[PATCH] powerpc: merge semaphore.h

powerpc: Merge semaphore.h

Adopted the ppc64 version of semaphore.h.  The 32-bit version used
smp_wmb(), but recent updates to atomic.h mean this is no longer required.
The 64-bit version made use of unlikely(), which has been retained in the
combined version.

This patch requires the recent atomic.h patch.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>
Signed-off-by: Kumar Gala <kumar.gala@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 98 insertions, 0 deletions

diff --git a/include/asm-powerpc/semaphore.h b/include/asm-powerpc/semaphore.h
new file mode 100644
index 00000000000..fd42fe97158
--- /dev/null
+++ b/include/asm-powerpc/semaphore.h
@@ -0,0 +1,98 @@
+#ifndef _ASM_POWERPC_SEMAPHORE_H
+#define _ASM_POWERPC_SEMAPHORE_H
+
+/*
+ * Remove spinlock-based RW semaphores; RW semaphore definitions are
+ * now in rwsem.h and we use the generic lib/rwsem.c implementation.
+ * Rework semaphores to use atomic_dec_if_positive.
+ * -- Paul Mackerras (paulus@samba.org)
+ */
+
+#ifdef __KERNEL__
+
+#include <asm/atomic.h>
+#include <asm/system.h>
+#include <linux/wait.h>
+#include <linux/rwsem.h>
+
+struct semaphore {
+	/*
+	 * Note that any negative value of count is equivalent to 0,
+	 * but additionally indicates that some process(es) might be
+	 * sleeping on `wait'.
+	 */
+	atomic_t count;
+	wait_queue_head_t wait;
+};
+
+#define __SEMAPHORE_INITIALIZER(name, n)				\
+{									\
+	.count		= ATOMIC_INIT(n),				\
+	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
+}
+
+#define __MUTEX_INITIALIZER(name) \
+	__SEMAPHORE_INITIALIZER(name, 1)
+
+#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
+	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
+
+#define DECLARE_MUTEX(name)		__DECLARE_SEMAPHORE_GENERIC(name, 1)
+#define DECLARE_MUTEX_LOCKED(name)	__DECLARE_SEMAPHORE_GENERIC(name, 0)
+
+static inline void sema_init (struct semaphore *sem, int val)
+{
+	atomic_set(&sem->count, val);
+	init_waitqueue_head(&sem->wait);
+}
+
+static inline void init_MUTEX (struct semaphore *sem)
+{
+	sema_init(sem, 1);
+}
+
+static inline void init_MUTEX_LOCKED (struct semaphore *sem)
+{
+	sema_init(sem, 0);
+}
+
+extern void __down(struct semaphore * sem);
+extern int  __down_interruptible(struct semaphore * sem);
+extern void __up(struct semaphore * sem);
+
+static inline void down(struct semaphore * sem)
+{
+	might_sleep();
+
+	/*
+	 * Try to get the semaphore, take the slow path if we fail.
+	 */
+	if (unlikely(atomic_dec_return(&sem->count) < 0))
+		__down(sem);
+}
+
+static inline int down_interruptible(struct semaphore * sem)
+{
+	int ret = 0;
+
+	might_sleep();
+
+	if (unlikely(atomic_dec_return(&sem->count) < 0))
+		ret = __down_interruptible(sem);
+	return ret;
+}
+
+static inline int down_trylock(struct semaphore * sem)
+{
+	return atomic_dec_if_positive(&sem->count) < 0;
+}
+
+static inline void up(struct semaphore * sem)
+{
+	if (unlikely(atomic_inc_return(&sem->count) <= 0))
+		__up(sem);
+}
+
+#endif /* __KERNEL__ */
+
+#endif /* _ASM_POWERPC_SEMAPHORE_H */