kernel/rcu/update.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Read-Copy Update mechanism for mutual exclusion
   4  *
   5  * Copyright IBM Corporation, 2001
   6  *
   7  * Authors: Dipankar Sarma <dipankar@in.ibm.com>
   8  *          Manfred Spraul <manfred@colorfullife.com>
   9  *
  10  * Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
  11  * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  12  * Papers:
  13  * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
  14  * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
  15  *
  16  * For detailed explanation of Read-Copy Update mechanism see -
  17  *              http://lse.sourceforge.net/locking/rcupdate.html
  18  *
  19  */
  20 #include <linux/types.h>
  21 #include <linux/kernel.h>
  22 #include <linux/init.h>
  23 #include <linux/spinlock.h>
  24 #include <linux/smp.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/sched/signal.h>
  27 #include <linux/sched/debug.h>
  28 #include <linux/atomic.h>
  29 #include <linux/bitops.h>
  30 #include <linux/percpu.h>
  31 #include <linux/notifier.h>
  32 #include <linux/cpu.h>
  33 #include <linux/mutex.h>
  34 #include <linux/export.h>
  35 #include <linux/hardirq.h>
  36 #include <linux/delay.h>
  37 #include <linux/moduleparam.h>
  38 #include <linux/kthread.h>
  39 #include <linux/tick.h>
  40 #include <linux/rcupdate_wait.h>
  41 #include <linux/sched/isolation.h>
  42 #include <linux/kprobes.h>
  43 #include <linux/slab.h>
  44 #include <linux/irq_work.h>
  45 #include <linux/rcupdate_trace.h>
  46
  47 #define CREATE_TRACE_POINTS
  48
  49 #include "rcu.h"
  50
  51 #ifdef MODULE_PARAM_PREFIX
  52 #undef MODULE_PARAM_PREFIX
  53 #endif
  54 #define MODULE_PARAM_PREFIX "rcupdate."
  55
  56 #ifndef CONFIG_TINY_RCU
  57 module_param(rcu_expedited, int, 0);
  58 module_param(rcu_normal, int, 0);
  59 static int rcu_normal_after_boot;
  60 module_param(rcu_normal_after_boot, int, 0);
  61 #endif /* #ifndef CONFIG_TINY_RCU */
  62
  63 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  64 /**
  65  * rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
  66  * @ret:        Best guess answer if lockdep cannot be relied on
  67  *
  68  * Returns true if lockdep must be ignored, in which case ``*ret`` contains
  69  * the best guess described below.  Otherwise returns false, in which
  70  * case ``*ret`` tells the caller nothing and the caller should instead
  71  * consult lockdep.
  72  *
  73  * If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to nonzero iff in an
  74  * RCU-sched read-side critical section.  In absence of
  75  * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
  76  * critical section unless it can prove otherwise.  Note that disabling
  77  * of preemption (including disabling irqs) counts as an RCU-sched
  78  * read-side critical section.  This is useful for debug checks in functions
  79  * that required that they be called within an RCU-sched read-side
  80  * critical section.
  81  *
  82  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
  83  * and while lockdep is disabled.
  84  *
  85  * Note that if the CPU is in the idle loop from an RCU point of view (ie:
  86  * that we are in the section between rcu_idle_enter() and rcu_idle_exit())
  87  * then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an
  88  * rcu_read_lock().  The reason for this is that RCU ignores CPUs that are
  89  * in such a section, considering these as in extended quiescent state,
  90  * so such a CPU is effectively never in an RCU read-side critical section
  91  * regardless of what RCU primitives it invokes.  This state of affairs is
  92  * required --- we need to keep an RCU-free window in idle where the CPU may
  93  * possibly enter into low power mode. This way we can notice an extended
  94  * quiescent state to other CPUs that started a grace period. Otherwise
  95  * we would delay any grace period as long as we run in the idle task.
  96  *
  97  * Similarly, we avoid claiming an RCU read lock held if the current
  98  * CPU is offline.
