sínpár

Sínpár is a programming concept that refers to a pair of semaphores used to control access to a shared resource. Semaphores are signaling mechanisms used in concurrent programming to manage access to a common resource by multiple processes or threads. A sínpár typically involves two semaphores, one acting as a mutex (mutual exclusion) to ensure that only one process or thread can access the resource at a time, and the other acting as a counter to manage the number of available resources.

The first semaphore, the mutex semaphore, is initialized to 1. When a process or thread wishes to access the shared resource, it first attempts to acquire the mutex semaphore. If the semaphore's value is 1, it is decremented to 0, and the process gains exclusive access. If the semaphore's value is already 0, the process will block until the semaphore is released by another process.

The second semaphore, often called a counting semaphore, is initialized to the number of available instances of the shared resource. When a process or thread acquires the mutex semaphore, it then decrements the counting semaphore. This signifies that one instance of the resource has been taken. If a process wishes to release the resource, it first increments the counting semaphore and then releases the mutex semaphore. This allows another waiting process to acquire the mutex and access a resource.

Sínpárs are a fundamental tool for implementing synchronization primitives in operating systems and concurrent programming environments. They help prevent race conditions and ensure data integrity when multiple processes or threads are operating on shared data. The specific implementation and naming of sínpárs can vary across different programming languages and operating system interfaces.