1 /* 2 * Read-Copy Update mechanism for mutual exclusion (tree-based version) 3 * Internal non-public definitions. 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, you can access it online at 17 * http://www.gnu.org/licenses/gpl-2.0.html. 18 * 19 * Copyright IBM Corporation, 2008 20 * 21 * Author: Ingo Molnar <mingo@elte.hu> 22 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> 23 */ 24 25 #include <linux/cache.h> 26 #include <linux/spinlock.h> 27 #include <linux/rtmutex.h> 28 #include <linux/threads.h> 29 #include <linux/cpumask.h> 30 #include <linux/seqlock.h> 31 #include <linux/swait.h> 32 #include <linux/stop_machine.h> 33 #include <linux/rcu_node_tree.h> 34 35 #include "rcu_segcblist.h" 36 37 /* 38 * Dynticks per-CPU state. 39 */ 40 struct rcu_dynticks { 41 long dynticks_nesting; /* Track process nesting level. */ 42 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */ 43 atomic_t dynticks; /* Even value for idle, else odd. */ 44 bool rcu_need_heavy_qs; /* GP old, need heavy quiescent state. */ 45 unsigned long rcu_qs_ctr; /* Light universal quiescent state ctr. */ 46 bool rcu_urgent_qs; /* GP old need light quiescent state. */ 47 #ifdef CONFIG_RCU_FAST_NO_HZ 48 bool all_lazy; /* Are all CPU's CBs lazy? */ 49 unsigned long nonlazy_posted; 50 /* # times non-lazy CBs posted to CPU. */ 51 unsigned long nonlazy_posted_snap; 52 /* idle-period nonlazy_posted snapshot. */ 53 unsigned long last_accelerate; 54 /* Last jiffy CBs were accelerated. */ 55 unsigned long last_advance_all; 56 /* Last jiffy CBs were all advanced. */ 57 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ 58 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ 59 }; 60 61 /* Communicate arguments to a workqueue handler. */ 62 struct rcu_exp_work { 63 smp_call_func_t rew_func; 64 struct rcu_state *rew_rsp; 65 unsigned long rew_s; 66 struct work_struct rew_work; 67 }; 68 69 /* RCU's kthread states for tracing. */ 70 #define RCU_KTHREAD_STOPPED 0 71 #define RCU_KTHREAD_RUNNING 1 72 #define RCU_KTHREAD_WAITING 2 73 #define RCU_KTHREAD_OFFCPU 3 74 #define RCU_KTHREAD_YIELDING 4 75 #define RCU_KTHREAD_MAX 4 76 77 /* 78 * Definition for node within the RCU grace-period-detection hierarchy. 79 */ 80 struct rcu_node { 81 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */ 82 /* some rcu_state fields as well as */ 83 /* following. */ 84 unsigned long gp_seq; /* Track rsp->rcu_gp_seq. */ 85 unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed. */ 86 unsigned long completedqs; /* All QSes done for this node. */ 87 unsigned long qsmask; /* CPUs or groups that need to switch in */ 88 /* order for current grace period to proceed.*/ 89 /* In leaf rcu_node, each bit corresponds to */ 90 /* an rcu_data structure, otherwise, each */ 91 /* bit corresponds to a child rcu_node */ 92 /* structure. */ 93 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ 94 unsigned long qsmaskinit; 95 /* Per-GP initial value for qsmask. */ 96 /* Initialized from ->qsmaskinitnext at the */ 97 /* beginning of each grace period. */ 98 unsigned long qsmaskinitnext; 99 /* Online CPUs for next grace period. */ 100 unsigned long expmask; /* CPUs or groups that need to check in */ 101 /* to allow the current expedited GP */ 102 /* to complete. */ 103 unsigned long expmaskinit; 104 /* Per-GP initial values for expmask. */ 105 /* Initialized from ->expmaskinitnext at the */ 106 /* beginning of each expedited GP. */ 107 unsigned long expmaskinitnext; 108 /* Online CPUs for next expedited GP. */ 109 /* Any CPU that has ever been online will */ 110 /* have its bit set. */ 111 unsigned long ffmask; /* Fully functional CPUs. */ 112 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 113 /* Only one bit will be set in this mask. */ 114 int grplo; /* lowest-numbered CPU or group here. */ 115 int grphi; /* highest-numbered CPU or group here. */ 116 u8 grpnum; /* CPU/group number for next level up. */ 117 u8 level; /* root is at level 0. */ 118 