1/* 2 * Read-Copy Update mechanism for mutual exclusion 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, you can access it online at 16 * http://www.gnu.org/licenses/gpl-2.0.html. 17 * 18 * Copyright IBM Corporation, 2001 19 * 20 * Author: Dipankar Sarma <dipankar@in.ibm.com> 21 * 22 * Based on the original work by Paul McKenney <paulmck@us.ibm.com> 23 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. 24 * Papers: 25 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf 26 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) 27 * 28 * For detailed explanation of Read-Copy Update mechanism see - 29 * http://lse.sourceforge.net/locking/rcupdate.html 30 * 31 */ 32 33#ifndef __LINUX_RCUPDATE_H 34#define __LINUX_RCUPDATE_H 35 36#include <linux/types.h> 37#include <linux/cache.h> 38#include <linux/spinlock.h> 39#include <linux/threads.h> 40#include <linux/cpumask.h> 41#include <linux/seqlock.h> 42#include <linux/lockdep.h> 43#include <linux/completion.h> 44#include <linux/debugobjects.h> 45#include <linux/bug.h> 46#include <linux/compiler.h> 47#include <asm/barrier.h> 48 49extern int rcu_expedited; /* for sysctl */ 50 51#ifdef CONFIG_TINY_RCU 52/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ 53static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */ 54{ 55 return false; 56} 57 58static inline void rcu_expedite_gp(void) 59{ 60} 61 62static inline void rcu_unexpedite_gp(void) 63{ 64} 65#else /* #ifdef CONFIG_TINY_RCU */ 66bool rcu_gp_is_expedited(void); /* Internal RCU use. */ 67void rcu_expedite_gp(void); 68void rcu_unexpedite_gp(void); 69#endif /* #else #ifdef CONFIG_TINY_RCU */ 70 71enum rcutorture_type { 72 RCU_FLAVOR, 73 RCU_BH_FLAVOR, 74 RCU_SCHED_FLAVOR, 75 RCU_TASKS_FLAVOR, 76 SRCU_FLAVOR, 77 INVALID_RCU_FLAVOR 78}; 79 80#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) 81void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, 82 unsigned long *gpnum, unsigned long *completed); 83void rcutorture_record_test_transition(void); 84void rcutorture_record_progress(unsigned long vernum); 85void do_trace_rcu_torture_read(const char *rcutorturename, 86 struct rcu_head *rhp, 87 unsigned long secs, 88 unsigned long c_old, 89 unsigned long c); 90#else 91static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, 92 int *flags, 93 unsigned long *gpnum, 94 unsigned long *completed) 95{ 96 *flags = 0; 97 *gpnum = 0; 98 *completed = 0; 99} 100static inline void rcutorture_record_test_transition(void) 101{ 102} 103static inline void rcutorture_record_progress(unsigned long vernum) 104{ 105} 106#ifdef CONFIG_RCU_TRACE 107void do_trace_rcu_torture_read(const char *rcutorturename, 108 struct rcu_head *rhp, 109 unsigned long secs, 110 unsigned long c_old, 111 unsigned long c); 112#else 113#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ 114 do { } while (0) 115#endif 116#endif 117 118#define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) 119#define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) 120#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) 121#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) 122#define ulong2long(a) (*(long *)(&(a))) 123 124/* Exported common interfaces */ 125 126#ifdef CONFIG_PREEMPT_RCU 127 128/** 129 * call_rcu() - Queue an RCU callback for invocation after a grace period. 130 * @head: structure to be used for queueing the RCU updates. 131 * @func: actual callback function to be invoked after the grace period 132 * 133 * The callback function will be invoked some time after a full grace 134 * period elapses, in other words after all pre-existing RCU read-side 135 * critical sections have completed. However, the callback function 136 * might well execute concurrently with RCU read-side critical sections 137 * that started after call_rcu() was invoked. RCU read-side critical 138 * sections are delimited by rcu_read_lock() and rcu_read_unlock(), 139 * and may be nested. 140 * 141 * Note that all CPUs must agree that the grace period extended beyond 142 * all pre-existing RCU read-side critical section. On systems with more 143 * than one CPU, this means that when "func()" is invoked, each CPU is 144 * guaranteed to have executed a full memory barrier since the end of its 145 * last RCU read-side critical section whose beginning preceded the call 146 * to call_rcu(). It also means that each CPU executing an RCU read-side 147 * critical section that continues beyond the start of "func()" must have 148 * executed a memory barrier after the call_rcu() but before the beginning 149 * of that RCU read-side critical section. Note that these guarantees 150 * include CPUs that are offline, idle, or executing in user mode, as 151 * well as CPUs that are executing in the kernel. 152 * 153 * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the 154 * resulting RCU callback function "func()", then both CPU A and CPU B are 155 * guaranteed to execute a full memory barrier during the time interval 156 * between the call to call_rcu() and the invocation of "func()" -- even 157 * if CPU A and CPU B are the same CPU (but again only if the system has 158 * more than one CPU). 159 */ 160void call_rcu(struct rcu_head *head, 161 void (*func)(struct rcu_head *head)); 162 163#else /* #ifdef CONFIG_PREEMPT_RCU */ 164 165/* In classic RCU, call_rcu() is just call_rcu_sched(). */ 166#define call_rcu call_rcu_sched 167 168#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 169 170/** 171 * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. 172 * @head: structure to be used for queueing the RCU updates. 