[GitHub/mt8127/android_kernel_alcatel_ttab.git] / include / asm-x86 / rwsem.h

/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for i486+
 *
 * Written by David Howells (dhowells@redhat.com).
 *
 * Derived from asm-x86/semaphore.h
 *
 *
 * 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 0xffff0001 for the case of an
 * uncontended lock. This can be determined because XADD returns the old value.
 * 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).
 *
 * The value of WAITING_BIAS supports up to 32766 waiting processes. This can
 * be extended to 65534 by manually checking the whole MSW rather than relying
 * on the S flag.
 *
 * The value of ACTIVE_BIAS supports up to 65535 active processes.
 *
 * This should be totally fair - if anything is waiting, a process that wants a
 * lock will go to the back of the queue. When the currently active lock is
 * released, if there's a writer at the front of the queue, then that and only
 * that will be woken up; if there's a bunch of consequtive readers at the
 * front, then they'll all be woken up, but no other readers will be.
 */

#ifndef ASM_X86__RWSEM_H
#define ASM_X86__RWSEM_H

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

#ifdef __KERNEL__

#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/lockdep.h>

struct rwsem_waiter;

extern asmregparm struct rw_semaphore *
 rwsem_down_read_failed(struct rw_semaphore *sem);
extern asmregparm struct rw_semaphore *
 rwsem_down_write_failed(struct rw_semaphore *sem);
extern asmregparm struct rw_semaphore *
 rwsem_wake(struct rw_semaphore *);
extern asmregparm struct rw_semaphore *
 rwsem_downgrade_wake(struct rw_semaphore *sem);

/*
 * the semaphore definition
 */

#define RWSEM_UNLOCKED_VALUE		0x00000000
#define RWSEM_ACTIVE_BIAS		0x00000001
#define RWSEM_ACTIVE_MASK		0x0000ffff
#define RWSEM_WAITING_BIAS		(-0x00010000)
#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)

struct rw_semaphore {
	signed long		count;
	spinlock_t		wait_lock;
	struct list_head	wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map dep_map;
#endif
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
#else
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif


#define __RWSEM_INITIALIZER(name)				\
{								\
	RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
	LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) \
}

#define DECLARE_RWSEM(name)					\
	struct rw_semaphore name = __RWSEM_INITIALIZER(name)

extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
			 struct lock_class_key *key);

#define init_rwsem(sem)						\
do {								\
	static struct lock_class_key __key;			\
								\
	__init_rwsem((sem), #sem, &__key);			\
} while (0)

/*
 * lock for reading
 */
static inline void __down_read(struct rw_semaphore *sem)
{
	asm volatile("# beginning down_read\n\t"
		     LOCK_PREFIX "  incl      (%%eax)\n\t"
		     /* adds 0x00000001, returns the old value */
		     "  jns        1f\n"
		     "  call call_rwsem_down_read_failed\n"
		     "1:\n\t"
		     "# ending down_read\n\t"
		     : "+m" (sem->count)
		     : "a" (sem)
		     : "memory", "cc");
}

/*
 * trylock for reading -- returns 1 if successful, 0 if contention
 */
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
	__s32 result, tmp;
	asm volatile("# beginning __down_read_trylock\n\t"
		     "  movl      %0,%1\n\t"
		     "1:\n\t"
		     "  movl	     %1,%2\n\t"
		     "  addl      %3,%2\n\t"
		     "  jle	     2f\n\t"
		     LOCK_PREFIX "  cmpxchgl  %2,%0\n\t"
		     "  jnz	     1b\n\t"
		     "2:\n\t"
		     "# ending __down_read_trylock\n\t"
		     : "+m" (sem->count), "=&a" (result), "=&r" (tmp)
		     : "i" (RWSEM_ACTIVE_READ_BIAS)
		     : "memory", "cc");
	return result >= 0 ? 1 : 0;
}

/*
 * lock for writing
 */
static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
	int tmp;

	tmp = RWSEM_ACTIVE_WRITE_BIAS;
	asm volatile("# beginning down_write\n\t"
		     LOCK_PREFIX "  xadd      %%edx,(%%eax)\n\t"
		     /* subtract 0x0000ffff, returns the old value */
		     "  testl     %%edx,%%edx\n\t"
		     /* was the count 0 before? */
		     "  jz        1f\n"
		     "  call call_rwsem_down_write_failed\n"
		     "1:\n"
		     "# ending down_write"
		     : "+m" (sem->count), "=d" (tmp)
		     : "a" (sem), "1" (tmp)
		     : "memory", "cc");
}

static inline void __down_write(struct rw_semaphore *sem)
{
	__down_write_nested(sem, 0);
}

