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include/linux/rwsem-spinlock.h 2.28 KB
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1da177e4c   Linus Torvalds   Linux-2.6.12-rc2 
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  /* rwsem-spinlock.h: fallback C implementation
   *
   * Copyright (c) 2001   David Howells (dhowells@redhat.com).
   * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
   * - Derived also from comments by Linus
   */
  
  #ifndef _LINUX_RWSEM_SPINLOCK_H
  #define _LINUX_RWSEM_SPINLOCK_H
  
  #ifndef _LINUX_RWSEM_H
  #error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
  #endif
  
  #include <linux/spinlock.h>
  #include <linux/list.h>
  
  #ifdef __KERNEL__
  
  #include <linux/types.h>
  
  struct rwsem_waiter;
  
  /*
   * the rw-semaphore definition
   * - if activity is 0 then there are no active readers or writers
   * - if activity is +ve then that is the number of active readers
   * - if activity is -1 then there is one active writer
   * - if wait_list is not empty, then there are processes waiting for the semaphore
   */
  struct rw_semaphore {
  	__s32			activity;
  	spinlock_t		wait_lock;
  	struct list_head	wait_list;
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  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  	struct lockdep_map dep_map;
  #endif
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  };
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  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  # define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
  #else
  # define __RWSEM_DEP_MAP_INIT(lockname)
  #endif
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  #define __RWSEM_INITIALIZER(name) \
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  { 0, __SPIN_LOCK_UNLOCKED(name.wait_lock), LIST_HEAD_INIT((name).wait_list) \
    __RWSEM_DEP_MAP_INIT(name) }
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  #define DECLARE_RWSEM(name) \
  	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
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  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)
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  extern void FASTCALL(__down_read(struct rw_semaphore *sem));
  extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
  extern void FASTCALL(__down_write(struct rw_semaphore *sem));
4ea2176df   Ingo Molnar   [PATCH] lockdep: ... 
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  extern void FASTCALL(__down_write_nested(struct rw_semaphore *sem, int subclass));
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  extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
  extern void FASTCALL(__up_read(struct rw_semaphore *sem));
  extern void FASTCALL(__up_write(struct rw_semaphore *sem));
  extern void FASTCALL(__downgrade_write(struct rw_semaphore *sem));
eb92f4ef3   Rik Van Riel   [PATCH] add sem_i... 
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  static inline int rwsem_is_locked(struct rw_semaphore *sem)
  {
  	return (sem->activity != 0);
  }
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  #endif /* __KERNEL__ */
  #endif /* _LINUX_RWSEM_SPINLOCK_H */