[mirror_spl.git] / include / sys / rwlock.h

/*****************************************************************************\
 *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
 *  Copyright (C) 2007 The Regents of the University of California.
 *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
 *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
 *  UCRL-CODE-235197
 *
 *  This file is part of the SPL, Solaris Porting Layer.
 *  For details, see <http://zfsonlinux.org/>.
 *
 *  The SPL 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.
 *
 *  The SPL 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.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
\*****************************************************************************/

#ifndef _SPL_RWLOCK_H
#define _SPL_RWLOCK_H

#include <sys/types.h>
#include <linux/rwsem.h>
#include <linux/rwsem_compat.h>

typedef enum {
        RW_DRIVER  = 2,
        RW_DEFAULT = 4
} krw_type_t;

typedef enum {
        RW_NONE   = 0,
        RW_WRITER = 1,
        RW_READER = 2
} krw_t;

/*
 * If CONFIG_RWSEM_SPIN_ON_OWNER is defined, rw_semaphore will have an owner
 * field, so we don't need our own.
 */
typedef struct {
        struct rw_semaphore rw_rwlock;
#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
        kthread_t *rw_owner;
#endif
} krwlock_t;

#define SEM(rwp)	(&(rwp)->rw_rwlock)

static inline void
spl_rw_set_owner(krwlock_t *rwp)
{
/*
 * If CONFIG_RWSEM_SPIN_ON_OWNER is defined, down_write, up_write,
 * downgrade_write and __init_rwsem will set/clear owner for us.
 */
#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
	rwp->rw_owner = current;
#endif
}

static inline void
spl_rw_clear_owner(krwlock_t *rwp)
{
#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
	rwp->rw_owner = NULL;
#endif
}

static inline kthread_t *
rw_owner(krwlock_t *rwp)
{
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	return SEM(rwp)->owner;
#else
	return rwp->rw_owner;
#endif
}

static inline int
RW_READ_HELD(krwlock_t *rwp)
{
	return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL);
}

static inline int
RW_WRITE_HELD(krwlock_t *rwp)
{
	return (rw_owner(rwp) == current);
}

static inline int
RW_LOCK_HELD(krwlock_t *rwp)
{
	return spl_rwsem_is_locked(SEM(rwp));
}

/*
 * The following functions must be a #define and not static inline.
 * This ensures that the native linux semaphore functions (down/up)
 * will be correctly located in the users code which is important
 * for the built in kernel lock analysis tools
 */
#define rw_init(rwp, name, type, arg)                                   \
({                                                                      \
        static struct lock_class_key __key;                             \
                                                                        \
        __init_rwsem(SEM(rwp), #rwp, &__key);                           \
        spl_rw_clear_owner(rwp);                                        \
})

#define rw_destroy(rwp)                                                 \
({                                                                      \
        VERIFY(!RW_LOCK_HELD(rwp));                                     \
})

#define rw_tryenter(rwp, rw)                                            \
({                                                                      \
        int _rc_ = 0;                                                   \
                                                                        \
        switch (rw) {                                                   \
        case RW_READER:                                                 \
                _rc_ = down_read_trylock(SEM(rwp));                     \
                break;                                                  \
        case RW_WRITER:                                                 \
                if ((_rc_ = down_write_trylock(SEM(rwp))))              \
                        spl_rw_set_owner(rwp);                          \
                break;                                                  \
        default:                                                        \
                VERIFY(0);                                              \
        }                                                               \
        _rc_;                                                           \
})

#define rw_enter(rwp, rw)                                               \
({                                                                      \
        switch (rw) {                                                   \
        case RW_READER:                                                 \
                down_read(SEM(rwp));                                    \
                break;                                                  \
        case RW_WRITER:                                                 \
                down_write(SEM(rwp));                                   \
                spl_rw_set_owner(rwp);                                  \
                break;                                                  \
        default:                                                        \
                VERIFY(0);                                              \
        }                                                               \
})

#define rw_exit(rwp)                                                    \
({                                                                      \
        if (RW_WRITE_HELD(rwp)) {                                       \
                spl_rw_clear_owner(rwp);                                \
                up_write(SEM(rwp));                                     \
        } else {                                                        \
                ASSERT(RW_READ_HELD(rwp));                              \
                up_read(SEM(rwp));                                      \
        }                                                               \
})

#define rw_downgrade(rwp)                                               \
({                                                                      \
        spl_rw_clear_owner(rwp);                                        \
        downgrade_write(SEM(rwp));                                      \
})

#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
#error spinlock rwsem should not have spin on owner
#endif
/*
 * For the generic implementations of rw-semaphores the following is
 * true.  If your semaphore implementation internally represents the
 * semaphore state differently then special case handling is required.
 * - if activity/count is 0 then there are no active readers or writers
 * - if activity/count is +ve then that is the number of active readers
 * - if activity/count is -1 then there is one active writer
 */

extern void __up_read_locked(struct rw_semaphore *);
extern int __down_write_trylock_locked(struct rw_semaphore *);