173 * @func: actual callback function to be invoked after the grace period 174 * 175 * The callback function will be invoked some time after a full grace 176 * period elapses, in other words after all currently executing RCU 177 * read-side critical sections have completed. call_rcu_bh() assumes 178 * that the read-side critical sections end on completion of a softirq 179 * handler. This means that read-side critical sections in process 180 * context must not be interrupted by softirqs. This interface is to be 181 * used when most of the read-side critical sections are in softirq context. 182 * RCU read-side critical sections are delimited by : 183 * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. 184 * OR 185 * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. 186 * These may be nested. 187 * 188 * See the description of call_rcu() for more detailed information on 189 * memory ordering guarantees. 190 */ 191void call_rcu_bh(struct rcu_head *head, 192 void (*func)(struct rcu_head *head)); 193 194/** 195 * call_rcu_sched() - Queue an RCU for invocation after sched grace period. 196 * @head: structure to be used for queueing the RCU updates. 197 * @func: actual callback function to be invoked after the grace period 198 * 199 * The callback function will be invoked some time after a full grace 200 * period elapses, in other words after all currently executing RCU 201 * read-side critical sections have completed. call_rcu_sched() assumes 202 * that the read-side critical sections end on enabling of preemption 203 * or on voluntary preemption. 204 * RCU read-side critical sections are delimited by : 205 * - rcu_read_lock_sched() and rcu_read_unlock_sched(), 206 * OR 207 * anything that disables preemption. 208 * These may be nested. 209 * 210 * See the description of call_rcu() for more detailed information on 211 * memory ordering guarantees. 212 */ 213void call_rcu_sched(struct rcu_head *head, 214 void (*func)(struct rcu_head *rcu)); 215 216void synchronize_sched(void); 217 218/* 219 * Structure allowing asynchronous waiting on RCU. 220 */ 221struct rcu_synchronize { 222 struct rcu_head head; 223 struct completion completion; 224}; 225void wakeme_after_rcu(struct rcu_head *head); 226 227/** 228 * call_rcu_tasks() - Queue an RCU for invocation task-based grace period 229 * @head: structure to be used for queueing the RCU updates. 230 * @func: actual callback function to be invoked after the grace period 231 * 232 * The callback function will be invoked some time after a full grace 233 * period elapses, in other words after all currently executing RCU 234 * read-side critical sections have completed. call_rcu_tasks() assumes 235 * that the read-side critical sections end at a voluntary context 236 * switch (not a preemption!), entry into idle, or transition to usermode 237 * execution. As such, there are no read-side primitives analogous to 238 * rcu_read_lock() and rcu_read_unlock() because this primitive is intended 239 * to determine that all tasks have passed through a safe state, not so 240 * much for data-strcuture synchronization. 241 * 242 * See the description of call_rcu() for more detailed information on 243 * memory ordering guarantees. 244 */ 245void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head)); 246void synchronize_rcu_tasks(void); 247void rcu_barrier_tasks(void); 248 249#ifdef CONFIG_PREEMPT_RCU 250 251void __rcu_read_lock(void); 252void __rcu_read_unlock(void); 253void rcu_read_unlock_special(struct task_struct *t); 254void synchronize_rcu(void); 255 256/* 257 * Defined as a macro as it is a very low level header included from 258 * areas that don't even know about current. This gives the rcu_read_lock() 259 * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other 260 * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. 261 */ 262#define rcu_preempt_depth() (current->rcu_read_lock_nesting) 263 264#else /* #ifdef CONFIG_PREEMPT_RCU */ 265 266static inline void __rcu_read_lock(void) 267{ 268 preempt_disable(); 269} 270 271static inline void __rcu_read_unlock(void) 272{ 273 preempt_enable(); 274} 275 276static inline void synchronize_rcu(void) 277{ 278 synchronize_sched(); 279} 280 281static inline int rcu_preempt_depth(void) 282{ 283 return 0; 284} 285 286#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 287 288/* Internal to kernel */ 289void rcu_init(void); 290void rcu_end_inkernel_boot(void); 291void rcu_sched_qs(void); 292void rcu_bh_qs(void); 293void rcu_check_callbacks(int user); 294struct notifier_block; 295void rcu_idle_enter(void); 296void rcu_idle_exit(void); 297void rcu_irq_enter(void); 298void rcu_irq_exit(void); 299int rcu_cpu_notify(struct notifier_block *self, 300 unsigned long action, void *hcpu); 301 302#ifdef CONFIG_RCU_STALL_COMMON 303void rcu_sysrq_start(void); 304void rcu_sysrq_end(void); 305#else /* #ifdef CONFIG_RCU_STALL_COMMON */ 306static inline void rcu_sysrq_start(void) 307{ 308} 309static inline void rcu_sysrq_end(void) 310{ 311} 312#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ 313 314#ifdef CONFIG_RCU_USER_QS 315void rcu_user_enter(void); 316void rcu_user_exit(void); 317#else 318static inline void rcu_user_enter(void) { } 319static inline void rcu_user_exit(void) { } 320static inline void rcu_user_hooks_switch(struct task_struct *prev, 321 struct task_struct *next) { } 322#endif /* CONFIG_RCU_USER_QS */ 323 324#ifdef CONFIG_RCU_NOCB_CPU 325void rcu_init_nohz(void); 326#else /* #ifdef CONFIG_RCU_NOCB_CPU */ 327static inline void rcu_init_nohz(void) 328{ 329} 330#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 331 332/** 333 * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers 334 * @a: Code that RCU needs to pay attention to. 335 * 336 * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden 337 * in the inner idle loop, that is, between the rcu_idle_enter() and 338 * the rcu_idle_exit() -- RCU will happily ignore any such read-side 339 * critical sections. However, things like powertop need tracepoints 340 * in the inner idle loop. 341 * 342 * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) 343 * will tell RCU that it needs to pay attending, invoke its argument 344 * (in this example, a call to the do_something_with_RCU() function), 345 * and then tell RCU to go back to ignoring this CPU. It is permissible 346 * to nest RCU_NONIDLE() wrappers, but the nesting level is currently 347 * quite limited. If deeper nesting is required, it will be necessary 348 * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. 