| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef __LINUX_OSQ_LOCK_H |
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| 3 | #define __LINUX_OSQ_LOCK_H |
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| 4 | |
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| 5 | /* |
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| 6 | * An MCS like lock especially tailored for optimistic spinning for sleeping |
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| 7 | * lock implementations (mutex, rwsem, etc). |
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| 8 | */ |
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| 9 | |
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| 10 | struct optimistic_spin_queue { |
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| 11 | /* |
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| 12 | * Stores an encoded value of the CPU # of the tail node in the queue. |
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| 13 | * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL. |
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| 14 | */ |
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| 15 | atomic_t tail; |
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| 16 | }; |
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| 17 | |
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| 18 | #define OSQ_UNLOCKED_VAL (0) |
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| 19 | |
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| 20 | /* Init macro and function. */ |
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| 21 | #define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) } |
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| 22 | |
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| 23 | static inline void osq_lock_init(struct optimistic_spin_queue *lock) |
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| 24 | { |
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| 25 | atomic_set(v: &lock->tail, OSQ_UNLOCKED_VAL); |
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| 26 | } |
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| 27 | |
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| 28 | extern bool osq_lock(struct optimistic_spin_queue *lock); |
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| 29 | extern void osq_unlock(struct optimistic_spin_queue *lock); |
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| 30 | |
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| 31 | static inline bool osq_is_locked(struct optimistic_spin_queue *lock) |
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| 32 | { |
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| 33 | return atomic_read(v: &lock->tail) != OSQ_UNLOCKED_VAL; |
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| 34 | } |
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| 35 | |
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| 36 | #endif |
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| 37 | |
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