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_start(struct rcu_sync *);
41extern void rcu_sync_enter(struct rcu_sync *);
42extern void rcu_sync_exit(struct rcu_sync *);
43extern void rcu_sync_dtor(struct rcu_sync *);
44
45#define __RCU_SYNC_INITIALIZER(name) {					\
46		.gp_state = 0,						\
47		.gp_count = 0,						\
48		.gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait),	\
49	}
50
51#define	DEFINE_RCU_SYNC(name)	\
52	struct rcu_sync name = __RCU_SYNC_INITIALIZER(name)
53
54#endif /* _LINUX_RCU_SYNC_H_ */