kernel/rcu/tree.h

   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 gpnum;    /* Current grace period for this node. */
  85                                 /*  This will either be equal to or one */
  86                                 /*  behind the root rcu_node's gpnum. */
  87         unsigned long completed; /* Last GP completed for this node. */
  88                                 /*  This will either be equal to or one */
  89                                 /*  behind the root rcu_node's gpnum. */
  90         unsigned long qsmask;   /* CPUs or groups that need to switch in */
  91                                 /*  order for current grace period to proceed.*/
  92                                 /*  In leaf rcu_node, each bit corresponds to */
  93                                 /*  an rcu_data structure, otherwise, each */
  94                                 /*  bit corresponds to a child rcu_node */
  95                                 /*  structure. */
  96         unsigned long qsmaskinit;
  97                                 /* Per-GP initial value for qsmask. */
  98                                 /*  Initialized from ->qsmaskinitnext at the */
  99                                 /*  beginning of each grace period. */
 100         unsigned long qsmaskinitnext;
 101                                 /* Online CPUs for next grace period. */
 102         unsigned long expmask;  /* CPUs or groups that need to check in */
 103                                 /*  to allow the current expedited GP */
 104                                 /*  to complete. */
 105         unsigned long expmaskinit;
 106                                 /* Per-GP initial values for expmask. */
 107                                 /*  Initialized from ->expmaskinitnext at the */
 108                                 /*  beginning of each expedited GP. */
 109         unsigned long expmaskinitnext;
 110                                 /* Online CPUs for next expedited GP. */
 111                                 /*  Any CPU that has ever been online will */
 112                                 /*  have its bit set. */
 113         unsigned long ffmask;   /* Fully functional CPUs. */
 114         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
 115                                 /*  Only one bit will be set in this mask. */
 116         int     grplo;          /* lowest-numbered CPU or group here. */
 117         int     grphi;          /* highest-numbered CPU or group here. */
 118         u8      grpnum;         /* CPU/group number for next level up. */
 119         u8      level;          /* root is at level 0. */
 120         bool    wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
 121                                 /*  exit RCU read-side critical sections */
 122                                 /*  before propagating offline up the */
 123                                 /*  rcu_node tree? */
 124         struct rcu_node *parent;
 125         struct list_head blkd_tasks;
 126                                 /* Tasks blocked in RCU read-side critical */
 127                                 /*  section.  Tasks are placed at the head */
 128                                 /*  of this list and age towards the tail. */
 129         struct list_head *gp_tasks;
 130                                 /* Pointer to the first task blocking the */
 131                                 /*  current grace period, or NULL if there */
 132                                 /*  is no such task. */
 133         struct list_head *exp_tasks;
 134                                 /* Pointer to the first task blocking the */
 135                                 /*  current expedited grace period, or NULL */
 136                                 /*  if there is no such task.  If there */
 137                                 /*  is no current expedited grace period, */
 138                                 /*  then there can cannot be any such task. */
 139         struct list_head *boost_tasks;
 140                                 /* Pointer to first task that needs to be */
 141                                 /*  priority boosted, or NULL if no priority */
 142                                 /*  boosting is needed for this rcu_node */
 143                                 /*  structure.  If there are no tasks */
 144                                 /*  queued on this rcu_node structure that */
 145                                 /*  are blocking the current grace period, */
 146                                 /*  there can be no such task. */
 147         struct rt_mutex boost_mtx;
 148                                 /* Used only for the priority-boosting */
 149                                 /*  side effect, not as a lock. */
 150         unsigned long boost_time;
 151                                 /* When to start boosting (jiffies). */
 152         struct task_struct *boost_kthread_task;
 153                                 /* kthread that takes care of priority */
