[mirror_ubuntu-focal-kernel.git] / arch / ia64 / include / asm / rwsem.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * R/W semaphores for ia64
 *
 * Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com>
 * Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com>
 * Copyright (C) 2005 Christoph Lameter <cl@linux.com>
 *
 * Based on asm-i386/rwsem.h and other architecture implementation.
 *
 * The MSW of the count is the negated number of active writers and
 * waiting lockers, and the LSW is the total number of active locks.
 *
 * The lock count is initialized to 0 (no active and no waiting lockers).
 *
 * When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for
 * the case of an uncontended lock. Readers increment by 1 and see a positive
 * value when uncontended, negative if there are writers (and maybe) readers
 * waiting (in which case it goes to sleep).
 */

#ifndef _ASM_IA64_RWSEM_H
#define _ASM_IA64_RWSEM_H

#ifndef _LINUX_RWSEM_H
#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
#endif

#include <asm/intrinsics.h>

#define RWSEM_UNLOCKED_VALUE		__IA64_UL_CONST(0x0000000000000000)
#define RWSEM_ACTIVE_BIAS		(1L)
#define RWSEM_ACTIVE_MASK		(0xffffffffL)
#define RWSEM_WAITING_BIAS		(-0x100000000L)
#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)

/*
 * lock for reading
 */
static inline void
__down_read (struct rw_semaphore *sem)
{
	long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1);

	if (result < 0)
		rwsem_down_read_failed(sem);
}

/*
 * lock for writing
 */
static inline long
___down_write (struct rw_semaphore *sem)
{
	long old, new;

	do {
		old = atomic_long_read(&sem->count);
		new = old + RWSEM_ACTIVE_WRITE_BIAS;
	} while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old);

	return old;
}

static inline void
__down_write (struct rw_semaphore *sem)
{
	if (___down_write(sem))
		rwsem_down_write_failed(sem);
}

static inline int
__down_write_killable (struct rw_semaphore *sem)
{
	if (___down_write(sem))
		if (IS_ERR(rwsem_down_write_failed_killable(sem)))
			return -EINTR;

	return 0;
}

/*
 * unlock after reading
 */
static inline void
__up_read (struct rw_semaphore *sem)
{
	long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1);

	if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
		rwsem_wake(sem);
}

/*
 * unlock after writing
 */
static inline void
__up_write (struct rw_semaphore *sem)
{
	long old, new;

	do {
		old = atomic_long_read(&sem->count);
		new = old - RWSEM_ACTIVE_WRITE_BIAS;
	} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);

	if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
		rwsem_wake(sem);
}

/*
 * trylock for reading -- returns 1 if successful, 0 if contention
 */
static inline int
__down_read_trylock (struct rw_semaphore *sem)
{
	long tmp;
	while ((tmp = atomic_long_read(&sem->count)) >= 0) {
		if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) {
			return 1;
		}
	}
	return 0;
}

/*
 * trylock for writing -- returns 1 if successful, 0 if contention
 */
static inline int
__down_write_trylock (struct rw_semaphore *sem)
{
	long tmp = atomic_long_cmpxchg_acquire(&sem->count,
			RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS);
	return tmp == RWSEM_UNLOCKED_VALUE;
}

/*
 * downgrade write lock to read lock
 */
static inline void
__downgrade_write (struct rw_semaphore *sem)
{
	long old, new;

	do {
		old = atomic_long_read(&sem->count);
		new = old - RWSEM_WAITING_BIAS;
	} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);

