True/False: In Signal and Wait, the signaller finishes execution while the signalled process waits for its turn

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1 Question Define the Rate Monotonic algorithm and the Earliest Deadline First algorithm. Give and example of both algorithms using execution history of processes.

2 True/False: In Signal and Wait, the signaller finishes execution while the signalled process waits for its turn

3 What is the difference between preemptive and non-preemptive scheduling?

4 True/False: An example of deferred thread cancellation would be the kernel terminating it before it could finish its task.

5 Midterm Sample Question Q: When a command is entered into an operating system command line, what is the first thing that happens? A: The O.S. checks for correct syntax

6 Explain the difference between round robin scheduling and multiqueue scheduling. How do these systems differ from a realtime system?

7 What is the difference between user and kernel mode?

8 Define one similarity and one difference between parallel and concurrent: Similarity Answer: Both being executed Different Answer: Parallel: Two threads actively running no waiting at the same time Concurrent: One may be waiting on another

9 What is the main advantage of a named pipe over an ordinary pipe? a. They continue to exist after communicating processes have finished. b. No parent-child relationship is required to use them. c. Communication can be bidirectional. d. All of the above Correct Answer: d.

10 What are the steps the kernel takes to perform a context switch?

11 Explain the difference between Asynchronous cancellation and Deferred cancellation

12 Question: Briefly describe deadlock and provide an example of how deadlock could be caused using semaphores. Answer: During concurrency, a deadlock is a state in which each member of a group of threads is waiting for another thread (possibly itself) to take action, such as sending a message or releasing a lock. Below is a visual example of this:

13 Provide an example of a process that might be given low priority and explain your reasoning.

14 When would you use a semaphore instead of a mutex?

15 What are the five main criteria for devising a CPU scheduling algorithm?

16 What is preemptive and non-preemptive scheduling? What are their pros and cons?

17 Specify which of the following is an advantage or disadvantage of using threads. If an option is neither, indicate neither. a. Economy b. Interprocess communication c. Data splitting d. One-to-one e. Scalability f. Concurrency g. Responsiveness h. Modularity i. Identifying tasks j. Balance

18 Question: What are the process items that are inherited in a child created using fork();? fork() creates a new process by duplicating the calling process. The new referred to as the child, is an exact duplicate of the calling process, referred to as the parent, except for the following points: The child has its own unique process ID, and this PID does not match the ID of any existing process group ( setpgid (2)). The child's parent process ID is the same as the parent's process ID. The child does not inherit its parent's memory locks ( mlock (2), mlockall (2)). Process resource utilizations ( getrusage (2)) and CPU time counters ( times (2)) are reset to zero in the child. The child's set of pending signals is initially empty ( sigpending (2)). The child does not inherit semaphore adjustments from its parent ( semop (2)). The child does not inherit record locks from its parent ( fcntl (2)). The child does not inherit timers from its parent ( setitimer (2), alarm (2), timer_create (2)). The child does not inherit outstanding asynchronous I/O operations from its parent ( aio_read (3), aio_write (3)), nor does it inherit any asynchronous I/O contexts from its parent (see io_setup (2)).

19 What is a reason for initializing a semaphore to a non-zero value?

20 Assume two threads, A and B, are executed concurrently. They each perform an operation on the shared variable c. Each instruction has three steps: (1) load, (2) execute, (3) store. Thread A I1: c = c+1 Thread B I2: c = c 3 If both threads run to complete, provide four possible result values for c, and provide a history for each result that could have produced that value. The starting value of c is 4.

21 sample midterm question. Q: Which of the following are not process execution states from chapter 3? : a) Ready b) Waiting c) Kernel Mode d) Running e) New f) Interrupted g) Child h) Zombie

22 A: (b) kernel mode, Kernel mode is an execution mode. (e) Interrupted, when a process is interrupted it will typically start waiting for input, but interrupted isn t itself a mode. (f) Child, a process can create child processes, but Child processes are not a state. (h) Zombie processes are processes whose parent processes finished executing before them. Section has more information on process execution states.

23 Matthew Alleria Rowan Sample Midterm Question Draw the diagrams for the three possible User-to-Kernel thread configurations and label them. User Thread(s) User Thread(s) User Thread(s) Kernel Thread(s) Kernel Thread(s) Kernel Thread(s)

24 "What is the subtle difference that separates the meanings of the words parallelism and concurrency in relation to process execution?"

25 Question What's the distinction between short term scheduler and long term scheduler? Answer: The frequency of execution, the short term scheduler must select a new process for the cpu frequently while the long term scheduler average rate of process creation must be equal to the average rate of process leaving the system.

26 What makes two processes independent? A. There is no overlap between the read set of one process and the read and write sets of the other process. B. There is no overlap between the write set of one process and the read and write sets of the other process. C. There is no overlap between the read set of one process and the write set of the other process. D. There is no overlap between the read sets of both processes. E. There is no overlap between the write sets of both processes.

27 Assume integer variable x is shared between two threads. The two semaphore objects in the lines below may be incremented using Up() and decremented using Down() methods. They are each initialized to 0. Using your knowledge of semaphores and the code provided below, indicate which semaphore calls should be incremented and which should be decremented to get the output: 7852 Executed: A_Semaphore.Init(0); B_Semaphore.Init(0); Unexecuted: Thread A: y=10; B_Semaphore.ReplaceMe(); ++x; Print(x+y); Print(x); A_Semaphore.ReplaceMe(); Thread B: z=5; x=x+z; Print(x+z); B_Semaphore.ReplaceMe(); A_Semaphore.ReplaceMe(); x=2; Print(x); Answer: From top to bottom for each thread: A:.Down();.Up(); B:.Up();.Down();

28 What is the difference between Asynchronous and Deferred cancelation?

29 State the three user/kernel thread modes, and draw diagrams as to show what the relationship between the user threads and kernel threads.

Operating Systems Comprehensive Exam. Spring Student ID # 3/16/2006

Operating Systems Comprehensive Exam Spring 2006 Student ID # 3/16/2006 You must complete all of part I (60%) You must complete two of the three sections in part II (20% each) In Part I, circle or select