1 /* 2 * Sleepable Read-Copy Update mechanism for mutual exclusion 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 (C) IBM Corporation, 2006 19 * 20 * Author: Paul McKenney <[email protected]> 21 * 22 * For detailed explanation of Read-Copy Update mechanism see - 23 * Documentation/RCU/ *.txt 24 * 25 */ 26 27 #ifndef _LINUX_SRCU_H 28 #define _LINUX_SRCU_H 29 30 struct srcu_struct_array { 31 int c[2]; 32 }; 33 34 struct srcu_struct { 35 int completed; 36 struct srcu_struct_array __percpu *per_cpu_ref; 37 struct mutex mutex; 38 #ifdef CONFIG_DEBUG_LOCK_ALLOC 39 struct lockdep_map dep_map; 40 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 41 }; 42 43 #ifndef CONFIG_PREEMPT 44 #define srcu_barrier() barrier() 45 #else /* #ifndef CONFIG_PREEMPT */ 46 #define srcu_barrier() 47 #endif /* #else #ifndef CONFIG_PREEMPT */ 48 49 #ifdef CONFIG_DEBUG_LOCK_ALLOC 50 51 int __init_srcu_struct(struct srcu_struct *sp, const char *name, 52 struct lock_class_key *key); 53 54 #define init_srcu_struct(sp) \ 55 ({ \ 56 static struct lock_class_key __srcu_key; \ 57 \ 58 __init_srcu_struct((sp), #sp, &__srcu_key); \ 59 }) 60 61 # define srcu_read_acquire(sp) \ 62 lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_) 63 # define srcu_read_release(sp) \ 64 lock_release(&(sp)->dep_map, 1, _THIS_IP_) 65 66 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 67 68 int init_srcu_struct(struct srcu_struct *sp); 69 70 # define srcu_read_acquire(sp) do { } while (0) 71 # define srcu_read_release(sp) do { } while (0) 72 73 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 74 75 void cleanup_srcu_struct(struct srcu_struct *sp); 76 int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); 77 void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); 78 void synchronize_srcu(struct srcu_struct *sp); 79 void synchronize_srcu_expedited(struct srcu_struct *sp); 80 long srcu_batches_completed(struct srcu_struct *sp); 81 82 #ifdef CONFIG_DEBUG_LOCK_ALLOC 83 84 /** 85 * srcu_read_lock_held - might we be in SRCU read-side critical section? 86 * 87 * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in 88 * an SRCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, 89 * this assumes we are in an SRCU read-side critical section unless it can 90 * prove otherwise. 91 */ 92 static inline int srcu_read_lock_held(struct srcu_struct *sp) 93 { 94 if (debug_locks) 95 return lock_is_held(&sp->dep_map); 96 return 1; 97 } 98 99 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 100 101 static inline int srcu_read_lock_held(struct srcu_struct *sp) 102 { 103 return 1; 104 } 105 106 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 107 108 /** 109 * srcu_dereference - fetch SRCU-protected pointer with checking 110 * 111 * Makes rcu_dereference_check() do the dirty work. 112 */ 113 #define srcu_dereference(p, sp) \ 114 rcu_dereference_check(p, srcu_read_lock_held(sp)) 115 116 /** 117 * srcu_read_lock - register a new reader for an SRCU-protected structure. 118 * @sp: srcu_struct in which to register the new reader. 119 * 120 * Enter an SRCU read-side critical section. Note that SRCU read-side 121 * critical sections may be nested. 122 */ 123 static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) 124 { 125 int retval = __srcu_read_lock(sp); 126 127 srcu_read_acquire(sp); 128 return retval; 129 } 130 131 /** 132 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 133 * @sp: srcu_struct in which to unregister the old reader. 134 * @idx: return value from corresponding srcu_read_lock(). 135 * 136 * Exit an SRCU read-side critical section. 137 */ 138 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) 139 __releases(sp) 140 { 141 srcu_read_release(sp); 142 __srcu_read_unlock(sp, idx); 143 } 144 145 #endif 146