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/*
* Copyright (c) 2000-2004 Silicon Graphics, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of version 2 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.
*
* Further, this software is distributed without any warranty that it is
* free of the rightful claim of any third person regarding infringement
* or the like. Any license provided herein, whether implied or
* otherwise, applies only to this software file. Patent licenses, if
* any, provided herein do not apply to combinations of this program with
* other software, or any other product whatsoever.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write the Free Software Foundation, Inc., 59
* Temple Place - Suite 330, Boston MA 02111-1307, USA.
*
* Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
* Mountain View, CA 94043, or:
*
* http://www.sgi.com
*
* For further information regarding this notice, see:
*
* http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
*/
#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) \
( (mrp)->mr_writer = 0, init_rwsem(&(mrp)->mr_lock) )
#define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
#define mrfree(mrp) do { } while (0)
#define mraccess(mrp) mraccessf(mrp, 0)
#define mrupdate(mrp) mrupdatef(mrp, 0)
static inline void mraccessf(mrlock_t *mrp, int flags)
{
down_read(&mrp->mr_lock);
}
static inline void mrupdatef(mrlock_t *mrp, int flags)
{
down_write(&mrp->mr_lock);
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 positivies, 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__ */
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