1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Sleepable Read-Copy Update mechanism for mutual exclusion 4 * 5 * Copyright (C) IBM Corporation, 2006 6 * Copyright (C) Fujitsu, 2012 7 * 8 * Author: Paul McKenney <paulmck@linux.ibm.com> 9 * Lai Jiangshan <laijs@cn.fujitsu.com> 10 * 11 * For detailed explanation of Read-Copy Update mechanism see - 12 * Documentation/RCU/ *.txt 13 * 14 */ 15 16 #ifndef _LINUX_SRCU_H 17 #define _LINUX_SRCU_H 18 19 #include <linux/mutex.h> 20 #include <linux/rcupdate.h> 21 #include <linux/workqueue.h> 22 #include <linux/rcu_segcblist.h> 23 24 struct srcu_struct; 25 26 #ifdef CONFIG_DEBUG_LOCK_ALLOC 27 28 int __init_srcu_struct(struct srcu_struct *ssp, const char *name, 29 struct lock_class_key *key); 30 31 #define init_srcu_struct(ssp) \ 32 ({ \ 33 static struct lock_class_key __srcu_key; \ 34 \ 35 __init_srcu_struct((ssp), #ssp, &__srcu_key); \ 36 }) 37 38 #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, 39 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 40 41 int init_srcu_struct(struct srcu_struct *ssp); 42 43 #define __SRCU_DEP_MAP_INIT(srcu_name) 44 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 45 46 #ifdef CONFIG_TINY_SRCU 47 #include <linux/srcutiny.h> 48 #elif defined(CONFIG_TREE_SRCU) 49 #include <linux/srcutree.h> 50 #elif defined(CONFIG_SRCU) 51 #error "Unknown SRCU implementation specified to kernel configuration" 52 #else 53 /* Dummy definition for things like notifiers. Actual use gets link error. */ 54 struct srcu_struct { }; 55 #endif 56 57 void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, 58 void (*func)(struct rcu_head *head)); 59 void cleanup_srcu_struct(struct srcu_struct *ssp); 60 int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); 61 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); 62 void synchronize_srcu(struct srcu_struct *ssp); 63 unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); 64 unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); 65 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); 66 67 #ifdef CONFIG_SRCU 68 void srcu_init(void); 69 #else /* #ifdef CONFIG_SRCU */ 70 static inline void srcu_init(void) { } 71 #endif /* #else #ifdef CONFIG_SRCU */ 72 73 #ifdef CONFIG_DEBUG_LOCK_ALLOC 74 75 /** 76 * srcu_read_lock_held - might we be in SRCU read-side critical section? 77 * @ssp: The srcu_struct structure to check 78 * 79 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 80 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 81 * this assumes we are in an SRCU read-side critical section unless it can 82 * prove otherwise. 83 * 84 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 85 * and while lockdep is disabled. 86 * 87 * Note that SRCU is based on its own statemachine and it doesn't 88 * relies on normal RCU, it can be called from the CPU which 89 * is in the idle loop from an RCU point of view or offline. 90 */ 91 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 92 { 93 if (!debug_lockdep_rcu_enabled()) 94 return 1; 95 return lock_is_held(&ssp->dep_map); 96 } 97 98 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 99 100 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 101 { 102 return 1; 103 } 104 105 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 106 107 /** 108 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 109 * @p: the pointer to fetch and protect for later dereferencing 110 * @ssp: pointer to the srcu_struct, which is used to check that we 111 * really are in an SRCU read-side critical section. 112 * @c: condition to check for update-side use 113 * 114 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 115 * critical section will result in an RCU-lockdep splat, unless @c evaluates 116 * to 1. The @c argument will normally be a logical expression containing 117 * lockdep_is_held() calls. 118 */ 119 #define srcu_dereference_check(p, ssp, c) \ 120 __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ 121 (c) || srcu_read_lock_held(ssp), __rcu) 122 123 /** 124 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 125 * @p: the pointer to fetch and protect for later dereferencing 126 * @ssp: pointer to the srcu_struct, which is used to check that we 127 * really are in an SRCU read-side critical section. 128 * 129 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 130 * is enabled, invoking this outside of an RCU read-side critical 131 * section will result in an RCU-lockdep splat. 132 */ 133 #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) 134 135 /** 136 * srcu_dereference_notrace - no tracing and no lockdep calls from here 137 * @p: the pointer to fetch and protect for later dereferencing 138 * @ssp: pointer to the srcu_struct, which is used to check that we 139 * really are in an SRCU read-side critical section. 140 */ 141 #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) 142 143 /** 144 * srcu_read_lock - register a new reader for an SRCU-protected structure. 145 * @ssp: srcu_struct in which to register the new reader. 146 * 147 * Enter an SRCU read-side critical section. Note that SRCU read-side 148 * critical sections may be nested. However, it is illegal to 149 * call anything that waits on an SRCU grace period for the same 150 * srcu_struct, whether directly or indirectly. Please note that 151 * one way to indirectly wait on an SRCU grace period is to acquire 152 * a mutex that is held elsewhere while calling synchronize_srcu() or 153 * synchronize_srcu_expedited(). 154 * 155 * Note that srcu_read_lock() and the matching srcu_read_unlock() must 156 * occur in the same context, for example, it is illegal to invoke 157 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() 158 * was invoked in process context. 159 */ 160 static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) 161 { 162 int retval; 163 164 retval = __srcu_read_lock(ssp); 165 rcu_lock_acquire(&(ssp)->dep_map); 166 return retval; 167 } 168 169 /* Used by tracing, cannot be traced and cannot invoke lockdep. */ 170 static inline notrace int 171 srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) 172 { 173 int retval; 174 175 retval = __srcu_read_lock(ssp); 176 return retval; 177 } 178 179 /** 180 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 181 * @ssp: srcu_struct in which to unregister the old reader. 182 * @idx: return value from corresponding srcu_read_lock(). 183 * 184 * Exit an SRCU read-side critical section. 185 */ 186 static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) 187 __releases(ssp) 188 { 189 WARN_ON_ONCE(idx & ~0x1); 190 rcu_lock_release(&(ssp)->dep_map); 191 __srcu_read_unlock(ssp, idx); 192 } 193 194 /* Used by tracing, cannot be traced and cannot call lockdep. */ 195 static inline notrace void 196 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) 197 { 198 __srcu_read_unlock(ssp, idx); 199 } 200 201 /** 202 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock 203 * 204 * Converts the preceding srcu_read_unlock into a two-way memory barrier. 205 * 206 * Call this after srcu_read_unlock, to guarantee that all memory operations 207 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after 208 * the preceding srcu_read_unlock. 209 */ 210 static inline void smp_mb__after_srcu_read_unlock(void) 211 { 212 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ 213 } 214 215 #endif 216