#define rw_tryupgrade(rwp)                                              \
({                                                                      \
        unsigned long _flags_;                                          \
        int _rc_ = 0;                                                   \
                                                                        \
        spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, _flags_);           \
        if ((list_empty(&SEM(rwp)->wait_list)) &&                       \
            (SEM(rwp)->activity == 1)) {                                \
                __up_read_locked(SEM(rwp));                             \
                VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp)));   \
                (rwp)->rw_owner = current;                              \
        }                                                               \
        spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_);      \
        _rc_;                                                           \
})
#else
/*
 * rw_tryupgrade() can be implemented correctly but for each supported
 * arch we will need a custom implementation.  For the x86 implementation
 * it looks like a custom cmpxchg() to atomically check and promote the
 * rwsem would be safe.  For now that's not worth the trouble so in this
 * case rw_tryupgrade() has just been disabled.
 */
#define rw_tryupgrade(rwp)      ({ 0; })
#endif

int spl_rw_init(void);
void spl_rw_fini(void);

#endif /* _SPL_RWLOCK_H */
Commit	Line	Data
716154c5 BB	1	/*****************************************************************************\
	2	* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
	3	* Copyright (C) 2007 The Regents of the University of California.
	4	* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
	5	* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
715f6251	6	* UCRL-CODE-235197
715f6251	7	*
716154c5	8	* This file is part of the SPL, Solaris Porting Layer.
3d6af2dd	9	* For details, see <http://zfsonlinux.org/>.
716154c5 BB	10	*
	11	* The SPL is free software; you can redistribute it and/or modify it
	12	* under the terms of the GNU General Public License as published by the
	13	* Free Software Foundation; either version 2 of the License, or (at your
	14	* option) any later version.
715f6251	15	*
716154c5	16	* The SPL is distributed in the hope that it will be useful, but WITHOUT
715f6251	17	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	18	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	19	* for more details.
	20	*
	21	* You should have received a copy of the GNU General Public License along
716154c5 BB	22	* with the SPL. If not, see <http://www.gnu.org/licenses/>.
716154c5 BB	23	\*****************************************************************************/
715f6251	24
09b414e8	25	#ifndef _SPL_RWLOCK_H
e8b31e84	26	#define _SPL_RWLOCK_H
f1ca4da6	27
f4b37741	28	#include <sys/types.h>
d28db80f	29	#include <linux/rwsem.h>
46aa7b39	30	#include <linux/rwsem_compat.h>
f1ca4da6	31
f1ca4da6	32	typedef enum {
e811949a BB	33	RW_DRIVER = 2,
e811949a BB	34	RW_DEFAULT = 4
f1ca4da6	35	} krw_type_t;
	36
	37	typedef enum {
d28db80f	38	RW_NONE = 0,
e811949a BB	39	RW_WRITER = 1,
e811949a BB	40	RW_READER = 2
f1ca4da6	41	} krw_t;
f1ca4da6	42
a00b3eb5 CC	43	/*
	44	* If CONFIG_RWSEM_SPIN_ON_OWNER is defined, rw_semaphore will have an owner
	45	* field, so we don't need our own.
	46	*/
d28db80f BB	47	typedef struct {
d28db80f BB	48	struct rw_semaphore rw_rwlock;
a00b3eb5	49	#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
d28db80f	50	kthread_t *rw_owner;
a00b3eb5	51	#endif
d28db80f	52	} krwlock_t;
f1ca4da6	53
a00b3eb5	54	#define SEM(rwp) (&(rwp)->rw_rwlock)
d28db80f	55
d28db80f BB	56	static inline void
	57	spl_rw_set_owner(krwlock_t *rwp)
	58	{
a00b3eb5 CC	59	/*
	60	* If CONFIG_RWSEM_SPIN_ON_OWNER is defined, down_write, up_write,
	61	* downgrade_write and __init_rwsem will set/clear owner for us.
	62	*/
	63	#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
4f8e643a	64	rwp->rw_owner = current;
a00b3eb5	65	#endif
d28db80f BB	66	}
	67
	68	static inline void
	69	spl_rw_clear_owner(krwlock_t *rwp)
	70	{
a00b3eb5	71	#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
4f8e643a	72	rwp->rw_owner = NULL;
a00b3eb5	73	#endif
d28db80f BB	74	}
	75
	76	static inline kthread_t *
