1 files changed, 77 insertions, 0 deletions

diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h
new file mode 100644
index 000000000000..6b20af0bbb79
--- /dev/null
+++ b/include/linux/bit_spinlock.h
@@ -0,0 +1,77 @@
+#ifndef __LINUX_BIT_SPINLOCK_H
+#define __LINUX_BIT_SPINLOCK_H
+
+/*
+ *  bit-based spin_lock()
+ *
+ * Don't use this unless you really need to: spin_lock() and spin_unlock()
+ * are significantly faster.
+ */
+static inline void bit_spin_lock(int bitnum, unsigned long *addr)
+{
+        /*
+         * Assuming the lock is uncontended, this never enters
+         * the body of the outer loop. If it is contended, then
+         * within the inner loop a non-atomic test is used to
+         * busywait with less bus contention for a good time to
+         * attempt to acquire the lock bit.
+         */
+        preempt_disable();
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+        while (test_and_set_bit(bitnum, addr)) {
+                while (test_bit(bitnum, addr)) {
+                        preempt_enable();
+                        cpu_relax();
+                        preempt_disable();
+                }
+        }
+#endif
+        __acquire(bitlock);
+}
+
+/*
+ * Return true if it was acquired
+ */
+static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
+{
+        preempt_disable();
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+        if (test_and_set_bit(bitnum, addr)) {
+                preempt_enable();
+                return 0;
+        }
+#endif
+        __acquire(bitlock);
+        return 1;
+}
+
+/*
+ *  bit-based spin_unlock()
+ */
+static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
+{
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+        BUG_ON(!test_bit(bitnum, addr));
+        smp_mb__before_clear_bit();
+        clear_bit(bitnum, addr);
+#endif
+        preempt_enable();
+        __release(bitlock);
+}
+
+/*
+ * Return true if the lock is held.
+ */
+static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
+{
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+        return test_bit(bitnum, addr);
+#elif defined CONFIG_PREEMPT
+        return preempt_count();
+#else
+        return 1;
+#endif
+}
+
+#endif /* __LINUX_BIT_SPINLOCK_H */
+