349 */ 350#define RCU_NONIDLE(a) \ 351 do { \ 352 rcu_irq_enter(); \ 353 do { a; } while (0); \ 354 rcu_irq_exit(); \ 355 } while (0) 356 357/* 358 * Note a voluntary context switch for RCU-tasks benefit. This is a 359 * macro rather than an inline function to avoid #include hell. 360 */ 361#ifdef CONFIG_TASKS_RCU 362#define TASKS_RCU(x) x 363extern struct srcu_struct tasks_rcu_exit_srcu; 364#define rcu_note_voluntary_context_switch(t) \ 365 do { \ 366 rcu_all_qs(); \ 367 if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \ 368 ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \ 369 } while (0) 370#else /* #ifdef CONFIG_TASKS_RCU */ 371#define TASKS_RCU(x) do { } while (0) 372#define rcu_note_voluntary_context_switch(t) rcu_all_qs() 373#endif /* #else #ifdef CONFIG_TASKS_RCU */ 374 375/** 376 * cond_resched_rcu_qs - Report potential quiescent states to RCU 377 * 378 * This macro resembles cond_resched(), except that it is defined to 379 * report potential quiescent states to RCU-tasks even if the cond_resched() 380 * machinery were to be shut off, as some advocate for PREEMPT kernels. 381 */ 382#define cond_resched_rcu_qs() \ 383do { \ 384 if (!cond_resched()) \ 385 rcu_note_voluntary_context_switch(current); \ 386} while (0) 387 388#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) 389bool __rcu_is_watching(void); 390#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */ 391 392/* 393 * Infrastructure to implement the synchronize_() primitives in 394 * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. 395 */ 396 397typedef void call_rcu_func_t(struct rcu_head *head, 398 void (*func)(struct rcu_head *head)); 399void wait_rcu_gp(call_rcu_func_t crf); 400 401#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) 402#include <linux/rcutree.h> 403#elif defined(CONFIG_TINY_RCU) 404#include <linux/rcutiny.h> 405#else 406#error "Unknown RCU implementation specified to kernel configuration" 407#endif 408 409/* 410 * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic 411 * initialization and destruction of rcu_head on the stack. rcu_head structures 412 * allocated dynamically in the heap or defined statically don't need any 413 * initialization. 414 */ 415#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD 416void init_rcu_head(struct rcu_head *head); 417void destroy_rcu_head(struct rcu_head *head); 418void init_rcu_head_on_stack(struct rcu_head *head); 419void destroy_rcu_head_on_stack(struct rcu_head *head); 420#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 421static inline void init_rcu_head(struct rcu_head *head) 422{ 423} 424 425static inline void destroy_rcu_head(struct rcu_head *head) 426{ 427} 428 429static inline void init_rcu_head_on_stack(struct rcu_head *head) 430{ 431} 432 433static inline void destroy_rcu_head_on_stack(struct rcu_head *head) 434{ 435} 436#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 437 438#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) 439bool rcu_lockdep_current_cpu_online(void); 440#else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ 441static inline bool rcu_lockdep_current_cpu_online(void) 442{ 443 return true; 444} 445#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ 446 447#ifdef CONFIG_DEBUG_LOCK_ALLOC 448 449static inline void rcu_lock_acquire(struct lockdep_map *map) 450{ 451 lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); 452} 453 454static inline void rcu_lock_release(struct lockdep_map *map) 455{ 456 lock_release(map, 1, _THIS_IP_); 457} 458 459extern struct lockdep_map rcu_lock_map; 460extern struct lockdep_map rcu_bh_lock_map; 461extern struct lockdep_map rcu_sched_lock_map; 462extern struct lockdep_map rcu_callback_map; 463int debug_lockdep_rcu_enabled(void); 464 465int rcu_read_lock_held(void); 466int rcu_read_lock_bh_held(void); 467 468/** 469 * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? 470 * 471 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an 472 * RCU-sched read-side critical section. In absence of 473 * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side 474 * critical section unless it can prove otherwise. Note that disabling 475 * of preemption (including disabling irqs) counts as an RCU-sched 476 * read-side critical section. This is useful for debug checks in functions 477 * that required that they be called within an RCU-sched read-side 478 * critical section. 479 * 480 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot 481 * and while lockdep is disabled. 482 * 483 * Note that if the CPU is in the idle loop from an RCU point of 484 * view (ie: that we are in the section between rcu_idle_enter() and 485 * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU 486 * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs 487 * that are in such a section, considering these as in extended quiescent 488 * state, so such a CPU is effectively never in an RCU read-side critical 489 * section regardless of what RCU primitives it invokes. This state of 490 * affairs is required --- we need to keep an RCU-free window in idle 491 * where the CPU may possibly enter into low power mode. This way we can 492 * notice an extended quiescent state to other CPUs that started a grace 493 * period. Otherwise we would delay any grace period as long as we run in 494 * the idle task. 495 * 496 * Similarly, we avoid claiming an SRCU read lock held if the current 497 * CPU is offline. 