42 lines
1.0 KiB
C
42 lines
1.0 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_OSQ_LOCK_H
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#define __LINUX_OSQ_LOCK_H
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/*
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* An MCS like lock especially tailored for optimistic spinning for sleeping
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* lock implementations (mutex, rwsem, etc).
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*/
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struct optimistic_spin_node {
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struct optimistic_spin_node *next, *prev;
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int locked; /* 1 if lock acquired */
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int cpu; /* encoded CPU # + 1 value */
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};
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struct optimistic_spin_queue {
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/*
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* Stores an encoded value of the CPU # of the tail node in the queue.
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* If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
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*/
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atomic_t tail;
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};
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#define OSQ_UNLOCKED_VAL (0)
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/* Init macro and function. */
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#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
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static inline void osq_lock_init(struct optimistic_spin_queue *lock)
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{
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atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
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}
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extern bool osq_lock(struct optimistic_spin_queue *lock);
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extern void osq_unlock(struct optimistic_spin_queue *lock);
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static inline bool osq_is_locked(struct optimistic_spin_queue *lock)
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{
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return atomic_read(&lock->tail) != OSQ_UNLOCKED_VAL;
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}
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#endif
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