1. In the example of producer-and-consumer problem (slide-31), which semaphore is used to implement a critical section for the shared variable, buffer?
   1. s
   2. n
   3. e
   4. all of them
   5. None of tem

2. Deadlock may happen due to
   1. User consumes too much resource
   2. User holds some resources and waits for more
   3. System does not have shared resources
   4. There are no mutual exclusions of user processes
   5. Users hate each other.

3. Which of the following OS scheduling policy has the worst performance (response time)?
   1. Shortest Job First
   2. Round Robin with fixed quantum
   3. Round Robin with variable quantum
   4. First-Come-First-Serve
   5. No difference, all are about the same

4. How does OS resolve the problem of starvation of low priority jobs in the priority scheduling policy?
   1. Request the user to resubmit the job with a higher priority
   2. Continue waiting until the high priority jobs are completed.
   3. Increate the priority of aging process in the Ready state.
   4. Allocate more CPU time to do processing.
   5. Stop the preemptive scheduling when there are too many aging processes.

var s: semaphore (1); /* critical section */ n: semaphore (0); /* underflow */ e: semaphore (sizeofbuffer); /* overflow */ procedure producer; begin repeat produce item for buffer; wait(e); wait(s); append to buffer; signal(s); signal(n); forever; end; procedure consumer; begin repeat wait(n); wait(s); take from buffer; signal(s); signal(e); consume item forever; end; 10/03/2019 TDC411-04