498 */ 499#ifdef CONFIG_PREEMPT_COUNT 500static inline int rcu_read_lock_sched_held(void) 501{ 502 int lockdep_opinion = 0; 503 504 if (!debug_lockdep_rcu_enabled()) 505 return 1; 506 if (!rcu_is_watching()) 507 return 0; 508 if (!rcu_lockdep_current_cpu_online()) 509 return 0; 510 if (debug_locks) 511 lockdep_opinion = lock_is_held(&rcu_sched_lock_map); 512 return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); 513} 514#else /* #ifdef CONFIG_PREEMPT_COUNT */ 515static inline int rcu_read_lock_sched_held(void) 516{ 517 return 1; 518} 519#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ 520 521#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 522 523# define rcu_lock_acquire(a) do { } while (0) 524# define rcu_lock_release(a) do { } while (0) 525 526static inline int rcu_read_lock_held(void) 527{ 528 return 1; 529} 530 531static inline int rcu_read_lock_bh_held(void) 532{ 533 return 1; 534} 535 536#ifdef CONFIG_PREEMPT_COUNT 537static inline int rcu_read_lock_sched_held(void) 538{ 539 return preempt_count() != 0 || irqs_disabled(); 540} 541#else /* #ifdef CONFIG_PREEMPT_COUNT */ 542static inline int rcu_read_lock_sched_held(void) 543{ 544 return 1; 545} 546#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ 547 548#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 549 550#ifdef CONFIG_PROVE_RCU 551 552/** 553 * rcu_lockdep_assert - emit lockdep splat if specified condition not met 554 * @c: condition to check 555 * @s: informative message 556 */ 557#define rcu_lockdep_assert(c, s) \ 558 do { \ 559 static bool __section(.data.unlikely) __warned; \ 560 if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ 561 __warned = true; \ 562 lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ 563 } \ 564 } while (0) 565 566#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) 567static inline void rcu_preempt_sleep_check(void) 568{ 569 rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), 570 "Illegal context switch in RCU read-side critical section"); 571} 572#else /* #ifdef CONFIG_PROVE_RCU */ 573static inline void rcu_preempt_sleep_check(void) 574{ 575} 576#endif /* #else #ifdef CONFIG_PROVE_RCU */ 577 578#define rcu_sleep_check() \ 579 do { \ 580 rcu_preempt_sleep_check(); \ 581 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ 582 "Illegal context switch in RCU-bh read-side critical section"); \ 583 rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ 584 "Illegal context switch in RCU-sched read-side critical section"); \ 585 } while (0) 586 587#else /* #ifdef CONFIG_PROVE_RCU */ 588 589#define rcu_lockdep_assert(c, s) do { } while (0) 590#define rcu_sleep_check() do { } while (0) 591 592#endif /* #else #ifdef CONFIG_PROVE_RCU */ 593 594/* 595 * Helper functions for rcu_dereference_check(), rcu_dereference_protected() 596 * and rcu_assign_pointer(). Some of these could be folded into their 597 * callers, but they are left separate in order to ease introduction of 598 * multiple flavors of pointers to match the multiple flavors of RCU 599 * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in 600 * the future. 601 */ 602 603#ifdef __CHECKER__ 604#define rcu_dereference_sparse(p, space) \ 605 ((void)(((typeof(*p) space *)p) == p)) 606#else /* #ifdef __CHECKER__ */ 607#define rcu_dereference_sparse(p, space) 608#endif /* #else #ifdef __CHECKER__ */ 609 610#define __rcu_access_pointer(p, space) \ 611({ \ 612 typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \ 613 rcu_dereference_sparse(p, space); \ 614 ((typeof(*p) __force __kernel *)(_________p1)); \ 615}) 616#define __rcu_dereference_check(p, c, space) \ 617({ \ 618 /* Dependency order vs. p above. */ \ 619 typeof(*p) *________p1 = (typeof(*p) *__force)lockless_dereference(p); \ 620 rcu_lockdep_assert(c, "suspicious rcu_dereference_check() usage"); \ 621 rcu_dereference_sparse(p, space); \ 622 ((typeof(*p) __force __kernel *)(________p1)); \ 623}) 624#define __rcu_dereference_protected(p, c, space) \ 625({ \ 626 rcu_lockdep_assert(c, "suspicious rcu_dereference_protected() usage"); \ 627 rcu_dereference_sparse(p, space); \ 628 ((typeof(*p) __force __kernel *)(p)); \ 629}) 630 631#define __rcu_access_index(p, space) \ 632({ \ 633 typeof(p) _________p1 = ACCESS_ONCE(p); \ 634 rcu_dereference_sparse(p, space); \ 635 (_________p1); \ 636}) 637#define __rcu_dereference_index_check(p, c) \ 638({ \ 639 /* Dependency order vs. p above. */ \ 640 typeof(p) _________p1 = lockless_dereference(p); \ 641 rcu_lockdep_assert(c, \ 642 "suspicious rcu_dereference_index_check() usage"); \ 643 (_________p1); \ 644}) 645 646/** 647 * RCU_INITIALIZER() - statically initialize an RCU-protected global variable 648 * @v: The value to statically initialize with. 649 */ 650#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) 651 652/** 653 * lockless_dereference() - safely load a pointer for later dereference 654 * @p: The pointer to load 655 * 656 * Similar to rcu_dereference(), but for situations where the pointed-to 657 * object's lifetime is managed by something other than RCU. That 658 * "something other" might be reference counting or simple immortality. 