Skip to content
Related Articles
Get the best out of our app
GeeksforGeeks App
Open App

Related Articles

Maekawa’s Algorithm for Mutual Exclusion in Distributed System

Improve Article
Save Article
Like Article
Improve Article
Save Article
Like Article

Prerequisite – Mutual exclusion in distributed systems Maekawa’s Algorithm is quorum based approach to ensure mutual exclusion in distributed systems. As we know, In permission based algorithms like Lamport’s Algorithm, Ricart-Agrawala Algorithm etc. a site request permission from every other site but in quorum based approach, A site does not request permission from every other site but from a subset of sites which is called quorum. In this algorithm:

  • Three type of messages ( REQUEST, REPLY and RELEASE) are used.
  • A site send a REQUEST message to all other site in its request set or quorum to get their permission to enter critical section.
  • A site send a REPLY message to requesting site to give its permission to enter the critical section.
  • A site send a RELEASE message to all other site in its request set or quorum upon exiting the critical section.

The construction of request set or Quorum: A request set or Quorum in Maekawa’s algorithm must satisfy the following properties:

∀i ∀j : i ≠ j, 1 ≤ i, j ≤ N :: Ri ⋂ Rj ≠ ∅ 
  1. i.e there is at least one common site between the request sets of any two sites.
∀i : 1 ≤ i ≤ N :: Si ∊ Ri 
∀i : 1 ≤ i ≤ N :: |Ri| = K 
  1. Any site Si is contained in exactly K sets.
N = K(K - 1) +1 and |Ri| = √N 


  • To enter Critical section:
    • When a site Si wants to enter the critical section, it sends a request message REQUEST(i) to all other sites in the request set Ri.
    • When a site Sj receives the request message REQUEST(i) from site Si, it returns a REPLY message to site Si if it has not sent a REPLY message to the site from the time it received the last RELEASE message. Otherwise, it queues up the request.
  • To execute the critical section:
    • A site Si can enter the critical section if it has received the REPLY message from all the site in request set Ri
  • To release the critical section:
    • When a site Si exits the critical section, it sends RELEASE(i) message to all other sites in request set Ri
    • When a site Sj receives the RELEASE(i) message from site Si, it send REPLY message to the next site waiting in the queue and deletes that entry from the queue
    • In case queue is empty, site Sj update its status to show that it has not sent any REPLY message since the receipt of the last RELEASE message

Message Complexity: Maekawa’s Algorithm requires invocation of 3√N messages per critical section execution as the size of a request set is √N. These 3√N messages involves.

  • √N request messages
  • √N reply messages
  • √N release messages

Drawbacks of Maekawa’s Algorithm:

  • This algorithm is deadlock prone because a site is exclusively locked by other sites and requests are not prioritized by their timestamp.


  • Synchronization delay is equal to twice the message propagation delay time
  • It requires 3√n messages per critical section execution.

Advantages of Maekawa’s Algorithm:

  • Low Message Complexity: Maekawa’s algorithm requires only O(sqrt(N)) messages per critical section invocation, where N is the total number of processes in the system. This makes it more efficient than many other distributed mutual exclusion algorithms.
  • Scalability: The algorithm is highly scalable and can be used in large-scale distributed systems without any problems.
  • Fairness: The algorithm provides fairness by allowing only one process per group to enter the critical section. It guarantees that every process will eventually get a chance to enter the critical section.

Disadvantages of Maekawa’s Algorithm:

  • High Overhead: The algorithm requires a lot of overhead to maintain the group membership information and to update it when a process joins or leaves the system. This can lead to increased network traffic and latency.
  • Limited Flexibility: The algorithm requires a fixed number of groups to be defined before the system starts running. This makes it less flexible than other algorithms that can dynamically adjust to changes in the system.
  • Delayed Execution: The algorithm can lead to delays in the execution of critical sections because a process may have to wait for messages to arrive from other groups before entering the critical section.
My Personal Notes arrow_drop_up
Last Updated : 13 May, 2023
Like Article
Save Article
Similar Reads