修改下面生产者——消费者总是的解法中的错误：

修改下面生产者——消费者总是的解法中的错误：

producer                    consumer

begin                       begin

repeat                       repeat

.                           p(mutex);

produce a new message m;      p(empty);

p(mutex);                    m:=buffer(out);

p(full);                      out:=out+1;

buffer(in):=m;                v(mutex);

v(mutex);                    consume message m;

until false                    until false

end                         end