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

/*
 * unlock after reading
 */
static inline void __up_read(struct rw_semaphore *sem)
{
	__s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
	asm volatile("# beginning __up_read\n\t"
		     LOCK_PREFIX "  xadd      %%edx,(%%eax)\n\t"
		     /* subtracts 1, returns the old value */
		     "  jns        1f\n\t"
		     "  call call_rwsem_wake\n"
		     "1:\n"
		     "# ending __up_read\n"
		     : "+m" (sem->count), "=d" (tmp)
		     : "a" (sem), "1" (tmp)
		     : "memory", "cc");
}

/*
 * unlock after writing
 */
static inline void __up_write(struct rw_semaphore *sem)
{
	asm volatile("# beginning __up_write\n\t"
		     "  movl      %2,%%edx\n\t"
		     LOCK_PREFIX "  xaddl     %%edx,(%%eax)\n\t"
		     /* tries to transition
			0xffff0001 -> 0x00000000 */
		     "  jz       1f\n"
		     "  call call_rwsem_wake\n"
		     "1:\n\t"
		     "# ending __up_write\n"
		     : "+m" (sem->count)
		     : "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS)
		     : "memory", "cc", "edx");
}

/*
 * downgrade write lock to read lock
 */
static inline void __downgrade_write(struct rw_semaphore *sem)
{
	asm volatile("# beginning __downgrade_write\n\t"
		     LOCK_PREFIX "  addl      %2,(%%eax)\n\t"
		     /* transitions 0xZZZZ0001 -> 0xYYYY0001 */
		     "  jns       1f\n\t"
		     "  call call_rwsem_downgrade_wake\n"
		     "1:\n\t"
		     "# ending __downgrade_write\n"
		     : "+m" (sem->count)
		     : "a" (sem), "i" (-RWSEM_WAITING_BIAS)
		     : "memory", "cc");
}

/*
 * implement atomic add functionality
 */
static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
{
	asm volatile(LOCK_PREFIX "addl %1,%0"
		     : "+m" (sem->count)
		     : "ir" (delta));
}

/*
 * implement exchange and add functionality
 */
static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
{
	int tmp = delta;

	asm volatile(LOCK_PREFIX "xadd %0,%1"
		     : "+r" (tmp), "+m" (sem->count)
		     : : "memory");

	return tmp + delta;
}

static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
	return (sem->count != 0);
}

