1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Read-Copy Update mechanism for mutual exclusion (tree-based version) 4 * Internal non-public definitions. 5 * 6 * Copyright IBM Corporation, 2008 7 * 8 * Author: Ingo Molnar <mingo@elte.hu> 9 * Paul E. McKenney <paulmck@linux.ibm.com> 10 */ 11 12 #include <linux/cache.h> 13 #include <linux/kthread.h> 14 #include <linux/spinlock.h> 15 #include <linux/rtmutex.h> 16 #include <linux/threads.h> 17 #include <linux/cpumask.h> 18 #include <linux/seqlock.h> 19 #include <linux/swait.h> 20 #include <linux/rcu_node_tree.h> 21 22 #include "rcu_segcblist.h" 23 24 /* Communicate arguments to a workqueue handler. */ 25 struct rcu_exp_work { 26 unsigned long rew_s; 27 #ifdef CONFIG_RCU_EXP_KTHREAD 28 struct kthread_work rew_work; 29 #else 30 struct work_struct rew_work; 31 #endif /* CONFIG_RCU_EXP_KTHREAD */ 32 }; 33 34 /* RCU's kthread states for tracing. */ 35 #define RCU_KTHREAD_STOPPED 0 36 #define RCU_KTHREAD_RUNNING 1 37 #define RCU_KTHREAD_WAITING 2 38 #define RCU_KTHREAD_OFFCPU 3 39 #define RCU_KTHREAD_YIELDING 4 40 #define RCU_KTHREAD_MAX 4 41 42 /* 43 * Definition for node within the RCU grace-period-detection hierarchy. 44 */ 45 struct rcu_node { 46 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */ 47 /* some rcu_state fields as well as */ 48 /* following. */ 49 unsigned long gp_seq; /* Track rsp->gp_seq. */ 50 unsigned long gp_seq_needed; /* Track furthest future GP request. */ 51 unsigned long completedqs; /* All QSes done for this node. */ 52 unsigned long qsmask; /* CPUs or groups that need to switch in */ 53 /* order for current grace period to proceed.*/ 54 /* In leaf rcu_node, each bit corresponds to */ 55 /* an rcu_data structure, otherwise, each */ 56 /* bit corresponds to a child rcu_node */ 57 /* structure. */ 58 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ 59 unsigned long qsmaskinit; 60 /* Per-GP initial value for qsmask. */ 61 /* Initialized from ->qsmaskinitnext at the */ 62 /* beginning of each grace period. */ 63 unsigned long qsmaskinitnext; 64 unsigned long expmask; /* CPUs or groups that need to check in */ 65 /* to allow the current expedited GP */ 66 /* to complete. */ 67 unsigned long expmaskinit; 68 /* Per-GP initial values for expmask. */ 69 /* Initialized from ->expmaskinitnext at the */ 70 /* beginning of each expedited GP. */ 71 unsigned long expmaskinitnext; 72 /* Online CPUs for next expedited GP. */ 73 /* Any CPU that has ever been online will */ 74 /* have its bit set. */ 75 unsigned long cbovldmask; 76 /* CPUs experiencing callback overload. */ 77 unsigned long ffmask; /* Fully functional CPUs. */ 78 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 79 /* Only one bit will be set in this mask. */ 80 int grplo; /* lowest-numbered CPU here. */ 81 int grphi; /* highest-numbered CPU here. */ 82 u8 grpnum; /* group number for next level up. */ 83 u8 level; /* root is at level 0. */ 84 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ 85 /* exit RCU read-side critical sections */ 86 /* before propagating offline up the */ 87 /* rcu_node tree? */ 88 struct rcu_node *parent; 89 struct list_head blkd_tasks; 90 /* Tasks blocked in RCU read-side critical */ 91 /* section. Tasks are placed at the head */ 92 /* of this list and age towards the tail. */ 93 struct list_head *gp_tasks; 94 /* Pointer to the first task blocking the */ 95 /* current grace period, or NULL if there */ 96 /* is no such task. */ 97 struct list_head *exp_tasks; 98 /* Pointer to the first task blocking the */ 99 /* current expedited grace period, or NULL */ 100 /* if there is no such task. If there */ 101 /* is no current expedited grace period, */ 102 /* then there can cannot be any such task. */ 103 struct list_head *boost_tasks; 104 /* Pointer to first task that needs to be */ 105 /* priority boosted, or NULL if no priority */ 106 /* boosting is needed for this rcu_node */ 107 /* structure. If there are no tasks */ 108 /* queued on this rcu_node structure that */ 109 /* are blocking the current grace period, */ 110 /* there can be no such task. */ 111 struct rt_mutex boost_mtx; 112 /* Used only for the priority-boosting */ 113 /* side effect, not as a lock. */ 114 unsigned long boost_time; 115 /* When to start boosting (jiffies). */ 116 struct mutex boost_kthread_mutex; 117 /* Exclusion for thread spawning and affinity */ 118 /* manipulation. */ 119 struct task_struct *boost_kthread_task; 120 /* kthread that takes care of priority */ 121 /* boosting for this rcu_node structure. */ 122 unsigned int boost_kthread_status; 123 /* State of boost_kthread_task for tracing. */ 124 unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */ 125 #ifdef CONFIG_RCU_NOCB_CPU 126 struct swait_queue_head nocb_gp_wq[2]; 127 /* Place for rcu_nocb_kthread() to wait GP. */ 128 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 129 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; 130 131 spinlock_t exp_lock ____cacheline_internodealigned_in_smp; 132 unsigned long exp_seq_rq; 133 wait_queue_head_t exp_wq[4]; 134 struct rcu_exp_work rew; 135 bool exp_need_flush; /* Need to flush workitem? */ 136 } ____cacheline_internodealigned_in_smp; 137 138 /* 139 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and 140 * are indexed relative to this interval rather than the global CPU ID space. 