[linux-2.6-block.git] / include / asm-generic / qspinlock.h

/*
 * Queued spinlock
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * (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
a33fda35 WL	1	/*
	2	* Queued spinlock
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
64d816cb	15	* (C) Copyright 2015 Hewlett-Packard Enterprise Development LP
a33fda35	16	*
64d816cb	17	* Authors: Waiman Long <waiman.long@hpe.com>
a33fda35 WL	18	*/
	19	#ifndef __ASM_GENERIC_QSPINLOCK_H
	20	#define __ASM_GENERIC_QSPINLOCK_H
	21
	22	#include <asm-generic/qspinlock_types.h>
	23
	24	/**
	25	* queued_spin_is_locked - is the spinlock locked?
	26	* @lock: Pointer to queued spinlock structure
	27	* Return: 1 if it is locked, 0 otherwise
	28	*/
	29	static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
	30	{
54cf809b	31	/*
2c610022 PZ	32	* Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
2c610022 PZ	33	* isn't immediately observable.
54cf809b	34	*/
2c610022	35	return atomic_read(&lock->val);
a33fda35 WL	36	}
	37
	38	/**
	39	* queued_spin_value_unlocked - is the spinlock structure unlocked?
	40	* @lock: queued spinlock structure
	41	* Return: 1 if it is unlocked, 0 otherwise
	42	*
	43	* N.B. Whenever there are tasks waiting for the lock, it is considered
	44	* locked wrt the lockref code to avoid lock stealing by the lockref
	45	* code and change things underneath the lock. This also allows some
	46	* optimizations to be applied without conflict with lockref.
	47	*/
	48	static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
	49	{
	50	return !atomic_read(&lock.val);
	51	}
	52
	53	/**
	54	* queued_spin_is_contended - check if the lock is contended
	55	* @lock : Pointer to queued spinlock structure
	56	* Return: 1 if lock contended, 0 otherwise
	57	*/
	58	static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
	59	{
	60	return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
	61	}
	62	/**
	63	* queued_spin_trylock - try to acquire the queued spinlock
	64	* @lock : Pointer to queued spinlock structure
	65	* Return: 1 if lock acquired, 0 if failed
	66	*/
	67	static __always_inline int queued_spin_trylock(struct qspinlock *lock)
	68	{
27df8968 MW	69	u32 val = atomic_read(&lock->val);
	70
	71	if (unlikely(val))
	72	return 0;
	73
	74	return likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL));
a33fda35 WL	75	}
	76
	77	extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
	78
	79	/**
	80	* queued_spin_lock - acquire a queued spinlock
	81	* @lock: Pointer to queued spinlock structure
	82	*/
	83	static __always_inline void queued_spin_lock(struct qspinlock *lock)
	84	{
27df8968	85	u32 val = 0;
a33fda35	86
27df8968	87	if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL)))
a33fda35	88	return;
27df8968	89
a33fda35 WL	90	queued_spin_lock_slowpath(lock, val);
	91	}
	92
	93	#ifndef queued_spin_unlock
	94	/**
	95	* queued_spin_unlock - release a queued spinlock
	96	* @lock : Pointer to queued spinlock structure
	97	*/
	98	static __always_inline void queued_spin_unlock(struct qspinlock *lock)
	99	{
	100	/*
ca50e426	101	* unlock() needs release semantics:
a33fda35	102	*/
626e5fbc	103	smp_store_release(&lock->locked, 0);
a33fda35 WL	104	}
	105	#endif
	106
43b3f028 PZ	107	#ifndef virt_spin_lock
43b3f028 PZ	108	static __always_inline bool virt_spin_lock(struct qspinlock *lock)
2aa79af6 PZI	109	{
	110	return false;
	111	}
	112	#endif
	113
a33fda35 WL	114	/*
	115	* Remapping spinlock architecture specific functions to the corresponding
	116	* queued spinlock functions.
	117	*/
	118	#define arch_spin_is_locked(l) queued_spin_is_locked(l)
	119	#define arch_spin_is_contended(l) queued_spin_is_contended(l)
	120	#define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
	121	#define arch_spin_lock(l) queued_spin_lock(l)
	122	#define arch_spin_trylock(l) queued_spin_trylock(l)
	123	#define arch_spin_unlock(l) queued_spin_unlock(l)
a33fda35 WL	124
a33fda35 WL	125	#endif /* __ASM_GENERIC_QSPINLOCK_H */