Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
Nathan Scott | 7b71876 | 2005-11-02 14:58:39 +1100 | [diff] [blame] | 2 | * Copyright (c) 2000-2005 Silicon Graphics, Inc. |
| 3 | * All Rights Reserved. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4 | * |
Nathan Scott | 7b71876 | 2005-11-02 14:58:39 +1100 | [diff] [blame] | 5 | * 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 Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 7 | * published by the Free Software Foundation. |
| 8 | * |
Nathan Scott | 7b71876 | 2005-11-02 14:58:39 +1100 | [diff] [blame] | 9 | * 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 Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 13 | * |
Nathan Scott | 7b71876 | 2005-11-02 14:58:39 +1100 | [diff] [blame] | 14 | * 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 Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 17 | */ |
| 18 | #ifndef __XFS_SUPPORT_MRLOCK_H__ |
| 19 | #define __XFS_SUPPORT_MRLOCK_H__ |
| 20 | |
| 21 | #include <linux/rwsem.h> |
| 22 | |
| 23 | enum { MR_NONE, MR_ACCESS, MR_UPDATE }; |
| 24 | |
| 25 | typedef 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 | |
| 37 | static inline void mraccessf(mrlock_t *mrp, int flags) |
| 38 | { |
| 39 | down_read(&mrp->mr_lock); |
| 40 | } |
| 41 | |
| 42 | static inline void mrupdatef(mrlock_t *mrp, int flags) |
| 43 | { |
| 44 | down_write(&mrp->mr_lock); |
| 45 | mrp->mr_writer = 1; |
| 46 | } |
| 47 | |
| 48 | static inline int mrtryaccess(mrlock_t *mrp) |
| 49 | { |
| 50 | return down_read_trylock(&mrp->mr_lock); |
| 51 | } |
| 52 | |
| 53 | static 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 | |
| 61 | static 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 | |
| 71 | static 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 | */ |
| 84 | static 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__ */ |