141 * This generates the bit for a CPU in node-local masks. 142 */ 143 #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo)) 144 145 /* 146 * Union to allow "aggregate OR" operation on the need for a quiescent 147 * state by the normal and expedited grace periods. 148 */ 149 union rcu_noqs { 150 struct { 151 u8 norm; 152 u8 exp; 153 } b; /* Bits. */ 154 u16 s; /* Set of bits, aggregate OR here. */ 155 }; 156 157 /* Per-CPU data for read-copy update. */ 158 struct rcu_data { 159 /* 1) quiescent-state and grace-period handling : */ 160 unsigned long gp_seq; /* Track rsp->gp_seq counter. */ 161 unsigned long gp_seq_needed; /* Track furthest future GP request. */ 162 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ 163 bool core_needs_qs; /* Core waits for quiescent state. */ 164 bool beenonline; /* CPU online at least once. */ 165 bool gpwrap; /* Possible ->gp_seq wrap. */ 166 bool cpu_started; /* RCU watching this onlining CPU. */ 167 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 168 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 169 unsigned long ticks_this_gp; /* The number of scheduling-clock */ 170 /* ticks this CPU has handled */ 171 /* during and after the last grace */ 172 /* period it is aware of. */ 173 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */ 174 bool defer_qs_iw_pending; /* Scheduler attention pending? */ 175 struct work_struct strict_work; /* Schedule readers for strict GPs. */ 176 177 /* 2) batch handling */ 178 struct rcu_segcblist cblist; /* Segmented callback list, with */ 179 /* different callbacks waiting for */ 180 /* different grace periods. */ 181 long qlen_last_fqs_check; 182 /* qlen at last check for QS forcing */ 183 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */ 184 unsigned long n_force_qs_snap; 185 /* did other CPU force QS recently? */ 186 long blimit; /* Upper limit on a processed batch */ 187 188 /* 3) dynticks interface. */ 189 int dynticks_snap; /* Per-GP tracking for dynticks. */ 190 long dynticks_nesting; /* Track process nesting level. */ 191 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */ 192 atomic_t dynticks; /* Even value for idle, else odd. */ 193 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ 194 bool rcu_urgent_qs; /* GP old need light quiescent state. */ 195 bool rcu_forced_tick; /* Forced tick to provide QS. */ 196 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */ 197 198 /* 4) rcu_barrier(), OOM callbacks, and expediting. */ 199 unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */ 200 struct rcu_head barrier_head; 201 int exp_dynticks_snap; /* Double-check need for IPI. */ 202 203 /* 5) Callback offloading. */ 204 #ifdef CONFIG_RCU_NOCB_CPU 205 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */ 206 struct swait_queue_head nocb_state_wq; /* For offloading state changes */ 207 struct task_struct *nocb_gp_kthread; 208 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ 209 atomic_t nocb_lock_contended; /* Contention experienced. */ 210 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ 211 struct timer_list nocb_timer; /* Enforce finite deferral. */ 212 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */ 213 struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */ 214 /* spawning */ 215 216 /* The following fields are used by call_rcu, hence own cacheline. */ 217 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp; 218 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */ 219 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */ 220 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */ 221 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */ 222 223 /* The following fields are used by GP kthread, hence own cacheline. */ 224 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp; 225 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */ 226 u8 nocb_gp_bypass; /* Found a bypass on last scan? */ 227 u8 nocb_gp_gp; /* GP to wait for on last scan? */ 228 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */ 229 unsigned long nocb_gp_loops; /* # passes through wait code. */ 230 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ 231 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ 232 struct task_struct *nocb_cb_kthread; 233 struct list_head nocb_head_rdp; /* 234 * Head of rcu_data list in wakeup chain, 235 * if rdp_gp. 236 */ 237 struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */ 238 239 /* The following fields are used by CB kthread, hence new cacheline. */ 240 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp; 241 /* GP rdp takes GP-end wakeups. */ 242 