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 <[email protected]> 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 int cb_state; 23 struct rcu_head cb_head; 24 }; 25 26 /** 27 * rcu_sync_is_idle() - Are readers permitted to use their fastpaths? 28 * @rsp: Pointer to rcu_sync structure to use for synchronization 29 * 30 * Returns true if readers are permitted to use their fastpaths. Must be 31 * invoked within some flavor of RCU read-side critical section. 32 */ 33 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp) 34 { 35 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && 36 !rcu_read_lock_bh_held() && 37 !rcu_read_lock_sched_held(), 38 "suspicious rcu_sync_is_idle() usage"); 39 return !rsp->gp_state; /* GP_IDLE */ 40 } 41 42 extern void rcu_sync_init(struct rcu_sync *); 43 extern void rcu_sync_enter_start(struct rcu_sync *); 44 extern void rcu_sync_enter(struct rcu_sync *); 45 extern void rcu_sync_exit(struct rcu_sync *); 46 extern void rcu_sync_dtor(struct rcu_sync *); 47 48 #define __RCU_SYNC_INITIALIZER(name) { \ 49 .gp_state = 0, \ 50 .gp_count = 0, \ 51 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \ 52 .cb_state = 0, \ 53 } 54 55 #define DEFINE_RCU_SYNC(name) \ 56 struct rcu_sync name = __RCU_SYNC_INITIALIZER(name) 57 58 #endif /* _LINUX_RCU_SYNC_H_ */ 59