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ 119 /* exit RCU read-side critical sections */ 120 /* before propagating offline up the */ 121 /* rcu_node tree? */ 122 struct rcu_node *parent; 123 struct list_head blkd_tasks; 124 /* Tasks blocked in RCU read-side critical */ 125 /* section. Tasks are placed at the head */ 126 /* of this list and age towards the tail. */ 127 struct list_head *gp_tasks; 128 /* Pointer to the first task blocking the */ 129 /* current grace period, or NULL if there */ 130 /* is no such task. */ 131 struct list_head *exp_tasks; 132 /* Pointer to the first task blocking the */ 133 /* current expedited grace period, or NULL */ 134 /* if there is no such task. If there */ 135 /* is no current expedited grace period, */ 136 /* then there can cannot be any such task. */ 137 struct list_head *boost_tasks; 138 /* Pointer to first task that needs to be */ 139 /* priority boosted, or NULL if no priority */ 140 /* boosting is needed for this rcu_node */ 141 /* structure. If there are no tasks */ 142 /* queued on this rcu_node structure that */ 143 /* are blocking the current grace period, */ 144 /* there can be no such task. */ 145 struct rt_mutex boost_mtx; 146 /* Used only for the priority-boosting */ 147 /* side effect, not as a lock. */ 148 unsigned long boost_time; 149 /* When to start boosting (jiffies). */ 150 struct task_struct *boost_kthread_task; 151 /* kthread that takes care of priority */ 152 /* boosting for this rcu_node structure. */ 153 unsigned int boost_kthread_status; 154 /* State of boost_kthread_task for tracing. */ 155 #ifdef CONFIG_RCU_NOCB_CPU 156 struct swait_queue_head nocb_gp_wq[2]; 157 /* Place for rcu_nocb_kthread() to wait GP. */ 158 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 159 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; 160 161 spinlock_t exp_lock ____cacheline_internodealigned_in_smp; 162 unsigned long exp_seq_rq; 163 wait_queue_head_t exp_wq[4]; 164 struct rcu_exp_work rew; 165 bool exp_need_flush; /* Need to flush workitem? */ 166 } ____cacheline_internodealigned_in_smp; 167 168 /* 169 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and 170 * are indexed relative to this interval rather than the global CPU ID space. 171 * This generates the bit for a CPU in node-local masks. 172 */ 173 #define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo)) 174 175 /* 176 * Union to allow "aggregate OR" operation on the need for a quiescent 177 * state by the normal and expedited grace periods. 178 */ 179 union rcu_noqs { 180 struct { 181 u8 norm; 182 u8 exp; 183 } b; /* Bits. */ 184 u16 s; /* Set of bits, aggregate OR here. */ 185 }; 186 187 /* Per-CPU data for read-copy update. */ 188 struct rcu_data { 189 /* 1) quiescent-state and grace-period handling : */ 190 unsigned long gp_seq; /* Track rsp->rcu_gp_seq counter. */ 191 unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed ctr. */ 192 unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */ 193 /* for rcu_all_qs() invocations. */ 194 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ 195 bool core_needs_qs; /* Core waits for quiesc state. */ 196 bool beenonline; /* CPU online at least once. */ 197 bool gpwrap; /* Possible ->gp_seq wrap. */ 198 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 199 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 200 unsigned long ticks_this_gp; /* The number of scheduling-clock */ 201 /* ticks this CPU has handled */ 202 /* during and after the last grace */ 203 /* period it is aware of. */ 204 205 /* 2) batch handling */ 206 struct rcu_segcblist cblist; /* Segmented callback list, with */ 207 /* different callbacks waiting for */ 208 /* different grace periods. */ 209 long qlen_last_fqs_check; 210 /* qlen at last check for QS forcing */ 211 unsigned long n_force_qs_snap; 212 /* did other CPU force QS recently? */ 213 long blimit; /* Upper limit on a processed batch */ 214 215 /* 3) dynticks interface. */ 216 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ 217 int dynticks_snap; /* Per-GP tracking for dynticks. */ 218 219 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ 220 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ 221 unsigned long cond_resched_completed; 222 /* Grace period that needs help */ 223 /* from cond_resched(). */ 224 225 /* 5) _rcu_barrier(), OOM callbacks, and expediting. */ 226 struct rcu_head barrier_head; 227 #ifdef CONFIG_RCU_FAST_NO_HZ 228 struct rcu_head oom_head; 229 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ 230 int exp_dynticks_snap; /* Double-check need for IPI. */ 231 232 /* 6) Callback offloading. */ 233 #ifdef CONFIG_RCU_NOCB_CPU 234 struct rcu_head *nocb_head; /* CBs waiting for kthread. */ 235 struct rcu_head **nocb_tail; 236 atomic_long_t nocb_q_count; /* # CBs waiting for nocb */ 237 atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */ 238 struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */ 239 struct rcu_head **nocb_follower_tail; 240 struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */ 241 struct task_struct *nocb_kthread; 242 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ 243 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ 244 struct timer_list nocb_timer; /* Enforce finite deferral. */ 245 246 /* The following fields are used by the leader, hence own cacheline. */ 247 struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp; 248 /* CBs waiting for GP. */ 249 struct rcu_head **nocb_gp_tail; 250 bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */ 251 struct rcu_data *nocb_next_follower; 252 /* Next follower in wakeup chain. */ 253 254 /* The following fields are used by the follower, hence new cachline. */ 255 struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp; 256 /* Leader CPU takes GP-end wakeups. */ 257 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 258 259 /* 7) Diagnostic data, including RCU CPU stall warnings. */ 260 unsigned int softirq_snap; /* Snapshot of softirq activity. */ 261 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ 262 struct irq_work rcu_iw; /* Check for non-irq activity. */ 263 bool rcu_iw_pending; /* Is ->rcu_iw pending? */ 264 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ 265 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ 266 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ 267 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ 268 short rcu_onl_gp_flags; /* ->gp_flags at last online. */ 269 270 int cpu; 271 struct rcu_state *rsp; 272 }; 273 274 /* Values for nocb_defer_wakeup field in struct rcu_data. */ 275 #define RCU_NOCB_WAKE_NOT 0 276 #define RCU_NOCB_WAKE 1 277 #define RCU_NOCB_WAKE_FORCE 2 278 279 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) 280 /* For jiffies_till_first_fqs and */ 281 /* and jiffies_till_next_fqs. */ 282 283 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ 284 /* delay between bouts of */ 285 /* quiescent-state forcing. */ 286 287 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ 288 /* at least one scheduling clock */ 289 /* irq before ratting on them. */ 290 291 #define rcu_wait(cond) \ 292 do { \ 293 for (;;) { \ 294 set_current_state(TASK_INTERRUPTIBLE); \ 295 if (cond) \ 296 break; \ 297 schedule(); \ 298 } \ 299 __set_current_state(TASK_RUNNING); \ 300 } while (0) 301 302 /* 303 * RCU global state, including node hierarchy. This hierarchy is 304 * represented in "heap" form in a dense array. The root (first level) 305 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 306 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 307 * and the third level in ->node[m+1] and following (->node[m+1] referenced 308 * by ->level[2]). The number of levels is determined by the number of 309 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 310 * consisting of a single rcu_node. 311 */ 312 struct rcu_state { 313 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 314 struct rcu_node *level[RCU_NUM_LVLS + 1]; 315 /* Hierarchy levels (+1 to */ 