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 kthread worker handler. */ 25 struct rcu_exp_work { 26 unsigned long rew_s; 27 struct kthread_work rew_work; 28 }; 29 30 /* RCU's kthread states for tracing. */ 31 #define RCU_KTHREAD_STOPPED 0 32 #define RCU_KTHREAD_RUNNING 1 33 #define RCU_KTHREAD_WAITING 2 34 #define RCU_KTHREAD_OFFCPU 3 35 #define RCU_KTHREAD_YIELDING 4 36 #define RCU_KTHREAD_MAX 4 37 38 /* 39 * Definition for node within the RCU grace-period-detection hierarchy. 40 */ 41 struct rcu_node { 42 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */ 43 /* some rcu_state fields as well as */ 44 /* following. */ 45 unsigned long gp_seq; /* Track rsp->gp_seq. */ 46 unsigned long gp_seq_needed; /* Track furthest future GP request. */ 47 unsigned long completedqs; /* All QSes done for this node. */ 48 unsigned long qsmask; /* CPUs or groups that need to switch in */ 49 /* order for current grace period to proceed.*/ 50 /* In leaf rcu_node, each bit corresponds to */ 51 /* an rcu_data structure, otherwise, each */ 52 /* bit corresponds to a child rcu_node */ 53 /* structure. */ 54 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ 55 unsigned long qsmaskinit; 56 /* Per-GP initial value for qsmask. */ 57 /* Initialized from ->qsmaskinitnext at the */ 58 /* beginning of each grace period. */ 59 unsigned long qsmaskinitnext; 60 unsigned long expmask; /* CPUs or groups that need to check in */ 61 /* to allow the current expedited GP */ 62 /* to complete. */ 63 unsigned long expmaskinit; 64 /* Per-GP initial values for expmask. */ 65 /* Initialized from ->expmaskinitnext at the */ 66 /* beginning of each expedited GP. */ 67 unsigned long expmaskinitnext; 68 /* Online CPUs for next expedited GP. */ 69 /* Any CPU that has ever been online will */ 70 /* have its bit set. */ 71 struct kthread_worker *exp_kworker; 72 /* Workers performing per node expedited GP */ 73 /* initialization. */ 74 unsigned long cbovldmask; 75 /* CPUs experiencing callback overload. */ 76 unsigned long ffmask; /* Fully functional CPUs. */ 77 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 78 /* Only one bit will be set in this mask. */ 79 int grplo; /* lowest-numbered CPU here. */ 80 int grphi; /* highest-numbered CPU here. */ 81 u8 grpnum; /* group number for next level up. */ 82 u8 level; /* root is at level 0. */ 83 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ 84 /* exit RCU read-side critical sections */ 85 /* before propagating offline up the */ 86 /* rcu_node tree? */ 87 struct rcu_node *parent; 88 struct list_head blkd_tasks; 89 /* Tasks blocked in RCU read-side critical */ 90 /* section. Tasks are placed at the head */ 91 /* of this list and age towards the tail. */ 92 struct list_head *gp_tasks; 93 /* Pointer to the first task blocking the */ 94 /* current grace period, or NULL if there */ 95 /* is no such task. */ 96 struct list_head *exp_tasks; 97 /* Pointer to the first task blocking the */ 98 /* current expedited grace period, or NULL */ 99 /* if there is no such task. If there */ 100 /* is no current expedited grace period, */ 101 /* then there can cannot be any such task. */ 102 struct list_head *boost_tasks; 103 /* Pointer to first task that needs to be */ 104 /* priority boosted, or NULL if no priority */ 105 /* boosting is needed for this rcu_node */ 106 /* structure. If there are no tasks */ 107 /* queued on this rcu_node structure that */ 108 /* are blocking the current grace period, */ 109 /* there can be no such task. */ 110 struct rt_mutex boost_mtx; 111 /* Used only for the priority-boosting */ 112 /* side effect, not as a lock. */ 113 unsigned long boost_time; 114 /* When to start boosting (jiffies). */ 115 struct mutex kthread_mutex; 116 /* Exclusion for thread spawning and affinity */ 117 /* manipulation. */ 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 unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */ 124 #ifdef CONFIG_RCU_NOCB_CPU 125 struct swait_queue_head nocb_gp_wq[2]; 126 /* Place for rcu_nocb_kthread() to wait GP. */ 127 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 128 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; 129 130 spinlock_t exp_lock ____cacheline_internodealigned_in_smp; 131 unsigned long exp_seq_rq; 132 wait_queue_head_t exp_wq[4]; 133 struct rcu_exp_work rew; 134 bool exp_need_flush; /* Need to flush workitem? */ 135 raw_spinlock_t exp_poll_lock; 136 /* Lock and data for polled expedited grace periods. */ 137 unsigned long exp_seq_poll_rq; 138 struct work_struct exp_poll_wq; 139 } ____cacheline_internodealigned_in_smp; 140 141 /* 142 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and 143 * are indexed relative to this interval rather than the global CPU ID space. 