 154                                 /*  boosting for this rcu_node structure. */
 155         unsigned int boost_kthread_status;
 156                                 /* State of boost_kthread_task for tracing. */
 157 #ifdef CONFIG_RCU_NOCB_CPU
 158         struct swait_queue_head nocb_gp_wq[2];
 159                                 /* Place for rcu_nocb_kthread() to wait GP. */
 160 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 161         u8 need_future_gp[4];   /* Counts of upcoming GP requests. */
 162         raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
 163
 164         spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
 165         unsigned long exp_seq_rq;
 166         wait_queue_head_t exp_wq[4];
 167         struct rcu_exp_work rew;
 168         bool exp_need_flush;    /* Need to flush workitem? */
 169 } ____cacheline_internodealigned_in_smp;
 170
 171 /* Accessors for ->need_future_gp[] array. */
 172 #define need_future_gp_mask() \
 173         (ARRAY_SIZE(((struct rcu_node *)NULL)->need_future_gp) - 1)
 174 #define need_future_gp_element(rnp, c) \
 175         ((rnp)->need_future_gp[(c) & need_future_gp_mask()])
 176 #define need_any_future_gp(rnp)                                         \
 177 ({                                                                      \
 178         int __i;                                                        \
 179         bool __nonzero = false;                                         \
 180                                                                         \
 181         for (__i = 0; __i < ARRAY_SIZE((rnp)->need_future_gp); __i++)   \
 182                 __nonzero = __nonzero ||                                \
 183                             READ_ONCE((rnp)->need_future_gp[__i]);      \
 184         __nonzero;                                                      \
 185 })
 186
 187 /*
 188  * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
 189  * are indexed relative to this interval rather than the global CPU ID space.
 190  * This generates the bit for a CPU in node-local masks.
 191  */
 192 #define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo))
 193
 194 /*
 195  * Union to allow "aggregate OR" operation on the need for a quiescent
 196  * state by the normal and expedited grace periods.
 197  */
 198 union rcu_noqs {
 199         struct {
 200                 u8 norm;
 201                 u8 exp;
 202         } b; /* Bits. */
 203         u16 s; /* Set of bits, aggregate OR here. */
 204 };
 205
 206 /* Per-CPU data for read-copy update. */
 207 struct rcu_data {
 208         /* 1) quiescent-state and grace-period handling : */
 209         unsigned long   completed;      /* Track rsp->completed gp number */
 210                                         /*  in order to detect GP end. */
 211         unsigned long   gpnum;          /* Highest gp number that this CPU */
 212                                         /*  is aware of having started. */
 213         unsigned long   rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
 214                                         /*  for rcu_all_qs() invocations. */
 215         union rcu_noqs  cpu_no_qs;      /* No QSes yet for this CPU. */
 216         bool            core_needs_qs;  /* Core waits for quiesc state. */
 217         bool            beenonline;     /* CPU online at least once. */
 218         bool            gpwrap;         /* Possible gpnum/completed wrap. */
 219         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 220         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 221         unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
 222                                         /*  ticks this CPU has handled */
 223                                         /*  during and after the last grace */
 224                                         /* period it is aware of. */
 225
 226         /* 2) batch handling */
 227         struct rcu_segcblist cblist;    /* Segmented callback list, with */
 228                                         /* different callbacks waiting for */
 229                                         /* different grace periods. */
 230         long            qlen_last_fqs_check;
 231                                         /* qlen at last check for QS forcing */
 232         unsigned long   n_force_qs_snap;
 233                                         /* did other CPU force QS recently? */
 234         long            blimit;         /* Upper limit on a processed batch */
 235
 236         /* 3) dynticks interface. */
 237         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
 238         int dynticks_snap;              /* Per-GP tracking for dynticks. */
 239
 240         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
 241         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
 242         unsigned long offline_fqs;      /* Kicked due to being offline. */
 243         unsigned long cond_resched_completed;
 244                                         /* Grace period that needs help */
