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_DEBUG_LOCK_ALLOC 68 69 /** 70 * srcu_read_lock_held - might we be in SRCU read-side critical section? 71 * @ssp: The srcu_struct structure to check 72 * 73 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 74 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 75 * this assumes we are in an SRCU read-side critical section unless it can 76 * prove otherwise. 77 * 78 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 79 * and while lockdep is disabled. 80 * 81 * Note that SRCU is based on its own statemachine and it doesn't 82 * relies on normal RCU, it can be called from the CPU which 83 * is in the idle loop from an RCU point of view or offline. 84 */ 85 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 86 { 87 if (!debug_lockdep_rcu_enabled()) 88 return 1; 89 return lock_is_held(&ssp->dep_map); 90 } 91 92 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 93 94 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 95 { 96 return 1; 97 } 98 99 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 100 101 /** 102 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 103 * @p: the pointer to fetch and protect for later dereferencing 104 * @ssp: pointer to the srcu_struct, which is used to check that we 105 * really are in an SRCU read-side critical section. 106 * @c: condition to check for update-side use 107 * 108 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 109 * critical section will result in an RCU-lockdep splat, unless @c evaluates 110 * to 1. The @c argument will normally be a logical expression containing 111 * lockdep_is_held() calls. 112 */ 113 #define srcu_dereference_check(p, ssp, c) \ 114 __rcu_dereference_check((p), (c) || srcu_read_lock_held(ssp), __rcu) 115 116 /** 117 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 118 * @p: the pointer to fetch and protect for later dereferencing 119 * @ssp: pointer to the srcu_struct, which is used to check that we 120 * really are in an SRCU read-side critical section. 121 * 122 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 123 * is enabled, invoking this outside of an RCU read-side critical 124 * section will result in an RCU-lockdep splat. 125 */ 126 #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) 127 128 /** 129 * srcu_dereference_notrace - no tracing and no lockdep calls from here 130 * @p: the pointer to fetch and protect for later dereferencing 131 * @ssp: pointer to the srcu_struct, which is used to check that we 132 * really are in an SRCU read-side critical section. 133 */ 134 #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) 135 136 /** 137 * srcu_read_lock - register a new reader for an SRCU-protected structure. 138 * @ssp: srcu_struct in which to register the new reader. 139 * 140 * Enter an SRCU read-side critical section. Note that SRCU read-side 141 * critical sections may be nested. However, it is illegal to 142 * call anything that waits on an SRCU grace period for the same 143 * srcu_struct, whether directly or indirectly. Please note that 144 * one way to indirectly wait on an SRCU grace period is to acquire 145 * a mutex that is held elsewhere while calling synchronize_srcu() or 146 * synchronize_srcu_expedited(). 147 * 148 * Note that srcu_read_lock() and the matching srcu_read_unlock() must 149 * occur in the same context, for example, it is illegal to invoke 150 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() 151 * was invoked in process context. 152 */ 153 static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) 154 { 155 int retval; 156 157 retval = __srcu_read_lock(ssp); 158 rcu_lock_acquire(&(ssp)->dep_map); 159 return retval; 160 } 161 162 /* Used by tracing, cannot be traced and cannot invoke lockdep. */ 163 static inline notrace int 164 srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) 165 { 166 int retval; 167 168 retval = __srcu_read_lock(ssp); 169 return retval; 170 } 171 172 /** 173 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 174 * @ssp: srcu_struct in which to unregister the old reader. 175 * @idx: return value from corresponding srcu_read_lock(). 176 * 177 * Exit an SRCU read-side critical section. 178 */ 179 static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) 180 __releases(ssp) 181 { 182 WARN_ON_ONCE(idx & ~0x1); 183 rcu_lock_release(&(ssp)->dep_map); 184 __srcu_read_unlock(ssp, idx); 185 } 186 187 /* Used by tracing, cannot be traced and cannot call lockdep. */ 188 static inline notrace void 189 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) 190 { 191 __srcu_read_unlock(ssp, idx); 192 } 193 194 /** 195 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock 196 * 197 * Converts the preceding srcu_read_unlock into a two-way memory barrier. 198 * 199 * Call this after srcu_read_unlock, to guarantee that all memory operations 200 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after 201 * the preceding srcu_read_unlock. 202 */ 203 static inline void smp_mb__after_srcu_read_unlock(void) 204 { 205 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ 206 } 207 208 #endif 209