144 * This generates the bit for a CPU in node-local masks. 145 */ 146 #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo)) 147 148 /* 149 * Union to allow "aggregate OR" operation on the need for a quiescent 150 * state by the normal and expedited grace periods. 151 */ 152 union rcu_noqs { 153 struct { 154 u8 norm; 155 u8 exp; 156 } b; /* Bits. */ 157 u16 s; /* Set of bits, aggregate OR here. */ 158 }; 159 160 /* 161 * Record the snapshot of the core stats at half of the first RCU stall timeout. 162 * The member gp_seq is used to ensure that all members are updated only once 163 * during the sampling period. The snapshot is taken only if this gp_seq is not 164 * equal to rdp->gp_seq. 165 */ 166 struct rcu_snap_record { 167 unsigned long gp_seq; /* Track rdp->gp_seq counter */ 168 u64 cputime_irq; /* Accumulated cputime of hard irqs */ 169 u64 cputime_softirq;/* Accumulated cputime of soft irqs */ 170 u64 cputime_system; /* Accumulated cputime of kernel tasks */ 171 unsigned long nr_hardirqs; /* Accumulated number of hard irqs */ 172 unsigned int nr_softirqs; /* Accumulated number of soft irqs */ 173 unsigned long long nr_csw; /* Accumulated number of task switches */ 174 unsigned long jiffies; /* Track jiffies value */ 175 }; 176 177 /* Per-CPU data for read-copy update. */ 178 struct rcu_data { 179 /* 1) quiescent-state and grace-period handling : */ 180 unsigned long gp_seq; /* Track rsp->gp_seq counter. */ 181 unsigned long gp_seq_needed; /* Track furthest future GP request. */ 182 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ 183 bool core_needs_qs; /* Core waits for quiescent state. */ 184 bool beenonline; /* CPU online at least once. */ 185 bool gpwrap; /* Possible ->gp_seq wrap. */ 186 bool cpu_started; /* RCU watching this onlining CPU. */ 187 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 188 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 189 unsigned long ticks_this_gp; /* The number of scheduling-clock */ 190 /* ticks this CPU has handled */ 191 /* during and after the last grace */ 192 /* period it is aware of. */ 193 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */ 194 bool defer_qs_iw_pending; /* Scheduler attention pending? */ 195 struct work_struct strict_work; /* Schedule readers for strict GPs. */ 196 197 /* 2) batch handling */ 198 struct rcu_segcblist cblist; /* Segmented callback list, with */ 199 /* different callbacks waiting for */ 200 /* different grace periods. */ 201 long qlen_last_fqs_check; 202 /* qlen at last check for QS forcing */ 203 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */ 204 unsigned long n_force_qs_snap; 205 /* did other CPU force QS recently? */ 206 long blimit; /* Upper limit on a processed batch */ 207 208 /* 3) dynticks interface. */ 209 int watching_snap; /* Per-GP tracking for dynticks. */ 210 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ 211 bool rcu_urgent_qs; /* GP old need light quiescent state. */ 212 bool rcu_forced_tick; /* Forced tick to provide QS. */ 213 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */ 214 215 /* 4) rcu_barrier(), OOM callbacks, and expediting. */ 216 unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */ 217 struct rcu_head barrier_head; 218 int exp_watching_snap; /* Double-check need for IPI. */ 219 220 /* 5) Callback offloading. */ 221 #ifdef CONFIG_RCU_NOCB_CPU 222 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */ 223 struct swait_queue_head nocb_state_wq; /* For offloading state changes */ 224 struct task_struct *nocb_gp_kthread; 225 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ 226 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ 227 struct timer_list nocb_timer; /* Enforce finite deferral. */ 228 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */ 229 struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */ 230 /* spawning */ 231 232 /* The following fields are used by call_rcu, hence own cacheline. */ 233 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp; 