1 files changed, 64 insertions, 0 deletions
diff --git a/src/arch/x86/include/arch/smp/spinlock.h b/src/arch/x86/include/arch/smp/spinlock.h
new file mode 100644
index 0000000000..5c1dd94c36
--- /dev/null
+++ b/src/arch/x86/include/arch/smp/spinlock.h
@@ -0,0 +1,64 @@
+#ifndef ARCH_SMP_SPINLOCK_H
+#define ARCH_SMP_SPINLOCK_H
+
+/*
+ * Your basic SMP spinlocks, allowing only a single CPU anywhere
+ */
+
+typedef struct {
+	volatile unsigned int lock;
+} spinlock_t;
+
+
+#define SPIN_LOCK_UNLOCKED (spinlock_t) { 1 }
+#define DECLARE_SPIN_LOCK(x) static spinlock_t x = SPIN_LOCK_UNLOCKED;
+
+/*
+ * Simple spin lock operations.  There are two variants, one clears IRQ's
+ * on the local processor, one does not.
+ *
+ * We make no fairness assumptions. They have a cost.
+ */
+#define barrier() __asm__ __volatile__("": : :"memory")
+#define spin_is_locked(x)	(*(volatile char *)(&(x)->lock) <= 0)
+#define spin_unlock_wait(x)	do { barrier(); } while(spin_is_locked(x))
+
+#define spin_lock_string \
+	"\n1:\t" \
+	"lock ; decb %0\n\t" \
+	"js 2f\n" \
+	".section .text.lock,\"ax\"\n" \
+	"2:\t" \
+	"cmpb $0,%0\n\t" \
+	"rep;nop\n\t" \
+	"jle 2b\n\t" \
+	"jmp 1b\n" \
+	".previous"
+
+/*
+ * This works. Despite all the confusion.
+ */
+#define spin_unlock_string \
+	"movb $1,%0"
+
+static inline __attribute__((always_inline)) void spin_lock(spinlock_t *lock)
+{
+	__asm__ __volatile__(
+		spin_lock_string
+		:"=m" (lock->lock) : : "memory");
+}
+
+static inline __attribute__((always_inline)) void spin_unlock(spinlock_t *lock)
+{
+	__asm__ __volatile__(
+		spin_unlock_string
+		:"=m" (lock->lock) : : "memory");
+}
+
+/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
+static inline __attribute__((always_inline)) void cpu_relax(void)
+{
+	__asm__ __volatile__("rep;nop": : :"memory");
+}
+
+#endif /* ARCH_SMP_SPINLOCK_H */