  99  */
 100 static bool rcu_read_lock_held_common(bool *ret)
 101 {
 102         if (!debug_lockdep_rcu_enabled()) {
 103                 *ret = true;
 104                 return true;
 105         }
 106         if (!rcu_is_watching()) {
 107                 *ret = false;
 108                 return true;
 109         }
 110         if (!rcu_lockdep_current_cpu_online()) {
 111                 *ret = false;
 112                 return true;
 113         }
 114         return false;
 115 }
 116
 117 int rcu_read_lock_sched_held(void)
 118 {
 119         bool ret;
 120
 121         if (rcu_read_lock_held_common(&ret))
 122                 return ret;
 123         return lock_is_held(&rcu_sched_lock_map) || !preemptible();
 124 }
 125 EXPORT_SYMBOL(rcu_read_lock_sched_held);
 126 #endif
 127
 128 #ifndef CONFIG_TINY_RCU
 129
 130 /*
 131  * Should expedited grace-period primitives always fall back to their
 132  * non-expedited counterparts?  Intended for use within RCU.  Note
 133  * that if the user specifies both rcu_expedited and rcu_normal, then
 134  * rcu_normal wins.  (Except during the time period during boot from
 135  * when the first task is spawned until the rcu_set_runtime_mode()
 136  * core_initcall() is invoked, at which point everything is expedited.)
 137  */
 138 bool rcu_gp_is_normal(void)
 139 {
 140         return READ_ONCE(rcu_normal) &&
 141                rcu_scheduler_active != RCU_SCHEDULER_INIT;
 142 }
 143 EXPORT_SYMBOL_GPL(rcu_gp_is_normal);
 144
 145 static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
 146
 147 /*
 148  * Should normal grace-period primitives be expedited?  Intended for
 149  * use within RCU.  Note that this function takes the rcu_expedited
 150  * sysfs/boot variable and rcu_scheduler_active into account as well
 151  * as the rcu_expedite_gp() nesting.  So looping on rcu_unexpedite_gp()
 152  * until rcu_gp_is_expedited() returns false is a -really- bad idea.
 153  */
 154 bool rcu_gp_is_expedited(void)
 155 {
 156         return rcu_expedited || atomic_read(&rcu_expedited_nesting);
 157 }
 158 EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
 159
 160 /**
 161  * rcu_expedite_gp - Expedite future RCU grace periods
 162  *
 163  * After a call to this function, future calls to synchronize_rcu() and
 164  * friends act as the corresponding synchronize_rcu_expedited() function
 165  * had instead been called.
 166  */
 167 void rcu_expedite_gp(void)
 168 {
 169         atomic_inc(&rcu_expedited_nesting);
 170 }
 171 EXPORT_SYMBOL_GPL(rcu_expedite_gp);
 172
 173 /**
 174  * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
 175  *
 176  * Undo a prior call to rcu_expedite_gp().  If all prior calls to
 177  * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
 178  * and if the rcu_expedited sysfs/boot parameter is not set, then all
 179  * subsequent calls to synchronize_rcu() and friends will return to
 180  * their normal non-expedited behavior.
 181  */
 182 void rcu_unexpedite_gp(void)
 183 {
 184         atomic_dec(&rcu_expedited_nesting);
 185 }
 186 EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
 187
 188 static bool rcu_boot_ended __read_mostly;
 189
 190 /*
 191  * Inform RCU of the end of the in-kernel boot sequence.
 192  */
 193 void rcu_end_inkernel_boot(void)
 194 {
 195         rcu_unexpedite_gp();
 196         if (rcu_normal_after_boot)
 197                 WRITE_ONCE(rcu_normal, 1);
 198         rcu_boot_ended = true;
 199 }
 200
 201 /*
 202  * Let rcutorture know when it is OK to turn it up to eleven.
 203  */
 204 bool rcu_inkernel_boot_has_ended(void)
 205 {
 206         return rcu_boot_ended;
 207 }
 208 EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);
 209
 210 #endif /* #ifndef CONFIG_TINY_RCU */
 211
 212 /*
 213  * Test each non-SRCU synchronous grace-period wait API.  This is
 214  * useful just after a change in mode for these primitives, and
 215  * during early boot.
