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1 | /* |
2 | * Copyright (c) 2000-2004 Silicon Graphics, Inc. All Rights Reserved. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify it | |
5 | * under the terms of version 2 of the GNU General Public License as | |
6 | * published by the Free Software Foundation. | |
7 | * | |
8 | * This program is distributed in the hope that it would be useful, but | |
9 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. | |
11 | * | |
12 | * Further, this software is distributed without any warranty that it is | |
13 | * free of the rightful claim of any third person regarding infringement | |
14 | * or the like. Any license provided herein, whether implied or | |
15 | * otherwise, applies only to this software file. Patent licenses, if | |
16 | * any, provided herein do not apply to combinations of this program with | |
17 | * other software, or any other product whatsoever. | |
18 | * | |
19 | * You should have received a copy of the GNU General Public License along | |
20 | * with this program; if not, write the Free Software Foundation, Inc., 59 | |
21 | * Temple Place - Suite 330, Boston MA 02111-1307, USA. | |
22 | * | |
23 | * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy, | |
24 | * Mountain View, CA 94043, or: | |
25 | * | |
26 | * http://www.sgi.com | |
27 | * | |
28 | * For further information regarding this notice, see: | |
29 | * | |
30 | * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/ | |
31 | */ | |
32 | #ifndef __XFS_SUPPORT_MRLOCK_H__ | |
33 | #define __XFS_SUPPORT_MRLOCK_H__ | |
34 | ||
35 | #include <linux/rwsem.h> | |
36 | ||
37 | enum { MR_NONE, MR_ACCESS, MR_UPDATE }; | |
38 | ||
39 | typedef struct { | |
40 | struct rw_semaphore mr_lock; | |
41 | int mr_writer; | |
42 | } mrlock_t; | |
43 | ||
44 | #define mrinit(mrp, name) \ | |
45 | ( (mrp)->mr_writer = 0, init_rwsem(&(mrp)->mr_lock) ) | |
46 | #define mrlock_init(mrp, t,n,s) mrinit(mrp, n) | |
47 | #define mrfree(mrp) do { } while (0) | |
48 | #define mraccess(mrp) mraccessf(mrp, 0) | |
49 | #define mrupdate(mrp) mrupdatef(mrp, 0) | |
50 | ||
51 | static inline void mraccessf(mrlock_t *mrp, int flags) | |
52 | { | |
53 | down_read(&mrp->mr_lock); | |
54 | } | |
55 | ||
56 | static inline void mrupdatef(mrlock_t *mrp, int flags) | |
57 | { | |
58 | down_write(&mrp->mr_lock); | |
59 | mrp->mr_writer = 1; | |
60 | } | |
61 | ||
62 | static inline int mrtryaccess(mrlock_t *mrp) | |
63 | { | |
64 | return down_read_trylock(&mrp->mr_lock); | |
65 | } | |
66 | ||
67 | static inline int mrtryupdate(mrlock_t *mrp) | |
68 | { | |
69 | if (!down_write_trylock(&mrp->mr_lock)) | |
70 | return 0; | |
71 | mrp->mr_writer = 1; | |
72 | return 1; | |
73 | } | |
74 | ||
75 | static inline void mrunlock(mrlock_t *mrp) | |
76 | { | |
77 | if (mrp->mr_writer) { | |
78 | mrp->mr_writer = 0; | |
79 | up_write(&mrp->mr_lock); | |
80 | } else { | |
81 | up_read(&mrp->mr_lock); | |
82 | } | |
83 | } | |
84 | ||
85 | static inline void mrdemote(mrlock_t *mrp) | |
86 | { | |
87 | mrp->mr_writer = 0; | |
88 | downgrade_write(&mrp->mr_lock); | |
89 | } | |
90 | ||
91 | #ifdef DEBUG | |
92 | /* | |
93 | * Debug-only routine, without some platform-specific asm code, we can | |
94 | * now only answer requests regarding whether we hold the lock for write | |
95 | * (reader state is outside our visibility, we only track writer state). | |
96 | * Note: means !ismrlocked would give false positivies, so don't do that. | |
97 | */ | |
98 | static inline int ismrlocked(mrlock_t *mrp, int type) | |
99 | { | |
100 | if (mrp && type == MR_UPDATE) | |
101 | return mrp->mr_writer; | |
102 | return 1; | |
103 | } | |
104 | #endif | |
105 | ||
106 | #endif /* __XFS_SUPPORT_MRLOCK_H__ */ |