Khyati sanghavi ,53003230018
Semaphores
A semaphore is an integer variable used for signalling among processes. It has three atomic operations:
- Initialisation: The semaphore is initialised with a non-negative integer value, which represents the number of available slots or resources.
- Decrement (semWait): When a process wants to access a shared resource, it decrements the semaphore value. If the resulting value is non-negative, the process can proceed. If the value becomes negative, the process is blocked and added to a waiting queue.
- Increment (semSignal): When a process releases a shared resource, it increments the semaphore value. If there are processes waiting in the queue, one of them is awakened and allowed to proceed.
How Semaphores Work
The value of a semaphore determines how many processes can proceed without blocking. When a process decrements the semaphore and the value becomes negative, it means that there are no more available slots or resources. The process is then blocked, waiting for another process to release a resource and increment the semaphore.
When a process increments the semaphore, it signals that a resource has been released. If there are processes waiting in the queue, one of them is awakened and allowed to proceed. This process can then decrement the semaphore and access the shared resource.
Advantages of Semaphores
- Supports coordination between multiple processes
- Provides a flexible and robust way to manage shared resources.
- It can be used to implement critical sections in a program.
- It can be used to avoid race conditions.
Disadvantages of Semaphores
- It Can lead to performance degradation due to overhead associated with wait and signal operations.
- Can result in deadlock if used incorrectly.
- It can cause performance issues in a program if not used properly.
- It can be difficult to debug and maintain.
- It can be vulnerable to certain types of attacks, such as denial of service attacks.