 216  */
 217 void rcu_test_sync_prims(void)
 218 {
 219         if (!IS_ENABLED(CONFIG_PROVE_RCU))
 220                 return;
 221         synchronize_rcu();
 222         synchronize_rcu_expedited();
 223 }
 224
 225 #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
 226
 227 /*
 228  * Switch to run-time mode once RCU has fully initialized.
 229  */
 230 static int __init rcu_set_runtime_mode(void)
 231 {
 232         rcu_test_sync_prims();
 233         rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
 234         kfree_rcu_scheduler_running();
 235         rcu_test_sync_prims();
 236         return 0;
 237 }
 238 core_initcall(rcu_set_runtime_mode);
 239
 240 #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
 241
 242 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 243 static struct lock_class_key rcu_lock_key;
 244 struct lockdep_map rcu_lock_map = {
 245         .name = "rcu_read_lock",
 246         .key = &rcu_lock_key,
 247         .wait_type_outer = LD_WAIT_FREE,
 248         .wait_type_inner = LD_WAIT_CONFIG, /* XXX PREEMPT_RCU ? */
 249 };
 250 EXPORT_SYMBOL_GPL(rcu_lock_map);
 251
 252 static struct lock_class_key rcu_bh_lock_key;
 253 struct lockdep_map rcu_bh_lock_map = {
 254         .name = "rcu_read_lock_bh",
 255         .key = &rcu_bh_lock_key,
 256         .wait_type_outer = LD_WAIT_FREE,
 257         .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_LOCK also makes BH preemptible */
 258 };
 259 EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
 260
 261 static struct lock_class_key rcu_sched_lock_key;
 262 struct lockdep_map rcu_sched_lock_map = {
 263         .name = "rcu_read_lock_sched",
 264         .key = &rcu_sched_lock_key,
 265         .wait_type_outer = LD_WAIT_FREE,
 266         .wait_type_inner = LD_WAIT_SPIN,
 267 };
 268 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
 269
 270 // Tell lockdep when RCU callbacks are being invoked.
 271 static struct lock_class_key rcu_callback_key;
 272 struct lockdep_map rcu_callback_map =
 273         STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
 274 EXPORT_SYMBOL_GPL(rcu_callback_map);
 275
 276 noinstr int notrace debug_lockdep_rcu_enabled(void)
 277 {
 278         return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks &&
 279                current->lockdep_recursion == 0;
 280 }
 281 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
 282
 283 /**
 284  * rcu_read_lock_held() - might we be in RCU read-side critical section?
 285  *
 286  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
 287  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
 288  * this assumes we are in an RCU read-side critical section unless it can
 289  * prove otherwise.  This is useful for debug checks in functions that
 290  * require that they be called within an RCU read-side critical section.
 291  *
 292  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
 293  * and while lockdep is disabled.
 294  *
 295  * Note that rcu_read_lock() and the matching rcu_read_unlock() must
 296  * occur in the same context, for example, it is illegal to invoke
 297  * rcu_read_unlock() in process context if the matching rcu_read_lock()
 298  * was invoked from within an irq handler.
 299  *
 300  * Note that rcu_read_lock() is disallowed if the CPU is either idle or
 301  * offline from an RCU perspective, so check for those as well.
 302  */
 303 int rcu_read_lock_held(void)
 304 {
 305         bool ret;
 306
 307         if (rcu_read_lock_held_common(&ret))
 308                 return ret;
 309         return lock_is_held(&rcu_lock_map);
 310 }
 311 EXPORT_SYMBOL_GPL(rcu_read_lock_held);
 312
 313 /**
 314  * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
 315  *
 316  * Check for bottom half being disabled, which covers both the
 317  * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
 318  * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
 319  * will show the situation.  This is useful for debug checks in functions
 320  * that require that they be called within an RCU read-side critical
 321  * section.
 322  *
 323  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
 324  *
 325  * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
 326  * offline from an RCU perspective, so check for those as well.