659 */ 660#define lockless_dereference(p) \ 661({ \ 662 typeof(p) _________p1 = ACCESS_ONCE(p); \ 663 smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ 664 (_________p1); \ 665}) 666 667/** 668 * rcu_assign_pointer() - assign to RCU-protected pointer 669 * @p: pointer to assign to 670 * @v: value to assign (publish) 671 * 672 * Assigns the specified value to the specified RCU-protected 673 * pointer, ensuring that any concurrent RCU readers will see 674 * any prior initialization. 675 * 676 * Inserts memory barriers on architectures that require them 677 * (which is most of them), and also prevents the compiler from 678 * reordering the code that initializes the structure after the pointer 679 * assignment. More importantly, this call documents which pointers 680 * will be dereferenced by RCU read-side code. 681 * 682 * In some special cases, you may use RCU_INIT_POINTER() instead 683 * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due 684 * to the fact that it does not constrain either the CPU or the compiler. 685 * That said, using RCU_INIT_POINTER() when you should have used 686 * rcu_assign_pointer() is a very bad thing that results in 687 * impossible-to-diagnose memory corruption. So please be careful. 688 * See the RCU_INIT_POINTER() comment header for details. 689 * 690 * Note that rcu_assign_pointer() evaluates each of its arguments only 691 * once, appearances notwithstanding. One of the "extra" evaluations 692 * is in typeof() and the other visible only to sparse (__CHECKER__), 693 * neither of which actually execute the argument. As with most cpp 694 * macros, this execute-arguments-only-once property is important, so 695 * please be careful when making changes to rcu_assign_pointer() and the 696 * other macros that it invokes. 697 */ 698#define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v)) 699 700/** 701 * rcu_access_pointer() - fetch RCU pointer with no dereferencing 702 * @p: The pointer to read 703 * 704 * Return the value of the specified RCU-protected pointer, but omit the 705 * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful 706 * when the value of this pointer is accessed, but the pointer is not 707 * dereferenced, for example, when testing an RCU-protected pointer against 708 * NULL. Although rcu_access_pointer() may also be used in cases where 709 * update-side locks prevent the value of the pointer from changing, you 710 * should instead use rcu_dereference_protected() for this use case. 711 * 712 * It is also permissible to use rcu_access_pointer() when read-side 713 * access to the pointer was removed at least one grace period ago, as 714 * is the case in the context of the RCU callback that is freeing up 715 * the data, or after a synchronize_rcu() returns. This can be useful 716 * when tearing down multi-linked structures after a grace period 717 * has elapsed. 718 */ 719#define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) 720 721/** 722 * rcu_dereference_check() - rcu_dereference with debug checking 723 * @p: The pointer to read, prior to dereferencing 724 * @c: The conditions under which the dereference will take place 725 * 726 * Do an rcu_dereference(), but check that the conditions under which the 727 * dereference will take place are correct. Typically the conditions 728 * indicate the various locking conditions that should be held at that 729 * point. The check should return true if the conditions are satisfied. 730 * An implicit check for being in an RCU read-side critical section 731 * (rcu_read_lock()) is included. 732 * 733 * For example: 734 * 735 * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); 736 * 737 * could be used to indicate to lockdep that foo->bar may only be dereferenced 738 * if either rcu_read_lock() is held, or that the lock required to replace 739 * the bar struct at foo->bar is held. 740 * 741 * Note that the list of conditions may also include indications of when a lock 742 * need not be held, for example during initialisation or destruction of the 743 * target struct: 744 * 745 * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || 746 * atomic_read(&foo->usage) == 0); 747 * 748 * Inserts memory barriers on architectures that require them 749 * (currently only the Alpha), prevents the compiler from refetching 750 * (and from merging fetches), and, more importantly, documents exactly 751 * which pointers are protected by RCU and checks that the pointer is 752 * annotated as __rcu. 753 */ 754#define rcu_dereference_check(p, c) \ 755 __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) 756 757/** 758 * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking 759 * @p: The pointer to read, prior to dereferencing 760 * @c: The conditions under which the dereference will take place 761 * 762 * This is the RCU-bh counterpart to rcu_dereference_check(). 763 */ 764#define rcu_dereference_bh_check(p, c) \ 765 __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu) 766 767/** 768 * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking 769 * @p: The pointer to read, prior to dereferencing 770 * @c: The conditions under which the dereference will take place 771 * 772 * This is the RCU-sched counterpart to rcu_dereference_check(). 773 */ 774#define rcu_dereference_sched_check(p, c) \ 775 __rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \ 776 __rcu) 777 778#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ 779 780/* 781 * The tracing infrastructure traces RCU (we want that), but unfortunately 782 * some of the RCU checks causes tracing to lock up the system. 783 * 784 * The tracing version of rcu_dereference_raw() must not call 785 * rcu_read_lock_held(). 