1 /*
2 * RCU-based infrastructure for lightweight reader-writer locking
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will 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.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
17 *
18 * Copyright (c) 2015, Red Hat, Inc.
19 *
20 * Author: Oleg Nesterov <oleg@redhat.com>
21 */
22
23 #ifndef _LINUX_RCU_SYNC_H_
24 #define _LINUX_RCU_SYNC_H_
25
26 #include <linux/wait.h>
27 #include <linux/rcupdate.h>
28
29 enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
30
31 /* Structure to mediate between updaters and fastpath-using readers. */
32 struct rcu_sync {
33 int gp_state;
34 int gp_count;
35 wait_queue_head_t gp_wait;
36
37 int cb_state;
38 struct rcu_head cb_head;
39
40 enum rcu_sync_type gp_type;
41 };
42
43 extern void rcu_sync_lockdep_assert(struct rcu_sync *);
44
45 /**
46 * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
47 * @rsp: Pointer to rcu_sync structure to use for synchronization
48 *
49 * Returns true if readers are permitted to use their fastpaths.
50 * Must be invoked within an RCU read-side critical section whose
51 * flavor matches that of the rcu_sync struture.
52 */
rcu_sync_is_idle(struct rcu_sync * rsp)53 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
54 {
55 #ifdef CONFIG_PROVE_RCU
56 rcu_sync_lockdep_assert(rsp);
57 #endif
58 return !rsp->gp_state; /* GP_IDLE */
59 }
60
61 extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
62 extern void rcu_sync_enter_start(struct rcu_sync *);
63 extern void rcu_sync_enter(struct rcu_sync *);
64 extern void rcu_sync_exit(struct rcu_sync *);
65 extern void rcu_sync_dtor(struct rcu_sync *);
66
67 #define __RCU_SYNC_INITIALIZER(name, type) { \
68 .gp_state = 0, \
69 .gp_count = 0, \
70 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
71 .cb_state = 0, \
72 .gp_type = type, \
73 }
74
75 #define __DEFINE_RCU_SYNC(name, type) \
76 struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
77
78 #define DEFINE_RCU_SYNC(name) \
79 __DEFINE_RCU_SYNC(name, RCU_SYNC)
80
81 #define DEFINE_RCU_SCHED_SYNC(name) \
82 __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
83
84 #define DEFINE_RCU_BH_SYNC(name) \
85 __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
86
87 #endif /* _LINUX_RCU_SYNC_H_ */
88