#endif /* __KERNEL__ */
#endif /* ASM_X86__RWSEM_H */
Commit	Line	Data
1da177e4 LT	1	/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for i486+
	2	*
	3	* Written by David Howells (dhowells@redhat.com).
	4	*
99122a3f	5	* Derived from asm-x86/semaphore.h
1da177e4 LT	6	*
	7	*
	8	* The MSW of the count is the negated number of active writers and waiting
	9	* lockers, and the LSW is the total number of active locks
	10	*
	11	* The lock count is initialized to 0 (no active and no waiting lockers).
	12	*
	13	* When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
	14	* uncontended lock. This can be determined because XADD returns the old value.
	15	* Readers increment by 1 and see a positive value when uncontended, negative
	16	* if there are writers (and maybe) readers waiting (in which case it goes to
	17	* sleep).
	18	*
	19	* The value of WAITING_BIAS supports up to 32766 waiting processes. This can
	20	* be extended to 65534 by manually checking the whole MSW rather than relying
	21	* on the S flag.
	22	*
	23	* The value of ACTIVE_BIAS supports up to 65535 active processes.
	24	*
	25	* This should be totally fair - if anything is waiting, a process that wants a
	26	* lock will go to the back of the queue. When the currently active lock is
	27	* released, if there's a writer at the front of the queue, then that and only
	28	* that will be woken up; if there's a bunch of consequtive readers at the
	29	* front, then they'll all be woken up, but no other readers will be.
	30	*/
	31
77ef50a5 VN	32	#ifndef ASM_X86__RWSEM_H
77ef50a5 VN	33	#define ASM_X86__RWSEM_H
1da177e4 LT	34
	35	#ifndef _LINUX_RWSEM_H
	36	#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
	37	#endif
	38
	39	#ifdef __KERNEL__
	40
	41	#include <linux/list.h>
	42	#include <linux/spinlock.h>
4ea2176d	43	#include <linux/lockdep.h>
1da177e4 LT	44
	45	struct rwsem_waiter;
	46
d50efc6c IM	47	extern asmregparm struct rw_semaphore *
	48	rwsem_down_read_failed(struct rw_semaphore *sem);
	49	extern asmregparm struct rw_semaphore *
	50	rwsem_down_write_failed(struct rw_semaphore *sem);
	51	extern asmregparm struct rw_semaphore *
	52	rwsem_wake(struct rw_semaphore *);
	53	extern asmregparm struct rw_semaphore *
	54	rwsem_downgrade_wake(struct rw_semaphore *sem);
1da177e4 LT	55
	56	/*
	57	* the semaphore definition
	58	*/
6e5609a9	59
1da177e4 LT	60	#define RWSEM_UNLOCKED_VALUE 0x00000000
	61	#define RWSEM_ACTIVE_BIAS 0x00000001
	62	#define RWSEM_ACTIVE_MASK 0x0000ffff
	63	#define RWSEM_WAITING_BIAS (-0x00010000)
	64	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
	65	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
6e5609a9 JP	66
	67	struct rw_semaphore {
	68	signed long count;
1da177e4 LT	69	spinlock_t wait_lock;
1da177e4 LT	70	struct list_head wait_list;
4ea2176d IM	71	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	72	struct lockdep_map dep_map;
	73	#endif
1da177e4 LT	74	};
1da177e4 LT	75
4ea2176d IM	76	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	77	# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
	78	#else
	79	# define __RWSEM_DEP_MAP_INIT(lockname)
	80	#endif
	81
	82
6e5609a9 JP	83	#define __RWSEM_INITIALIZER(name) \
	84	{ \
	85	RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
	86	LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) \
	87	}
1da177e4	88
6e5609a9	89	#define DECLARE_RWSEM(name) \
1da177e4 LT	90	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
1da177e4 LT	91
4ea2176d IM	92	extern void __init_rwsem(struct rw_semaphore sem, const char name,
	93	struct lock_class_key *key);
	94
	95	#define init_rwsem(sem) \
	96	do { \
	97	static struct lock_class_key __key; \
	98	\
	99	__init_rwsem((sem), #sem, &__key); \
	100	} while (0)
1da177e4 LT	101
	102	/*
	103	* lock for reading
	104	*/
	105	static inline void __down_read(struct rw_semaphore *sem)
	106	{
6e5609a9 JP	107	asm volatile("# beginning down_read\n\t"
	108	LOCK_PREFIX " incl (%%eax)\n\t"
	109	/* adds 0x00000001, returns the old value */
	110	" jns 1f\n"
	111	" call call_rwsem_down_read_failed\n"
	112	"1:\n\t"
	113	"# ending down_read\n\t"
	114	: "+m" (sem->count)
	115	: "a" (sem)
	116	: "memory", "cc");
1da177e4 LT	117	}
