1 /* 2 * Read-Copy Update mechanism for mutual exclusion (tree-based version) 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 17 * 18 * Copyright IBM Corporation, 2008 19 * 20 * Author: Dipankar Sarma <[email protected]> 21 * Paul E. McKenney <[email protected]> Hierarchical algorithm 22 * 23 * Based on the original work by Paul McKenney <[email protected]> 24 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. 25 * 26 * For detailed explanation of Read-Copy Update mechanism see - 27 * Documentation/RCU 28 */ 29 30 #ifndef __LINUX_RCUTREE_H 31 #define __LINUX_RCUTREE_H 32 33 extern void rcu_sched_qs(int cpu); 34 extern void rcu_bh_qs(int cpu); 35 36 extern int rcu_needs_cpu(int cpu); 37 38 #ifdef CONFIG_TREE_PREEMPT_RCU 39 40 extern void __rcu_read_lock(void); 41 extern void __rcu_read_unlock(void); 42 extern void exit_rcu(void); 43 44 #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ 45 46 static inline void __rcu_read_lock(void) 47 { 48 preempt_disable(); 49 } 50 51 static inline void __rcu_read_unlock(void) 52 { 53 preempt_enable(); 54 } 55 56 #define __synchronize_sched() synchronize_rcu() 57 58 static inline void exit_rcu(void) 59 { 60 } 61 62 #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ 63 64 static inline void __rcu_read_lock_bh(void) 65 { 66 local_bh_disable(); 67 } 68 static inline void __rcu_read_unlock_bh(void) 69 { 70 local_bh_enable(); 71 } 72 73 extern void call_rcu_sched(struct rcu_head *head, 74 void (*func)(struct rcu_head *rcu)); 75 76 static inline void synchronize_rcu_expedited(void) 77 { 78 synchronize_sched_expedited(); 79 } 80 81 static inline void synchronize_rcu_bh_expedited(void) 82 { 83 synchronize_sched_expedited(); 84 } 85 86 extern void __rcu_init(void); 87 extern void rcu_check_callbacks(int cpu, int user); 88 extern void rcu_restart_cpu(int cpu); 89 90 extern long rcu_batches_completed(void); 91 extern long rcu_batches_completed_bh(void); 92 extern long rcu_batches_completed_sched(void); 93 94 static inline void rcu_init_sched(void) 95 { 96 } 97 98 #ifdef CONFIG_NO_HZ 99 void rcu_enter_nohz(void); 100 void rcu_exit_nohz(void); 101 #else /* CONFIG_NO_HZ */ 102 static inline void rcu_enter_nohz(void) 103 { 104 } 105 static inline void rcu_exit_nohz(void) 106 { 107 } 108 #endif /* CONFIG_NO_HZ */ 109 110 /* A context switch is a grace period for rcutree. */ 111 static inline int rcu_blocking_is_gp(void) 112 { 113 return num_online_cpus() == 1; 114 } 115 116 #endif /* __LINUX_RCUTREE_H */ 117