:integer)
Var keyi: integer;
Begin
repeat
keyi:=1
repeat exchange(keyi,bolt)
until keyi=0;
<critical section>
exchange(keyi,bolt) ;
<remainder>
Until false
end