Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[linux-2.6-microblaze.git] / include / linux / rcu_sync.h
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  */
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_ */