786 */ 787#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) 788 789/** 790 * rcu_access_index() - fetch RCU index with no dereferencing 791 * @p: The index to read 792 * 793 * Return the value of the specified RCU-protected index, but omit the 794 * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful 795 * when the value of this index is accessed, but the index is not 796 * dereferenced, for example, when testing an RCU-protected index against 797 * -1. Although rcu_access_index() may also be used in cases where 798 * update-side locks prevent the value of the index from changing, you 799 * should instead use rcu_dereference_index_protected() for this use case. 800 */ 801#define rcu_access_index(p) __rcu_access_index((p), __rcu) 802 803/** 804 * rcu_dereference_index_check() - rcu_dereference for indices with debug checking 805 * @p: The pointer to read, prior to dereferencing 806 * @c: The conditions under which the dereference will take place 807 * 808 * Similar to rcu_dereference_check(), but omits the sparse checking. 809 * This allows rcu_dereference_index_check() to be used on integers, 810 * which can then be used as array indices. Attempting to use 811 * rcu_dereference_check() on an integer will give compiler warnings 812 * because the sparse address-space mechanism relies on dereferencing 813 * the RCU-protected pointer. Dereferencing integers is not something 814 * that even gcc will put up with. 815 * 816 * Note that this function does not implicitly check for RCU read-side 817 * critical sections. If this function gains lots of uses, it might 818 * make sense to provide versions for each flavor of RCU, but it does 819 * not make sense as of early 2010. 820 */ 821#define rcu_dereference_index_check(p, c) \ 822 __rcu_dereference_index_check((p), (c)) 823 824/** 825 * rcu_dereference_protected() - fetch RCU pointer when updates prevented 826 * @p: The pointer to read, prior to dereferencing 827 * @c: The conditions under which the dereference will take place 828 * 829 * Return the value of the specified RCU-protected pointer, but omit 830 * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This 831 * is useful in cases where update-side locks prevent the value of the 832 * pointer from changing. Please note that this primitive does -not- 833 * prevent the compiler from repeating this reference or combining it 834 * with other references, so it should not be used without protection 835 * of appropriate locks. 836 * 837 * This function is only for update-side use. Using this function 838 * when protected only by rcu_read_lock() will result in infrequent 839 * but very ugly failures. 840 */ 841#define rcu_dereference_protected(p, c) \ 842 __rcu_dereference_protected((p), (c), __rcu) 843 844 845/** 846 * rcu_dereference() - fetch RCU-protected pointer for dereferencing 847 * @p: The pointer to read, prior to dereferencing 848 * 849 * This is a simple wrapper around rcu_dereference_check(). 850 */ 851#define rcu_dereference(p) rcu_dereference_check(p, 0) 852 853/** 854 * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing 855 * @p: The pointer to read, prior to dereferencing 856 * 857 * Makes rcu_dereference_check() do the dirty work. 858 */ 859#define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) 860 861/** 862 * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing 863 * @p: The pointer to read, prior to dereferencing 864 * 865 * Makes rcu_dereference_check() do the dirty work. 866 */ 867#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) 868 869/** 870 * rcu_read_lock() - mark the beginning of an RCU read-side critical section 871 * 872 * When synchronize_rcu() is invoked on one CPU while other CPUs 873 * are within RCU read-side critical sections, then the 874 * synchronize_rcu() is guaranteed to block until after all the other 875 * CPUs exit their critical sections. Similarly, if call_rcu() is invoked 876 * on one CPU while other CPUs are within RCU read-side critical 877 * sections, invocation of the corresponding RCU callback is deferred 878 * until after the all the other CPUs exit their critical sections. 879 * 880 * Note, however, that RCU callbacks are permitted to run concurrently 881 * with new RCU read-side critical sections. One way that this can happen 882 * is via the following sequence of events: (1) CPU 0 enters an RCU 883 * read-side critical section, (2) CPU 1 invokes call_rcu() to register 884 * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, 885 * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU 886 * callback is invoked. This is legal, because the RCU read-side critical 887 * section that was running concurrently with the call_rcu() (and which 888 * therefore might be referencing something that the corresponding RCU 889 * callback would free up) has completed before the corresponding 890 * RCU callback is invoked. 891 * 892 * RCU read-side critical sections may be nested. Any deferred actions 893 * will be deferred until the outermost RCU read-side critical section 894 * completes. 895 * 896 * You can avoid reading and understanding the next paragraph by 897 * following this rule: don't put anything in an rcu_read_lock() RCU 898 * read-side critical section that would block in a !PREEMPT kernel. 899 * But if you want the full story, read on! 900 * 901 * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), 902 * it is illegal to block while in an RCU read-side critical section. 903 * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT 904 * kernel builds, RCU read-side critical sections may be preempted, 905 * but explicit blocking is illegal. Finally, in preemptible RCU 906 * implementations in real-time (with -rt patchset) kernel builds, RCU 907 * read-side critical sections may be preempted and they may also block, but 908 * only when acquiring spinlocks that are subject to priority inheritance. 