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Starvation and Deadlock
Starvation and Deadlock are situations that occur when processes requiring resources are delayed for a long time. However, they are quite different concepts with distinct causes and solutions.
Starvation
Starvation occurs when a process is indefinitely postponed from accessing resources or CPU time it needs for execution. The process remains ready to run but never gets the opportunity to proceed, potentially waiting forever.
Common Causes of Starvation
Priority-based scheduling − Lower priority processes may wait forever if higher priority processes constantly monopolize the processor.
Faulty resource allocation − If a process is never provided the resources it requires due to poor allocation decisions.
Resource scarcity − Insufficient resources to satisfy all process requirements simultaneously.
Random selection − Non-deterministic process selection may cause some processes to wait indefinitely.
Solutions to Prevent Starvation
Aging technique − Gradually increase the priority of waiting processes over time to ensure eventual execution.
Fair resource allocation − Use an independent resource manager that distributes resources equitably among processes.
Round-robin scheduling − Avoid random selection by implementing time-sharing mechanisms that guarantee each process gets CPU time.
Deadlock
A deadlock occurs when two or more processes are blocked forever, waiting for each other to release resources. Each process holds at least one resource needed by another process in the cycle, creating a circular dependency.
Coffman Conditions for Deadlock
A deadlock occurs if and only if all four Coffman conditions are satisfied simultaneously −
| Condition | Description |
|---|---|
| Mutual Exclusion | Resources cannot be shared; only one process can use a resource at a time |
| Hold and Wait | A process can hold resources while requesting additional resources from others |
| No Preemption | Resources cannot be forcibly taken from a process; they must be released voluntarily |
| Circular Wait | A circular chain of processes exists where each waits for a resource held by the next |
Comparison
| Aspect | Starvation | Deadlock |
|---|---|---|
| Definition | Indefinite postponement of process execution | Circular waiting where no process can proceed |
| Recovery | Process can eventually execute with proper scheduling | Requires external intervention to break the cycle |
| Resources | May or may not involve resource conflicts | Always involves resource allocation conflicts |
| Prevention | Aging, fair scheduling, resource management | Break one of the four Coffman conditions |
Conclusion
Starvation and deadlock are both serious resource allocation problems in operating systems. Starvation involves indefinite waiting due to unfair scheduling, while deadlock creates a circular dependency where no process can proceed. Understanding these concepts is crucial for designing efficient resource allocation algorithms and preventing system failures.
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