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53 lines
1.5 KiB
53 lines
1.5 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef __LINUX_LOCKREF_H |
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#define __LINUX_LOCKREF_H |
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/* |
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* Locked reference counts. |
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* |
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* These are different from just plain atomic refcounts in that they |
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* are atomic with respect to the spinlock that goes with them. In |
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* particular, there can be implementations that don't actually get |
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* the spinlock for the common decrement/increment operations, but they |
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* still have to check that the operation is done semantically as if |
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* the spinlock had been taken (using a cmpxchg operation that covers |
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* both the lock and the count word, or using memory transactions, for |
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* example). |
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*/ |
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#include <linux/spinlock.h> |
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#include <generated/bounds.h> |
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#define USE_CMPXCHG_LOCKREF \ |
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(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \ |
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IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4) |
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struct lockref { |
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union { |
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#if USE_CMPXCHG_LOCKREF |
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aligned_u64 lock_count; |
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#endif |
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struct { |
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spinlock_t lock; |
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int count; |
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}; |
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}; |
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}; |
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extern void lockref_get(struct lockref *); |
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extern int lockref_put_return(struct lockref *); |
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extern int lockref_get_not_zero(struct lockref *); |
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extern int lockref_put_not_zero(struct lockref *); |
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extern int lockref_get_or_lock(struct lockref *); |
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extern int lockref_put_or_lock(struct lockref *); |
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extern void lockref_mark_dead(struct lockref *); |
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extern int lockref_get_not_dead(struct lockref *); |
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/* Must be called under spinlock for reliable results */ |
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static inline bool __lockref_is_dead(const struct lockref *l) |
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{ |
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return ((int)l->count < 0); |
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} |
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#endif /* __LINUX_LOCKREF_H */
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