909 */ 910static inline void rcu_read_lock(void) 911{ 912 __rcu_read_lock(); 913 __acquire(RCU); 914 rcu_lock_acquire(&rcu_lock_map); 915 rcu_lockdep_assert(rcu_is_watching(), 916 "rcu_read_lock() used illegally while idle"); 917} 918 919/* 920 * So where is rcu_write_lock()? It does not exist, as there is no 921 * way for writers to lock out RCU readers. This is a feature, not 922 * a bug -- this property is what provides RCU's performance benefits. 923 * Of course, writers must coordinate with each other. The normal 924 * spinlock primitives work well for this, but any other technique may be 925 * used as well. RCU does not care how the writers keep out of each 926 * others' way, as long as they do so. 927 */ 928 929/** 930 * rcu_read_unlock() - marks the end of an RCU read-side critical section. 931 * 932 * In most situations, rcu_read_unlock() is immune from deadlock. 933 * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() 934 * is responsible for deboosting, which it does via rt_mutex_unlock(). 935 * Unfortunately, this function acquires the scheduler's runqueue and 936 * priority-inheritance spinlocks. This means that deadlock could result 937 * if the caller of rcu_read_unlock() already holds one of these locks or 938 * any lock that is ever acquired while holding them; or any lock which 939 * can be taken from interrupt context because rcu_boost()->rt_mutex_lock() 940 * does not disable irqs while taking ->wait_lock. 941 * 942 * That said, RCU readers are never priority boosted unless they were 943 * preempted. Therefore, one way to avoid deadlock is to make sure 944 * that preemption never happens within any RCU read-side critical 945 * section whose outermost rcu_read_unlock() is called with one of 946 * rt_mutex_unlock()'s locks held. Such preemption can be avoided in 947 * a number of ways, for example, by invoking preempt_disable() before 948 * critical section's outermost rcu_read_lock(). 949 * 950 * Given that the set of locks acquired by rt_mutex_unlock() might change 951 * at any time, a somewhat more future-proofed approach is to make sure 952 * that that preemption never happens within any RCU read-side critical 953 * section whose outermost rcu_read_unlock() is called with irqs disabled. 954 * This approach relies on the fact that rt_mutex_unlock() currently only 955 * acquires irq-disabled locks. 956 * 957 * The second of these two approaches is best in most situations, 958 * however, the first approach can also be useful, at least to those 959 * developers willing to keep abreast of the set of locks acquired by 960 * rt_mutex_unlock(). 961 * 962 * See rcu_read_lock() for more information. 963 */ 964static inline void rcu_read_unlock(void) 965{ 966 rcu_lockdep_assert(rcu_is_watching(), 967 "rcu_read_unlock() used illegally while idle"); 968 __release(RCU); 969 __rcu_read_unlock(); 970 rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ 971} 972 973/** 974 * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section 975 * 976 * This is equivalent of rcu_read_lock(), but to be used when updates 977 * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since 978 * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a 979 * softirq handler to be a quiescent state, a process in RCU read-side 980 * critical section must be protected by disabling softirqs. Read-side 981 * critical sections in interrupt context can use just rcu_read_lock(), 982 * though this should at least be commented to avoid confusing people 983 * reading the code. 984 * 985 * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() 986 * must occur in the same context, for example, it is illegal to invoke 987 * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() 988 * was invoked from some other task. 989 */ 990static inline void rcu_read_lock_bh(void) 991{ 992 local_bh_disable(); 993 __acquire(RCU_BH); 994 rcu_lock_acquire(&rcu_bh_lock_map); 995 rcu_lockdep_assert(rcu_is_watching(), 996 "rcu_read_lock_bh() used illegally while idle"); 997} 998 999/* 1000 * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section 1001 * 1002 * See rcu_read_lock_bh() for more information. 1003 */ 1004static inline void rcu_read_unlock_bh(void) 1005{ 1006 rcu_lockdep_assert(rcu_is_watching(), 1007 "rcu_read_unlock_bh() used illegally while idle"); 1008 rcu_lock_release(&rcu_bh_lock_map); 1009 __release(RCU_BH); 1010 local_bh_enable(); 1011} 1012 1013/** 1014 * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section 1015 * 1016 * This is equivalent of rcu_read_lock(), but to be used when updates 1017 * are being done using call_rcu_sched() or synchronize_rcu_sched(). 1018 * Read-side critical sections can also be introduced by anything that 1019 * disables preemption, including local_irq_disable() and friends. 1020 * 1021 * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() 1022 * must occur in the same context, for example, it is illegal to invoke 1023 * rcu_read_unlock_sched() from process context if the matching 1024 * rcu_read_lock_sched() was invoked from an NMI handler. 1025 */ 1026static inline void rcu_read_lock_sched(void) 1027{ 1028 preempt_disable(); 1029 __acquire(RCU_SCHED); 1030 rcu_lock_acquire(&rcu_sched_lock_map); 1031 rcu_lockdep_assert(rcu_is_watching(), 1032 "rcu_read_lock_sched() used illegally while idle"); 1033} 1034 1035/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ 1036static inline notrace void rcu_read_lock_sched_notrace(void) 1037{ 1038 preempt_disable_notrace(); 1039 __acquire(RCU_SCHED); 1040} 1041 1042/* 1043 * rcu_read_unlock_sched - marks the end of a RCU-classic critical section 1044 * 1045 * See rcu_read_lock_sched for more information. 