[mirror_ubuntu-eoan-kernel.git] / include / asm-generic / qspinlock.h

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Queued spinlock
 *
 * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
 * (C) Copyright 2015 Hewlett-Packard Enterprise Development LP
 *
 * Authors: Waiman Long <waiman.long@hpe.com>
 */
#ifndef __ASM_GENERIC_QSPINLOCK_H
#define __ASM_GENERIC_QSPINLOCK_H

#include <asm-generic/qspinlock_types.h>

/**
 * queued_spin_is_locked - is the spinlock locked?
 * @lock: Pointer to queued spinlock structure
 * Return: 1 if it is locked, 0 otherwise
 */
static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
{
	/*
	 * Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
	 * isn't immediately observable.
	 */
	return atomic_read(&lock->val);
}

/**
 * queued_spin_value_unlocked - is the spinlock structure unlocked?
 * @lock: queued spinlock structure
 * Return: 1 if it is unlocked, 0 otherwise
 *
 * N.B. Whenever there are tasks waiting for the lock, it is considered
 *      locked wrt the lockref code to avoid lock stealing by the lockref
 *      code and change things underneath the lock. This also allows some
 *      optimizations to be applied without conflict with lockref.
 */
static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
{
	return !atomic_read(&lock.val);
}

/**
 * queued_spin_is_contended - check if the lock is contended
 * @lock : Pointer to queued spinlock structure
 * Return: 1 if lock contended, 0 otherwise
 */
static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
{
	return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
}
/**
 * queued_spin_trylock - try to acquire the queued spinlock
 * @lock : Pointer to queued spinlock structure
 * Return: 1 if lock acquired, 0 if failed
 */
static __always_inline int queued_spin_trylock(struct qspinlock *lock)
{
	u32 val = atomic_read(&lock->val);

	if (unlikely(val))
		return 0;

	return likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL));
}

extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);

/**
 * queued_spin_lock - acquire a queued spinlock
 * @lock: Pointer to queued spinlock structure
 */
static __always_inline void queued_spin_lock(struct qspinlock *lock)
{
	u32 val = 0;

	if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)))
		return;

	queued_spin_lock_slowpath(lock, val);
}

#ifndef queued_spin_unlock
/**
 * queued_spin_unlock - release a queued spinlock
 * @lock : Pointer to queued spinlock structure
 */
static __always_inline void queued_spin_unlock(struct qspinlock *lock)
{
	/*
	 * unlock() needs release semantics:
	 */
	smp_store_release(&lock->locked, 0);
}
#endif

#ifndef virt_spin_lock
static __always_inline bool virt_spin_lock(struct qspinlock *lock)
{
	return false;
}
#endif

/*
 * Remapping spinlock architecture specific functions to the corresponding
 * queued spinlock functions.
 */
#define arch_spin_is_locked(l)		queued_spin_is_locked(l)
#define arch_spin_is_contended(l)	queued_spin_is_contended(l)
#define arch_spin_value_unlocked(l)	queued_spin_value_unlocked(l)
#define arch_spin_lock(l)		queued_spin_lock(l)
#define arch_spin_trylock(l)		queued_spin_trylock(l)
#define arch_spin_unlock(l)		queued_spin_unlock(l)

#endif /* __ASM_GENERIC_QSPINLOCK_H */
Commit	Line	Data
	1	/* SPDX-License-Identifier: GPL-2.0-or-later */
	2	/*
	3	* Queued spinlock
	4	*
	5	* (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
	6	* (C) Copyright 2015 Hewlett-Packard Enterprise Development LP
	7	*
	8	* Authors: Waiman Long <waiman.long@hpe.com>
	9	*/
	10	#ifndef __ASM_GENERIC_QSPINLOCK_H
	11	#define __ASM_GENERIC_QSPINLOCK_H
	12
	13	#include <asm-generic/qspinlock_types.h>
	14
	15	/**
	16	* queued_spin_is_locked - is the spinlock locked?
	17	* @lock: Pointer to queued spinlock structure
	18	* Return: 1 if it is locked, 0 otherwise
	19	*/
	20	static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
	21	{
	22	/*
	23	* Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
	24	* isn't immediately observable.
	25	*/
	26	return atomic_read(&lock->val);
	27	}
	28
	29	/**
	30	* queued_spin_value_unlocked - is the spinlock structure unlocked?
	31	* @lock: queued spinlock structure
	32	* Return: 1 if it is unlocked, 0 otherwise
	33	*
	34	* N.B. Whenever there are tasks waiting for the lock, it is considered
	35	* locked wrt the lockref code to avoid lock stealing by the lockref
	36	* code and change things underneath the lock. This also allows some
	37	* optimizations to be applied without conflict with lockref.
	38	*/
	39	static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
	40	{
	41	return !atomic_read(&lock.val);
	42	}
	43
	44	/**
	45	* queued_spin_is_contended - check if the lock is contended
	46	* @lock : Pointer to queued spinlock structure
	47	* Return: 1 if lock contended, 0 otherwise
	48	*/
	49	static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
	50	{
	51	return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
	52	}
	53	/**
	54	* queued_spin_trylock - try to acquire the queued spinlock
	55	* @lock : Pointer to queued spinlock structure
	56	* Return: 1 if lock acquired, 0 if failed
	57	*/
	58	static __always_inline int queued_spin_trylock(struct qspinlock *lock)
	59	{
	60	u32 val = atomic_read(&lock->val);
	61
	62	if (unlikely(val))
	63	return 0;
	64
	65	return likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL));
	66	}
	67
	68	extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
	69
	70	/**
	71	* queued_spin_lock - acquire a queued spinlock
	72	* @lock: Pointer to queued spinlock structure
	73	*/
	74	static __always_inline void queued_spin_lock(struct qspinlock *lock)
	75	{
	76	u32 val = 0;
	77
	78	if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)))
	79	return;
	80
	81	queued_spin_lock_slowpath(lock, val);
	82	}
	83
	84	#ifndef queued_spin_unlock
	85	/**
	86	* queued_spin_unlock - release a queued spinlock
	87	* @lock : Pointer to queued spinlock structure
	88	*/
	89	static __always_inline void queued_spin_unlock(struct qspinlock *lock)
	90	{
	91	/*
	92	* unlock() needs release semantics:
	93	*/
	94	smp_store_release(&lock->locked, 0);
	95	}
	96	#endif
	97
	98	#ifndef virt_spin_lock
	99	static __always_inline bool virt_spin_lock(struct qspinlock *lock)
	100	{
	101	return false;
	102	}
	103	#endif
	104
	105	/*
	106	* Remapping spinlock architecture specific functions to the corresponding
	107	* queued spinlock functions.
	108	*/
	109	#define arch_spin_is_locked(l) queued_spin_is_locked(l)
	110	#define arch_spin_is_contended(l) queued_spin_is_contended(l)
	111	#define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
	112	#define arch_spin_lock(l) queued_spin_lock(l)
	113	#define arch_spin_trylock(l) queued_spin_trylock(l)
	114	#define arch_spin_unlock(l) queued_spin_unlock(l)
	115
	116	#endif /* __ASM_GENERIC_QSPINLOCK_H */