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rwsem.h

/*
 * rwsem.h: R/W semaphores implemented using CAS
 *
 * Written by David S. Miller (davem@redhat.com), 2001.
 * Derived from asm-i386/rwsem.h
 */
#ifndef _SPARC64_RWSEM_H
#define _SPARC64_RWSEM_H

#ifndef _LINUX_RWSEM_H
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
#endif

#ifdef __KERNEL__

#include <linux/list.h>
#include <linux/spinlock.h>
#include <asm/rwsem-const.h>

struct rwsem_waiter;

struct rw_semaphore {
      signed int count;
      spinlock_t        wait_lock;
      struct list_head  wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
      struct lockdep_map      dep_map;
#endif
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
#else
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif

#define __RWSEM_INITIALIZER(name) \
{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) \
  __RWSEM_DEP_MAP_INIT(name) }

#define DECLARE_RWSEM(name) \
      struct rw_semaphore name = __RWSEM_INITIALIZER(name)

extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
                   struct lock_class_key *key);

#define init_rwsem(sem)                               \
do {                                            \
      static struct lock_class_key __key;             \
                                                \
      __init_rwsem((sem), #sem, &__key);              \
} while (0)

extern void __down_read(struct rw_semaphore *sem);
extern int __down_read_trylock(struct rw_semaphore *sem);
extern void __down_write(struct rw_semaphore *sem);
extern int __down_write_trylock(struct rw_semaphore *sem);
extern void __up_read(struct rw_semaphore *sem);
extern void __up_write(struct rw_semaphore *sem);
extern void __downgrade_write(struct rw_semaphore *sem);

static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
      __down_write(sem);
}

static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
{
      return atomic_add_return(delta, (atomic_t *)(&sem->count));
}

static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
{
      atomic_add(delta, (atomic_t *)(&sem->count));
}

static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
      return (sem->count != 0);
}

#endif /* __KERNEL__ */

#endif /* _SPARC64_RWSEM_H */

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