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kernel/include/sched/spinlock.h

@@ -0,0 +1,44 @@
+#ifndef SPINLOCK_H
+#define SPINLOCK_H
+
+#include <stdint.h>
+
+typedef struct {
+    volatile uint32_t ticket;
+    volatile uint32_t serving;
+} spinlock_t;
+
+#define SPINLOCK_INIT { .ticket = 0, .serving = 0 }
+
+static inline void spinlock_acquire(spinlock_t* lock) {
+    uint32_t my_ticket = __atomic_fetch_add(&lock->ticket, 1, __ATOMIC_RELAXED);
+    while (__atomic_load_n(&lock->serving, __ATOMIC_ACQUIRE) != my_ticket)
+        asm volatile("pause");
+}
+
+static inline void spinlock_release(spinlock_t* lock) {
+    __atomic_fetch_add(&lock->serving, 1, __ATOMIC_RELEASE);
+}
+
+static inline int spinlock_try_acquire(spinlock_t* lock) {
+    uint32_t serving = __atomic_load_n(&lock->serving, __ATOMIC_RELAXED);
+    uint32_t ticket  = __atomic_load_n(&lock->ticket,  __ATOMIC_RELAXED);
+    if (serving != ticket) return 0;
+    uint32_t expected = serving;
+    return __atomic_compare_exchange_n(&lock->ticket, &expected, serving + 1,
+                                       0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
+}
+
+static inline uint64_t spinlock_acquire_irqsave(spinlock_t* lock) {
+    uint64_t flags;
+    asm volatile("pushfq; pop %0; cli" : "=r"(flags) :: "memory");
+    spinlock_acquire(lock);
+    return flags;
+}
+
+static inline void spinlock_release_irqrestore(spinlock_t* lock, uint64_t flags) {
+    spinlock_release(lock);
+    asm volatile("push %0; popfq" :: "r"(flags) : "memory", "cc");
+}
+
+#endif