| 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 | /* |
| 106 | * Annotations provide deadlock detection for SRCU. |
| 107 | * |
| 108 | * Similar to other lockdep annotations, except there is an additional |
| 109 | * srcu_lock_sync(), which is basically an empty *write*-side critical section, |
| 110 | * see lock_sync() for more information. |
| 111 | */ |
| 112 | |
| 113 | /* Annotates a srcu_read_lock() */ |
| 114 | static inline void srcu_lock_acquire(struct lockdep_map *map) |
| 115 | { |
| 116 | lock_map_acquire_read(map); |
| 117 | } |
| 118 | |
| 119 | /* Annotates a srcu_read_lock() */ |
| 120 | static inline void srcu_lock_release(struct lockdep_map *map) |
| 121 | { |
| 122 | lock_map_release(map); |
| 123 | } |
| 124 | |
| 125 | /* Annotates a synchronize_srcu() */ |
| 126 | static inline void srcu_lock_sync(struct lockdep_map *map) |
| 127 | { |
| 128 | lock_map_sync(map); |
| 129 | } |
| 130 | |
| 131 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 132 | |
| 133 | static inline int srcu_read_lock_held(const struct srcu_struct *ssp) |
| 134 | { |
| 135 | return 1; |
| 136 | } |
| 137 | |
| 138 | #define srcu_lock_acquire(m) do { } while (0) |
| 139 | #define srcu_lock_release(m) do { } while (0) |
| 140 | #define srcu_lock_sync(m) do { } while (0) |
| 141 | |
| 142 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 143 | |
| 144 | #define SRCU_NMI_UNKNOWN 0x0 |
| 145 | #define SRCU_NMI_UNSAFE 0x1 |
| 146 | #define SRCU_NMI_SAFE 0x2 |
| 147 | |
| 148 | #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) |
| 149 | void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); |
| 150 | #else |
| 151 | static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, |
| 152 | bool nmi_safe) { } |
| 153 | #endif |
| 154 | |
| 155 | |
| 156 | /** |
| 157 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
| 158 | * @p: the pointer to fetch and protect for later dereferencing |
| 159 | * @ssp: pointer to the srcu_struct, which is used to check that we |
| 160 | * really are in an SRCU read-side critical section. |
| 161 | * @c: condition to check for update-side use |
| 162 | * |
| 163 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side |
| 164 | * critical section will result in an RCU-lockdep splat, unless @c evaluates |
| 165 | * to 1. The @c argument will normally be a logical expression containing |
| 166 | * lockdep_is_held() calls. |
| 167 | */ |
| 168 | #define srcu_dereference_check(p, ssp, c) \ |
| 169 | __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ |
| 170 | (c) || srcu_read_lock_held(ssp), __rcu) |
| 171 | |
| 172 | /** |
| 173 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing |
| 174 | * @p: the pointer to fetch and protect for later dereferencing |
| 175 | * @ssp: pointer to the srcu_struct, which is used to check that we |
| 176 | * really are in an SRCU read-side critical section. |
| 177 | * |
| 178 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU |
| 179 | * is enabled, invoking this outside of an RCU read-side critical |
| 180 | * section will result in an RCU-lockdep splat. |
| 181 | */ |
| 182 | #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) |
| 183 | |
| 184 | /** |
| 185 | * srcu_dereference_notrace - no tracing and no lockdep calls from here |
| 186 | * @p: the pointer to fetch and protect for later dereferencing |
| 187 | * @ssp: pointer to the srcu_struct, which is used to check that we |
| 188 | * really are in an SRCU read-side critical section. |
| 189 | */ |
| 190 | #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) |
| 191 | |
| 192 | /** |
| 193 | * srcu_read_lock - register a new reader for an SRCU-protected structure. |
| 194 | * @ssp: srcu_struct in which to register the new reader. |
| 195 | * |
| 196 | * Enter an SRCU read-side critical section. Note that SRCU read-side |
| 197 | * critical sections may be nested. However, it is illegal to |
| 198 | * call anything that waits on an SRCU grace period for the same |
| 199 | * srcu_struct, whether directly or indirectly. Please note that |
| 200 | * one way to indirectly wait on an SRCU grace period is to acquire |
| 201 | * a mutex that is held elsewhere while calling synchronize_srcu() or |
| 202 | * synchronize_srcu_expedited(). |
| 203 | * |
| 204 | * Note that srcu_read_lock() and the matching srcu_read_unlock() must |
| 205 | * occur in the same context, for example, it is illegal to invoke |
| 206 | * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() |
| 207 | * was invoked in process context. |
| 208 | */ |
| 209 | static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) |
| 210 | { |
| 211 | int retval; |
| 212 | |
| 213 | srcu_check_nmi_safety(ssp, false); |
| 214 | retval = __srcu_read_lock(ssp); |
| 215 | srcu_lock_acquire(&(ssp)->dep_map); |
| 216 | return retval; |
| 217 | } |
| 218 | |
| 219 | /** |
| 220 | * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. |
| 221 | * @ssp: srcu_struct in which to register the new reader. |
| 222 | * |
| 223 | * Enter an SRCU read-side critical section, but in an NMI-safe manner. |
