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 #include <linux/mutex.h> 31 32 struct srcu_struct_array { 33 int c[2]; 34 }; 35 36 struct srcu_struct { 37 int completed; 38 struct srcu_struct_array __percpu *per_cpu_ref; 39 struct mutex mutex; 40 #ifdef CONFIG_DEBUG_LOCK_ALLOC 41 struct lockdep_map dep_map; 42 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 43 }; 44 45 #ifndef CONFIG_PREEMPT 46 #define srcu_barrier() barrier() 47 #else /* #ifndef CONFIG_PREEMPT */ 48 #define srcu_barrier() 49 #endif /* #else #ifndef CONFIG_PREEMPT */ 50 51 #ifdef CONFIG_DEBUG_LOCK_ALLOC 52 53 int __init_srcu_struct(struct srcu_struct *sp, const char *name, 54 struct lock_class_key *key); 55 56 #define init_srcu_struct(sp) \ 57 ({ \ 58 static struct lock_class_key __srcu_key; \ 59 \ 60 __init_srcu_struct((sp), #sp, &__srcu_key); \ 61 }) 62 63 # define srcu_read_acquire(sp) \ 64 lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_) 65 # define srcu_read_release(sp) \ 66 lock_release(&(sp)->dep_map, 1, _THIS_IP_) 67 68 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 69 70 int init_srcu_struct(struct srcu_struct *sp); 71 72 # define srcu_read_acquire(sp) do { } while (0) 73 # define srcu_read_release(sp) do { } while (0) 74 75 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 76 77 void cleanup_srcu_struct(struct srcu_struct *sp); 78 int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); 79 void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); 80 void synchronize_srcu(struct srcu_struct *sp); 81 void synchronize_srcu_expedited(struct srcu_struct *sp); 82 long srcu_batches_completed(struct srcu_struct *sp); 83 84 #ifdef CONFIG_DEBUG_LOCK_ALLOC 85 86 /** 87 * srcu_read_lock_held - might we be in SRCU read-side critical section? 88 * 89 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 90 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 91 * this assumes we are in an SRCU read-side critical section unless it can 92 * prove otherwise. 93 */ 94 static inline int srcu_read_lock_held(struct srcu_struct *sp) 95 { 96 if (debug_locks) 97 return lock_is_held(&sp->dep_map); 98 return 1; 99 } 100 101 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 102 103 static inline int srcu_read_lock_held(struct srcu_struct *sp) 104 { 105 return 1; 106 } 107 108 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 109 110 /** 111 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 112 * @p: the pointer to fetch and protect for later dereferencing 113 * @sp: pointer to the srcu_struct, which is used to check that we 114 * really are in an SRCU read-side critical section. 115 * @c: condition to check for update-side use 116 * 117 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 118 * critical section will result in an RCU-lockdep splat, unless @c evaluates 119 * to 1. The @c argument will normally be a logical expression containing 120 * lockdep_is_held() calls. 121 */ 122 #define srcu_dereference_check(p, sp, c) \ 123 __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) 124 125 /** 126 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 127 * @p: the pointer to fetch and protect for later dereferencing 128 * @sp: pointer to the srcu_struct, which is used to check that we 129 * really are in an SRCU read-side critical section. 130 * 131 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 132 * is enabled, invoking this outside of an RCU read-side critical 133 * section will result in an RCU-lockdep splat. 134 */ 135 #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) 136 137 /** 138 * srcu_read_lock - register a new reader for an SRCU-protected structure. 139 * @sp: srcu_struct in which to register the new reader. 140 * 141 * Enter an SRCU read-side critical section. Note that SRCU read-side 142 * critical sections may be nested. However, it is illegal to 143 * call anything that waits on an SRCU grace period for the same 144 * srcu_struct, whether directly or indirectly. Please note that 145 * one way to indirectly wait on an SRCU grace period is to acquire 146 * a mutex that is held elsewhere while calling synchronize_srcu() or 147 * synchronize_srcu_expedited(). 148 */ 149 static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) 150 { 151 int retval = __srcu_read_lock(sp); 152 153 srcu_read_acquire(sp); 154 return retval; 155 } 156 157 /** 158 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 159 * @sp: srcu_struct in which to unregister the old reader. 160 * @idx: return value from corresponding srcu_read_lock(). 161 * 162 * Exit an SRCU read-side critical section. 163 */ 164 static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) 165 __releases(sp) 166 { 167 srcu_read_release(sp); 168 __srcu_read_unlock(sp, idx); 169 } 170 171 #endif 172