234 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */ 235 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */ 236 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */ 237 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */ 238 239 /* The following fields are used by GP kthread, hence own cacheline. */ 240 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp; 241 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */ 242 u8 nocb_gp_bypass; /* Found a bypass on last scan? */ 243 u8 nocb_gp_gp; /* GP to wait for on last scan? */ 244 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */ 245 unsigned long nocb_gp_loops; /* # passes through wait code. */ 246 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ 247 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ 248 struct task_struct *nocb_cb_kthread; 249 struct list_head nocb_head_rdp; /* 250 * Head of rcu_data list in wakeup chain, 251 * if rdp_gp. 252 */ 253 struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */ 254 struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */ 255 256 /* The following fields are used by CB kthread, hence new cacheline. */ 257 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp; 258 /* GP rdp takes GP-end wakeups. */ 259 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 260 261 /* 6) RCU priority boosting. */ 262 struct task_struct *rcu_cpu_kthread_task; 263 /* rcuc per-CPU kthread or NULL. */ 264 unsigned int rcu_cpu_kthread_status; 265 char rcu_cpu_has_work; 266 unsigned long rcuc_activity; 267 268 /* 7) Diagnostic data, including RCU CPU stall warnings. */ 269 unsigned int softirq_snap; /* Snapshot of softirq activity. */ 270 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ 271 struct irq_work rcu_iw; /* Check for non-irq activity. */ 272 bool rcu_iw_pending; /* Is ->rcu_iw pending? */ 273 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ 274 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ 275 short rcu_ofl_gp_state; /* ->gp_state at last offline. */ 276 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ 277 short rcu_onl_gp_state; /* ->gp_state at last online. */ 278 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ 279 unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ 280 struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */ 281 /* the first RCU stall timeout */ 282 283 long lazy_len; /* Length of buffered lazy callbacks. */ 284 int cpu; 285 }; 286 287 /* Values for nocb_defer_wakeup field in struct rcu_data. */ 288 #define RCU_NOCB_WAKE_NOT 0 289 #define RCU_NOCB_WAKE_BYPASS 1 290 #define RCU_NOCB_WAKE_LAZY 2 291 #define RCU_NOCB_WAKE 3 292 #define RCU_NOCB_WAKE_FORCE 4 293 294 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) 295 /* For jiffies_till_first_fqs and */ 296 /* and jiffies_till_next_fqs. */ 297 298 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ 299 /* delay between bouts of */ 300 /* quiescent-state forcing. */ 301 302 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ 303 /* at least one scheduling clock */ 304 /* irq before ratting on them. */ 305 306 #define rcu_wait(cond) \ 307 do { \ 308 for (;;) { \ 309 set_current_state(TASK_INTERRUPTIBLE); \ 310 if (cond) \ 311 break; \ 312 schedule(); \ 313 } \ 314 __set_current_state(TASK_RUNNING); \ 315 } while (0) 316 317 /* 318 * A max threshold for synchronize_rcu() users which are 319 * awaken directly by the rcu_gp_kthread(). Left part is 320 * deferred to the main worker. 321 */ 322 #define SR_MAX_USERS_WAKE_FROM_GP 5 323 #define SR_NORMAL_GP_WAIT_HEAD_MAX 5 324 325 struct sr_wait_node { 326 atomic_t inuse; 327 struct llist_node node; 328 }; 329 330 /* 331 * RCU global state, including node hierarchy. This hierarchy is 332 * represented in "heap" form in a dense array. The root (first level) 333 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 334 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 335 * and the third level in ->node[m+1] and following (->node[m+1] referenced 336 * by ->level[2]). The number of levels is determined by the number of 337 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 338 * consisting of a single rcu_node. 339 */ 340 struct rcu_state { 341 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 342 struct rcu_node *level[RCU_NUM_LVLS + 1]; 343 /* Hierarchy levels (+1 to */ 344 /* shut bogus gcc warning) */ 345 int