| 224 | * See srcu_read_lock() for more information. |
| 225 | */ |
| 226 | static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) |
| 227 | { |
| 228 | int retval; |
| 229 | |
| 230 | srcu_check_nmi_safety(ssp, true); |
| 231 | retval = __srcu_read_lock_nmisafe(ssp); |
| 232 | rcu_lock_acquire(&(ssp)->dep_map); |
| 233 | return retval; |
| 234 | } |
| 235 | |
| 236 | /* Used by tracing, cannot be traced and cannot invoke lockdep. */ |
| 237 | static inline notrace int |
| 238 | srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) |
| 239 | { |
| 240 | int retval; |
| 241 | |
| 242 | srcu_check_nmi_safety(ssp, false); |
| 243 | retval = __srcu_read_lock(ssp); |
| 244 | return retval; |
| 245 | } |
| 246 | |
| 247 | /** |
| 248 | * srcu_down_read - register a new reader for an SRCU-protected structure. |
| 249 | * @ssp: srcu_struct in which to register the new reader. |
| 250 | * |
| 251 | * Enter a semaphore-like SRCU read-side critical section. Note that |
| 252 | * SRCU read-side critical sections may be nested. However, it is |
| 253 | * illegal to call anything that waits on an SRCU grace period for the |
| 254 | * same srcu_struct, whether directly or indirectly. Please note that |
| 255 | * one way to indirectly wait on an SRCU grace period is to acquire |
| 256 | * a mutex that is held elsewhere while calling synchronize_srcu() or |
| 257 | * synchronize_srcu_expedited(). But if you want lockdep to help you |
| 258 | * keep this stuff straight, you should instead use srcu_read_lock(). |
| 259 | * |
| 260 | * The semaphore-like nature of srcu_down_read() means that the matching |
| 261 | * srcu_up_read() can be invoked from some other context, for example, |
| 262 | * from some other task or from an irq handler. However, neither |
| 263 | * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler. |
| 264 | * |
| 265 | * Calls to srcu_down_read() may be nested, similar to the manner in |
| 266 | * which calls to down_read() may be nested. |
| 267 | */ |
| 268 | static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) |
| 269 | { |
| 270 | WARN_ON_ONCE(in_nmi()); |
| 271 | srcu_check_nmi_safety(ssp, false); |
| 272 | return __srcu_read_lock(ssp); |
| 273 | } |
| 274 | |
| 275 | /** |
| 276 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. |
| 277 | * @ssp: srcu_struct in which to unregister the old reader. |
| 278 | * @idx: return value from corresponding srcu_read_lock(). |
| 279 | * |
| 280 | * Exit an SRCU read-side critical section. |
| 281 | */ |
| 282 | static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) |
| 283 | __releases(ssp) |
| 284 | { |
| 285 | WARN_ON_ONCE(idx & ~0x1); |
| 286 | srcu_check_nmi_safety(ssp, false); |
| 287 | srcu_lock_release(&(ssp)->dep_map); |
| 288 | __srcu_read_unlock(ssp, idx); |
| 289 | } |
| 290 | |
| 291 | /** |
| 292 | * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. |
| 293 | * @ssp: srcu_struct in which to unregister the old reader. |
| 294 | * @idx: return value from corresponding srcu_read_lock(). |
| 295 | * |
| 296 | * Exit an SRCU read-side critical section, but in an NMI-safe manner. |
| 297 | */ |
| 298 | static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) |
| 299 | __releases(ssp) |
| 300 | { |
| 301 | WARN_ON_ONCE(idx & ~0x1); |
| 302 | srcu_check_nmi_safety(ssp, true); |
| 303 | rcu_lock_release(&(ssp)->dep_map); |
| 304 | __srcu_read_unlock_nmisafe(ssp, idx); |
| 305 | } |
| 306 | |
| 307 | /* Used by tracing, cannot be traced and cannot call lockdep. */ |
| 308 | static inline notrace void |
| 309 | srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) |
| 310 | { |
| 311 | srcu_check_nmi_safety(ssp, false); |
| 312 | __srcu_read_unlock(ssp, idx); |
| 313 | } |
| 314 | |
| 315 | /** |
| 316 | * srcu_up_read - unregister a old reader from an SRCU-protected structure. |
| 317 | * @ssp: srcu_struct in which to unregister the old reader. |
| 318 | * @idx: return value from corresponding srcu_read_lock(). |
| 319 | * |
| 320 | * Exit an SRCU read-side critical section, but not necessarily from |
| 321 | * the same context as the maching srcu_down_read(). |
| 322 | */ |
| 323 | static inline void srcu_up_read(struct srcu_struct *ssp, int idx) |
| 324 | __releases(ssp) |
| 325 | { |
| 326 | WARN_ON_ONCE(idx & ~0x1); |
| 327 | WARN_ON_ONCE(in_nmi()); |
| 328 | srcu_check_nmi_safety(ssp, false); |
| 329 | __srcu_read_unlock(ssp, idx); |
| 330 | } |
| 331 | |
| 332 | /** |
| 333 | * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock |
| 334 | * |
| 335 | * Converts the preceding srcu_read_unlock into a two-way memory barrier. |
| 336 | * |
| 337 | * Call this after srcu_read_unlock, to guarantee that all memory operations |
| 338 | * that occur after smp_mb__after_srcu_read_unlock will appear to happen after |
| 339 | * the preceding srcu_read_unlock. |
| 340 | */ |
| 341 | static inline void smp_mb__after_srcu_read_unlock(void) |
| 342 | { |
| 343 | /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ |
| 344 | } |
| 345 | |
| 346 | #endif |