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 ofl_seq; /* CPU-hotplug operation sequence count. */ 65 /* Online CPUs for next grace period. */ 66 unsigned long expmask; /* CPUs or groups that need to check in */ 67 /* to allow the current expedited GP */ 68 /* to complete. */ 69 unsigned long expmaskinit; 70 /* Per-GP initial values for expmask. */ 71 /* Initialized from ->expmaskinitnext at the */ 72 /* beginning of each expedited GP. */ 73 unsigned long expmaskinitnext; 74 /* Online CPUs for next expedited GP. */ 75 /* Any CPU that has ever been online will */ 76 /* have its bit set. */ 77 unsigned long cbovldmask; 78 /* CPUs experiencing callback overload. */ 79 unsigned long ffmask; /* Fully functional CPUs. */ 80 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 81 /* Only one bit will be set in this mask. */ 82 int grplo; /* lowest-numbered CPU here. */ 83 int grphi; /* highest-numbered CPU here. */ 84 u8 grpnum; /* group number for next level up. */ 85 u8 level; /* root is at level 0. */ 86 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ 87 /* exit RCU read-side critical sections */ 88 /* before propagating offline up the */ 89 /* rcu_node tree? */ 90 struct rcu_node *parent; 91 struct list_head blkd_tasks; 92 /* Tasks blocked in RCU read-side critical */ 93 /* section. Tasks are placed at the head */ 94 /* of this list and age towards the tail. */ 95 struct list_head *gp_tasks; 96 /* Pointer to the first task blocking the */ 97 /* current grace period, or NULL if there */ 98 /* is no such task. */ 99 struct list_head *exp_tasks; 100 /* Pointer to the first task blocking the */ 101 /* current expedited grace period, or NULL */ 102 /* if there is no such task. If there */ 103 /* is no current expedited grace period, */ 104 /* then there can cannot be any such task. */ 105 struct list_head *boost_tasks; 106 /* Pointer to first task that needs to be */ 107 /* priority boosted, or NULL if no priority */ 108 /* boosting is needed for this rcu_node */ 109 /* structure. If there are no tasks */ 110 /* queued on this rcu_node structure that */ 111 /* are blocking the current grace period, */ 112 /* there can be no such task. */ 113 struct rt_mutex boost_mtx; 114 /* Used only for the priority-boosting */ 115 /* side effect, not as a lock. */ 116 unsigned long boost_time; 117 /* When to start boosting (jiffies). */ 118 struct task_struct *boost_kthread_task; 119 /* kthread that takes care of priority */ 120 /* boosting for this rcu_node structure. */ 121 unsigned int boost_kthread_status; 122 /* State of boost_kthread_task for tracing. */ 123 #ifdef CONFIG_RCU_NOCB_CPU 124 struct swait_queue_head nocb_gp_wq[2]; 125 /* Place for rcu_nocb_kthread() to wait GP. */ 126 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 127 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; 128 129 spinlock_t exp_lock ____cacheline_internodealigned_in_smp; 130 unsigned long exp_seq_rq; 131 wait_queue_head_t exp_wq[4]; 132 struct rcu_exp_work rew; 133 bool exp_need_flush; /* Need to flush workitem? */ 134 } ____cacheline_internodealigned_in_smp; 135 136 /* 137 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and 138 * are indexed relative to this interval rather than the global CPU ID space. 139 * This generates the bit for a CPU in node-local masks. 140 */ 141 #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo)) 142 143 /* 144 * Union to allow "aggregate OR" operation on the need for a quiescent 145 * state by the normal and expedited grace periods. 146 */ 147 union rcu_noqs { 148 struct { 149 u8 norm; 150 u8 exp; 151 } b; /* Bits. */ 152 u16 s; /* Set of bits, aggregate OR here. */ 153 }; 154 155 /* Per-CPU data for read-copy update. */ 156 struct rcu_data { 157 /* 1) quiescent-state and grace-period handling : */ 158 unsigned long gp_seq; /* Track rsp->gp_seq counter. */ 159 unsigned long gp_seq_needed; /* Track furthest future GP request. */ 160 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ 161 bool core_needs_qs; /* Core waits for quiesc state. */ 162 bool beenonline; /* CPU online at least once. */ 163 bool gpwrap; /* Possible ->gp_seq wrap. */ 164 bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */ 165 bool cpu_started; /* RCU watching this onlining CPU. */ 166 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 167 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 168 unsigned long ticks_this_gp; /* The number of scheduling-clock */ 169 /* ticks this CPU has handled */ 170 /* during and after the last grace */ 171 /* period it is aware of. */ 172 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */ 173 bool defer_qs_iw_pending; /* Scheduler attention pending? */ 174 struct work_struct strict_work; /* Schedule readers for strict GPs. */ 175 176 /* 2) batch handling */ 177 struct rcu_segcblist cblist; /* Segmented callback list, with */ 178 /* different callbacks waiting for */ 179 /* different grace periods. */ 180 long qlen_last_fqs_check; 181 /* qlen at last check for QS forcing */ 182 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */ 183 unsigned long n_force_qs_snap; 184 /* did other CPU force QS recently? */ 185 long blimit; /* Upper limit on a processed batch */ 186 187 /* 3) dynticks interface. */ 188 int dynticks_snap; /* Per-GP tracking for dynticks. */ 189 long dynticks_nesting; /* Track process nesting level. */ 190 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */ 191 atomic_t dynticks; /* Even value for idle, else odd. */ 192 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ 193 bool rcu_urgent_qs; /* GP old need light quiescent state. */ 194 bool rcu_forced_tick; /* Forced tick to provide QS. */ 195 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */ 196 #ifdef CONFIG_RCU_FAST_NO_HZ 197 unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */ 198 unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */ 199 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ 200 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ 201 202 /* 4) rcu_barrier(), OOM callbacks, and expediting. */ 203 struct rcu_head barrier_head; 204 int exp_dynticks_snap; /* Double-check need for IPI. */ 205 206 /* 5) Callback offloading. */ 207 #ifdef CONFIG_RCU_NOCB_CPU 208 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */ 209 struct task_struct *nocb_gp_kthread; 210 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ 211 atomic_t nocb_lock_contended; /* Contention experienced. */ 212 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ 213 struct timer_list nocb_timer; /* Enforce finite deferral. */ 214 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */ 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 struct timer_list nocb_bypass_timer; /* Force nocb_bypass flush. */ 226 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */ 227 u8 nocb_gp_bypass; /* Found a bypass on last scan? */ 228 u8 nocb_gp_gp; /* GP to wait for on last scan? */ 229 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */ 230 unsigned long nocb_gp_loops; /* # passes through wait code. */ 231 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ 232 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ 233 struct task_struct *nocb_cb_kthread; 234 struct rcu_data *nocb_next_cb_rdp; 235 /* Next rcu_data in wakeup chain. */ 236 237 /* The following fields are used by CB kthread, hence new cacheline. */ 238 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp; 239 /* GP rdp takes GP-end wakeups. */ 240 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 241 242 /* 6) RCU priority boosting. */ 243 struct task_struct *rcu_cpu_kthread_task; 244 /* rcuc per-CPU kthread or NULL. */ 245 unsigned int rcu_cpu_kthread_status; 246 char rcu_cpu_has_work; 247 248 /* 7) Diagnostic data, including RCU CPU stall warnings. */ 249 unsigned int softirq_snap; /* Snapshot of softirq activity. */ 250 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ 251 struct irq_work rcu_iw; /* Check for non-irq activity. */ 252 bool rcu_iw_pending; /* Is ->rcu_iw pending? */ 253 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ 254 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ 255 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ 256 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ 257 short rcu_onl_gp_flags; /* ->gp_flags at last online. */ 258 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ 259 260 int cpu; 261 }; 262 263 /* Values for nocb_defer_wakeup field in struct rcu_data. */ 264 #define RCU_NOCB_WAKE_NOT 0 265 #define RCU_NOCB_WAKE 1 266 #define RCU_NOCB_WAKE_FORCE 2 267 268 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) 269 /* For jiffies_till_first_fqs and */ 270 /* and jiffies_till_next_fqs. */ 271 272 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ 273 /* delay between bouts of */ 274 /* quiescent-state forcing. */ 275 276 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ 277 /* at least one scheduling clock */ 278 /* irq before ratting on them. */ 279 280 #define rcu_wait(cond) \ 281 do { \ 282 for (;;) { \ 283 set_current_state(TASK_INTERRUPTIBLE); \ 284 if (cond) \ 285 break; \ 286 schedule(); \ 287 } \ 288 __set_current_state(TASK_RUNNING); \ 289 } while (0) 290 291 /* 292 * RCU global state, including node hierarchy. This hierarchy is 293 * represented in "heap" form in a dense array. The root (first level) 294 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 295 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 296 * and the third level in ->node[m+1] and following (->node[m+1] referenced 297 * by ->level[2]). The number of levels is determined by the number of 298 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 299 * consisting of a single rcu_node. 300 */ 301 struct rcu_state { 302 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 303 struct rcu_node *level[RCU_NUM_LVLS + 1]; 304 /* Hierarchy levels (+1 to */ 305 /* shut bogus gcc warning) */ 306 int ncpus; /* # CPUs seen so far. */ 307 308 /* The following fields are guarded by the root rcu_node's lock. */ 309 310 u8 boost ____cacheline_internodealigned_in_smp; 311 /* Subject to priority boost. */ 312 unsigned long gp_seq; /* Grace-period sequence #. */ 313 unsigned long gp_max; /* Maximum GP duration in */ 314 /* jiffies. */ 315 struct task_struct *gp_kthread; /* Task for grace periods. */ 316 struct swait_queue_head gp_wq; /* Where GP task waits. */ 317 short gp_flags; /* Commands for GP task. */ 318 short gp_state; /* GP kthread sleep state. */ 319 unsigned long gp_wake_time; /* Last GP kthread wake. */ 320 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ 321 322 /* End of fields guarded by root rcu_node's lock. */ 323 324 struct mutex barrier_mutex; /* Guards barrier fields. */ 325 atomic_t barrier_cpu_count; /* # CPUs waiting on. */ 326 struct completion barrier_completion; /* Wake at barrier end. */ 327 unsigned long barrier_sequence; /* ++ at start and end of */ 328 /* rcu_barrier(). */ 329 /* End of fields guarded by barrier_mutex. */ 330 331 struct mutex exp_mutex; /* Serialize expedited GP. */ 332 struct mutex exp_wake_mutex; /* Serialize wakeup. */ 333 unsigned long expedited_sequence; /* Take a ticket. */ 334 atomic_t expedited_need_qs; /* # CPUs left to check in. */ 335 struct swait_queue_head expedited_wq; /* Wait for check-ins. */ 336 int ncpus_snap; /* # CPUs seen last time. */ 337 u8 cbovld; /* Callback overload now? */ 338 u8 cbovldnext; /* ^ ^ next time? */ 339 340 unsigned long jiffies_force_qs; /* Time at which to invoke */ 341 /* force_quiescent_state(). */ 342 unsigned long jiffies_kick_kthreads; /* Time at which to kick */ 343 /* kthreads, if configured. */ 344 unsigned long n_force_qs; /* Number of calls to */ 345 /* force_quiescent_state(). */ 346 unsigned long gp_start; /* Time at which GP started, */ 347 /* but in jiffies. */ 348 unsigned long gp_end; /* Time last GP ended, again */ 349 /* in jiffies. */ 350 unsigned long gp_activity; /* Time of last GP kthread */ 351 /* activity in jiffies. */ 352 unsigned long gp_req_activity; /* Time of last GP request */ 353 /* in jiffies. */ 354 unsigned long jiffies_stall; /* Time at which to check */ 355 /* for CPU stalls. */ 356 unsigned long jiffies_resched; /* Time at which to resched */ 357 /* a reluctant CPU. */ 358 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ 359 /* GP start. */ 360 const char *name; /* Name of structure. */ 361 char abbr; /* Abbreviated name. */ 362 363 raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; 364 /* Synchronize offline with */ 365 /* GP pre-initialization. */ 366 }; 367 368 /* Values for rcu_state structure's gp_flags field. */ 369 #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ 370 #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ 371 #define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */ 372 373 /* Values for rcu_state structure's gp_state field. */ 374 #define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ 375 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ 376 #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ 377 #define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ 378 #define RCU_GP_INIT 4 /* Grace-period initialization. */ 379 #define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ 380 #define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ 381 #define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ 382 #define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ 383 384 /* 385 * In order to export the rcu_state name to the tracing tools, it 386 * needs to be added in the __tracepoint_string section. 