How do I implement spinlocks in C?

What is a spinlock and how does it work in C?

A spinlock is a type of synchronization mechanism that uses busy-waiting to acquire a lock. In C, it typically involves a loop that repeatedly checks if the lock is available.

Can you show me a simple implementation of a spinlock in C?

Sure! Here's a basic implementation:

typedef struct {
    volatile int lock;
} spinlock_t;

void spinlock_init(spinlock_t *s) {
    s->lock = 0;
}

void spinlock_lock(spinlock_t *s) {
    while (__sync_lock_test_and_set(&s->lock, 1)) {
        while (s->lock);
    }
}

void spinlock_unlock(spinlock_t *s) {
    __sync_lock_release(&s->lock);
}

What are the advantages and disadvantages of using spinlocks?

Advantages of spinlocks include low overhead for acquiring and releasing locks, making them suitable for short critical sections. However, they can lead to CPU wastage if the lock is held for a long time, as they keep the CPU busy while waiting.

When should I avoid using spinlocks?

You should avoid using spinlocks in scenarios where the lock might be held for a long time or in situations where thread scheduling is important, as they can lead to performance degradation.