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1 | /*****************************************************************************\ |
2 | * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. | |
3 | * Copyright (C) 2007 The Regents of the University of California. | |
4 | * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). | |
5 | * Written by Brian Behlendorf <behlendorf1@llnl.gov>. | |
6 | * UCRL-CODE-235197 | |
7 | * | |
8 | * This file is part of the SPL, Solaris Porting Layer. | |
9 | * For details, see <http://zfsonlinux.org/>. | |
10 | * | |
11 | * The SPL is free software; you can redistribute it and/or modify it | |
12 | * under the terms of the GNU General Public License as published by the | |
13 | * Free Software Foundation; either version 2 of the License, or (at your | |
14 | * option) any later version. | |
15 | * | |
16 | * The SPL is distributed in the hope that it will be useful, but WITHOUT | |
17 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
18 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
19 | * for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU General Public License along | |
22 | * with the SPL. If not, see <http://www.gnu.org/licenses/>. | |
23 | \*****************************************************************************/ | |
24 | ||
25 | #ifndef _SPL_RWLOCK_H | |
26 | #define _SPL_RWLOCK_H | |
27 | ||
28 | #include <sys/types.h> | |
29 | #include <linux/rwsem.h> | |
30 | #include <linux/rwsem_compat.h> | |
31 | ||
32 | typedef enum { | |
33 | RW_DRIVER = 2, | |
34 | RW_DEFAULT = 4 | |
35 | } krw_type_t; | |
36 | ||
37 | typedef enum { | |
38 | RW_NONE = 0, | |
39 | RW_WRITER = 1, | |
40 | RW_READER = 2 | |
41 | } krw_t; | |
42 | ||
43 | typedef struct { | |
44 | struct rw_semaphore rw_rwlock; | |
45 | kthread_t *rw_owner; | |
46 | } krwlock_t; | |
47 | ||
48 | #define SEM(rwp) ((struct rw_semaphore *)(rwp)) | |
49 | ||
50 | static inline void | |
51 | spl_rw_set_owner(krwlock_t *rwp) | |
52 | { | |
53 | unsigned long flags; | |
54 | ||
55 | spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags); | |
56 | rwp->rw_owner = current; | |
57 | spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); | |
58 | } | |
59 | ||
60 | static inline void | |
61 | spl_rw_clear_owner(krwlock_t *rwp) | |
62 | { | |
63 | unsigned long flags; | |
64 | ||
65 | spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags); | |
66 | rwp->rw_owner = NULL; | |
67 | spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); | |
68 | } | |
69 | ||
70 | static inline kthread_t * | |
71 | rw_owner(krwlock_t *rwp) | |
72 | { | |
73 | unsigned long flags; | |
74 | kthread_t *owner; | |
75 | ||
76 | spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags); | |
77 | owner = rwp->rw_owner; | |
78 | spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); | |
79 | ||
80 | return owner; | |
81 | } | |
82 | ||
83 | static inline int | |
84 | RW_READ_HELD(krwlock_t *rwp) | |
85 | { | |
86 | /* | |
87 | * Linux 4.8 will set owner to 1 when read held instead of leave it | |
88 | * NULL. So we check whether owner <= 1. | |
89 | */ | |
90 | return (spl_rwsem_is_locked(SEM(rwp)) && | |
91 | (unsigned long)rw_owner(rwp) <= 1); | |
92 | } | |
93 | ||
94 | static inline int | |
95 | RW_WRITE_HELD(krwlock_t *rwp) | |
96 | { | |
97 | return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == current); | |
98 | } | |
99 | ||
100 | static inline int | |
101 | RW_LOCK_HELD(krwlock_t *rwp) | |
102 | { | |
103 | return spl_rwsem_is_locked(SEM(rwp)); | |
104 | } | |
105 | ||
106 | /* | |
107 | * The following functions must be a #define and not static inline. | |
108 | * This ensures that the native linux semaphore functions (down/up) | |
109 | * will be correctly located in the users code which is important | |
110 | * for the built in kernel lock analysis tools | |
111 | */ | |
112 | #define rw_init(rwp, name, type, arg) \ | |
113 | ({ \ | |
114 | static struct lock_class_key __key; \ | |
115 | \ | |
116 | __init_rwsem(SEM(rwp), #rwp, &__key); \ | |
117 | spl_rw_clear_owner(rwp); \ | |
118 | }) | |
119 | ||
120 | #define rw_destroy(rwp) \ | |
121 | ({ \ | |
122 | VERIFY(!RW_LOCK_HELD(rwp)); \ | |
123 | }) | |
124 | ||
125 | #define rw_tryenter(rwp, rw) \ | |
126 | ({ \ | |
127 | int _rc_ = 0; \ | |
128 | \ | |
129 | switch (rw) { \ | |
130 | case RW_READER: \ | |
131 | _rc_ = down_read_trylock(SEM(rwp)); \ | |
132 | break; \ | |
133 | case RW_WRITER: \ | |
134 | if ((_rc_ = down_write_trylock(SEM(rwp)))) \ | |
135 | spl_rw_set_owner(rwp); \ | |
136 | break; \ | |
137 | default: \ | |
138 | VERIFY(0); \ | |
139 | } \ | |
140 | _rc_; \ | |
141 | }) | |
142 | ||
143 | #define rw_enter(rwp, rw) \ | |
144 | ({ \ | |
145 | switch (rw) { \ | |
146 | case RW_READER: \ | |
147 | down_read(SEM(rwp)); \ | |
148 | break; \ | |
149 | case RW_WRITER: \ | |
150 | down_write(SEM(rwp)); \ | |
151 | spl_rw_set_owner(rwp); \ | |
152 | break; \ | |
153 | default: \ | |
154 | VERIFY(0); \ | |
155 | } \ | |
156 | }) | |
157 | ||
158 | #define rw_exit(rwp) \ | |
159 | ({ \ | |
160 | if (RW_WRITE_HELD(rwp)) { \ | |
161 | spl_rw_clear_owner(rwp); \ | |
162 | up_write(SEM(rwp)); \ | |
163 | } else { \ | |
164 | ASSERT(RW_READ_HELD(rwp)); \ | |
165 | up_read(SEM(rwp)); \ | |
166 | } \ | |
167 | }) | |
168 | ||
169 | #define rw_downgrade(rwp) \ | |
170 | ({ \ | |
171 | spl_rw_clear_owner(rwp); \ | |
172 | downgrade_write(SEM(rwp)); \ | |
173 | }) | |
174 | ||
175 | /* | |
176 | * This implementation of rw_tryupgrade() behaves slightly differently | |
177 | * from its counterparts on other platforms. It drops the RW_READER lock | |
178 | * and then acquires the RW_WRITER lock leaving a small window where no | |
179 | * lock is held. On other platforms the lock is never released during | |
180 | * the upgrade process. This is necessary under Linux because the kernel | |
181 | * does not provide an upgrade function. | |
182 | */ | |
183 | #define rw_tryupgrade(rwp) \ | |
184 | ({ \ | |
185 | int _rc_ = 0; \ | |
186 | \ | |
187 | if (RW_WRITE_HELD(rwp)) { \ | |
188 | _rc_ = 1; \ | |
189 | } else { \ | |
190 | if ((_rc_ = rwsem_tryupgrade(SEM(rwp)))) \ | |
191 | spl_rw_set_owner(rwp); \ | |
192 | } \ | |
193 | _rc_; \ | |
194 | }) | |
195 | ||
196 | int spl_rw_init(void); | |
197 | void spl_rw_fini(void); | |
198 | ||
199 | #endif /* _SPL_RWLOCK_H */ |