1 files changed, 132 insertions, 0 deletions

diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h
new file mode 100644
index 000000000000..bb1e2cdeb9bf
--- /dev/null
+++ b/include/asm-generic/rwsem.h
@@ -0,0 +1,132 @@
+#ifndef _ASM_POWERPC_RWSEM_H
+#define _ASM_POWERPC_RWSEM_H
+
+#ifndef _LINUX_RWSEM_H
+#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
+#endif
+
+#ifdef __KERNEL__
+
+/*
+ * R/W semaphores for PPC using the stuff in lib/rwsem.c.
+ * Adapted largely from include/asm-i386/rwsem.h
+ * by Paul Mackerras <paulus@samba.org>.
+ */
+
+/*
+ * the semaphore definition
+ */
+#ifdef CONFIG_PPC64
+# define RWSEM_ACTIVE_MASK              0xffffffffL
+#else
+# define RWSEM_ACTIVE_MASK              0x0000ffffL
+#endif
+
+#define RWSEM_UNLOCKED_VALUE            0x00000000L
+#define RWSEM_ACTIVE_BIAS               0x00000001L
+#define RWSEM_WAITING_BIAS              (-RWSEM_ACTIVE_MASK-1)
+#define RWSEM_ACTIVE_READ_BIAS          RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS         (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+
+/*
+ * lock for reading
+ */
+static inline void __down_read(struct rw_semaphore *sem)
+{
+        if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
+                rwsem_down_read_failed(sem);
+}
+
+static inline int __down_read_trylock(struct rw_semaphore *sem)
+{
+        long tmp;
+
+        while ((tmp = sem->count) >= 0) {
+                if (tmp == cmpxchg(&sem->count, tmp,
+                                   tmp + RWSEM_ACTIVE_READ_BIAS)) {
+                        return 1;
+                }
+        }
+        return 0;
+}
+
+/*
+ * lock for writing
+ */
+static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
+{
+        long tmp;
+
+        tmp = atomic_long_add_return(RWSEM_ACTIVE_WRITE_BIAS,
+                                     (atomic_long_t *)&sem->count);
+        if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
+                rwsem_down_write_failed(sem);
+}
+
+static inline void __down_write(struct rw_semaphore *sem)
+{
+        __down_write_nested(sem, 0);
+}
+
+static inline int __down_write_trylock(struct rw_semaphore *sem)
+{
+        long tmp;
+
+        tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
+                      RWSEM_ACTIVE_WRITE_BIAS);
+        return tmp == RWSEM_UNLOCKED_VALUE;
+}
+
+/*
+ * unlock after reading
+ */
+static inline void __up_read(struct rw_semaphore *sem)
+{
+        long tmp;
+
+        tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
+        if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
+                rwsem_wake(sem);
+}
+
+/*
+ * unlock after writing
+ */
+static inline void __up_write(struct rw_semaphore *sem)
+{
+        if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
+                                 (atomic_long_t *)&sem->count) < 0))
+                rwsem_wake(sem);
+}
+
+/*
+ * implement atomic add functionality
+ */
+static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
+{
+        atomic_long_add(delta, (atomic_long_t *)&sem->count);
+}
+
+/*
+ * downgrade write lock to read lock
+ */
+static inline void __downgrade_write(struct rw_semaphore *sem)
+{
+        long tmp;
+
+        tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
+                                     (atomic_long_t *)&sem->count);
+        if (tmp < 0)
+                rwsem_downgrade_wake(sem);
+}
+
+/*
+ * implement exchange and add functionality
+ */
+static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
+{
+        return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
+}
+
+#endif  /* __KERNEL__ */
+#endif  /* _ASM_POWERPC_RWSEM_H */