From 8a6d48c0542876eb3acfc0970c0ab7872db08d5f Mon Sep 17 00:00:00 2001
From: Zheng Da <zhengda1936@gmail.com>
Date: Sun, 6 Dec 2009 05:26:23 +0100
Subject: check in the original version of dde linux26.

---
 libdde_linux26/contrib/include/linux/rwsem.h | 91 ++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 libdde_linux26/contrib/include/linux/rwsem.h

(limited to 'libdde_linux26/contrib/include/linux/rwsem.h')

diff --git a/libdde_linux26/contrib/include/linux/rwsem.h b/libdde_linux26/contrib/include/linux/rwsem.h
new file mode 100644
index 00000000..efd348fe
--- /dev/null
+++ b/libdde_linux26/contrib/include/linux/rwsem.h
@@ -0,0 +1,91 @@
+/* rwsem.h: R/W semaphores, public interface
+ *
+ * Written by David Howells (dhowells@redhat.com).
+ * Derived from asm-i386/semaphore.h
+ */
+
+#ifndef _LINUX_RWSEM_H
+#define _LINUX_RWSEM_H
+
+#include <linux/linkage.h>
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <asm/system.h>
+#include <asm/atomic.h>
+
+struct rw_semaphore;
+
+#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
+#include <linux/rwsem-spinlock.h> /* use a generic implementation */
+#else
+#include <asm/rwsem.h> /* use an arch-specific implementation */
+#endif
+
+/*
+ * lock for reading
+ */
+extern void down_read(struct rw_semaphore *sem);
+
+/*
+ * trylock for reading -- returns 1 if successful, 0 if contention
+ */
+extern int down_read_trylock(struct rw_semaphore *sem);
+
+/*
+ * lock for writing
+ */
+extern void down_write(struct rw_semaphore *sem);
+
+/*
+ * trylock for writing -- returns 1 if successful, 0 if contention
+ */
+extern int down_write_trylock(struct rw_semaphore *sem);
+
+/*
+ * release a read lock
+ */
+extern void up_read(struct rw_semaphore *sem);
+
+/*
+ * release a write lock
+ */
+extern void up_write(struct rw_semaphore *sem);
+
+/*
+ * downgrade write lock to read lock
+ */
+extern void downgrade_write(struct rw_semaphore *sem);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+/*
+ * nested locking. NOTE: rwsems are not allowed to recurse
+ * (which occurs if the same task tries to acquire the same
+ * lock instance multiple times), but multiple locks of the
+ * same lock class might be taken, if the order of the locks
+ * is always the same. This ordering rule can be expressed
+ * to lockdep via the _nested() APIs, but enumerating the
+ * subclasses that are used. (If the nesting relationship is
+ * static then another method for expressing nested locking is
+ * the explicit definition of lock class keys and the use of
+ * lockdep_set_class() at lock initialization time.
+ * See Documentation/lockdep-design.txt for more details.)
+ */
+extern void down_read_nested(struct rw_semaphore *sem, int subclass);
+extern void down_write_nested(struct rw_semaphore *sem, int subclass);
+/*
+ * Take/release a lock when not the owner will release it.
+ *
+ * [ This API should be avoided as much as possible - the
+ *   proper abstraction for this case is completions. ]
+ */
+extern void down_read_non_owner(struct rw_semaphore *sem);
+extern void up_read_non_owner(struct rw_semaphore *sem);
+#else
+# define down_read_nested(sem, subclass)		down_read(sem)
+# define down_write_nested(sem, subclass)	down_write(sem)
+# define down_read_non_owner(sem)		down_read(sem)
+# define up_read_non_owner(sem)			up_read(sem)
+#endif
+
+#endif /* _LINUX_RWSEM_H */
-- 
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