[理工] [OS] semaphore

[mqazz1 (無法顯示)]

the following program uses two semaphores, mutex and delay,

implementing a critical region.

what problem might occur?

how to fix it with still the same semaphores or other assumption?

initially, mutex=1, delay=0, count=0

=================================================================

wait(mutex);
while(!B)
{
        count++;
        if(count>0) signal(delay);
        else signal(mutex);
        wait(delay);
        count--;
}
S;

if(count>0) signal(delay);
else signal(mutex);

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推 christianSK:請問B 跟 S是什麼？
→ mqazz1:這個....題目沒說耶
推 christianSK:delay的初值是否要為1
推 christianSK:不然第一個人wait(delay)之後會變成-1
→ christianSK:既使後來有人signal(delay) 也還是會被卡住
→ christianSK:一點想法