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 243 244 /* 6) RCU priority boosting. */ 245 struct task_struct *rcu_cpu_kthread_task; 246 /* rcuc per-CPU kthread or NULL. */ 247 unsigned int rcu_cpu_kthread_status; 248 char rcu_cpu_has_work; 249 unsigned long rcuc_activity; 250 251 /* 7) Diagnostic data, including RCU CPU stall warnings. */ 252 unsigned int softirq_snap; /* Snapshot of softirq activity. */ 253 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ 254 struct irq_work rcu_iw; /* Check for non-irq activity. */ 255 bool rcu_iw_pending; /* Is ->rcu_iw pending? */ 256 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ 257 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ 258 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ 259 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ 260 short rcu_onl_gp_flags; /* ->gp_flags at last online. */ 261 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ 262 unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ 263 264 int cpu; 265 }; 266 267 /* Values for nocb_defer_wakeup field in struct rcu_data. */ 268 #define RCU_NOCB_WAKE_NOT 0 269 #define RCU_NOCB_WAKE_BYPASS 1 270 #define RCU_NOCB_WAKE 2 271 #define RCU_NOCB_WAKE_FORCE 3 272 273 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) 274 /* For jiffies_till_first_fqs and */ 275 /* and jiffies_till_next_fqs. */ 276 277 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ 278 /* delay between bouts of */ 279 /* quiescent-state forcing. */ 280 281 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ 282 /* at least one scheduling clock */ 283 /* irq before ratting on them. */ 284 285 #define rcu_wait(cond) \ 286 do { \ 287 for (;;) { \ 288 set_current_state(TASK_INTERRUPTIBLE); \ 289 if (cond) \ 290 break; \ 291 schedule(); \ 292 } \ 293 __set_current_state(TASK_RUNNING); \ 294 } while (0) 295 296 /* 297 * RCU global state, including node hierarchy. This hierarchy is 298 * represented in "heap" form in a dense array. The root (first level) 299 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 300 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 301 * and the third level in ->node[m+1] and following (->node[m+1] referenced 302 * by ->level[2]). The number of levels is determined by the number of 303 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 304 * consisting of a single rcu_node. 305 */ 306 struct rcu_state { 307 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 308 struct rcu_node *level[RCU_NUM_LVLS + 1]; 309 /* Hierarchy levels (+1 to */ 310 /* shut bogus gcc warning) */ 311 int ncpus; /* # CPUs seen so far. */ 312 int n_online_cpus; /* # CPUs online for RCU. */ 313 314 /* The following fields are guarded by the root rcu_node's lock. */ 315 316 unsigned long gp_seq ____cacheline_internodealigned_in_smp; 317 /* Grace-period sequence #. */ 318 unsigned long gp_max; /* Maximum GP duration in */ 319 /* jiffies. */ 320 struct task_struct *gp_kthread; /* Task for grace periods. */ 321 struct swait_queue_head gp_wq; /* Where GP task waits. */ 322 short gp_flags; /* Commands for GP task. */ 323 short gp_state; /* GP kthread sleep state. */ 324 unsigned long gp_wake_time; /* Last GP kthread wake. */ 325 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ 326 327 /* End of fields guarded by root rcu_node's lock. */ 328 329 struct mutex barrier_mutex; /* Guards barrier fields. */ 330 atomic_t barrier_cpu_count; /* # CPUs waiting on. */ 331 struct completion barrier_completion; /* Wake at barrier end. */ 332 unsigned long barrier_sequence; /* ++ at start and end of */ 333 /* rcu_barrier(). */ 334 /* End of fields guarded by barrier_mutex. */ 335 336 raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */ 337 338 struct mutex exp_mutex; /* Serialize expedited GP. */ 339 struct mutex exp_wake_mutex; /* Serialize wakeup. */ 340 unsigned long expedited_sequence; /* Take a ticket. */ 341 atomic_t expedited_need_qs; /* # CPUs left to check in. */ 342 struct swait_queue_head expedited_wq; /* Wait for check-ins. */ 343 int ncpus_snap; /* # CPUs seen last time. */ 344 u8 cbovld; /* Callback overload now? */ 345 u8 cbovldnext; /* ^ ^ next 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_end; /* Time last GP ended, again */ 356 /* in jiffies. */ 357 unsigned long gp_activity; /* Time of last GP kthread */ 358 /* activity in jiffies. */ 359 unsigned long gp_req_activity; /* Time of last GP request */ 360 /* in jiffies. */ 361 unsigned long jiffies_stall; /* Time at which to check */ 362 /* for CPU stalls. */ 363 unsigned long jiffies_resched; /* Time at which to resched */ 364 /* a reluctant CPU. */ 365 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ 366 /* GP start. */ 367 const char *name; /* Name of structure. */ 368 char abbr; /* Abbreviated name. */ 369 370 arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; 371 /* Synchronize offline with */ 372 /* GP pre-initialization. */ 373 int nocb_is_setup; /* nocb is setup from boot */ 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 #define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */ 380 381 /* Values for rcu_state structure's gp_state field. */ 382 #define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ 383 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ 384 #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ 385 #define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ 386 #define RCU_GP_INIT 4 /* Grace-period initialization. */ 387 #define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ 388 #define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ 389 #define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ 390 #define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ 391 392 /* 393 * In order to export the rcu_state name to the tracing tools, it 394 * needs to be added in the __tracepoint_string section. 395 * This requires defining a separate variable tp_<sname>_varname 396 * that points to the string being used, and this will allow 397 * the tracing userspace tools to be able to decipher the string 398 * address to the matching string. 399 */ 400 #ifdef CONFIG_PREEMPT_RCU 401 #define RCU_ABBR 'p' 402 #define RCU_NAME_RAW "rcu_preempt" 403 #else /* #ifdef CONFIG_PREEMPT_RCU */ 404 #define RCU_ABBR 's' 405 #define RCU_NAME_RAW "rcu_sched" 406 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 407 #ifndef CONFIG_TRACING 408 #define RCU_NAME RCU_NAME_RAW 409 #else /* #ifdef CONFIG_TRACING */ 410 static char rcu_name[] = RCU_NAME_RAW; 411 static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; 412 #define RCU_NAME rcu_name 413 #endif /* #else #ifdef CONFIG_TRACING */ 414 415 /* Forward declarations for tree_plugin.h */ 416 static void rcu_bootup_announce(void); 417 static void rcu_qs(void); 418 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 419 #ifdef CONFIG_HOTPLUG_CPU 420 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 421 #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 422 static int rcu_print_task_exp_stall(struct rcu_node *rnp); 423 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); 424 static void rcu_flavor_sched_clock_irq(int user); 425 static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); 426 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 427 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 428 static bool rcu_is_callbacks_kthread(void); 429 static void rcu_cpu_kthread_setup(unsigned int cpu); 430 static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp); 431 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 432 static bool rcu_preempt_need_deferred_qs(struct task_struct *t); 433 static void rcu_preempt_deferred_qs(struct task_struct *t); 434 static void zero_cpu_stall_ticks(struct rcu_data *rdp); 435 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); 436 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); 437 static void rcu_init_one_nocb(struct rcu_node *rnp); 438 static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 439 unsigned long j); 440 static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 441 bool *was_alldone, unsigned long flags); 442 static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, 443 unsigned long flags); 444 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); 445 static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); 446 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); 447 static void rcu_spawn_cpu_nocb_kthread(int cpu); 448 static void show_rcu_nocb_state(struct rcu_data *rdp); 449 static void rcu_nocb_lock(struct rcu_data *rdp); 450 static void rcu_nocb_unlock(struct rcu_data *rdp); 451 static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, 452 unsigned long flags); 453 static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp); 454 #ifdef CONFIG_RCU_NOCB_CPU 455 static void __init rcu_organize_nocb_kthreads(void); 456 457 /* 458 * Disable IRQs before checking offloaded state so that local 459 * locking is safe against concurrent de-offloading. 460 */ 461 #define rcu_nocb_lock_irqsave(rdp, flags) \ 462 do { \ 463 local_irq_save(flags); \ 464 if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \ 465 raw_spin_lock(&(rdp)->nocb_lock); \ 466 } while (0) 467 #else /* #ifdef CONFIG_RCU_NOCB_CPU */ 468 #define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags) 469 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 470 471 static void rcu_bind_gp_kthread(void); 472 static bool rcu_nohz_full_cpu(void); 473 static void rcu_dynticks_task_enter(void); 474 static void rcu_dynticks_task_exit(void); 475 static void rcu_dynticks_task_trace_enter(void); 476 static void rcu_dynticks_task_trace_exit(void); 477 478 /* Forward declarations for tree_stall.h */ 479 static void record_gp_stall_check_time(void); 480 static void rcu_iw_handler(struct irq_work *iwp); 481 static void check_cpu_stall(struct rcu_data *rdp); 482 static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, 483 const unsigned long gpssdelay); 484