 327  */
 328 int rcu_read_lock_bh_held(void)
 329 {
 330         bool ret;
 331
 332         if (rcu_read_lock_held_common(&ret))
 333                 return ret;
 334         return in_softirq() || irqs_disabled();
 335 }
 336 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 337
 338 int rcu_read_lock_any_held(void)
 339 {
 340         bool ret;
 341
 342         if (rcu_read_lock_held_common(&ret))
 343                 return ret;
 344         if (lock_is_held(&rcu_lock_map) ||
 345             lock_is_held(&rcu_bh_lock_map) ||
 346             lock_is_held(&rcu_sched_lock_map))
 347                 return 1;
 348         return !preemptible();
 349 }
 350 EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
 351
 352 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 353
 354 /**
 355  * wakeme_after_rcu() - Callback function to awaken a task after grace period
 356  * @head: Pointer to rcu_head member within rcu_synchronize structure
 357  *
 358  * Awaken the corresponding task now that a grace period has elapsed.
 359  */
 360 void wakeme_after_rcu(struct rcu_head *head)
 361 {
 362         struct rcu_synchronize *rcu;
 363
 364         rcu = container_of(head, struct rcu_synchronize, head);
 365         complete(&rcu->completion);
 366 }
 367 EXPORT_SYMBOL_GPL(wakeme_after_rcu);
 368
 369 void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
 370                    struct rcu_synchronize *rs_array)
 371 {
 372         int i;
 373         int j;
 374
 375         /* Initialize and register callbacks for each crcu_array element. */
 376         for (i = 0; i < n; i++) {
 377                 if (checktiny &&
 378                     (crcu_array[i] == call_rcu)) {
 379                         might_sleep();
 380                         continue;
 381                 }
 382                 for (j = 0; j < i; j++)
 383                         if (crcu_array[j] == crcu_array[i])
 384                                 break;
 385                 if (j == i) {
 386                         init_rcu_head_on_stack(&rs_array[i].head);
 387                         init_completion(&rs_array[i].completion);
 388                         (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
 389                 }
 390         }
 391
 392         /* Wait for all callbacks to be invoked. */
 393         for (i = 0; i < n; i++) {
 394                 if (checktiny &&
 395                     (crcu_array[i] == call_rcu))
 396                         continue;
 397                 for (j = 0; j < i; j++)
 398                         if (crcu_array[j] == crcu_array[i])
 399                                 break;
 400                 if (j == i) {
 401                         wait_for_completion(&rs_array[i].completion);
 402                         destroy_rcu_head_on_stack(&rs_array[i].head);
 403                 }
 404         }
 405 }
 406 EXPORT_SYMBOL_GPL(__wait_rcu_gp);
 407
 408 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
 409 void init_rcu_head(struct rcu_head *head)
 410 {
 411         debug_object_init(head, &rcuhead_debug_descr);
 412 }
 413 EXPORT_SYMBOL_GPL(init_rcu_head);
 414
 415 void destroy_rcu_head(struct rcu_head *head)
 416 {
 417         debug_object_free(head, &rcuhead_debug_descr);
 418 }
 419 EXPORT_SYMBOL_GPL(destroy_rcu_head);
 420
 421 static bool rcuhead_is_static_object(void *addr)
 422 {
 423         return true;
 424 }
 425
 426 /**
 427  * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
 428  * @head: pointer to rcu_head structure to be initialized
 429  *
 430  * This function informs debugobjects of a new rcu_head structure that
 431  * has been allocated as an auto variable on the stack.  This function
 432  * is not required for rcu_head structures that are statically defined or
 433  * that are dynamically allocated on the heap.  This function has no
 434  * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
 435  */
 436 void init_rcu_head_on_stack(struct rcu_head *head)
 437 {
 438         debug_object_init_on_stack(head, &rcuhead_debug_descr);
 439 }
 440 EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
 441
 442 /**
 443  * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
 444  * @head: pointer to rcu_head structure to be initialized
 445  *
 446  * This function informs debugobjects that an on-stack rcu_head structure
 447  * is about to go out of scope.  As with init_rcu_head_on_stack(), this
 448  * function is not required for rcu_head structures that are statically
 449  * defined or that are dynamically allocated on the heap.  Also as with
 450  * init_rcu_head_on_stack(), this function has no effect for
 451  * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
 452  */
 453 void destroy_rcu_head_on_stack(struct rcu_head *head)
 454 {
 455         debug_object_free(head, &rcuhead_debug_descr);
 456 }
 457 EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
 458
 459 const struct debug_obj_descr rcuhead_debug_descr = {
 460         .name = "rcu_head",
 461         .is_static_object = rcuhead_is_static_object,
 462 };
 463 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 464 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 465
 466 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
 467 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
 468                                unsigned long secs,
 469                                unsigned long c_old, unsigned long c)
 470 {
 471         trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
 472 }
 473 EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
 474 #else
 475 #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
 476         do { } while (0)
 477 #endif
 478
 479 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
 480 /* Get rcutorture access to sched_setaffinity(). */
 481 long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
 482 {
 483         int ret;
 484
 485         ret = sched_setaffinity(pid, in_mask);
 486         WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret);
 487         return ret;
 488 }
 489 EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
 490 #endif
 491
 492 #ifdef CONFIG_RCU_STALL_COMMON
 493 int rcu_cpu_stall_ftrace_dump __read_mostly;
 494 module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
 495 int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
 496 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
 497 module_param(rcu_cpu_stall_suppress, int, 0644);
 498 int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
 499 module_param(rcu_cpu_stall_timeout, int, 0644);
 500 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 501
 502 // Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
 503 // warnings.  Also used by rcutorture even if stall warnings are excluded.
