1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
4 * Copyright (C) 2007 The Regents of the University of California.
5 * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
6 * Written by Brian Behlendorf <behlendorf1@llnl.gov>.
7 * UCRL-CODE-235197
8 *
9 * This file is part of the SPL, Solaris Porting Layer.
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/sched.h>
31
32 typedef enum {
33 RW_DRIVER = 2,
34 RW_DEFAULT = 4,
35 RW_NOLOCKDEP = 5
36 } krw_type_t;
37
38 typedef enum {
39 RW_NONE = 0,
40 RW_WRITER = 1,
41 RW_READER = 2
42 } krw_t;
43
44 typedef struct {
45 struct rw_semaphore rw_rwlock;
46 kthread_t *rw_owner;
47 #ifdef CONFIG_LOCKDEP
48 krw_type_t rw_type;
49 #endif /* CONFIG_LOCKDEP */
50 } krwlock_t;
51
52 #define SEM(rwp) (&(rwp)->rw_rwlock)
53
54 static inline void
spl_rw_set_owner(krwlock_t * rwp)55 spl_rw_set_owner(krwlock_t *rwp)
56 {
57 rwp->rw_owner = current;
58 }
59
60 static inline void
spl_rw_clear_owner(krwlock_t * rwp)61 spl_rw_clear_owner(krwlock_t *rwp)
62 {
63 rwp->rw_owner = NULL;
64 }
65
66 static inline kthread_t *
rw_owner(krwlock_t * rwp)67 rw_owner(krwlock_t *rwp)
68 {
69 return (rwp->rw_owner);
70 }
71
72 #ifdef CONFIG_LOCKDEP
73 static inline void
spl_rw_set_type(krwlock_t * rwp,krw_type_t type)74 spl_rw_set_type(krwlock_t *rwp, krw_type_t type)
75 {
76 rwp->rw_type = type;
77 }
78 static inline void
spl_rw_lockdep_off_maybe(krwlock_t * rwp)79 spl_rw_lockdep_off_maybe(krwlock_t *rwp) \
80 { \
81 if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
82 lockdep_off(); \
83 }
84 static inline void
spl_rw_lockdep_on_maybe(krwlock_t * rwp)85 spl_rw_lockdep_on_maybe(krwlock_t *rwp) \
86 { \
87 if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
88 lockdep_on(); \
89 }
90 #else /* CONFIG_LOCKDEP */
91 #define spl_rw_set_type(rwp, type)
92 #define spl_rw_lockdep_off_maybe(rwp)
93 #define spl_rw_lockdep_on_maybe(rwp)
94 #endif /* CONFIG_LOCKDEP */
95
96 static inline int
RW_LOCK_HELD(krwlock_t * rwp)97 RW_LOCK_HELD(krwlock_t *rwp)
98 {
99 return (rwsem_is_locked(SEM(rwp)));
100 }
101
102 static inline int
RW_WRITE_HELD(krwlock_t * rwp)103 RW_WRITE_HELD(krwlock_t *rwp)
104 {
105 return (rw_owner(rwp) == current);
106 }
107
108 static inline int
RW_READ_HELD(krwlock_t * rwp)109 RW_READ_HELD(krwlock_t *rwp)
110 {
111 return (RW_LOCK_HELD(rwp) && rw_owner(rwp) == NULL);
112 }
113
114 /*
115 * The following functions must be a #define and not static inline.
116 * This ensures that the native linux semaphore functions (down/up)
117 * will be correctly located in the users code which is important
118 * for the built in kernel lock analysis tools
119 */
120 #define rw_init(rwp, name, type, arg) /* CSTYLED */ \
121 ({ \
122 static struct lock_class_key __key; \
123 ASSERT(type == RW_DEFAULT || type == RW_NOLOCKDEP); \
124 \
125 __init_rwsem(SEM(rwp), #rwp, &__key); \
126 spl_rw_clear_owner(rwp); \
127 spl_rw_set_type(rwp, type); \
128 })
129
130 /*
131 * The Linux rwsem implementation does not require a matching destroy.
132 */
133 #define rw_destroy(rwp) ((void) 0)
134
135 /*
136 * Upgrading a rwsem from a reader to a writer is not supported by the
137 * Linux kernel. The lock must be dropped and reacquired as a writer.
138 */
139 #define rw_tryupgrade(rwp) RW_WRITE_HELD(rwp)
140
141 #define rw_tryenter(rwp, rw) /* CSTYLED */ \
142 ({ \
143 int _rc_ = 0; \
144 \
145 spl_rw_lockdep_off_maybe(rwp); \
146 switch (rw) { \
147 case RW_READER: \
148 _rc_ = down_read_trylock(SEM(rwp)); \
149 break; \
150 case RW_WRITER: \
151 if ((_rc_ = down_write_trylock(SEM(rwp)))) \
152 spl_rw_set_owner(rwp); \
153 break; \
154 default: \
155 VERIFY(0); \
156 } \
157 spl_rw_lockdep_on_maybe(rwp); \
158 _rc_; \
159 })
160
161 #define rw_enter(rwp, rw) /* CSTYLED */ \
162 ({ \
163 spl_rw_lockdep_off_maybe(rwp); \
164 switch (rw) { \
165 case RW_READER: \
166 down_read(SEM(rwp)); \
167 break; \
168 case RW_WRITER: \
169 down_write(SEM(rwp)); \
170 spl_rw_set_owner(rwp); \
171 break; \
172 default: \
173 VERIFY(0); \
174 } \
175 spl_rw_lockdep_on_maybe(rwp); \
176 })
177
178 #define rw_exit(rwp) /* CSTYLED */ \
179 ({ \
180 spl_rw_lockdep_off_maybe(rwp); \
181 if (RW_WRITE_HELD(rwp)) { \
182 spl_rw_clear_owner(rwp); \
183 up_write(SEM(rwp)); \
184 } else { \
185 ASSERT(RW_READ_HELD(rwp)); \
186 up_read(SEM(rwp)); \
187 } \
188 spl_rw_lockdep_on_maybe(rwp); \
189 })
190
191 #define rw_downgrade(rwp) /* CSTYLED */ \
192 ({ \
193 spl_rw_lockdep_off_maybe(rwp); \
194 spl_rw_clear_owner(rwp); \
195 downgrade_write(SEM(rwp)); \
196 spl_rw_lockdep_on_maybe(rwp); \
197 })
198
199 #endif /* _SPL_RWLOCK_H */
200