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 /* Values for SRCU Tree srcu_data ->srcu_reader_flavor, but also used by rcutorture. */ 47 #define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). 48 #define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). 49 // 0x4 // SRCU-lite is no longer with us. 50 #define SRCU_READ_FLAVOR_FAST 0x8 // srcu_read_lock_fast(). 51 #define SRCU_READ_FLAVOR_ALL (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \ 52 SRCU_READ_FLAVOR_FAST) // All of the above. 53 #define SRCU_READ_FLAVOR_SLOWGP SRCU_READ_FLAVOR_FAST 54 // Flavors requiring synchronize_rcu() 55 // instead of smp_mb(). 56 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); 57 58 #ifdef CONFIG_TINY_SRCU 59 #include <linux/srcutiny.h> 60 #elif defined(CONFIG_TREE_SRCU) 61 #include <linux/srcutree.h> 62 #else 63 #error "Unknown SRCU implementation specified to kernel configuration" 64 #endif 65 66 void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, 67 void (*func)(struct rcu_head *head)); 68 void cleanup_srcu_struct(struct srcu_struct *ssp); 69 void synchronize_srcu(struct srcu_struct *ssp); 70 71 #define SRCU_GET_STATE_COMPLETED 0x1 72 73 /** 74 * get_completed_synchronize_srcu - Return a pre-completed polled state cookie 75 * 76 * Returns a value that poll_state_synchronize_srcu() will always treat 77 * as a cookie whose grace period has already completed. 78 */ 79 static inline unsigned long get_completed_synchronize_srcu(void) 80 { 81 return SRCU_GET_STATE_COMPLETED; 82 } 83 84 unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); 85 unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); 86 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); 87 88 // Maximum number of unsigned long values corresponding to 89 // not-yet-completed SRCU grace periods. 90 #define NUM_ACTIVE_SRCU_POLL_OLDSTATE 2 91 92 /** 93 * same_state_synchronize_srcu - Are two old-state values identical? 94 * @oldstate1: First old-state value. 95 * @oldstate2: Second old-state value. 96 * 97 * The two old-state values must have been obtained from either 98 * get_state_synchronize_srcu(), start_poll_synchronize_srcu(), or 99 * get_completed_synchronize_srcu(). Returns @true if the two values are 100 * identical and @false otherwise. This allows structures whose lifetimes 101 * are tracked by old-state values to push these values to a list header, 102 * allowing those structures to be slightly smaller. 103 */ 104 static inline bool same_state_synchronize_srcu(unsigned long oldstate1, unsigned long oldstate2) 105 { 106 return oldstate1 == oldstate2; 107 } 108 109 #ifdef CONFIG_NEED_SRCU_NMI_SAFE 110 int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); 111 void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); 112 #else 113 static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) 114 { 115 return __srcu_read_lock(ssp); 116 } 117 static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) 118 { 119 __srcu_read_unlock(ssp, idx); 120 } 121 #endif /* CONFIG_NEED_SRCU_NMI_SAFE */ 122 123 void srcu_init(void); 124 125 #ifdef CONFIG_DEBUG_LOCK_ALLOC 126 127 /** 128 * srcu_read_lock_held - might we be in SRCU read-side critical section? 129 * @ssp: The srcu_struct structure to check 130 * 131 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 132 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 133 * this assumes we are in an SRCU read-side critical section unless it can 134 * prove otherwise. 135 * 136 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 137 * and while lockdep is disabled. 138 * 139 * Note that SRCU is based on its own statemachine and it doesn't 140 * relies on normal RCU, it can be called from the CPU which 141 * is in the idle loop from an RCU point of view or offline. 142 */ 143 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 144 { 145 if (!debug_lockdep_rcu_enabled()) 146 return 1; 147 return lock_is_held(&ssp->dep_map); 148 } 149 150 /* 151 * Annotations provide deadlock detection for SRCU. 152 * 153 * Similar to other lockdep annotations, except there is an additional 154 * srcu_lock_sync(), which is basically an empty *write*-side critical section, 155 * see lock_sync() for more information. 