Stop recognizing answers. Start reconstructing them.

#include <stdatomic.h>

// Lock acquisition with acquire memory order
void spinlock_acquire(atomic_flag *lock) {
    // Acquire order: ensures subsequent critical-section reads and writes
    // cannot be reordered before this atomic test-and-set operation.
    while (atomic_flag_test_and_set_explicit(lock, memory_order_acquire)) {
        #if defined(__x86_64__) || defined(_M_X64)
        __builtin_ia32_pause(); // yield pipeline execution slot to reduce bus contention
        #endif
    }
}

// Lock release with release memory order
void spinlock_release(atomic_flag *lock) {
    // Release order: guarantees all prior memory operations in the
    // critical section are visible to other threads before clearing.
    atomic_flag_clear_explicit(lock, memory_order_release);
}

#include <stdatomic.h>

// Flawed: relaxed ordering provides no memory synchronization!
void spinlock_acquire(atomic_flag *lock) {
    while (atomic_flag_test_and_set_explicit(lock, memory_order_relaxed)) {
        // busy spin without barrier
    }
}

void spinlock_release(atomic_flag *lock) {
    atomic_flag_clear_explicit(lock, memory_order_relaxed);
}