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 *
10 *  The SPL is free software; you can redistribute it and/or modify it
11 *  under the terms of the GNU General Public License as published by the
12 *  Free Software Foundation; either version 2 of the License, or (at your
13 *  option) any later version.
14 *
15 *  The SPL is distributed in the hope that it will be useful, but WITHOUT
16 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
18 *  for more details.
19 *
20 *  You should have received a copy of the GNU General Public License along
21 *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
22 */
23
24#ifndef _SPL_RWLOCK_H
25#define	_SPL_RWLOCK_H
26
27#include <sys/types.h>
28#include <linux/rwsem.h>
29#include <linux/sched.h>
30
31typedef enum {
32	RW_DRIVER	= 2,
33	RW_DEFAULT	= 4,
34	RW_NOLOCKDEP	= 5
35} krw_type_t;
36
37typedef enum {
38	RW_NONE		= 0,
39	RW_WRITER	= 1,
40	RW_READER	= 2
41} krw_t;
42
43typedef struct {
44	struct rw_semaphore rw_rwlock;
45	kthread_t *rw_owner;
46#ifdef CONFIG_LOCKDEP
47	krw_type_t	rw_type;
48#endif /* CONFIG_LOCKDEP */
49} krwlock_t;
50
51#define	SEM(rwp)	(&(rwp)->rw_rwlock)
52
53static inline void
54spl_rw_set_owner(krwlock_t *rwp)
55{
56	rwp->rw_owner = current;
57}
58
59static inline void
60spl_rw_clear_owner(krwlock_t *rwp)
61{
62	rwp->rw_owner = NULL;
63}
64
65static inline kthread_t *
66rw_owner(krwlock_t *rwp)
67{
68	return (rwp->rw_owner);
69}
70
71#ifdef CONFIG_LOCKDEP
72static inline void
73spl_rw_set_type(krwlock_t *rwp, krw_type_t type)
74{
75	rwp->rw_type = type;
76}
77static inline void
78spl_rw_lockdep_off_maybe(krwlock_t *rwp)		\
79{							\
80	if (rwp && rwp->rw_type == RW_NOLOCKDEP)	\
81		lockdep_off();				\
82}
83static inline void
84spl_rw_lockdep_on_maybe(krwlock_t *rwp)			\
85{							\
86	if (rwp && rwp->rw_type == RW_NOLOCKDEP)	\
87		lockdep_on();				\
88}
89#else  /* CONFIG_LOCKDEP */
90#define	spl_rw_set_type(rwp, type)
91#define	spl_rw_lockdep_off_maybe(rwp)
92#define	spl_rw_lockdep_on_maybe(rwp)
93#endif /* CONFIG_LOCKDEP */
94
95static inline int
96RW_LOCK_HELD(krwlock_t *rwp)
97{
98	return (rwsem_is_locked(SEM(rwp)));
99}
100
101static inline int
102RW_WRITE_HELD(krwlock_t *rwp)
103{
104	return (rw_owner(rwp) == current);
105}
106
107static inline int
108RW_READ_HELD(krwlock_t *rwp)
109{
110	return (RW_LOCK_HELD(rwp) && rw_owner(rwp) == NULL);
111}
112
113/*
114 * The following functions must be a #define and not static inline.
115 * This ensures that the native linux semaphore functions (down/up)
116 * will be correctly located in the users code which is important
117 * for the built in kernel lock analysis tools
118 */
119#define	rw_init(rwp, name, type, arg) /* CSTYLED */			\
120({									\
121	static struct lock_class_key __key;				\
122	ASSERT(type == RW_DEFAULT || type == RW_NOLOCKDEP);		\
123									\
124	__init_rwsem(SEM(rwp), #rwp, &__key);				\
125	spl_rw_clear_owner(rwp);					\
126	spl_rw_set_type(rwp, type);					\
127})
128
129/*
130 * The Linux rwsem implementation does not require a matching destroy.
131 */
132#define	rw_destroy(rwp)		((void) 0)
133
134/*
135 * Upgrading a rwsem from a reader to a writer is not supported by the
136 * Linux kernel.  The lock must be dropped and reacquired as a writer.
137 */
138#define	rw_tryupgrade(rwp)	RW_WRITE_HELD(rwp)
139
140#define	rw_tryenter(rwp, rw) /* CSTYLED */				\
141({									\
142	int _rc_ = 0;							\
143									\
144	spl_rw_lockdep_off_maybe(rwp);					\
145	switch (rw) {							\
146	case RW_READER:							\
147		_rc_ = down_read_trylock(SEM(rwp));			\
148		break;							\
149	case RW_WRITER:							\
150		if ((_rc_ = down_write_trylock(SEM(rwp))))		\
151			spl_rw_set_owner(rwp);				\
152		break;							\
153	default:							\
154		VERIFY(0);						\
155	}								\
156	spl_rw_lockdep_on_maybe(rwp);					\
157	_rc_;								\
158})
159
160#define	rw_enter(rwp, rw) /* CSTYLED */					\
161({									\
162	spl_rw_lockdep_off_maybe(rwp);					\
163	switch (rw) {							\
164	case RW_READER:							\
165		down_read(SEM(rwp));					\
166		break;							\
167	case RW_WRITER:							\
168		down_write(SEM(rwp));					\
169		spl_rw_set_owner(rwp);					\
170		break;							\
171	default:							\
172		VERIFY(0);						\
173	}								\
174	spl_rw_lockdep_on_maybe(rwp);					\
175})
176
177#define	rw_exit(rwp) /* CSTYLED */					\
178({									\
179	spl_rw_lockdep_off_maybe(rwp);					\
180	if (RW_WRITE_HELD(rwp)) {					\
181		spl_rw_clear_owner(rwp);				\
182		up_write(SEM(rwp));					\
183	} else {							\
184		ASSERT(RW_READ_HELD(rwp));				\
185		up_read(SEM(rwp));					\
186	}								\
187	spl_rw_lockdep_on_maybe(rwp);					\
188})
189
190#define	rw_downgrade(rwp) /* CSTYLED */					\
191({									\
192	spl_rw_lockdep_off_maybe(rwp);					\
193	spl_rw_clear_owner(rwp);					\
194	downgrade_write(SEM(rwp));					\
195	spl_rw_lockdep_on_maybe(rwp);					\
196})
197
198#endif /* _SPL_RWLOCK_H */
199