1 files changed, 72 insertions, 0 deletions
diff --git a/machine/atomic.h b/machine/atomic.h
new file mode 100644
index 0000000..b23acae
--- /dev/null
+++ b/machine/atomic.h
@@ -0,0 +1,72 @@
+// See LICENSE for license details.
+
+#ifndef _RISCV_ATOMIC_H
+#define _RISCV_ATOMIC_H
+
+#include "config.h"
+#include "encoding.h"
+
+// Currently, interrupts are always disabled in M-mode.
+#define disable_irqsave() (0)
+#define enable_irqrestore(flags) ((void) (flags))
+
+typedef struct { int lock; } spinlock_t;
+#define SPINLOCK_INIT {0}
+
+#define mb() asm volatile ("fence" ::: "memory")
+#define atomic_set(ptr, val) (*(volatile typeof(*(ptr)) *)(ptr) = val)
+#define atomic_read(ptr) (*(volatile typeof(*(ptr)) *)(ptr))
+
+#ifdef __riscv_atomic
+# define atomic_add(ptr, inc) __sync_fetch_and_add(ptr, inc)
+# define atomic_or(ptr, inc) __sync_fetch_and_or(ptr, inc)
+# define atomic_swap(ptr, swp) __sync_lock_test_and_set(ptr, swp)
+# define atomic_cas(ptr, cmp, swp) __sync_val_compare_and_swap(ptr, cmp, swp)
+#else
+# define atomic_binop(ptr, inc, op) ({ \
+  long flags = disable_irqsave(); \
+  typeof(*(ptr)) res = atomic_read(ptr); \
+  atomic_set(ptr, op); \
+  enable_irqrestore(flags); \
+  res; })
+# define atomic_add(ptr, inc) atomic_binop(ptr, inc, res + (inc))
+# define atomic_or(ptr, inc) atomic_binop(ptr, inc, res | (inc))
+# define atomic_swap(ptr, inc) atomic_binop(ptr, inc, (inc))
+# define atomic_cas(ptr, cmp, swp) ({ \
+  long flags = disable_irqsave(); \
+  typeof(*(ptr)) res = *(volatile typeof(*(ptr)) *)(ptr); \
+  if (res == (cmp)) *(volatile typeof(ptr))(ptr) = (swp); \
+  enable_irqrestore(flags); \
+  res; })
+#endif
+
+static inline void spinlock_lock(spinlock_t* lock)
+{
+  do
+  {
+    while (atomic_read(&lock->lock))
+      ;
+  } while (atomic_swap(&lock->lock, -1));
+  mb();
+}
+
+static inline void spinlock_unlock(spinlock_t* lock)
+{
+  mb();
+  atomic_set(&lock->lock,0);
+}
+
+static inline long spinlock_lock_irqsave(spinlock_t* lock)
+{
+  long flags = disable_irqsave();
+  spinlock_lock(lock);
+  return flags;
+}
+
+static inline void spinlock_unlock_irqrestore(spinlock_t* lock, long flags)
+{
+  spinlock_unlock(lock);
+  enable_irqrestore(flags);
+}
+
+#endif