156 */ 157 158 /* Annotates a srcu_read_lock() */ 159 static inline void srcu_lock_acquire(struct lockdep_map *map) 160 { 161 lock_map_acquire_read(map); 162 } 163 164 /* Annotates a srcu_read_lock() */ 165 static inline void srcu_lock_release(struct lockdep_map *map) 166 { 167 lock_map_release(map); 168 } 169 170 /* Annotates a synchronize_srcu() */ 171 static inline void srcu_lock_sync(struct lockdep_map *map) 172 { 173 lock_map_sync(map); 174 } 175 176 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 177 178 static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 179 { 180 return 1; 181 } 182 183 #define srcu_lock_acquire(m) do { } while (0) 184 #define srcu_lock_release(m) do { } while (0) 185 #define srcu_lock_sync(m) do { } while (0) 186 187 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 188 189 190 /** 191 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 192 * @p: the pointer to fetch and protect for later dereferencing 193 * @ssp: pointer to the srcu_struct, which is used to check that we 194 * really are in an SRCU read-side critical section. 195 * @c: condition to check for update-side use 196 * 197 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 198 * critical section will result in an RCU-lockdep splat, unless @c evaluates 199 * to 1. The @c argument will normally be a logical expression containing 200 * lockdep_is_held() calls. 201 */ 202 #define srcu_dereference_check(p, ssp, c) \ 203 __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ 204 (c) || srcu_read_lock_held(ssp), __rcu) 205 206 /** 207 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 208 * @p: the pointer to fetch and protect for later dereferencing 209 * @ssp: pointer to the srcu_struct, which is used to check that we 210 * really are in an SRCU read-side critical section. 211 * 212 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 213 * is enabled, invoking this outside of an RCU read-side critical 214 * section will result in an RCU-lockdep splat. 215 */ 216 #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) 217 218 /** 219 * srcu_dereference_notrace - no tracing and no lockdep calls from here 220 * @p: the pointer to fetch and protect for later dereferencing 221 * @ssp: pointer to the srcu_struct, which is used to check that we 222 * really are in an SRCU read-side critical section. 223 */ 224 #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) 225 226 /** 227 * srcu_read_lock - register a new reader for an SRCU-protected structure. 228 * @ssp: srcu_struct in which to register the new reader. 229 * 230 * Enter an SRCU read-side critical section. Note that SRCU read-side 231 * critical sections may be nested. However, it is illegal to 232 * call anything that waits on an SRCU grace period for the same 233 * srcu_struct, whether directly or indirectly. Please note that 234 * one way to indirectly wait on an SRCU grace period is to acquire 235 * a mutex that is held elsewhere while calling synchronize_srcu() or 236 * synchronize_srcu_expedited(). 237 * 238 * The return value from srcu_read_lock() is guaranteed to be 239 * non-negative. This value must be passed unaltered to the matching 240 * srcu_read_unlock(). Note that srcu_read_lock() and the matching 241 * srcu_read_unlock() must occur in the same context, for example, it is 242 * illegal to invoke srcu_read_unlock() in an irq handler if the matching 243 * srcu_read_lock() was invoked in process context. Or, for that matter to 244 * invoke srcu_read_unlock() from one task and the matching srcu_read_lock() 245 * from another. 246 */ 247 static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) 248 { 249 int retval; 250 251 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); 252 retval = __srcu_read_lock(ssp); 253 srcu_lock_acquire(&ssp->dep_map); 254 return retval; 255 } 256 257 /** 258 * srcu_read_lock_fast - register a new reader for an SRCU-protected structure. 259 * @ssp: srcu_struct in which to register the new reader. 260 * 261 * Enter an SRCU read-side critical section, but for a light-weight 262 * smp_mb()-free reader. See srcu_read_lock() for more information. 263 * 264 * If srcu_read_lock_fast() is ever used on an srcu_struct structure, 265 * then none of the other flavors may be used, whether before, during, 266 * or after. Note that grace-period auto-expediting is disabled for _fast 267 * srcu_struct structures because auto-expedited grace periods invoke 268 * synchronize_rcu_expedited(), IPIs and all. 269 * 270 * Note that srcu_read_lock_fast() can be invoked only from those contexts 271 * where RCU is watching, that is, from contexts where it would be legal 272 * to invoke rcu_read_lock(). Otherwise, lockdep will complain. 