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/*
* This file is part of the SPL: Solaris Porting Layer.
*
* Copyright (c) 2009 Lawrence Livermore National Security, LLC.
* Produced at Lawrence Livermore National Laboratory
* Written by:
* Brian Behlendorf <behlendorf1@llnl.gov>,
* Herb Wartens <wartens2@llnl.gov>,
* Jim Garlick <garlick@llnl.gov>
* UCRL-CODE-235197
*
* This 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 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 this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef _SPL_RWLOCK_H
#define _SPL_RWLOCK_H
#include <sys/types.h>
#include <linux/rwsem.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;
typedef struct {
struct rw_semaphore rw_rwlock;
kthread_t *rw_owner;
} krwlock_t;
/*
* 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 will be
* required so RW_COUNT() provides these semantics:
* - 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
*/
#define SEM(rwp) ((struct rw_semaphore *)(rwp))
#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
# define RW_COUNT(rwp) (SEM(rwp)->activity)
# define rw_exit_locked(rwp) __up_read_locked(rwp)
# define rw_tryenter_locked(rwp) __down_write_trylock_locked(rwp)
extern void __up_read_locked(struct rw_semaphore *);
extern int __down_write_trylock_locked(struct rw_semaphore *);
#else
# ifdef _I386_RWSEM_H
# define RW_COUNT(rwp) ((SEM(rwp)->count < 0) ? (-1) : \
(SEM(rwp)->count & RWSEM_ACTIVE_MASK))
# else
# define RW_COUNT(rwp) (SEM(rwp)->count & RWSEM_ACTIVE_MASK)
# endif
# define rw_exit_locked(rwp) up_read(rwp)
# define rw_tryenter_locked(rwp) down_write_trylock(rwp)
#endif
static inline kthread_t *
spl_rw_get_owner(krwlock_t *rwp)
{
return rwp->rw_owner;
}
static inline void
spl_rw_set_owner(krwlock_t *rwp)
{
unsigned long flags;
spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rwp->rw_owner = current;
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
}
static inline void
spl_rw_clear_owner(krwlock_t *rwp)
{
unsigned long flags;
spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rwp->rw_owner = NULL;
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
}
static inline kthread_t *
rw_owner(krwlock_t *rwp)
{
unsigned long flags;
kthread_t *owner;
spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
owner = spl_rw_get_owner(rwp);
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
return owner;
}
static inline int
RW_READ_HELD(krwlock_t *rwp)
{
unsigned long flags;
int rc;
spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rc = ((RW_COUNT(rwp) > 0) && (spl_rw_get_owner(rwp) == NULL));
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
return rc;
}
static inline int
RW_WRITE_HELD(krwlock_t *rwp)
{
unsigned long flags;
int rc;
spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rc = ((RW_COUNT(rwp) < 0) && (spl_rw_get_owner(rwp) == current));
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
return rc;
}
static inline int
RW_LOCK_HELD(krwlock_t *rwp)
{
unsigned long flags;
int rc;
spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
rc = (RW_COUNT(rwp) != 0);
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
return rc;
}
/*
* 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: \
SBUG(); \
} \
_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: \
SBUG(); \
} \
})
#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)); \
})
#define rw_tryupgrade(rwp) \
({ \
unsigned long _flags_; \
int _rc_ = 0; \
\
spin_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \
if (list_empty(&SEM(rwp)->wait_list) && (RW_COUNT(rwp) == 1)) { \
rw_exit_locked(SEM(rwp)); \
VERIFY(_rc_ = rw_tryenter_locked(SEM(rwp))); \
(rwp)->rw_owner = current; \
} \
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \
_rc_; \
})
int spl_rw_init(void);
void spl_rw_fini(void);
#endif /* _SPL_RWLOCK_H */
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