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. */ 17 struct 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 */ rcu_sync_is_idle(struct rcu_sync * rsp)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 39 extern void rcu_sync_init(struct rcu_sync *); 40 extern void rcu_sync_enter_start(struct rcu_sync *); 41 extern void rcu_sync_enter(struct rcu_sync *); 42 extern void rcu_sync_exit(struct rcu_sync *); 43 extern 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_ */ 55