Semaphores in Concurrent Programming

A synchronization primitive with an integer value manipulated by sem_wait() and sem_post() functions.

A function that decrements the semaphore value. If the value is negative, it suspends the caller; otherwise, it returns immediately.

A function that increments the semaphore value and possibly wakes up a waiting thread.

A semaphore with an initial value of 1, used as a mutex (mutual exclusion).

Setting the initial value of a semaphore, crucial for proper synchronization.

The integer value of the semaphore, which controls access to shared resources.

A semaphore used by multiple threads in the same process.

A synchronization primitive that prevents race conditions when accessing shared resources.

A section of code that accesses shared resources, requiring synchronization to avoid race conditions.

This is the situation when multiple threads try to access and modify a shared resource concurrently, resulting in a non-deterministic outcome.

Semaphores offer a way to coordinate access to shared resources across multiple threads, preventing data corruption.

The calling thread is suspended and added to a queue of waiting threads.

It increases the semaphore value and if threads are waiting in the queue, awakens one of them.

The negative value indicates the number of threads currently waiting for a permit.

Multiple threads in the same process can access the same semaphore for synchronization.

A lightweight execution unit within a process, able to run independently.

To prevent race conditions and ensure data integrity when multiple threads modify the same data.

A situation where the outcome of a computation is undefined due to multiple threads accessing and modifying shared data concurrently.

A synchronization primitive that allows only one thread to access a shared resource at a time, ensuring mutual exclusion.

To prevent race conditions and ensure data integrity when multiple threads access and modify shared resources.

A segment of code that accesses shared resources, requiring synchronization to avoid race conditions.

Concurrency allows programs to execute multiple tasks simultaneously, improving performance and responsiveness.

Initialize a semaphore with a value of 1. Use sem_wait() to acquire the lock and sem_post() to release the lock.

Careful handling of waiting threads, preventing deadlocks, and ensuring proper synchronization.

A situation where two or more threads are blocked indefinitely, waiting for each other to release a resource.

Semaphores manage access based on 'permits', while condition variables wait for specific conditions to be met.

Different primitives have different strengths and weaknesses. The choice depends on the specific requirements of the task.

Producer-consumer, resource allocation, thread pools, database access, message queues.

They provide a simple and efficient way to manage concurrent access to shared resources. They are portable across different operating systems.

They can be difficult to debug properly, and they require careful attention to avoid deadlocks.

Mutex locks, condition variables, monitors, spinlocks, barriers.

Use mutexes for exclusive access and semaphores for managing shared resources and signaling.