| 1 |
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| 2 | #ifndef __LINUX_LOCKREF_H
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| 3 | #define __LINUX_LOCKREF_H
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| 4 |
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| 5 | |
| 6 | * Locked reference counts.
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| 7 | *
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| 8 | * These are different from just plain atomic refcounts in that they
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| 9 | * are atomic with respect to the spinlock that goes with them. In
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| 10 | * particular, there can be implementations that don't actually get
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| 11 | * the spinlock for the common decrement/increment operations, but they
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| 12 | * still have to check that the operation is done semantically as if
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| 13 | * the spinlock had been taken (using a cmpxchg operation that covers
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| 14 | * both the lock and the count word, or using memory transactions, for
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| 15 | * example).
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| 16 |
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| 17 |
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| 18 | #include <linux/spinlock.h>
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| 19 | #include <generated/bounds.h>
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| 20 |
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| 21 | #define USE_CMPXCHG_LOCKREF \
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| 22 | (IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
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| 23 | IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
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| 24 |
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| 25 | struct lockref {
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| 26 | union {
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| 27 | #if USE_CMPXCHG_LOCKREF
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| 28 | aligned_u64 lock_count;
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| 29 | #endif
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| 30 | struct {
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| 31 | spinlock_t lock;
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| 32 | int count;
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| 33 | };
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| 34 | };
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| 35 | };
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| 36 |
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| 37 | extern void lockref_get(struct lockref *);
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| 38 | extern int lockref_put_return(struct lockref *);
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| 39 | extern int lockref_get_not_zero(struct lockref *);
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| 40 | extern int lockref_put_not_zero(struct lockref *);
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| 41 | extern int lockref_put_or_lock(struct lockref *);
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| 42 |
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| 43 | extern void lockref_mark_dead(struct lockref *);
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| 44 | extern int lockref_get_not_dead(struct lockref *);
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| 45 |
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| 46 |
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| 47 | static inline bool __lockref_is_dead(const struct lockref *l)
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| 48 | {
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| 49 | return ((int)l->count < 0);
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| 50 | }
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| 51 |
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| 52 | #endif
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