	118
	119	/*
	120	* trylock for reading -- returns 1 if successful, 0 if contention
	121	*/
	122	static inline int __down_read_trylock(struct rw_semaphore *sem)
	123	{
	124	__s32 result, tmp;
6e5609a9 JP	125	asm volatile("# beginning __down_read_trylock\n\t"
	126	" movl %0,%1\n\t"
	127	"1:\n\t"
	128	" movl %1,%2\n\t"
	129	" addl %3,%2\n\t"
	130	" jle 2f\n\t"
	131	LOCK_PREFIX " cmpxchgl %2,%0\n\t"
	132	" jnz 1b\n\t"
	133	"2:\n\t"
	134	"# ending __down_read_trylock\n\t"
	135	: "+m" (sem->count), "=&a" (result), "=&r" (tmp)
	136	: "i" (RWSEM_ACTIVE_READ_BIAS)
	137	: "memory", "cc");
	138	return result >= 0 ? 1 : 0;
1da177e4 LT	139	}
	140
	141	/*
	142	* lock for writing
	143	*/
4ea2176d	144	static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
1da177e4 LT	145	{
	146	int tmp;
	147
	148	tmp = RWSEM_ACTIVE_WRITE_BIAS;
6e5609a9 JP	149	asm volatile("# beginning down_write\n\t"
	150	LOCK_PREFIX " xadd %%edx,(%%eax)\n\t"
	151	/* subtract 0x0000ffff, returns the old value */
	152	" testl %%edx,%%edx\n\t"
	153	/* was the count 0 before? */
	154	" jz 1f\n"
	155	" call call_rwsem_down_write_failed\n"
	156	"1:\n"
	157	"# ending down_write"
	158	: "+m" (sem->count), "=d" (tmp)
	159	: "a" (sem), "1" (tmp)
	160	: "memory", "cc");
1da177e4 LT	161	}
1da177e4 LT	162
4ea2176d IM	163	static inline void __down_write(struct rw_semaphore *sem)
	164	{
	165	__down_write_nested(sem, 0);
	166	}
	167
1da177e4 LT	168	/*
	169	* trylock for writing -- returns 1 if successful, 0 if contention
	170	*/
	171	static inline int __down_write_trylock(struct rw_semaphore *sem)
	172	{
	173	signed long ret = cmpxchg(&sem->count,
6e5609a9	174	RWSEM_UNLOCKED_VALUE,
1da177e4 LT	175	RWSEM_ACTIVE_WRITE_BIAS);
	176	if (ret == RWSEM_UNLOCKED_VALUE)
	177	return 1;
	178	return 0;
	179	}
	180
	181	/*
	182	* unlock after reading
	183	*/
	184	static inline void __up_read(struct rw_semaphore *sem)
	185	{
	186	__s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
6e5609a9 JP	187	asm volatile("# beginning __up_read\n\t"
	188	LOCK_PREFIX " xadd %%edx,(%%eax)\n\t"
	189	/* subtracts 1, returns the old value */
	190	" jns 1f\n\t"
	191	" call call_rwsem_wake\n"
	192	"1:\n"
	193	"# ending __up_read\n"
	194	: "+m" (sem->count), "=d" (tmp)
	195	: "a" (sem), "1" (tmp)
	196	: "memory", "cc");
1da177e4 LT	197	}
	198
	199	/*
	200	* unlock after writing
	201	*/
	202	static inline void __up_write(struct rw_semaphore *sem)
	203	{
6e5609a9 JP	204	asm volatile("# beginning __up_write\n\t"
	205	" movl %2,%%edx\n\t"
	206	LOCK_PREFIX " xaddl %%edx,(%%eax)\n\t"
	207	/* tries to transition
	208	0xffff0001 -> 0x00000000 */
	209	" jz 1f\n"
	210	" call call_rwsem_wake\n"
	211	"1:\n\t"
	212	"# ending __up_write\n"
	213	: "+m" (sem->count)
	214	: "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS)
	215	: "memory", "cc", "edx");
1da177e4 LT	216	}
	217
	218	/*
	219	* downgrade write lock to read lock
	220	*/
	221	static inline void __downgrade_write(struct rw_semaphore *sem)
	222	{
6e5609a9 JP	223	asm volatile("# beginning __downgrade_write\n\t"
	224	LOCK_PREFIX " addl %2,(%%eax)\n\t"
	225	/* transitions 0xZZZZ0001 -> 0xYYYY0001 */
	226	" jns 1f\n\t"
	227	" call call_rwsem_downgrade_wake\n"
	228	"1:\n\t"
	229	"# ending __downgrade_write\n"
	230	: "+m" (sem->count)
	231	: "a" (sem), "i" (-RWSEM_WAITING_BIAS)
	232	: "memory", "cc");
1da177e4 LT	233	}
	234
	235	/*
	236	* implement atomic add functionality
	237	*/
	238	static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
	239	{
6e5609a9 JP	240	asm volatile(LOCK_PREFIX "addl %1,%0"
	241	: "+m" (sem->count)
	242	: "ir" (delta));
1da177e4 LT	243	}
	244
	245	/*
	246	* implement exchange and add functionality
	247	*/
	248	static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
	249	{
	250	int tmp = delta;
	251
6e5609a9 JP	252	asm volatile(LOCK_PREFIX "xadd %0,%1"
	253	: "+r" (tmp), "+m" (sem->count)
	254	: : "memory");
1da177e4	255
6e5609a9	256	return tmp + delta;
1da177e4 LT	257	}
1da177e4 LT	258
eb92f4ef RVR	259	static inline int rwsem_is_locked(struct rw_semaphore *sem)
	260	{
	261	return (sem->count != 0);
	262	}
	263
1da177e4	264	#endif /* __KERNEL__ */
77ef50a5	265	#endif /* ASM_X86__RWSEM_H */