273 */ 274 static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct *ssp) __acquires(ssp) 275 { 276 struct srcu_ctr __percpu *retval; 277 278 RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_fast()."); 279 srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); 280 retval = __srcu_read_lock_fast(ssp); 281 rcu_try_lock_acquire(&ssp->dep_map); 282 return retval; 283 } 284 285 /* 286 * Used by tracing, cannot be traced and cannot call lockdep. 287 * See srcu_read_lock_fast() for more information. 288 */ 289 static inline struct srcu_ctr __percpu *srcu_read_lock_fast_notrace(struct srcu_struct *ssp) 290 __acquires(ssp) 291 { 292 struct srcu_ctr __percpu *retval; 293 294 srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); 295 retval = __srcu_read_lock_fast(ssp); 296 return retval; 297 } 298 299 /** 300 * srcu_down_read_fast - register a new reader for an SRCU-protected structure. 301 * @ssp: srcu_struct in which to register the new reader. 302 * 303 * Enter a semaphore-like SRCU read-side critical section, but for 304 * a light-weight smp_mb()-free reader. See srcu_read_lock_fast() and 305 * srcu_down_read() for more information. 306 * 307 * The same srcu_struct may be used concurrently by srcu_down_read_fast() 308 * and srcu_read_lock_fast(). 309 */ 310 static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct *ssp) __acquires(ssp) 311 { 312 WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); 313 RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_down_read_fast()."); 314 srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); 315 return __srcu_read_lock_fast(ssp); 316 } 317 318 /** 319 * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. 320 * @ssp: srcu_struct in which to register the new reader. 321 * 322 * Enter an SRCU read-side critical section, but in an NMI-safe manner. 323 * See srcu_read_lock() for more information. 324 * 325 * If srcu_read_lock_nmisafe() is ever used on an srcu_struct structure, 326 * then none of the other flavors may be used, whether before, during, 327 * or after. 328 */ 329 static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) 330 { 331 int retval; 332 333 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); 334 retval = __srcu_read_lock_nmisafe(ssp); 335 rcu_try_lock_acquire(&ssp->dep_map); 336 return retval; 337 } 338 339 /* Used by tracing, cannot be traced and cannot invoke lockdep. */ 340 static inline notrace int 341 srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) 342 { 343 int retval; 344 345 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); 346 retval = __srcu_read_lock(ssp); 347 return retval; 348 } 349 350 /** 351 * srcu_down_read - register a new reader for an SRCU-protected structure. 352 * @ssp: srcu_struct in which to register the new reader. 353 * 354 * Enter a semaphore-like SRCU read-side critical section. Note that 355 * SRCU read-side critical sections may be nested. However, it is 356 * illegal to call anything that waits on an SRCU grace period for the 357 * same srcu_struct, whether directly or indirectly. Please note that 358 * one way to indirectly wait on an SRCU grace period is to acquire 359 * a mutex that is held elsewhere while calling synchronize_srcu() or 360 * synchronize_srcu_expedited(). But if you want lockdep to help you 361 * keep this stuff straight, you should instead use srcu_read_lock(). 362 * 363 * The semaphore-like nature of srcu_down_read() means that the matching 364 * srcu_up_read() can be invoked from some other context, for example, 365 * from some other task or from an irq handler. However, neither 366 * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler. 367 * 368 * Calls to srcu_down_read() may be nested, similar to the manner in 369 * which calls to down_read() may be nested. The same srcu_struct may be 370 * used concurrently by srcu_down_read() and srcu_read_lock(). 371 */ 372 static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) 373 { 374 WARN_ON_ONCE(in_nmi()); 375 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); 376 return __srcu_read_lock(ssp); 377 } 378 379 /** 380 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 381 * @ssp: srcu_struct in which to unregister the old reader. 382 * @idx: return value from corresponding srcu_read_lock(). 383 * 384 * Exit an SRCU read-side critical section. 385 */ 386 static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) 387 __releases(ssp) 388 { 389 WARN_ON_ONCE(idx & ~0x1); 390 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); 391 srcu_lock_release(&ssp->dep_map); 392 __srcu_read_unlock(ssp, idx); 393 } 394 395 /** 396 * srcu_read_unlock_fast - unregister a old reader from an SRCU-protected structure. 397 * @ssp: srcu_struct in which to unregister the old reader. 