os

1. Concurrency: Principles of Deadlock Operating Systems Fall 2002

5. Deadlock in the everyday life 1 2 3 4

6. Deadlock in the everyday life

7. Deadlock when contending for the critical section

8. Example of Deadlock Progress of Q Release A Release B Get A Get B Get A Get B Release A Release B Progress of P A Required B Required A Required B Required deadlock inevitable 1 2 3 4 5 6 P and Q want A P and Q want B

9. Example of No Deadlock Progress of Q Release A Release B Get A Get B Get A Release A Get B Release B Progress of P A Required B Required A Required B Required 1 2 3 4 5 6 P and Q want A P and Q want B

15. Circular Wait P1 P2 P3 R1 R2 R3

16. No circular wait P1 P2 P3 R1 R2 R3

19. Preventing circular wait P1 P2 P3 R1 R2 R3

24. Determination of the safe state Claim Allocated Total 3 2 2 0 0 0 3 1 4 4 2 2 1 0 0 0 0 0 2 1 1 0 0 2 P1 P2 P3 P4 R1 R2 R3 R1 R2 R3 R1 R2 R3 9 3 6 Available 6 2 3 Claim Allocated Total 0 0 0 0 0 0 3 1 4 4 2 2 0 0 0 0 0 0 2 1 1 0 0 2 P1 P2 P3 P4 R1 R2 R3 R1 R2 R3 R1 R2 R3 9 3 6 Available 7 2 3

25. Determination of the safe state Claim Allocated Total 0 0 0 0 0 0 0 0 0 4 2 2 0 0 0 0 0 0 0 0 0 0 0 2 P1 P2 P3 P4 R1 R2 R3 R1 R2 R3 R1 R2 R3 9 3 6 Available 9 3 4 Claim Allocated Total 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 P1 P2 P3 P4 R1 R2 R3 R1 R2 R3 R1 R2 R3 9 3 6 Available 9 3 6 S0 is safe: P2->P1->P3->P4

27. Banker’s algorithm Claim Allocated Total 3 2 2 6 1 3 3 1 4 4 2 2 1 0 0 5 1 1 2 1 1 0 0 2 P1 P2 P3 P4 R1 R2 R3 R1 R2 R3 R1 R2 R3 9 3 6 Available 1 1 2 P2 requests (1, 0, 1): Grant or not? P1 requests (1, 0, 1): Grant or not?

30. Dining philosophers problem

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