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