398 * @scp: return value from corresponding srcu_read_lock_fast(). 399 * 400 * Exit a light-weight SRCU read-side critical section. 401 */ 402 static inline void srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) 403 __releases(ssp) 404 { 405 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); 406 srcu_lock_release(&ssp->dep_map); 407 __srcu_read_unlock_fast(ssp, scp); 408 RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_fast()."); 409 } 410 411 /* 412 * Used by tracing, cannot be traced and cannot call lockdep. 413 * See srcu_read_unlock_fast() for more information. 414 */ 415 static inline void srcu_read_unlock_fast_notrace(struct srcu_struct *ssp, 416 struct srcu_ctr __percpu *scp) __releases(ssp) 417 { 418 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); 419 __srcu_read_unlock_fast(ssp, scp); 420 } 421 422 /** 423 * srcu_up_read_fast - unregister a old reader from an SRCU-protected structure. 424 * @ssp: srcu_struct in which to unregister the old reader. 425 * @scp: return value from corresponding srcu_read_lock_fast(). 426 * 427 * Exit an SRCU read-side critical section, but not necessarily from 428 * the same context as the maching srcu_down_read_fast(). 429 */ 430 static inline void srcu_up_read_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) 431 __releases(ssp) 432 { 433 WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); 434 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); 435 __srcu_read_unlock_fast(ssp, scp); 436 RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_up_read_fast()."); 437 } 438 439 /** 440 * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. 441 * @ssp: srcu_struct in which to unregister the old reader. 442 * @idx: return value from corresponding srcu_read_lock_nmisafe(). 443 * 444 * Exit an SRCU read-side critical section, but in an NMI-safe manner. 445 */ 446 static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) 447 __releases(ssp) 448 { 449 WARN_ON_ONCE(idx & ~0x1); 450 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); 451 rcu_lock_release(&ssp->dep_map); 452 __srcu_read_unlock_nmisafe(ssp, idx); 453 } 454 455 /* Used by tracing, cannot be traced and cannot call lockdep. */ 456 static inline notrace void 457 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) 458 { 459 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); 460 __srcu_read_unlock(ssp, idx); 461 } 462 463 /** 464 * srcu_up_read - unregister a old reader from an SRCU-protected structure. 465 * @ssp: srcu_struct in which to unregister the old reader. 466 * @idx: return value from corresponding srcu_read_lock(). 467 * 468 * Exit an SRCU read-side critical section, but not necessarily from 469 * the same context as the maching srcu_down_read(). 470 */ 471 static inline void srcu_up_read(struct srcu_struct *ssp, int idx) 472 __releases(ssp) 473 { 474 WARN_ON_ONCE(idx & ~0x1); 475 WARN_ON_ONCE(in_nmi()); 476 srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); 477 __srcu_read_unlock(ssp, idx); 478 } 479 480 /** 481 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock 482 * 483 * Converts the preceding srcu_read_unlock into a two-way memory barrier. 484 * 485 * Call this after srcu_read_unlock, to guarantee that all memory operations 486 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after 487 * the preceding srcu_read_unlock. 488 */ 489 static inline void smp_mb__after_srcu_read_unlock(void) 490 { 491 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ 492 } 493 494 /** 495 * smp_mb__after_srcu_read_lock - ensure full ordering after srcu_read_lock 496 * 497 * Converts the preceding srcu_read_lock into a two-way memory barrier. 498 * 499 * Call this after srcu_read_lock, to guarantee that all memory operations 500 * that occur after smp_mb__after_srcu_read_lock will appear to happen after 501 * the preceding srcu_read_lock. 502 */ 503 static inline void smp_mb__after_srcu_read_lock(void) 504 { 505 /* __srcu_read_lock has smp_mb() internally so nothing to do here. */ 506 } 507 508 DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct, 509 _T->idx = srcu_read_lock(_T->lock), 510 srcu_read_unlock(_T->lock, _T->idx), 511 int idx) 512 513 DEFINE_LOCK_GUARD_1(srcu_fast, struct srcu_struct, 514 _T->scp = srcu_read_lock_fast(_T->lock), 515 srcu_read_unlock_fast(_T->lock, _T->scp), 516 struct srcu_ctr __percpu *scp) 517 518 DEFINE_LOCK_GUARD_1(srcu_fast_notrace, struct srcu_struct, 519 _T->scp = srcu_read_lock_fast_notrace(_T->lock), 520 srcu_read_unlock_fast_notrace(_T->lock, _T->scp), 521 struct srcu_ctr __percpu *scp) 522 523 #endif 524