ncpus; /* # CPUs seen so far. */ 346 int n_online_cpus; /* # CPUs online for RCU. */ 347 348 /* The following fields are guarded by the root rcu_node's lock. */ 349 350 unsigned long gp_seq ____cacheline_internodealigned_in_smp; 351 /* Grace-period sequence #. */ 352 unsigned long gp_max; /* Maximum GP duration in */ 353 /* jiffies. */ 354 struct task_struct *gp_kthread; /* Task for grace periods. */ 355 struct swait_queue_head gp_wq; /* Where GP task waits. */ 356 short gp_flags; /* Commands for GP task. */ 357 short gp_state; /* GP kthread sleep state. */ 358 unsigned long gp_wake_time; /* Last GP kthread wake. */ 359 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ 360 unsigned long gp_seq_polled; /* GP seq for polled API. */ 361 unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */ 362 unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */ 363 364 /* End of fields guarded by root rcu_node's lock. */ 365 366 struct mutex barrier_mutex; /* Guards barrier fields. */ 367 atomic_t barrier_cpu_count; /* # CPUs waiting on. */ 368 struct completion barrier_completion; /* Wake at barrier end. */ 369 unsigned long barrier_sequence; /* ++ at start and end of */ 370 /* rcu_barrier(). */ 371 /* End of fields guarded by barrier_mutex. */ 372 373 raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */ 374 375 struct mutex exp_mutex; /* Serialize expedited GP. */ 376 struct mutex exp_wake_mutex; /* Serialize wakeup. */ 377 unsigned long expedited_sequence; /* Take a ticket. */ 378 atomic_t expedited_need_qs; /* # CPUs left to check in. */ 379 struct swait_queue_head expedited_wq; /* Wait for check-ins. */ 380 int ncpus_snap; /* # CPUs seen last time. */ 381 u8 cbovld; /* Callback overload now? */ 382 u8 cbovldnext; /* ^ ^ next time? */ 383 384 unsigned long jiffies_force_qs; /* Time at which to invoke */ 385 /* force_quiescent_state(). */ 386 unsigned long jiffies_kick_kthreads; /* Time at which to kick */ 387 /* kthreads, if configured. */ 388 unsigned long n_force_qs; /* Number of calls to */ 389 /* force_quiescent_state(). */ 390 unsigned long gp_start; /* Time at which GP started, */ 391 /* but in jiffies. */ 392 unsigned long gp_end; /* Time last GP ended, again */ 393 /* in jiffies. */ 394 unsigned long gp_activity; /* Time of last GP kthread */ 395 /* activity in jiffies. */ 396 unsigned long gp_req_activity; /* Time of last GP request */ 397 /* in jiffies. */ 398 unsigned long jiffies_stall; /* Time at which to check */ 399 /* for CPU stalls. */ 400 int nr_fqs_jiffies_stall; /* Number of fqs loops after 401 * which read jiffies and set 402 * jiffies_stall. Stall 403 * warnings disabled if !0. */ 404 unsigned long jiffies_resched; /* Time at which to resched */ 405 /* a reluctant CPU. */ 406 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ 407 /* GP start. */ 408 const char *name; /* Name of structure. */ 409 char abbr; /* Abbreviated name. */ 410 411 arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; 412 /* Synchronize offline with */ 413 /* GP pre-initialization. */ 414 415 /* synchronize_rcu() part. */ 416 struct llist_head srs_next; /* request a GP users. */ 417 struct llist_node *srs_wait_tail; /* wait for GP users. */ 418 struct llist_node *srs_done_tail; /* ready for GP users. */ 419 struct sr_wait_node srs_wait_nodes[SR_NORMAL_GP_WAIT_HEAD_MAX]; 420 struct work_struct srs_cleanup_work; 421 atomic_t srs_cleanups_pending; /* srs inflight worker cleanups. */ 422 423 #ifdef CONFIG_RCU_NOCB_CPU 424 struct mutex nocb_mutex; /* Guards (de-)offloading */ 425 int nocb_is_setup; /* nocb is setup from boot */ 426 #endif 427 }; 428 429 /* Values for rcu_state structure's gp_flags field. */ 430 #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ 431 #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ 432 #define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */ 433 434 /* Values for rcu_state structure's gp_state field. */ 435 #define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ 436 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ 437 #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ 438 #define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ 439 #define RCU_GP_INIT 4 /* Grace-period initialization. */ 440 #define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ 441 #define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ 442 #define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ 443 #define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ 444 445 /* 446 * In order to export the rcu_state name to the tracing tools, it 447 * needs to be added in the __tracepoint_string section. 