/*
* Copyright (c) 2000-2006 Silicon Graphics, Inc.
* All Rights Reserved.
*
* This program 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.
*
* This program is distributed in the hope that it would 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 the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef __XFS_SUPPORT_MRLOCK_H__
#define __XFS_SUPPORT_MRLOCK_H__
#include <linux/rwsem.h>
enum { MR_NONE, MR_ACCESS, MR_UPDATE };
typedef struct {
struct rw_semaphore mr_lock;
int mr_writer;
} mrlock_t;
#define mrinit(mrp, name) \
do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
#define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
#define mrfree(mrp) do { } while (0)
static inline void mraccess(mrlock_t *mrp)
{
down_read(&mrp->mr_lock);
}
static inline void mrupdate(mrlock_t *mrp)
{
down_write(&mrp->mr_lock);
mrp->mr_writer = 1;
}
static inline void mraccess_nested(mrlock_t *mrp, int subclass)
{
down_read_nested(&mrp->mr_lock, subclass);
}
static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
{
down_write_nested(&mrp->mr_lock, subclass);
mrp->mr_writer = 1;
}
static inline int mrtryaccess(mrlock_t *mrp)
{
return down_read_trylock(&mrp->mr_lock);
}
static inline int mrtryupdate(mrlock_t *mrp)
{
if (!down_write_trylock(&mrp->mr_lock))
return 0;
mrp->mr_writer = 1;
return 1;
}
static inline void mrunlock(mrlock_t *mrp)
{
if (mrp->mr_writer) {
mrp->mr_writer = 0;
up_write(&mrp->mr_lock);
} else {
up_read(&mrp->mr_lock);
}
}
static inline void mrdemote(mrlock_t *mrp)
{
mrp->mr_writer = 0;
downgrade_write(&mrp->mr_lock);
}
#ifdef DEBUG
/*
* Debug-only routine, without some platform-specific asm code, we can
* now only answer requests regarding whether we hold the lock for write
* (reader state is outside our visibility, we only track writer state).
* Note: means !ismrlocked would give false positives, so don't do that.
*/
static inline int ismrlocked(mrlock_t *mrp, int type)
{
if (mrp && type == MR_UPDATE)
return mrp->mr_writer;
return 1;
}
#endif
#endif /* __XFS_SUPPORT_MRLOCK_H__ */
