Spinlocks

spinlocks/spinlock.h

@@ -0,0 +1,66 @@
+typedef struct {
+    volatile unsigned int locked; // 0 = unlocked, 1 = locked
+} spinlock_t;
+
+static inline void initlock(spinlock_t *lk) {
+    lk->locked = 0;
+}
+
+static inline void acquire(spinlock_t *lk) {
+    while (__sync_lock_test_and_set(&lk->locked, 1) != 0); // spin
+}
+
+static inline void release(spinlock_t *lk) {
+    __sync_lock_release(&lk->locked);
+}
+
+#ifdef ATOMIC_MUTEX
+
+#include <stdatomic.h>
+#include <stdbool.h>
+
+typedef struct {
+    atomic_int flag;
+} mutex_t;
+
+void mutex_init(mutex_t *m) {
+    atomic_store(&m->flag, 0);
+}
+
+void mutex_lock(mutex_t *m) {
+    int expected;
+    do {
+        expected = 0;
+    } while (!atomic_compare_exchange_weak(&m->flag, &expected, 1));
+}
+
+void mutex_unlock(mutex_t *m) {
+    atomic_store(&m->flag, 0);
+}
+
+#endif
+#ifdef ATOMIC_MUTEX_RISCV
+
+typedef struct {
+    volatile int locked;
+} spinlock_t;
+
+void spinlock_init(spinlock_t *lk) {
+    lk->locked = 0;
+}
+
+void spinlock_acquire(spinlock_t *lk) {
+    int tmp;
+    do {
+        __asm__ volatile("amoswap.w %0, %1, (%2)"
+                         : "=r"(tmp)                // old value in tmp
+                         : "r"(1), "r"(&lk->locked) // store 1 into memory
+                         : "memory");
+    } while (tmp != 0); // spin until old value was 0
+}
+
+void spinlock_release(spinlock_t *lk) {
+    __asm__ volatile("amoswap.w zero, %1, (%0)" : : "r"(&lk->locked), "r"(0) : "memory");
+}
+
+#endif