448 * This requires defining a separate variable tp_<sname>_varname 449 * that points to the string being used, and this will allow 450 * the tracing userspace tools to be able to decipher the string 451 * address to the matching string. 452 */ 453 #ifdef CONFIG_PREEMPT_RCU 454 #define RCU_ABBR 'p' 455 #define RCU_NAME_RAW "rcu_preempt" 456 #else /* #ifdef CONFIG_PREEMPT_RCU */ 457 #define RCU_ABBR 's' 458 #define RCU_NAME_RAW "rcu_sched" 459 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 460 #ifndef CONFIG_TRACING 461 #define RCU_NAME RCU_NAME_RAW 462 #else /* #ifdef CONFIG_TRACING */ 463 static char rcu_name[] = RCU_NAME_RAW; 464 static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; 465 #define RCU_NAME rcu_name 466 #endif /* #else #ifdef CONFIG_TRACING */ 467 468 /* Forward declarations for tree_plugin.h */ 469 static void rcu_bootup_announce(void); 470 static void rcu_qs(void); 471 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 472 #ifdef CONFIG_HOTPLUG_CPU 473 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 474 #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 475 static int rcu_print_task_exp_stall(struct rcu_node *rnp); 476 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); 477 static void rcu_flavor_sched_clock_irq(int user); 478 static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); 479 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 480 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 481 static bool rcu_is_callbacks_kthread(struct rcu_data *rdp); 482 static void rcu_cpu_kthread_setup(unsigned int cpu); 483 static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp); 484 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 485 static bool rcu_preempt_need_deferred_qs(struct task_struct *t); 486 static void zero_cpu_stall_ticks(struct rcu_data *rdp); 487 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); 488 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); 489 static void rcu_init_one_nocb(struct rcu_node *rnp); 490 static bool wake_nocb_gp(struct rcu_data *rdp, bool force); 491 static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 492 unsigned long j, bool lazy); 493 static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head, 494 rcu_callback_t func, unsigned long flags, bool lazy); 495 static void __maybe_unused __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, 496 unsigned long flags); 497 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); 498 static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); 499 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); 500 static void rcu_spawn_cpu_nocb_kthread(int cpu); 501 static void show_rcu_nocb_state(struct rcu_data *rdp); 502 static void rcu_nocb_lock(struct rcu_data *rdp); 503 static void rcu_nocb_unlock(struct rcu_data *rdp); 504 static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, 505 unsigned long flags); 506 static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp); 507 #ifdef CONFIG_RCU_NOCB_CPU 508 static void __init rcu_organize_nocb_kthreads(void); 509 510 /* 511 * Disable IRQs before checking offloaded state so that local 512 * locking is safe against concurrent de-offloading. 513 */ 514 #define rcu_nocb_lock_irqsave(rdp, flags) \ 515 do { \ 516 local_irq_save(flags); \ 517 if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \ 518 raw_spin_lock(&(rdp)->nocb_lock); \ 519 } while (0) 520 #else /* #ifdef CONFIG_RCU_NOCB_CPU */ 521 #define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags) 522 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 523 524 static void rcu_bind_gp_kthread(void); 525 static bool rcu_nohz_full_cpu(void); 526 527 /* Forward declarations for tree_stall.h */ 528 static void record_gp_stall_check_time(void); 529 static void rcu_iw_handler(struct irq_work *iwp); 530 static void check_cpu_stall(struct rcu_data *rdp); 531 static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, 532 const unsigned long gpssdelay); 533 534 /* Forward declarations for tree_exp.h. */ 535 static void sync_rcu_do_polled_gp(struct work_struct *wp); 536