From db2161a54f160301d1bda95f3af59a9de9b22435 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 29 Jun 2011 21:02:53 +0200
Subject: [PATCH 179/414] rwsem-add-rt-variant.patch

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/rwsem.h    |   6 +++
 include/linux/rwsem_rt.h | 128 +++++++++++++++++++++++++++++++++++++++++++++++
 lib/Makefile             |   3 ++
 3 files changed, 137 insertions(+)
 create mode 100644 include/linux/rwsem_rt.h

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 0616ffe45702..0ad60708685a 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -16,6 +16,10 @@
 
 #include <linux/atomic.h>
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+#include <linux/rwsem_rt.h>
+#else /* PREEMPT_RT_FULL */
+
 struct rw_semaphore;
 
 #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
@@ -149,4 +153,6 @@ extern void up_read_non_owner(struct rw_semaphore *sem);
 # define up_read_non_owner(sem)			up_read(sem)
 #endif
 
+#endif /* !PREEMPT_RT_FULL */
+
 #endif /* _LINUX_RWSEM_H */
diff --git a/include/linux/rwsem_rt.h b/include/linux/rwsem_rt.h
new file mode 100644
index 000000000000..e94d945c5844
--- /dev/null
+++ b/include/linux/rwsem_rt.h
@@ -0,0 +1,128 @@
+#ifndef _LINUX_RWSEM_RT_H
+#define _LINUX_RWSEM_RT_H
+
+#ifndef _LINUX_RWSEM_H
+#error "Include rwsem.h"
+#endif
+
+/*
+ * RW-semaphores are a spinlock plus a reader-depth count.
+ *
+ * Note that the semantics are different from the usual
+ * Linux rw-sems, in PREEMPT_RT mode we do not allow
+ * multiple readers to hold the lock at once, we only allow
+ * a read-lock owner to read-lock recursively. This is
+ * better for latency, makes the implementation inherently
+ * fair and makes it simpler as well.
+ */
+
+#include <linux/rtmutex.h>
+
+struct rw_semaphore {
+	struct rt_mutex		lock;
+	int			read_depth;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map	dep_map;
+#endif
+};
+
+#define __RWSEM_INITIALIZER(name) \
+	{ .lock = __RT_MUTEX_INITIALIZER(name.lock), \
+	  RW_DEP_MAP_INIT(name) }
+
+#define DECLARE_RWSEM(lockname) \
+	struct rw_semaphore lockname = __RWSEM_INITIALIZER(lockname)
+
+extern void  __rt_rwsem_init(struct rw_semaphore *rwsem, const char *name,
+				     struct lock_class_key *key);
+
+#define __rt_init_rwsem(sem, name, key)			\
+	do {						\
+		rt_mutex_init(&(sem)->lock);		\
+		__rt_rwsem_init((sem), (name), (key));\
+	} while (0)
+
+#define __init_rwsem(sem, name, key) __rt_init_rwsem(sem, name, key)
+
+# define rt_init_rwsem(sem)				\
+do {							\
+	static struct lock_class_key __key;		\
+							\
+	__rt_init_rwsem((sem), #sem, &__key);		\
+} while (0)
+
+extern void  rt_down_write(struct rw_semaphore *rwsem);
+extern void rt_down_read_nested(struct rw_semaphore *rwsem, int subclass);
+extern void rt_down_write_nested(struct rw_semaphore *rwsem, int subclass);
+extern void rt_down_write_nested_lock(struct rw_semaphore *rwsem,
+		struct lockdep_map *nest);
+extern void  rt_down_read(struct rw_semaphore *rwsem);
+extern int  rt_down_write_trylock(struct rw_semaphore *rwsem);
+extern int  rt_down_read_trylock(struct rw_semaphore *rwsem);
+extern void  rt_up_read(struct rw_semaphore *rwsem);
+extern void  rt_up_write(struct rw_semaphore *rwsem);
+extern void  rt_downgrade_write(struct rw_semaphore *rwsem);
+
+#define init_rwsem(sem)		rt_init_rwsem(sem)
+#define rwsem_is_locked(s)	rt_mutex_is_locked(&(s)->lock)
+
+static inline void down_read(struct rw_semaphore *sem)
+{
+	rt_down_read(sem);
+}
+
+static inline int down_read_trylock(struct rw_semaphore *sem)
+{
+	return rt_down_read_trylock(sem);
+}
+
+static inline void down_write(struct rw_semaphore *sem)
+{
+	rt_down_write(sem);
+}
+
+static inline int down_write_trylock(struct rw_semaphore *sem)
+{
+	return rt_down_write_trylock(sem);
+}
+
+static inline void up_read(struct rw_semaphore *sem)
+{
+	rt_up_read(sem);
+}
+
+static inline void up_write(struct rw_semaphore *sem)
+{
+	rt_up_write(sem);
+}
+
+static inline void downgrade_write(struct rw_semaphore *sem)
+{
+	rt_downgrade_write(sem);
+}
+
+static inline void down_read_nested(struct rw_semaphore *sem, int subclass)
+{
+	return rt_down_read_nested(sem, subclass);
+}
+
+static inline void down_write_nested(struct rw_semaphore *sem, int subclass)
+{
+	rt_down_write_nested(sem, subclass);
+}
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static inline void down_write_nest_lock(struct rw_semaphore *sem,
+		struct rw_semaphore *nest_lock)
+{
+	rt_down_write_nested_lock(sem, &nest_lock->dep_map);
+}
+
+#else
+
+static inline void down_write_nest_lock(struct rw_semaphore *sem,
+		struct rw_semaphore *nest_lock)
+{
+	rt_down_write_nested_lock(sem, NULL);
+}
+#endif
+#endif
diff --git a/lib/Makefile b/lib/Makefile
index 6af6fbb053e3..446159513a5f 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -43,8 +43,11 @@ obj-$(CONFIG_HAS_IOMEM) += iomap_copy.o devres.o
 obj-$(CONFIG_CHECK_SIGNATURE) += check_signature.o
 obj-$(CONFIG_DEBUG_LOCKING_API_SELFTESTS) += locking-selftest.o
 obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
+
+ifneq ($(CONFIG_PREEMPT_RT_FULL),y)
 lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
+endif
 lib-$(CONFIG_PERCPU_RWSEM) += percpu-rwsem.o
 
 GCOV_PROFILE_hweight.o := n
-- 
2.10.2

