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Semaphores (Avoiding Train Wrecks)

Semaphores (Avoiding Train Wrecks). Kevin O’Gorman CS 170 22 April 2002. Signalling. . . . A1 statement A2 sem.signal(). . . . B1 sem.wait() B2 statement. sem = 0. Signalling. . . . A1 statement A2 sem.signal(). . . . B1 sem.wait() B2 statement. sem = 0. Signalling.

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Semaphores (Avoiding Train Wrecks)

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  1. Semaphores(Avoiding Train Wrecks) Kevin O’Gorman CS 170 22 April 2002

  2. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  3. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  4. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  5. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  6. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  7. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = -1

  8. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = -1

  9. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = -1

  10. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  11. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  12. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  13. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  14. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  15. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  16. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  17. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  18. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . Success!

  19. (continued…)

  20. Semaphores Re-Run

  21. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  22. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  23. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  24. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  25. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  26. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  27. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  28. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 1

  29. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 1

  30. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 1

  31. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 1

  32. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 1

  33. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  34. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  35. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  36. Signalling . . . A1 statement A2 sem.signal() . . . . . . B1 sem.wait() B2 statement . . . sem = 0

  37. Signalling . . . A1 statement A2 sem.signal() . . . . . B1 sem.wait() B2 statement . . Success!

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