include/linux/lockref.h

   1 #ifndef __LINUX_LOCKREF_H
   2 #define __LINUX_LOCKREF_H
   3
   4 /*
   5  * Locked reference counts.
   6  *
   7  * These are different from just plain atomic refcounts in that they
   8  * are atomic with respect to the spinlock that goes with them.  In
   9  * particular, there can be implementations that don't actually get
  10  * the spinlock for the common decrement/increment operations, but they
  11  * still have to check that the operation is done semantically as if
  12  * the spinlock had been taken (using a cmpxchg operation that covers
  13  * both the lock and the count word, or using memory transactions, for
  14  * example).
  15  */
  16
  17 #include <linux/spinlock.h>
  18
  19 struct lockref {
  20         union {
  21 #ifdef CONFIG_CMPXCHG_LOCKREF
  22                 aligned_u64 lock_count;
  23 #endif
  24                 struct {
  25                         spinlock_t lock;
  26                         unsigned int count;
  27                 };
  28         };
  29 };
  30
  31 extern void lockref_get(struct lockref *);
  32 extern int lockref_get_not_zero(struct lockref *);
  33 extern int lockref_get_or_lock(struct lockref *);
  34 extern int lockref_put_or_lock(struct lockref *);
  35
  36 extern void lockref_mark_dead(struct lockref *);
  37 extern int lockref_get_not_dead(struct lockref *);
  38
  39 #endif /* __LINUX_LOCKREF_H */