316 /* shut bogus gcc warning) */ 317 struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ 318 call_rcu_func_t call; /* call_rcu() flavor. */ 319 int ncpus; /* # CPUs seen so far. */ 320 321 /* The following fields are guarded by the root rcu_node's lock. */ 322 323 u8 boost ____cacheline_internodealigned_in_smp; 324 /* Subject to priority boost. */ 325 unsigned long gp_seq; /* Grace-period sequence #. */ 326 struct task_struct *gp_kthread; /* Task for grace periods. */ 327 struct swait_queue_head gp_wq; /* Where GP task waits. */ 328 short gp_flags; /* Commands for GP task. */ 329 short gp_state; /* GP kthread sleep state. */ 330 331 /* End of fields guarded by root rcu_node's lock. */ 332 333 struct mutex barrier_mutex; /* Guards barrier fields. */ 334 atomic_t barrier_cpu_count; /* # CPUs waiting on. */ 335 struct completion barrier_completion; /* Wake at barrier end. */ 336 unsigned long barrier_sequence; /* ++ at start and end of */ 337 /* _rcu_barrier(). */ 338 /* End of fields guarded by barrier_mutex. */ 339 340 struct mutex exp_mutex; /* Serialize expedited GP. */ 341 struct mutex exp_wake_mutex; /* Serialize wakeup. */ 342 unsigned long expedited_sequence; /* Take a ticket. */ 343 atomic_t expedited_need_qs; /* # CPUs left to check in. */ 344 struct swait_queue_head expedited_wq; /* Wait for check-ins. */ 345 int ncpus_snap; /* # CPUs seen last time. */ 346 347 unsigned long jiffies_force_qs; /* Time at which to invoke */ 348 /* force_quiescent_state(). */ 349 unsigned long jiffies_kick_kthreads; /* Time at which to kick */ 350 /* kthreads, if configured. */ 351 unsigned long n_force_qs; /* Number of calls to */ 352 /* force_quiescent_state(). */ 353 unsigned long gp_start; /* Time at which GP started, */ 354 /* but in jiffies. */ 355 unsigned long gp_activity; /* Time of last GP kthread */ 356 /* activity in jiffies. */ 357 unsigned long gp_req_activity; /* Time of last GP request */ 358 /* in jiffies. */ 359 unsigned long jiffies_stall; /* Time at which to check */ 360 /* for CPU stalls. */ 361 unsigned long jiffies_resched; /* Time at which to resched */ 362 /* a reluctant CPU. */ 363 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ 364 /* GP start. */ 365 unsigned long gp_max; /* Maximum GP duration in */ 366 /* jiffies. */ 367 const char *name; /* Name of structure. */ 368 char abbr; /* Abbreviated name. */ 369 struct list_head flavors; /* List of RCU flavors. */ 370 371 spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; 372 /* Synchronize offline with */ 373 /* GP pre-initialization. */ 374 }; 375 376 /* Values for rcu_state structure's gp_flags field. */ 377 #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ 378 #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ 379 380 /* Values for rcu_state structure's gp_state field. */ 381 #define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ 382 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ 383 #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ 384 #define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ 385 #define RCU_GP_INIT 4 /* Grace-period initialization. */ 386 #define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ 387 #define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ 388 #define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ 389 #define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ 390 391 #ifndef RCU_TREE_NONCORE 392 static const char * const gp_state_names[] = { 393 "RCU_GP_IDLE", 394 "RCU_GP_WAIT_GPS", 395 "RCU_GP_DONE_GPS", 396 "RCU_GP_ONOFF", 397 "RCU_GP_INIT", 398 "RCU_GP_WAIT_FQS", 399 "RCU_GP_DOING_FQS", 400 "RCU_GP_CLEANUP", 401 "RCU_GP_CLEANED", 402 }; 403 #endif /* #ifndef RCU_TREE_NONCORE */ 404 405 extern struct list_head rcu_struct_flavors; 406 407 /* Sequence through rcu_state structures for each RCU flavor. */ 408 #define for_each_rcu_flavor(rsp) \ 409 list_for_each_entry((rsp), &rcu_struct_flavors, flavors) 410 411 /* 412 * RCU implementation internal