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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://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/sched.h>
typedef enum {
RW_DRIVER = 2,
RW_DEFAULT = 4,
RW_NOLOCKDEP = 5
} 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;
#ifdef CONFIG_LOCKDEP
krw_type_t rw_type;
#endif /* CONFIG_LOCKDEP */
} krwlock_t;
#define SEM(rwp) (&(rwp)->rw_rwlock)
static inline void
spl_rw_set_owner(krwlock_t *rwp)
{
rwp->rw_owner = current;
}
static inline void
spl_rw_clear_owner(krwlock_t *rwp)
{
rwp->rw_owner = NULL;
}
static inline kthread_t *
rw_owner(krwlock_t *rwp)
{
return (rwp->rw_owner);
}
#ifdef CONFIG_LOCKDEP
static inline void
spl_rw_set_type(krwlock_t *rwp, krw_type_t type)
{
rwp->rw_type = type;
}
static inline void
spl_rw_lockdep_off_maybe(krwlock_t *rwp) \
{ \
if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
lockdep_off(); \
}
static inline void
spl_rw_lockdep_on_maybe(krwlock_t *rwp) \
{ \
if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
lockdep_on(); \
}
#else /* CONFIG_LOCKDEP */
#define spl_rw_set_type(rwp, type)
#define spl_rw_lockdep_off_maybe(rwp)
#define spl_rw_lockdep_on_maybe(rwp)
#endif /* CONFIG_LOCKDEP */
static inline int
RW_LOCK_HELD(krwlock_t *rwp)
{
return (rwsem_is_locked(SEM(rwp)));
}
static inline int
RW_WRITE_HELD(krwlock_t *rwp)
{
return (rw_owner(rwp) == current);
}
static inline int
RW_READ_HELD(krwlock_t *rwp)
{
return (RW_LOCK_HELD(rwp) && rw_owner(rwp) == NULL);
}
/*
* 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
*/
/* BEGIN CSTYLED */
#define rw_init(rwp, name, type, arg) \
({ \
static struct lock_class_key __key; \
ASSERT(type == RW_DEFAULT || type == RW_NOLOCKDEP); \
\
__init_rwsem(SEM(rwp), #rwp, &__key); \
spl_rw_clear_owner(rwp); \
spl_rw_set_type(rwp, type); \
})
/*
* The Linux rwsem implementation does not require a matching destroy.
*/
#define rw_destroy(rwp) ((void) 0)
/*
* Upgrading a rwsem from a reader to a writer is not supported by the
* Linux kernel. The lock must be dropped and reacquired as a writer.
*/
#define rw_tryupgrade(rwp) RW_WRITE_HELD(rwp)
#define rw_tryenter(rwp, rw) \
({ \
int _rc_ = 0; \
\
spl_rw_lockdep_off_maybe(rwp); \
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); \
} \
spl_rw_lockdep_on_maybe(rwp); \
_rc_; \
})
#define rw_enter(rwp, rw) \
({ \
spl_rw_lockdep_off_maybe(rwp); \
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); \
} \
spl_rw_lockdep_on_maybe(rwp); \
})
#define rw_exit(rwp) \
({ \
spl_rw_lockdep_off_maybe(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)); \
} \
spl_rw_lockdep_on_maybe(rwp); \
})
#define rw_downgrade(rwp) \
({ \
spl_rw_lockdep_off_maybe(rwp); \
spl_rw_clear_owner(rwp); \
downgrade_write(SEM(rwp)); \
spl_rw_lockdep_on_maybe(rwp); \
})
/* END CSTYLED */
#endif /* _SPL_RWLOCK_H */
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