 504 int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
 505 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
 506 module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
 507
 508 #ifdef CONFIG_PROVE_RCU
 509
 510 /*
 511  * Early boot self test parameters.
 512  */
 513 static bool rcu_self_test;
 514 module_param(rcu_self_test, bool, 0444);
 515
 516 static int rcu_self_test_counter;
 517
 518 static void test_callback(struct rcu_head *r)
 519 {
 520         rcu_self_test_counter++;
 521         pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
 522 }
 523
 524 DEFINE_STATIC_SRCU(early_srcu);
 525
 526 struct early_boot_kfree_rcu {
 527         struct rcu_head rh;
 528 };
 529
 530 static void early_boot_test_call_rcu(void)
 531 {
 532         static struct rcu_head head;
 533         static struct rcu_head shead;
 534         struct early_boot_kfree_rcu *rhp;
 535
 536         call_rcu(&head, test_callback);
 537         if (IS_ENABLED(CONFIG_SRCU))
 538                 call_srcu(&early_srcu, &shead, test_callback);
 539         rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
 540         if (!WARN_ON_ONCE(!rhp))
 541                 kfree_rcu(rhp, rh);
 542 }
 543
 544 void rcu_early_boot_tests(void)
 545 {
 546         pr_info("Running RCU self tests\n");
 547
 548         if (rcu_self_test)
 549                 early_boot_test_call_rcu();
 550         rcu_test_sync_prims();
 551 }
 552
 553 static int rcu_verify_early_boot_tests(void)
 554 {
 555         int ret = 0;
 556         int early_boot_test_counter = 0;
 557
 558         if (rcu_self_test) {
 559                 early_boot_test_counter++;
 560                 rcu_barrier();
 561                 if (IS_ENABLED(CONFIG_SRCU)) {
 562                         early_boot_test_counter++;
 563                         srcu_barrier(&early_srcu);
 564                 }
 565         }
 566         if (rcu_self_test_counter != early_boot_test_counter) {
 567                 WARN_ON(1);
 568                 ret = -1;
 569         }
 570
 571         return ret;
 572 }
 573 late_initcall(rcu_verify_early_boot_tests);
 574 #else
 575 void rcu_early_boot_tests(void) {}
 576 #endif /* CONFIG_PROVE_RCU */
 577
 578 #include "tasks.h"
 579
 580 #ifndef CONFIG_TINY_RCU
 581
 582 /*
 583  * Print any significant non-default boot-time settings.
 584  */
 585 void __init rcupdate_announce_bootup_oddness(void)
 586 {
 587         if (rcu_normal)
 588                 pr_info("\tNo expedited grace period (rcu_normal).\n");
 589         else if (rcu_normal_after_boot)
 590                 pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
 591         else if (rcu_expedited)
 592                 pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
 593         if (rcu_cpu_stall_suppress)
 594                 pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
 595         if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
 596                 pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
 597         rcu_tasks_bootup_oddness();
 598 }
 599
 600 #endif /* #ifndef CONFIG_TINY_RCU */