	if (old < 0)
		rwsem_downgrade_wake(sem);
}

#endif /* _ASM_IA64_RWSEM_H */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
1da177e4	2	/*
7f30491c	3	* R/W semaphores for ia64
1da177e4 LT	4	*
	5	* Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com>
	6	* Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com>
93e205a7	7	* Copyright (C) 2005 Christoph Lameter <cl@linux.com>
1da177e4 LT	8	*
	9	* Based on asm-i386/rwsem.h and other architecture implementation.
	10	*
	11	* The MSW of the count is the negated number of active writers and
	12	* waiting lockers, and the LSW is the total number of active locks.
	13	*
	14	* The lock count is initialized to 0 (no active and no waiting lockers).
	15	*
16592d26 CL	16	* When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for
	17	* the case of an uncontended lock. Readers increment by 1 and see a positive
	18	* value when uncontended, negative if there are writers (and maybe) readers
1da177e4 LT	19	* waiting (in which case it goes to sleep).
	20	*/
	21
	22	#ifndef _ASM_IA64_RWSEM_H
	23	#define _ASM_IA64_RWSEM_H
	24
bd807f9c RD	25	#ifndef _LINUX_RWSEM_H
	26	#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
	27	#endif
	28
1da177e4 LT	29	#include <asm/intrinsics.h>
1da177e4 LT	30
16592d26	31	#define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000)
b680f097 TL	32	#define RWSEM_ACTIVE_BIAS (1L)
	33	#define RWSEM_ACTIVE_MASK (0xffffffffL)
	34	#define RWSEM_WAITING_BIAS (-0x100000000L)
1da177e4 LT	35	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
	36	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
	37
1da177e4 LT	38	/*
	39	* lock for reading
	40	*/
	41	static inline void
	42	__down_read (struct rw_semaphore *sem)
	43	{
8ee62b18	44	long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1);
1da177e4 LT	45
	46	if (result < 0)
	47	rwsem_down_read_failed(sem);
	48	}
	49
	50	/*
	51	* lock for writing
	52	*/
a02137eb MH	53	static inline long
a02137eb MH	54	___down_write (struct rw_semaphore *sem)
1da177e4	55	{
16592d26	56	long old, new;
1da177e4 LT	57
1da177e4 LT	58	do {
8ee62b18	59	old = atomic_long_read(&sem->count);
1da177e4	60	new = old + RWSEM_ACTIVE_WRITE_BIAS;
8ee62b18	61	} while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old);
1da177e4	62
a02137eb MH	63	return old;
	64	}
	65
	66	static inline void
	67	__down_write (struct rw_semaphore *sem)
	68	{
	69	if (___down_write(sem))
1da177e4 LT	70	rwsem_down_write_failed(sem);
	71	}
	72
a02137eb MH	73	static inline int
	74	__down_write_killable (struct rw_semaphore *sem)
	75	{
	76	if (___down_write(sem))
	77	if (IS_ERR(rwsem_down_write_failed_killable(sem)))
	78	return -EINTR;
	79
	80	return 0;
	81	}
	82
1da177e4 LT	83	/*
	84	* unlock after reading
	85	*/
	86	static inline void
	87	__up_read (struct rw_semaphore *sem)
	88	{
8ee62b18	89	long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1);
1da177e4 LT	90
	91	if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
	92	rwsem_wake(sem);
	93	}
	94
	95	/*
	96	* unlock after writing
	97	*/
	98	static inline void
	99	__up_write (struct rw_semaphore *sem)
	100	{
16592d26	101	long old, new;
1da177e4 LT	102
1da177e4 LT	103	do {
8ee62b18	104	old = atomic_long_read(&sem->count);
1da177e4	105	new = old - RWSEM_ACTIVE_WRITE_BIAS;
8ee62b18	106	} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
1da177e4 LT	107
	108	if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
	109	rwsem_wake(sem);
	110	}
	111
	112	/*
	113	* trylock for reading -- returns 1 if successful, 0 if contention
	114	*/
	115	static inline int
	116	__down_read_trylock (struct rw_semaphore *sem)
	117	{
16592d26	118	long tmp;
8ee62b18 JL	119	while ((tmp = atomic_long_read(&sem->count)) >= 0) {
8ee62b18 JL	120	if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) {
1da177e4 LT	121	return 1;
	122	}
	123	}
	124	return 0;
	125	}
	126
	127	/*
	128	* trylock for writing -- returns 1 if successful, 0 if contention
	129	*/
	130	static inline int
	131	__down_write_trylock (struct rw_semaphore *sem)
	132	{
8ee62b18 JL	133	long tmp = atomic_long_cmpxchg_acquire(&sem->count,
8ee62b18 JL	134	RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS);
1da177e4 LT	135	return tmp == RWSEM_UNLOCKED_VALUE;
	136	}
	137
	138	/*
	139	* downgrade write lock to read lock
	140	*/
	141	static inline void
	142	__downgrade_write (struct rw_semaphore *sem)
	143	{
16592d26	144	long old, new;
1da177e4 LT	145
1da177e4 LT	146	do {
8ee62b18	147	old = atomic_long_read(&sem->count);
1da177e4	148	new = old - RWSEM_WAITING_BIAS;
8ee62b18	149	} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
1da177e4 LT	150
	151	if (old < 0)
	152	rwsem_downgrade_wake(sem);
	153	}
	154
1da177e4	155	#endif /* _ASM_IA64_RWSEM_H */