Dijkstra algorithm for mutual exclusion

Execution

Open a terminal and run server_critical_section.py
Then open another terminal and run client_processes.py

Background

This is an implementation of Stable Algorithm for Mutual Exclusion (processes concurrence) in a distributed system, proposed by Edsger W. Dijkstra in 1974.

This implementation does not link processes trough socket, for this demonstration, processes are stored in a simple list.

Algorithm resume

When need_access_to_critical_section Do
	If (i = 0) then
		When ( L = S ) Do
			go_to_critical_section();
			S = (L + 1) mod K;
		EndWhen
	Else
		When ( L <> S ) Do
			go_to_critical_section();
			S = L;
		EndWhen
	EndIf
EndWhen

Since processes are stored in a list, we can skip a some steps.

Algorithm details

Synchronus comunication
Ring logic topology
Solution consider N processes, ranged from 0 to N - 1

Variables used:

i = Process id
S = Status of process i
L = Last process status
K = Constant bigger or iqual to N

Notes

In the source code, some variables and methods are defined but not used, they remains for future implementations and changes.

laar19/dijkstra-algorithm-for-mutual-exclusion