	77	rw_owner(krwlock_t *rwp)
	78	{
a00b3eb5 CC	79	#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	80	return SEM(rwp)->owner;
	81	#else
4f8e643a	82	return rwp->rw_owner;
a00b3eb5	83	#endif
d28db80f BB	84	}
	85
	86	static inline int
	87	RW_READ_HELD(krwlock_t *rwp)
	88	{
86c16c59	89	return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL);
d28db80f BB	90	}
	91
	92	static inline int
	93	RW_WRITE_HELD(krwlock_t *rwp)
	94	{
4f8e643a	95	return (rw_owner(rwp) == current);
d28db80f BB	96	}
	97
	98	static inline int
	99	RW_LOCK_HELD(krwlock_t *rwp)
	100	{
46aa7b39	101	return spl_rwsem_is_locked(SEM(rwp));
d28db80f BB	102	}
	103
	104	/*
	105	* The following functions must be a #define and not static inline.
	106	* This ensures that the native linux semaphore functions (down/up)
	107	* will be correctly located in the users code which is important
	108	* for the built in kernel lock analysis tools
	109	*/
	110	#define rw_init(rwp, name, type, arg) \
	111	({ \
0e77fc11 BB	112	static struct lock_class_key __key; \
	113	\
	114	__init_rwsem(SEM(rwp), #rwp, &__key); \
d28db80f	115	spl_rw_clear_owner(rwp); \
e811949a	116	})
f1ca4da6	117
d28db80f BB	118	#define rw_destroy(rwp) \
	119	({ \
	120	VERIFY(!RW_LOCK_HELD(rwp)); \
e811949a	121	})
ed61a7d0	122
d28db80f BB	123	#define rw_tryenter(rwp, rw) \
	124	({ \
	125	int _rc_ = 0; \
	126	\
	127	switch (rw) { \
	128	case RW_READER: \
	129	_rc_ = down_read_trylock(SEM(rwp)); \
	130	break; \
	131	case RW_WRITER: \
	132	if ((_rc_ = down_write_trylock(SEM(rwp)))) \
	133	spl_rw_set_owner(rwp); \
	134	break; \
	135	default: \
55abb092	136	VERIFY(0); \
d28db80f BB	137	} \
d28db80f BB	138	_rc_; \
e8b31e84	139	})
e8b31e84	140
d28db80f BB	141	#define rw_enter(rwp, rw) \
	142	({ \
	143	switch (rw) { \
	144	case RW_READER: \
	145	down_read(SEM(rwp)); \
	146	break; \
	147	case RW_WRITER: \
	148	down_write(SEM(rwp)); \
	149	spl_rw_set_owner(rwp); \
	150	break; \
	151	default: \
55abb092	152	VERIFY(0); \
d28db80f	153	} \
e811949a	154	})
f1ca4da6	155
d28db80f BB	156	#define rw_exit(rwp) \
	157	({ \
	158	if (RW_WRITE_HELD(rwp)) { \
	159	spl_rw_clear_owner(rwp); \
	160	up_write(SEM(rwp)); \
	161	} else { \
	162	ASSERT(RW_READ_HELD(rwp)); \
	163	up_read(SEM(rwp)); \
	164	} \
	165	})
	166
	167	#define rw_downgrade(rwp) \
	168	({ \
	169	spl_rw_clear_owner(rwp); \
	170	downgrade_write(SEM(rwp)); \
	171	})
	172
ef6c1368	173	#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
a00b3eb5 CC	174	#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
	175	#error spinlock rwsem should not have spin on owner
	176	#endif
32f5faff BB	177	/*
	178	* For the generic implementations of rw-semaphores the following is
	179	* true. If your semaphore implementation internally represents the
	180	* semaphore state differently then special case handling is required.
	181	* - if activity/count is 0 then there are no active readers or writers
	182	* - if activity/count is +ve then that is the number of active readers
	183	* - if activity/count is -1 then there is one active writer
	184	*/
	185
	186	extern void __up_read_locked(struct rw_semaphore *);
	187	extern int __down_write_trylock_locked(struct rw_semaphore *);
	188
d28db80f BB	189	#define rw_tryupgrade(rwp) \
	190	({ \
	191	unsigned long _flags_; \
	192	int _rc_ = 0; \
	193	\
588d9004	194	spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \
32f5faff BB	195	if ((list_empty(&SEM(rwp)->wait_list)) && \
	196	(SEM(rwp)->activity == 1)) { \
	197	__up_read_locked(SEM(rwp)); \
	198	VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp))); \
d28db80f BB	199	(rwp)->rw_owner = current; \
d28db80f BB	200	} \
588d9004	201	spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \
d28db80f BB	202	_rc_; \
d28db80f BB	203	})
ef6c1368 BB	204	#else
ef6c1368 BB	205	/*
32f5faff BB	206	* rw_tryupgrade() can be implemented correctly but for each supported
	207	* arch we will need a custom implementation. For the x86 implementation
	208	* it looks like a custom cmpxchg() to atomically check and promote the
	209	* rwsem would be safe. For now that's not worth the trouble so in this
	210	* case rw_tryupgrade() has just been disabled.
ef6c1368 BB	211	*/
	212	#define rw_tryupgrade(rwp) ({ 0; })
	213	#endif
d28db80f BB	214
	215	int spl_rw_init(void);
	216	void spl_rw_fini(void);
	217
e8b31e84	218	#endif /* _SPL_RWLOCK_H */