| 1 |
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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 | |
| 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 | |
| 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 |
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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(&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(&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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