[deliverable/linux.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)
{
	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)
{
	if (!atomic_read(&lock->val) &&
	   (atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL) == 0))
		return 1;
	return 0;
}

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;

	val = atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL);
	if (likely(val == 0))
		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)
{
	/*
	 * smp_mb__before_atomic() in order to guarantee release semantics
	 */
	smp_mb__before_atomic();
	atomic_sub(_Q_LOCKED_VAL, &lock->val);
}
#endif

/**
 * queued_spin_unlock_wait - wait until current lock holder releases the lock
 * @lock : Pointer to queued spinlock structure
 *
 * There is a very slight possibility of live-lock if the lockers keep coming
 * and the waiter is just unfortunate enough to not see any unlock state.
 */
static inline void queued_spin_unlock_wait(struct qspinlock *lock)
{
	while (atomic_read(&lock->val) & _Q_LOCKED_MASK)
		cpu_relax();
}

#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)
#define arch_spin_lock_flags(l, f)	queued_spin_lock(l)
#define arch_spin_unlock_wait(l)	queued_spin_unlock_wait(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	{
	31	return atomic_read(&lock->val);
	32	}
	33
	34	/**
	35	* queued_spin_value_unlocked - is the spinlock structure unlocked?
	36	* @lock: queued spinlock structure
	37	* Return: 1 if it is unlocked, 0 otherwise
	38	*
	39	* N.B. Whenever there are tasks waiting for the lock, it is considered
	40	* locked wrt the lockref code to avoid lock stealing by the lockref
	41	* code and change things underneath the lock. This also allows some
	42	* optimizations to be applied without conflict with lockref.
	43	*/
	44	static __always_inline int queued_spin_value_unlocked(struct qspinlock lock)
	45	{
	46	return !atomic_read(&lock.val);
	47	}
	48
	49	/**
	50	* queued_spin_is_contended - check if the lock is contended
	51	* @lock : Pointer to queued spinlock structure
	52	* Return: 1 if lock contended, 0 otherwise
	53	*/
	54	static __always_inline int queued_spin_is_contended(struct qspinlock *lock)
	55	{
	56	return atomic_read(&lock->val) & ~_Q_LOCKED_MASK;
	57	}
	58	/**
	59	* queued_spin_trylock - try to acquire the queued spinlock
	60	* @lock : Pointer to queued spinlock structure
	61	* Return: 1 if lock acquired, 0 if failed
	62	*/
	63	static __always_inline int queued_spin_trylock(struct qspinlock *lock)
	64	{
	65	if (!atomic_read(&lock->val) &&
64d816cb	66	(atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL) == 0))
a33fda35 WL	67	return 1;
	68	return 0;
	69	}
	70
	71	extern void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
	72
	73	/**
	74	* queued_spin_lock - acquire a queued spinlock
	75	* @lock: Pointer to queued spinlock structure
	76	*/
	77	static __always_inline void queued_spin_lock(struct qspinlock *lock)
	78	{
	79	u32 val;
	80
64d816cb	81	val = atomic_cmpxchg_acquire(&lock->val, 0, _Q_LOCKED_VAL);
a33fda35 WL	82	if (likely(val == 0))
	83	return;
	84	queued_spin_lock_slowpath(lock, val);
	85	}
	86
	87	#ifndef queued_spin_unlock
	88	/**
	89	* queued_spin_unlock - release a queued spinlock
	90	* @lock : Pointer to queued spinlock structure
	91	*/
	92	static __always_inline void queued_spin_unlock(struct qspinlock *lock)
	93	{
	94	/*
	95	* smp_mb__before_atomic() in order to guarantee release semantics
	96	*/
64d816cb	97	smp_mb__before_atomic();
a33fda35 WL	98	atomic_sub(_Q_LOCKED_VAL, &lock->val);
	99	}
	100	#endif
	101
	102	/**
	103	* queued_spin_unlock_wait - wait until current lock holder releases the lock
	104	* @lock : Pointer to queued spinlock structure
	105	*
	106	* There is a very slight possibility of live-lock if the lockers keep coming
	107	* and the waiter is just unfortunate enough to not see any unlock state.
	108	*/
	109	static inline void queued_spin_unlock_wait(struct qspinlock *lock)
	110	{
	111	while (atomic_read(&lock->val) & _Q_LOCKED_MASK)
	112	cpu_relax();
	113	}
	114
43b3f028 PZ	115	#ifndef virt_spin_lock
43b3f028 PZ	116	static __always_inline bool virt_spin_lock(struct qspinlock *lock)
2aa79af6 PZI	117	{
	118	return false;
	119	}
	120	#endif
	121
a33fda35 WL	122	/*
	123	* Remapping spinlock architecture specific functions to the corresponding
	124	* queued spinlock functions.
	125	*/
	126	#define arch_spin_is_locked(l) queued_spin_is_locked(l)
	127	#define arch_spin_is_contended(l) queued_spin_is_contended(l)
	128	#define arch_spin_value_unlocked(l) queued_spin_value_unlocked(l)
	129	#define arch_spin_lock(l) queued_spin_lock(l)
	130	#define arch_spin_trylock(l) queued_spin_trylock(l)
	131	#define arch_spin_unlock(l) queued_spin_unlock(l)
	132	#define arch_spin_lock_flags(l, f) queued_spin_lock(l)
	133	#define arch_spin_unlock_wait(l) queued_spin_unlock_wait(l)
	134
	135	#endif /* __ASM_GENERIC_QSPINLOCK_H */