387 * This requires defining a separate variable tp_<sname>_varname 388 * that points to the string being used, and this will allow 389 * the tracing userspace tools to be able to decipher the string 390 * address to the matching string. 391 */ 392 #ifdef CONFIG_PREEMPT_RCU 393 #define RCU_ABBR 'p' 394 #define RCU_NAME_RAW "rcu_preempt" 395 #else /* #ifdef CONFIG_PREEMPT_RCU */ 396 #define RCU_ABBR 's' 397 #define RCU_NAME_RAW "rcu_sched" 398 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 399 #ifndef CONFIG_TRACING 400 #define RCU_NAME RCU_NAME_RAW 401 #else /* #ifdef CONFIG_TRACING */ 402 static char rcu_name[] = RCU_NAME_RAW; 403 static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; 404 #define RCU_NAME rcu_name 405 #endif /* #else #ifdef CONFIG_TRACING */ 406 407 /* Forward declarations for tree_plugin.h */ 408 static void rcu_bootup_announce(void); 409 static void rcu_qs(void); 410 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 411 #ifdef CONFIG_HOTPLUG_CPU 412 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 413 #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 414 static int rcu_print_task_exp_stall(struct rcu_node *rnp); 415 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); 416 static void rcu_flavor_sched_clock_irq(int user); 417 static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); 418 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 419 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 420 static bool rcu_is_callbacks_kthread(void); 421 static void rcu_cpu_kthread_setup(unsigned int cpu); 422 static void __init rcu_spawn_boost_kthreads(void); 423 static void rcu_prepare_kthreads(int cpu); 424 static void rcu_cleanup_after_idle(void); 425 static void rcu_prepare_for_idle(void); 426 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 427 static bool rcu_preempt_need_deferred_qs(struct task_struct *t); 428 static void rcu_preempt_deferred_qs(struct task_struct *t); 429 static void zero_cpu_stall_ticks(struct rcu_data *rdp); 430 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); 431 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); 432 static void rcu_init_one_nocb(struct rcu_node *rnp); 433 static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 434 unsigned long j); 435 static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 436 bool *was_alldone, unsigned long flags); 437 static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, 438 unsigned long flags); 439 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); 440 static void do_nocb_deferred_wakeup(struct rcu_data *rdp); 441 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); 442 static void rcu_spawn_cpu_nocb_kthread(int cpu); 443 static void __init rcu_spawn_nocb_kthreads(void); 444 static void show_rcu_nocb_state(struct rcu_data *rdp); 445 static void rcu_nocb_lock(struct rcu_data *rdp); 446 static void rcu_nocb_unlock(struct rcu_data *rdp); 447 static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, 448 unsigned long flags); 449 static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp); 450 #ifdef CONFIG_RCU_NOCB_CPU 451 static void __init rcu_organize_nocb_kthreads(void); 452 #define rcu_nocb_lock_irqsave(rdp, flags) \ 453 do { \ 454 if (!rcu_segcblist_is_offloaded(&(rdp)->cblist)) \ 455 local_irq_save(flags); \ 456 else \ 457 raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags)); \ 458 } while (0) 459 #else /* #ifdef CONFIG_RCU_NOCB_CPU */ 460 #define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags) 461 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 462 463 static void rcu_bind_gp_kthread(void); 464 static bool rcu_nohz_full_cpu(void); 465 static void rcu_dynticks_task_enter(void); 466 static void rcu_dynticks_task_exit(void); 467 static void rcu_dynticks_task_trace_enter(void); 468 static void rcu_dynticks_task_trace_exit(void); 469 470 /* Forward declarations for tree_stall.h */ 471 static void record_gp_stall_check_time(void); 472 static void rcu_iw_handler(struct irq_work *iwp); 473 static void check_cpu_stall(struct rcu_data *rdp); 474 static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, 475 const unsigned long gpssdelay); 476