1046 */ 1047static inline void rcu_read_unlock_sched(void) 1048{ 1049 rcu_lockdep_assert(rcu_is_watching(), 1050 "rcu_read_unlock_sched() used illegally while idle"); 1051 rcu_lock_release(&rcu_sched_lock_map); 1052 __release(RCU_SCHED); 1053 preempt_enable(); 1054} 1055 1056/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ 1057static inline notrace void rcu_read_unlock_sched_notrace(void) 1058{ 1059 __release(RCU_SCHED); 1060 preempt_enable_notrace(); 1061} 1062 1063/** 1064 * RCU_INIT_POINTER() - initialize an RCU protected pointer 1065 * 1066 * Initialize an RCU-protected pointer in special cases where readers 1067 * do not need ordering constraints on the CPU or the compiler. These 1068 * special cases are: 1069 * 1070 * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- 1071 * 2. The caller has taken whatever steps are required to prevent 1072 * RCU readers from concurrently accessing this pointer -or- 1073 * 3. The referenced data structure has already been exposed to 1074 * readers either at compile time or via rcu_assign_pointer() -and- 1075 * a. You have not made -any- reader-visible changes to 1076 * this structure since then -or- 1077 * b. It is OK for readers accessing this structure from its 1078 * new location to see the old state of the structure. (For 1079 * example, the changes were to statistical counters or to 1080 * other state where exact synchronization is not required.) 1081 * 1082 * Failure to follow these rules governing use of RCU_INIT_POINTER() will 1083 * result in impossible-to-diagnose memory corruption. As in the structures 1084 * will look OK in crash dumps, but any concurrent RCU readers might 1085 * see pre-initialized values of the referenced data structure. So 1086 * please be very careful how you use RCU_INIT_POINTER()!!! 1087 * 1088 * If you are creating an RCU-protected linked structure that is accessed 1089 * by a single external-to-structure RCU-protected pointer, then you may 1090 * use RCU_INIT_POINTER() to initialize the internal RCU-protected 1091 * pointers, but you must use rcu_assign_pointer() to initialize the 1092 * external-to-structure pointer -after- you have completely initialized 1093 * the reader-accessible portions of the linked structure. 1094 * 1095 * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no 1096 * ordering guarantees for either the CPU or the compiler. 1097 */ 1098#define RCU_INIT_POINTER(p, v) \ 1099 do { \ 1100 rcu_dereference_sparse(p, __rcu); \ 1101 p = RCU_INITIALIZER(v); \ 1102 } while (0) 1103 1104/** 1105 * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer 1106 * 1107 * GCC-style initialization for an RCU-protected pointer in a structure field. 1108 */ 1109#define RCU_POINTER_INITIALIZER(p, v) \ 1110 .p = RCU_INITIALIZER(v) 1111 1112/* 1113 * Does the specified offset indicate that the corresponding rcu_head 1114 * structure can be handled by kfree_rcu()? 1115 */ 1116#define __is_kfree_rcu_offset(offset) ((offset) < 4096) 1117 1118/* 1119 * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. 1120 */ 1121#define __kfree_rcu(head, offset) \ 1122 do { \ 1123 BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ 1124 kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ 1125 } while (0) 1126 1127/** 1128 * kfree_rcu() - kfree an object after a grace period. 1129 * @ptr: pointer to kfree 1130 * @rcu_head: the name of the struct rcu_head within the type of @ptr. 1131 * 1132 * Many rcu callbacks functions just call kfree() on the base structure. 1133 * These functions are trivial, but their size adds up, and furthermore 1134 * when they are used in a kernel module, that module must invoke the 1135 * high-latency rcu_barrier() function at module-unload time. 1136 * 1137 * The kfree_rcu() function handles this issue. Rather than encoding a 1138 * function address in the embedded rcu_head structure, kfree_rcu() instead 1139 * encodes the offset of the rcu_head structure within the base structure. 1140 * Because the functions are not allowed in the low-order 4096 bytes of 1141 * kernel virtual memory, offsets up to 4095 bytes can be accommodated. 1142 * If the offset is larger than 4095 bytes, a compile-time error will 1143 * be generated in __kfree_rcu(). If this error is triggered, you can 1144 * either fall back to use of call_rcu() or rearrange the structure to 1145 * position the rcu_head structure into the first 4096 bytes. 1146 * 1147 * Note that the allowable offset might decrease in the future, for example, 1148 * to allow something like kmem_cache_free_rcu(). 1149 * 1150 * The BUILD_BUG_ON check must not involve any function calls, hence the 1151 * checks are done in macros here. 1152 */ 1153#define kfree_rcu(ptr, rcu_head) \ 1154 __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) 1155 1156#if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) 1157static inline int rcu_needs_cpu(unsigned long *delta_jiffies) 1158{ 1159 *delta_jiffies = ULONG_MAX; 1160 return 0; 1161} 1162#endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */ 1163 1164#if defined(CONFIG_RCU_NOCB_CPU_ALL) 1165static inline bool rcu_is_nocb_cpu(int cpu) { return true; } 1166#elif defined(CONFIG_RCU_NOCB_CPU) 1167bool rcu_is_nocb_cpu(int cpu); 1168#else 1169static inline bool rcu_is_nocb_cpu(int cpu) { return false; } 1170#endif 1171 1172 1173/* Only for use by adaptive-ticks code. */ 1174#ifdef CONFIG_NO_HZ_FULL_SYSIDLE 1175bool rcu_sys_is_idle(void); 1176void rcu_sysidle_force_exit(void); 1177#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ 1178 1179static inline bool rcu_sys_is_idle(void) 1180{ 1181 return false; 1182} 1183 1184static inline void rcu_sysidle_force_exit(void) 1185{ 1186} 1187 1188#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ 1189 1190 1191#endif /* __LINUX_RCUPDATE_H */ 1192