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1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * RCU-based infrastructure for lightweight reader-writer locking
4 *
5 * Copyright (c) 2015, Red Hat, Inc.
6 *
7 * Author: Oleg Nesterov <oleg@redhat.com>
8 */
9
10#ifndef _LINUX_RCU_SYNC_H_
11#define _LINUX_RCU_SYNC_H_
12
13#include <linux/wait.h>
14#include <linux/rcupdate.h>
15
16enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
17
18/* Structure to mediate between updaters and fastpath-using readers. */
19struct rcu_sync {
20 int gp_state;
21 int gp_count;
22 wait_queue_head_t gp_wait;
23
24 int cb_state;
25 struct rcu_head cb_head;
26
27 enum rcu_sync_type gp_type;
28};
29
30extern void rcu_sync_lockdep_assert(struct rcu_sync *);
31
32/**
33 * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
34 * @rsp: Pointer to rcu_sync structure to use for synchronization
35 *
36 * Returns true if readers are permitted to use their fastpaths.
37 * Must be invoked within an RCU read-side critical section whose
38 * flavor matches that of the rcu_sync struture.
39 */
40static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
41{
42#ifdef CONFIG_PROVE_RCU
43 rcu_sync_lockdep_assert(rsp);
44#endif
45 return !rsp->gp_state; /* GP_IDLE */
46}
47
48extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
49extern void rcu_sync_enter_start(struct rcu_sync *);
50extern void rcu_sync_enter(struct rcu_sync *);
51extern void rcu_sync_exit(struct rcu_sync *);
52extern void rcu_sync_dtor(struct rcu_sync *);
53
54#define __RCU_SYNC_INITIALIZER(name, type) { \
55 .gp_state = 0, \
56 .gp_count = 0, \
57 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
58 .cb_state = 0, \
59 .gp_type = type, \
60 }
61
62#define __DEFINE_RCU_SYNC(name, type) \
63 struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
64
65#define DEFINE_RCU_SYNC(name) \
66 __DEFINE_RCU_SYNC(name, RCU_SYNC)
67
68#define DEFINE_RCU_SCHED_SYNC(name) \
69 __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
70
71#define DEFINE_RCU_BH_SYNC(name) \
72 __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
73
74#endif /* _LINUX_RCU_SYNC_H_ */