declarations: 413 */ 414 extern struct rcu_state rcu_sched_state; 415 416 extern struct rcu_state rcu_bh_state; 417 418 #ifdef CONFIG_PREEMPT_RCU 419 extern struct rcu_state rcu_preempt_state; 420 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 421 422 int rcu_dynticks_snap(struct rcu_dynticks *rdtp); 423 424 #ifdef CONFIG_RCU_BOOST 425 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); 426 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu); 427 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); 428 DECLARE_PER_CPU(char, rcu_cpu_has_work); 429 #endif /* #ifdef CONFIG_RCU_BOOST */ 430 431 #ifndef RCU_TREE_NONCORE 432 433 /* Forward declarations for rcutree_plugin.h */ 434 static void rcu_bootup_announce(void); 435 static void rcu_preempt_note_context_switch(bool preempt); 436 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 437 #ifdef CONFIG_HOTPLUG_CPU 438 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 439 #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 440 static void rcu_print_detail_task_stall(struct rcu_state *rsp); 441 static int rcu_print_task_stall(struct rcu_node *rnp); 442 static int rcu_print_task_exp_stall(struct rcu_node *rnp); 443 static void rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, 444 struct rcu_node *rnp); 445 static void rcu_preempt_check_callbacks(void); 446 void call_rcu(struct rcu_head *head, rcu_callback_t func); 447 static void __init __rcu_init_preempt(void); 448 static void dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp, 449 int ncheck); 450 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 451 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 452 static void invoke_rcu_callbacks_kthread(void); 453 static bool rcu_is_callbacks_kthread(void); 454 #ifdef CONFIG_RCU_BOOST 455 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, 456 struct rcu_node *rnp); 457 #endif /* #ifdef CONFIG_RCU_BOOST */ 458 static void __init rcu_spawn_boost_kthreads(void); 459 static void rcu_prepare_kthreads(int cpu); 460 static void rcu_cleanup_after_idle(void); 461 static void rcu_prepare_for_idle(void); 462 static void rcu_idle_count_callbacks_posted(void); 463 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 464 static void print_cpu_stall_info_begin(void); 465 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu); 466 static void print_cpu_stall_info_end(void); 467 static void zero_cpu_stall_ticks(struct rcu_data *rdp); 468 static void increment_cpu_stall_ticks(void); 469 static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu); 470 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); 471 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); 472 static void rcu_init_one_nocb(struct rcu_node *rnp); 473 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, 474 bool lazy, unsigned long flags); 475 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, 476 struct rcu_data *rdp, 477 unsigned long flags); 478 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); 479 static void do_nocb_deferred_wakeup(struct rcu_data *rdp); 480 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); 481 static void rcu_spawn_all_nocb_kthreads(int cpu); 482 static void __init rcu_spawn_nocb_kthreads(void); 483 #ifdef CONFIG_RCU_NOCB_CPU 484 static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp); 485 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 486 static bool init_nocb_callback_list(struct rcu_data *rdp); 487 static void rcu_bind_gp_kthread(void); 488 static bool rcu_nohz_full_cpu(struct rcu_state *rsp); 489 static void rcu_dynticks_task_enter(void); 490 static void rcu_dynticks_task_exit(void); 491 492 #ifdef CONFIG_SRCU 493 void srcu_online_cpu(unsigned int cpu); 494 void srcu_offline_cpu(unsigned int cpu); 495 #else /* #ifdef CONFIG_SRCU */ 496 void srcu_online_cpu(unsigned int cpu) { } 497 void srcu_offline_cpu(unsigned int cpu) { } 498 #endif /* #else #ifdef CONFIG_SRCU */ 499 500 #endif /* #ifndef RCU_TREE_NONCORE */ 501