This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / include / asm-xtensa / rwsem.h

diff --git a/include/asm-xtensa/rwsem.h b/include/asm-xtensa/rwsem.h
new file mode 100644 (file)
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+++ b/include/asm-xtensa/rwsem.h
@@ -0,0 +1,175 @@
+/*
+ * include/asm-xtensa/rwsem.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Largely copied from include/asm-ppc/rwsem.h
+ *
+ * Copyright (C) 2001 - 2005 Tensilica Inc.
+ */
+
+#ifndef _XTENSA_RWSEM_H
+#define _XTENSA_RWSEM_H
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+#include <asm/system.h>
+
+/*
+ * the semaphore definition
+ */
+struct rw_semaphore {
+       signed long             count;
+#define RWSEM_UNLOCKED_VALUE           0x00000000
+#define RWSEM_ACTIVE_BIAS              0x00000001
+#define RWSEM_ACTIVE_MASK              0x0000ffff
+#define RWSEM_WAITING_BIAS             (-0x00010000)
+#define RWSEM_ACTIVE_READ_BIAS         RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS                (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+       spinlock_t              wait_lock;
+       struct list_head        wait_list;
+#if RWSEM_DEBUG
+       int                     debug;
+#endif
+};
+
+/*
+ * initialisation
+ */
+#if RWSEM_DEBUG
+#define __RWSEM_DEBUG_INIT      , 0
+#else
+#define __RWSEM_DEBUG_INIT     /* */
+#endif
+
+#define __RWSEM_INITIALIZER(name) \
+       { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
+         LIST_HEAD_INIT((name).wait_list) \
+         __RWSEM_DEBUG_INIT }
+
+#define DECLARE_RWSEM(name)            \
+       struct rw_semaphore name = __RWSEM_INITIALIZER(name)
+
+extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
+
+static inline void init_rwsem(struct rw_semaphore *sem)
+{
+       sem->count = RWSEM_UNLOCKED_VALUE;
+       spin_lock_init(&sem->wait_lock);
+       INIT_LIST_HEAD(&sem->wait_list);
+#if RWSEM_DEBUG
+       sem->debug = 0;
+#endif
+}
+
+/*
+ * lock for reading
+ */
+static inline void __down_read(struct rw_semaphore *sem)
+{
+       if (atomic_add_return(1,(atomic_t *)(&sem->count)) > 0)
+               smp_wmb();
+       else
+               rwsem_down_read_failed(sem);
+}
+
+static inline int __down_read_trylock(struct rw_semaphore *sem)
+{
+       int tmp;
+
+       while ((tmp = sem->count) >= 0) {
+               if (tmp == cmpxchg(&sem->count, tmp,
+                                  tmp + RWSEM_ACTIVE_READ_BIAS)) {
+                       smp_wmb();
+                       return 1;
+               }
+       }
+       return 0;
+}
+
+/*
+ * lock for writing
+ */
+static inline void __down_write(struct rw_semaphore *sem)
+{
+       int tmp;
+
+       tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
+                               (atomic_t *)(&sem->count));
+       if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
+               smp_wmb();
+       else
+               rwsem_down_write_failed(sem);
+}
+
+static inline int __down_write_trylock(struct rw_semaphore *sem)
+{
+       int tmp;
+
+       tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
+                     RWSEM_ACTIVE_WRITE_BIAS);
+       smp_wmb();
+       return tmp == RWSEM_UNLOCKED_VALUE;
+}
+
+/*
+ * unlock after reading
+ */
+static inline void __up_read(struct rw_semaphore *sem)
+{
+       int tmp;
+
+       smp_wmb();
+       tmp = atomic_sub_return(1,(atomic_t *)(&sem->count));
+       if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
+               rwsem_wake(sem);
+}
+
+/*
+ * unlock after writing
+ */
+static inline void __up_write(struct rw_semaphore *sem)
+{
+       smp_wmb();
+       if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
+                             (atomic_t *)(&sem->count)) < 0)
+               rwsem_wake(sem);
+}
+
+/*
+ * implement atomic add functionality
+ */
+static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
+{
+       atomic_add(delta, (atomic_t *)(&sem->count));
+}
+
+/*
+ * downgrade write lock to read lock
+ */
+static inline void __downgrade_write(struct rw_semaphore *sem)
+{
+       int tmp;
+
+       smp_wmb();
+       tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
+       if (tmp < 0)
+               rwsem_downgrade_wake(sem);
+}
+
+/*
+ * implement exchange and add functionality
+ */
+static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
+{
+       smp_mb();
+       return atomic_add_return(delta, (atomic_t *)(&sem->count));
+}
+
+#endif /* _XTENSA_RWSEM_XADD_H */