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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>.
8 * This file is part of the SPL, Solaris Porting Layer.
9 * For details, see <http://zfsonlinux.org/>.
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.
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
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 \*****************************************************************************/
28 #include <sys/types.h>
29 #include <linux/rwsem.h>
30 #include <linux/rwsem_compat.h>
44 struct rw_semaphore rw_rwlock
;
48 #define SEM(rwp) ((struct rw_semaphore *)(rwp))
51 spl_rw_set_owner(krwlock_t
*rwp
)
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
);
61 spl_rw_clear_owner(krwlock_t
*rwp
)
65 spl_rwsem_lock_irqsave(&SEM(rwp
)->wait_lock
, flags
);
67 spl_rwsem_unlock_irqrestore(&SEM(rwp
)->wait_lock
, flags
);
70 static inline kthread_t
*
71 rw_owner(krwlock_t
*rwp
)
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
);
84 RW_READ_HELD(krwlock_t
*rwp
)
86 return (spl_rwsem_is_locked(SEM(rwp
)) && rw_owner(rwp
) == NULL
);
90 RW_WRITE_HELD(krwlock_t
*rwp
)
92 return (spl_rwsem_is_locked(SEM(rwp
)) && rw_owner(rwp
) == current
);
96 RW_LOCK_HELD(krwlock_t
*rwp
)
98 return spl_rwsem_is_locked(SEM(rwp
));
102 * The following functions must be a #define and not static inline.
103 * This ensures that the native linux semaphore functions (down/up)
104 * will be correctly located in the users code which is important
105 * for the built in kernel lock analysis tools
107 #define rw_init(rwp, name, type, arg) \
109 static struct lock_class_key __key; \
111 __init_rwsem(SEM(rwp), #rwp, &__key); \
112 spl_rw_clear_owner(rwp); \
115 #define rw_destroy(rwp) \
117 VERIFY(!RW_LOCK_HELD(rwp)); \
120 #define rw_tryenter(rwp, rw) \
126 _rc_ = down_read_trylock(SEM(rwp)); \
129 if ((_rc_ = down_write_trylock(SEM(rwp)))) \
130 spl_rw_set_owner(rwp); \
138 #define rw_enter(rwp, rw) \
142 down_read(SEM(rwp)); \
145 down_write(SEM(rwp)); \
146 spl_rw_set_owner(rwp); \
153 #define rw_exit(rwp) \
155 if (RW_WRITE_HELD(rwp)) { \
156 spl_rw_clear_owner(rwp); \
157 up_write(SEM(rwp)); \
159 ASSERT(RW_READ_HELD(rwp)); \
164 #define rw_downgrade(rwp) \
166 spl_rw_clear_owner(rwp); \
167 downgrade_write(SEM(rwp)); \
170 #if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
172 * For the generic implementations of rw-semaphores the following is
173 * true. If your semaphore implementation internally represents the
174 * semaphore state differently then special case handling is required.
175 * - if activity/count is 0 then there are no active readers or writers
176 * - if activity/count is +ve then that is the number of active readers
177 * - if activity/count is -1 then there is one active writer
180 extern void __up_read_locked(struct rw_semaphore
*);
181 extern int __down_write_trylock_locked(struct rw_semaphore
*);
183 #define rw_tryupgrade(rwp) \
185 unsigned long _flags_; \
188 spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \
189 if ((list_empty(&SEM(rwp)->wait_list)) && \
190 (SEM(rwp)->activity == 1)) { \
191 __up_read_locked(SEM(rwp)); \
192 VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp))); \
193 (rwp)->rw_owner = current; \
195 spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \
200 * rw_tryupgrade() can be implemented correctly but for each supported
201 * arch we will need a custom implementation. For the x86 implementation
202 * it looks like a custom cmpxchg() to atomically check and promote the
203 * rwsem would be safe. For now that's not worth the trouble so in this
204 * case rw_tryupgrade() has just been disabled.
206 #define rw_tryupgrade(rwp) ({ 0; })
209 int spl_rw_init(void);
210 void spl_rw_fini(void);
212 #endif /* _SPL_RWLOCK_H */