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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Nathan Scott7b718762005-11-02 14:58:39 +11002 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
3 * All Rights Reserved.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004 *
Nathan Scott7b718762005-11-02 14:58:39 +11005 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License as
Linus Torvalds1da177e2005-04-16 15:20:36 -07007 * published by the Free Software Foundation.
8 *
Nathan Scott7b718762005-11-02 14:58:39 +11009 * This program is distributed in the hope that it would be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -070013 *
Nathan Scott7b718762005-11-02 14:58:39 +110014 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Linus Torvalds1da177e2005-04-16 15:20:36 -070017 */
18#ifndef __XFS_SUPPORT_MRLOCK_H__
19#define __XFS_SUPPORT_MRLOCK_H__
20
21#include <linux/rwsem.h>
22
23enum { MR_NONE, MR_ACCESS, MR_UPDATE };
24
25typedef struct {
26 struct rw_semaphore mr_lock;
27 int mr_writer;
28} mrlock_t;
29
30#define mrinit(mrp, name) \
31 ( (mrp)->mr_writer = 0, init_rwsem(&(mrp)->mr_lock) )
32#define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
33#define mrfree(mrp) do { } while (0)
34#define mraccess(mrp) mraccessf(mrp, 0)
35#define mrupdate(mrp) mrupdatef(mrp, 0)
36
37static inline void mraccessf(mrlock_t *mrp, int flags)
38{
39 down_read(&mrp->mr_lock);
40}
41
42static inline void mrupdatef(mrlock_t *mrp, int flags)
43{
44 down_write(&mrp->mr_lock);
45 mrp->mr_writer = 1;
46}
47
48static inline int mrtryaccess(mrlock_t *mrp)
49{
50 return down_read_trylock(&mrp->mr_lock);
51}
52
53static inline int mrtryupdate(mrlock_t *mrp)
54{
55 if (!down_write_trylock(&mrp->mr_lock))
56 return 0;
57 mrp->mr_writer = 1;
58 return 1;
59}
60
61static inline void mrunlock(mrlock_t *mrp)
62{
63 if (mrp->mr_writer) {
64 mrp->mr_writer = 0;
65 up_write(&mrp->mr_lock);
66 } else {
67 up_read(&mrp->mr_lock);
68 }
69}
70
71static inline void mrdemote(mrlock_t *mrp)
72{
73 mrp->mr_writer = 0;
74 downgrade_write(&mrp->mr_lock);
75}
76
77#ifdef DEBUG
78/*
79 * Debug-only routine, without some platform-specific asm code, we can
80 * now only answer requests regarding whether we hold the lock for write
81 * (reader state is outside our visibility, we only track writer state).
82 * Note: means !ismrlocked would give false positivies, so don't do that.
83 */
84static inline int ismrlocked(mrlock_t *mrp, int type)
85{
86 if (mrp && type == MR_UPDATE)
87 return mrp->mr_writer;
88 return 1;
89}
90#endif
91
92#endif /* __XFS_SUPPORT_MRLOCK_H__ */