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 #else 51 #error "Unknown SRCU implementation specified to kernel configuration" 52 #endif 53 54 void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, 55 void (*func)(struct rcu_head *head)); 56 void cleanup_srcu_struct(struct srcu_struct *ssp); 57 int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); 58 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); 59 void synchronize_srcu(struct srcu_struct *ssp); 60 unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); 61 unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); 62 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); 63 64 #ifdef CONFIG_NEED_SRCU_NMI_SAFE 65 int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); 66 void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); 67 #else 68 static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) 69 { 70 return __srcu_read_lock(ssp); 71 } 72 static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) 73 { 74 __srcu_read_unlock(ssp, idx); 75 } 76 #endif /* CONFIG_NEED_SRCU_NMI_SAFE */ 77 78 void srcu_init(void); 79 80 #ifdef CONFIG_DEBUG_LOCK_ALLOC 81 82 /** 83 * srcu_read_lock_held - might we be in SRCU read-side critical section? 84 * @ssp: The srcu_struct structure to check 85 * 86 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 87 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 88 * this assumes we are in an SRCU read-side critical section unless it can 89 * prove otherwise. 90 * 91 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 92 * and while lockdep is disabled. 93 * 94 * Note that SRCU is based on its own statemachine and it doesn't 95 * relies on normal RCU, it can be called from the CPU which 96 * is in the idle loop from an RCU point of view or offline. 97 */ 98 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 99 { 100 if (!debug_lockdep_rcu_enabled()) 101 return 1; 102 return lock_is_held(&ssp->dep_map); 103 } 104 105 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 106 107 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 108 { 109 return 1; 110 } 111 112 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 113 114 #define SRCU_NMI_UNKNOWN 0x0 115 #define SRCU_NMI_UNSAFE 0x1 116 #define SRCU_NMI_SAFE 0x2 117 118 #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) 119 void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); 120 #else 121 static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, 122 bool nmi_safe) { } 123 #endif 124 125 126 /** 127 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 128 * @p: the pointer to fetch and protect for later dereferencing 129 * @ssp: pointer to the srcu_struct, which is used to check that we 130 * really are in an SRCU read-side critical section. 131 * @c: condition to check for update-side use 132 * 133 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 134 * critical section will result in an RCU-lockdep splat, unless @c evaluates 135 * to 1. The @c argument will normally be a logical expression containing 136 * lockdep_is_held() calls. 137 */ 138 #define srcu_dereference_check(p, ssp, c) \ 139 __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ 140 (c) || srcu_read_lock_held(ssp), __rcu) 141 142 /** 143 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 144 * @p: the pointer to fetch and protect for later dereferencing 145 * @ssp: pointer to the srcu_struct, which is used to check that we 146 * really are in an SRCU read-side critical section. 147 * 148 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 149 * is enabled, invoking this outside of an RCU read-side critical 150 * section will result in an RCU-lockdep splat. 151 */ 152 #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) 153 154 /** 155 * srcu_dereference_notrace - no tracing and no lockdep calls from here 156 * @p: the pointer to fetch and protect for later dereferencing 157 * @ssp: pointer to the srcu_struct, which is used to check that we 158 * really are in an SRCU read-side critical section. 159 */ 160 #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) 161 162 /** 163 * srcu_read_lock - register a new reader for an SRCU-protected structure. 164 * @ssp: srcu_struct in which to register the new reader. 165 * 166 * Enter an SRCU read-side critical section. Note that SRCU read-side 167 * critical sections may be nested. However, it is illegal to 168 * call anything that waits on an SRCU grace period for the same 169 * srcu_struct, whether directly or indirectly. Please note that 170 * one way to indirectly wait on an SRCU grace period is to acquire 171 * a mutex that is held elsewhere while calling synchronize_srcu() or 172 * synchronize_srcu_expedited(). 173 * 174 * Note that srcu_read_lock() and the matching srcu_read_unlock() must 175 * occur in the same context, for example, it is illegal to invoke 176 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() 177 * was invoked in process context. 