Bakery Algorithm, Operating System Critical Section Problem. Operating System Made By Dedar Primeasia University

1. Bakery Algorithm
Name: S. M. Dedar Alam
ID: 171 016 042
Primeasia University

2.  Introduction
 Background
 Working Principle
 Real Life Example
 Analysis
 Conclusion

3. Introduction
This algorithm solves the critical section problem for n processes in software. The basic idea is
that of a bakery customers take numbers, and whoever has the lowest number gets service
next. Here, of course, "service" means entry to the critical section.

4. Background
In computer science, it is common for multiple threads to simultaneously access the same
resources. Data corruption can occur if two or more threads try to write into the same
memory location. Lamport's bakery algorithm is one of many mutual exclusion algorithms
designed to prevent concurrent threads entering critical sections of code concurrently to
eliminate the risk of data corruption.

5. Working Principle
 Before entering its critical section, the process receives a number. Holder of the smallest
number enters the critical section.
 If processes Pi and Pj receive the same number
if i < j
Pi is served first;
else
Pj is served first.
 The numbering scheme always generates numbers in increasing order of enumeration; i.e.,
1, 2, 3, 3, 3, 3, 4, 5................

6. Wait to Turn
When 245 Displayed go to Counter
Real Life Example

7. Simplified Analysis of Bakery Algorithm

8. Example
P0 P1 P2 P3 P4

9. Example
P0 P1 P2 P3 P4
0 0 0 0 0

10. Example
P0 P1 P2 P3 P4
0 0 1 0 0

11. Example
P0 P1 P2 P3 P4
0 0 1 2 0

12. Example
P0 P1 P2 P3 P4
0 0 1 2 3

13. Example
P0 P1 P2 P3 P4
0 4 1 2 3

14. Example
P0 P1 P2 P3 P4
0 4 1 2 3

15. Example
P0 P1 P2 P3 P4
0 4 0 2 3

16. Example
P0 P1 P2 P3 P4
0 4 0 0 3

17. Example
P0 P1 P2 P3 P4
0 4 0 0 0

18. Example
P0 P1 P2 P3 P4
0 0 0 0 0

19. Example
P0 P1 P2 P3 P4
0 0 2 2 0

20. Original Bakery Algorithm

21. Original Bakery Algorithm

22. Example
P0 P1 P2 P3 P4
0 1 2 2 3

23. Example
P0 P1 P2 P3 P4
0 0 2 2 3

24. Example
P0 P1 P2 P3 P4
0 0 0 2 3

25. Example
P0 P1 P2 P3 P4
0 0 0 0 3

26. Example
P0 P1 P2 P3 P4
0 0 0 0 0

27. Conclusion
 The Bakery algorithm offers a strong near-FIFO guarantee.
 The Bakery algorithm works with even weaker registers.