Starvation and Livelock

Starvation, and livelock are problems that can occur in computer systems when multiple processes compete for resources.

• Starvation occurs when a process is repeatedly denied access to resources because others with higher priority keep getting them first.
• Livelock is when processes keep changing their states to avoid conflict but still fail to make progress, similar to two people constantly stepping aside for each other without passing.

Starvation

Starvation is the problem that occurs when high priority processes keep executing and low priority processes get blocked for indefinite time. In heavily loaded computer system, a steady stream of higher-priority processes can prevent a low-priority process from ever getting the CPU.

Causes of Starvation :

• Priority Scheduling: If there are always higher-priority processes available, then the lower-priority processes may never be allowed to run.
• Resource Utilization: We see that resources are always used by more significant priority processes and leave a lesser priority process starved.

Livelock

Livelock is a situation where processes are not blocked (like in deadlock) but they continuously change their state in response to each other, without making any real progress. In short-> In livelock, processes keep moving but never reach completion.

Example: Two processes repeatedly give way to each other while trying to access a resource, so neither proceeds.

Note:The diagram illustrates a livelock scenario in an operating system where two processes (Process A and Process B) are actively trying to perform an action (fork()), but repeatedly fail because the process table is full.

Causes of Livelock:

1. Excessive resource preemption : processes keep releasing and re-requesting resources but never acquire them fully.
2. Over-politeness (cooperation issue) : processes continuously yield or back off to let others proceed, but all do the same.
3. Improper scheduling : CPU repeatedly switches processes in a way that none makes real progress.
4. Faulty recovery mechanisms : algorithms designed to avoid deadlock (like automatic rollback/retry) can lead to livelock if retries happen endlessly.
5. Busy-waiting loops : processes actively check and respond to conditions but without advancing execution.

Example: Imagine a pair of processes using two resources below

Difference between Starvation and Livelock

A livelock is similar to a deadlock, except that the states of the processes involved in the livelock constantly change with regard to one another, none progressing. Livelock is a special case of resource starvation.