178 */ 179 static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) 180 { 181 int retval; 182 183 srcu_check_nmi_safety(ssp, false); 184 retval = __srcu_read_lock(ssp); 185 rcu_lock_acquire(&(ssp)->dep_map); 186 return retval; 187 } 188 189 /** 190 * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. 191 * @ssp: srcu_struct in which to register the new reader. 192 * 193 * Enter an SRCU read-side critical section, but in an NMI-safe manner. 194 * See srcu_read_lock() for more information. 195 */ 196 static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) 197 { 198 int retval; 199 200 srcu_check_nmi_safety(ssp, true); 201 retval = __srcu_read_lock_nmisafe(ssp); 202 rcu_lock_acquire(&(ssp)->dep_map); 203 return retval; 204 } 205 206 /* Used by tracing, cannot be traced and cannot invoke lockdep. */ 207 static inline notrace int 208 srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) 209 { 210 int retval; 211 212 srcu_check_nmi_safety(ssp, false); 213 retval = __srcu_read_lock(ssp); 214 return retval; 215 } 216 217 /** 218 * srcu_down_read - register a new reader for an SRCU-protected structure. 219 * @ssp: srcu_struct in which to register the new reader. 220 * 221 * Enter a semaphore-like SRCU read-side critical section. Note that 222 * SRCU read-side critical sections may be nested. However, it is 223 * illegal to call anything that waits on an SRCU grace period for the 224 * same srcu_struct, whether directly or indirectly. Please note that 225 * one way to indirectly wait on an SRCU grace period is to acquire 226 * a mutex that is held elsewhere while calling synchronize_srcu() or 227 * synchronize_srcu_expedited(). But if you want lockdep to help you 228 * keep this stuff straight, you should instead use srcu_read_lock(). 229 * 230 * The semaphore-like nature of srcu_down_read() means that the matching 231 * srcu_up_read() can be invoked from some other context, for example, 232 * from some other task or from an irq handler. However, neither 233 * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler. 234 * 235 * Calls to srcu_down_read() may be nested, similar to the manner in 236 * which calls to down_read() may be nested. 237 */ 238 static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) 239 { 240 WARN_ON_ONCE(in_nmi()); 241 srcu_check_nmi_safety(ssp, false); 242 return __srcu_read_lock(ssp); 243 } 244 245 /** 246 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 247 * @ssp: srcu_struct in which to unregister the old reader. 248 * @idx: return value from corresponding srcu_read_lock(). 249 * 250 * Exit an SRCU read-side critical section. 251 */ 252 static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) 253 __releases(ssp) 254 { 255 WARN_ON_ONCE(idx & ~0x1); 256 srcu_check_nmi_safety(ssp, false); 257 rcu_lock_release(&(ssp)->dep_map); 258 __srcu_read_unlock(ssp, idx); 259 } 260 261 /** 262 * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. 263 * @ssp: srcu_struct in which to unregister the old reader. 264 * @idx: return value from corresponding srcu_read_lock(). 265 * 266 * Exit an SRCU read-side critical section, but in an NMI-safe manner. 267 */ 268 static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) 269 __releases(ssp) 270 { 271 WARN_ON_ONCE(idx & ~0x1); 272 srcu_check_nmi_safety(ssp, true); 273 rcu_lock_release(&(ssp)->dep_map); 274 __srcu_read_unlock_nmisafe(ssp, idx); 275 } 276 277 /* Used by tracing, cannot be traced and cannot call lockdep. */ 278 static inline notrace void 279 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) 280 { 281 srcu_check_nmi_safety(ssp, false); 282 __srcu_read_unlock(ssp, idx); 283 } 284 285 /** 286 * srcu_up_read - unregister a old reader from an SRCU-protected structure. 287 * @ssp: srcu_struct in which to unregister the old reader. 288 * @idx: return value from corresponding srcu_read_lock(). 289 * 290 * Exit an SRCU read-side critical section, but not necessarily from 291 * the same context as the maching srcu_down_read(). 292 */ 293 static inline void srcu_up_read(struct srcu_struct *ssp, int idx) 294 __releases(ssp) 295 { 296 WARN_ON_ONCE(idx & ~0x1); 297 WARN_ON_ONCE(in_nmi()); 298 srcu_check_nmi_safety(ssp, false); 299 __srcu_read_unlock(ssp, idx); 300 } 301 302 /** 303 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock 304 * 305 * Converts the preceding srcu_read_unlock into a two-way memory barrier. 306 * 307 * Call this after srcu_read_unlock, to guarantee that all memory operations 308 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after 309 * the preceding srcu_read_unlock. 310 */ 311 static inline void smp_mb__after_srcu_read_unlock(void) 312 { 313 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ 314 } 315 316 #endif 317