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/*****************************************************************************\
* 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://github.com/behlendorf/spl/>.
*
* 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;
typedef struct {
struct rw_semaphore rw_rwlock;
kthread_t *rw_owner;
} krwlock_t;
#define SEM(rwp) ((struct rw_semaphore *)(rwp))
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 = rwp->rw_owner;
spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
return owner;
}
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 (spl_rwsem_is_locked(SEM(rwp)) &&
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)
/*
* 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; \
\
spin_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; \
} \
spin_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 */
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