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 struct notifier_block; 34 35 extern void rcu_sched_qs(int cpu); 36 extern void rcu_bh_qs(int cpu); 37 extern int rcu_needs_cpu(int cpu); 38 extern void rcu_scheduler_starting(void); 39 extern int rcu_expedited_torture_stats(char *page); 40 41 #ifdef CONFIG_TREE_PREEMPT_RCU 42 43 extern void __rcu_read_lock(void); 44 extern void __rcu_read_unlock(void); 45 extern void synchronize_rcu(void); 46 extern void exit_rcu(void); 47 48 /* 49 * Defined as macro as it is a very low level header 50 * included from areas that don't even know about current 51 */ 52 #define rcu_preempt_depth() (current->rcu_read_lock_nesting) 53 54 #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ 55 56 static inline void __rcu_read_lock(void) 57 { 58 preempt_disable(); 59 } 60 61 static inline void __rcu_read_unlock(void) 62 { 63 preempt_enable(); 64 } 65 66 #define synchronize_rcu synchronize_sched 67 68 static inline void exit_rcu(void) 69 { 70 } 71 72 static inline int rcu_preempt_depth(void) 73 { 74 return 0; 75 } 76 77 #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ 78 79 static inline void __rcu_read_lock_bh(void) 80 { 81 local_bh_disable(); 82 } 83 static inline void __rcu_read_unlock_bh(void) 84 { 85 local_bh_enable(); 86 } 87 88 extern void call_rcu_sched(struct rcu_head *head, 89 void (*func)(struct rcu_head *rcu)); 90 extern void synchronize_rcu_expedited(void); 91 92 static inline void synchronize_rcu_bh_expedited(void) 93 { 94 synchronize_sched_expedited(); 95 } 96 97 extern void rcu_check_callbacks(int cpu, int user); 98 99 extern long rcu_batches_completed(void); 100 extern long rcu_batches_completed_bh(void); 101 extern long rcu_batches_completed_sched(void); 102 103 #ifdef CONFIG_NO_HZ 104 void rcu_enter_nohz(void); 105 void rcu_exit_nohz(void); 106 #else /* CONFIG_NO_HZ */ 107 static inline void rcu_enter_nohz(void) 108 { 109 } 110 static inline void rcu_exit_nohz(void) 111 { 112 } 113 #endif /* CONFIG_NO_HZ */ 114 115 /* A context switch is a grace period for RCU-sched and RCU-bh. */ 116 static inline int rcu_blocking_is_gp(void) 117 { 118 return num_online_cpus() == 1; 119 } 120 121 #endif /* __LINUX_RCUTREE_H */ 122