![Bakery Algorithm
Thread i
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-2-320.jpg)
![Bakery Algorithm
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;
Doorway](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-3-320.jpg)
![Bakery Algorithm
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;
I’m interested](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-4-320.jpg)
![Bakery Algorithm
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;
Take an number
numbers are always increasing!](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-5-320.jpg)
![Bakery Algorithm
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;
Someone is interested](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-6-320.jpg)
![Bakery Algorithm
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;
There is someone with a lower
number and identifier.
pair (a,b) > (c,d) if a>c, or a=c and b>d
(lexicographic order)](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-7-320.jpg)
![Deadlock freedom
• The bakery algorithm is deadlock free
• Some waiting thread A has a unique least
(number[A],A) pair, and that thread can enter
the critical section](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-8-320.jpg)
![FIFO
• The bakery algorithm is first-come-first-served
• If DA DB then A’s number is earlier
– writeA(number[A]) readB(number[A])
writeB(number[B]) readB(flag[A])
• So B is locked out while flag[A] is true
flag[i]=true;
number[i] = max(number[0], …,number[n-1])+1;
while ($ k!= i
flag[k] && (number[i],i) > (number[k],k)) {};
critical section
flag[i] = false;](https://image.slidesharecdn.com/bakeryalgorithm-181008064304/85/Bakery-algorithm-9-320.jpg)
Bakery algorithm
- 1. Bakery Algorithm • The idea is similar to a line at the bakery • A customer takes a number greater than numbers of other customers • Each of the threads gets a unique identifier
- 2. Bakery Algorithm Thread i flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false;
- 3. Bakery Algorithm flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false; Doorway
- 4. Bakery Algorithm flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false; I’m interested
- 5. Bakery Algorithm flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false; Take an number numbers are always increasing!
- 6. Bakery Algorithm flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false; Someone is interested
- 7. Bakery Algorithm flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false; There is someone with a lower number and identifier. pair (a,b) > (c,d) if a>c, or a=c and b>d (lexicographic order)
- 8. Deadlock freedom • The bakery algorithm is deadlock free • Some waiting thread A has a unique least (number[A],A) pair, and that thread can enter the critical section
- 9. FIFO • The bakery algorithm is first-come-first-served • If DA DB then A’s number is earlier – writeA(number[A]) readB(number[A]) writeB(number[B]) readB(flag[A]) • So B is locked out while flag[A] is true flag[i]=true; number[i] = max(number[0], …,number[n-1])+1; while ($ k!= i flag[k] && (number[i],i) > (number[k],k)) {}; critical section flag[i] = false;