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
16/* Structure to mediate between updaters and fastpath-using readers. */
17struct rcu_sync {
18 int gp_state;
19 int gp_count;
20 wait_queue_head_t gp_wait;
21
22 struct rcu_head cb_head;
23};
24
25/**
26 * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
27 * @rsp: Pointer to rcu_sync structure to use for synchronization
28 *
29 * Returns true if readers are permitted to use their fastpaths. Must be
30 * invoked within some flavor of RCU read-side critical section.
31 */
32static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
33{
34 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
35 "suspicious rcu_sync_is_idle() usage");
36 return !READ_ONCE(rsp->gp_state); /* GP_IDLE */
37}
38
39extern void rcu_sync_init(struct rcu_sync *);
40extern void rcu_sync_enter(struct rcu_sync *);
41extern void rcu_sync_exit(struct rcu_sync *);
42extern void rcu_sync_dtor(struct rcu_sync *);
43
44#define __RCU_SYNC_INITIALIZER(name) { \
45 .gp_state = 0, \
46 .gp_count = 0, \
47 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
48 }
49
50#define DEFINE_RCU_SYNC(name) \
51 struct rcu_sync name = __RCU_SYNC_INITIALIZER(name)
52
53#endif /* _LINUX_RCU_SYNC_H_ */
54