Semp mutex 1,mutex2,empty1,empty2,full1,full2;
Mutex1=1;
Mutex2=1;
Empty1=empty2=1;
Full1=full2=0;
PA()
{
While(true)
{
P(empty1);
P(mutex1);
将消息放入buf1;
V(mutex1);
V(full1);
}
}
PB()
{
While(true);\
{
P(full1);
P(mutex1);
从buf1复制信息；
V(mutex1);
V(empty1);
P(empty2);
P(mutex2);
将信息放入buf2
