试修改下面生产者-消费者问题解法中的错误。
producer:
begin
repeat
......
producer an item in nextp;
wait(mutex);
wait(full);
buffer(in):=nextp;
signal(mutex);
until false;
end
consumer:
begin
repeat
wait(mutex);
wait(empty);
nextc:=buffer(out);
out:=out+1;
signal(mutex);
consumer item in nextc;
until false;
end

【正确答案】producer: begin repeat ...... producer an item in nextp; wait(mutex); wait(full); /*应为wait(empty),而且还应该在wait(mutex)的前面*/ buffer(in) :=nextp; /*缓冲池数组游标应前移:in:=(in+1) mod n;*/ signal (mutex); /*signal (full);*/ until false; end consumer; begin repeat wait (mutex); wait (empty); /*应为wait (full),而且还应该在wait(mutex)的前面*/ nextc:=buffer(out); out:=out+1; /*考虑循环,应改为:out:=(out+1) mod n;*/ signal (mutex); /*signal (empty);*/ consumer item in nextc; until false; end

【答案解析】