 245                                         /*  from cond_resched(). */
 246
 247         /* 5) _rcu_barrier(), OOM callbacks, and expediting. */
 248         struct rcu_head barrier_head;
 249 #ifdef CONFIG_RCU_FAST_NO_HZ
 250         struct rcu_head oom_head;
 251 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 252         int exp_dynticks_snap;          /* Double-check need for IPI. */
 253
 254         /* 6) Callback offloading. */
 255 #ifdef CONFIG_RCU_NOCB_CPU
 256         struct rcu_head *nocb_head;     /* CBs waiting for kthread. */
 257         struct rcu_head **nocb_tail;
 258         atomic_long_t nocb_q_count;     /* # CBs waiting for nocb */
 259         atomic_long_t nocb_q_count_lazy; /*  invocation (all stages). */
 260         struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
 261         struct rcu_head **nocb_follower_tail;
 262         struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
 263         struct task_struct *nocb_kthread;
 264         raw_spinlock_t nocb_lock;       /* Guard following pair of fields. */
 265         int nocb_defer_wakeup;          /* Defer wakeup of nocb_kthread. */
 266         struct timer_list nocb_timer;   /* Enforce finite deferral. */
 267
 268         /* The following fields are used by the leader, hence own cacheline. */
 269         struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
 270                                         /* CBs waiting for GP. */
 271         struct rcu_head **nocb_gp_tail;
 272         bool nocb_leader_sleep;         /* Is the nocb leader thread asleep? */
 273         struct rcu_data *nocb_next_follower;
 274                                         /* Next follower in wakeup chain. */
 275
 276         /* The following fields are used by the follower, hence new cachline. */
 277         struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
 278                                         /* Leader CPU takes GP-end wakeups. */
 279 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 280
 281         /* 7) RCU CPU stall data. */
 282         unsigned int softirq_snap;      /* Snapshot of softirq activity. */
 283         /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
 284         struct irq_work rcu_iw;         /* Check for non-irq activity. */
 285         bool rcu_iw_pending;            /* Is ->rcu_iw pending? */
 286         unsigned long rcu_iw_gpnum;     /* ->gpnum associated with ->rcu_iw. */
 287
 288         int cpu;
 289         struct rcu_state *rsp;
 290 };
 291
 292 /* Values for nocb_defer_wakeup field in struct rcu_data. */
 293 #define RCU_NOCB_WAKE_NOT       0
 294 #define RCU_NOCB_WAKE           1
 295 #define RCU_NOCB_WAKE_FORCE     2
 296
 297 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
 298                                         /* For jiffies_till_first_fqs and */
 299                                         /*  and jiffies_till_next_fqs. */
 300
 301 #define RCU_JIFFIES_FQS_DIV     256     /* Very large systems need more */
 302                                         /*  delay between bouts of */
 303                                         /*  quiescent-state forcing. */
 304
 305 #define RCU_STALL_RAT_DELAY     2       /* Allow other CPUs time to take */
 306                                         /*  at least one scheduling clock */
 307                                         /*  irq before ratting on them. */
 308
 309 #define rcu_wait(cond)                                                  \
 310 do {                                                                    \
 311         for (;;) {                                                      \
 312                 set_current_state(TASK_INTERRUPTIBLE);                  \
 313                 if (cond)                                               \
 314                         break;                                          \
 315                 schedule();                                             \
 316         }                                                               \
 317         __set_current_state(TASK_RUNNING);                              \
 318 } while (0)
 319
 320 /*
 321  * RCU global state, including node hierarchy.  This hierarchy is
 322  * represented in "heap" form in a dense array.  The root (first level)
 323  * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 324  * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 325  * and the third level in ->node[m+1] and following (->node[m+1] referenced
 326  * by ->level[2]).  The number of levels is determined by the number of
 327  * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 328  * consisting of a single rcu_node.
 329  */
 330 struct rcu_state {
 331         struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 332         struct rcu_node *level[RCU_NUM_LVLS + 1];
 333                                                 /* Hierarchy levels (+1 to */
 334                                                 /*  shut bogus gcc warning) */
 335         struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
 336         call_rcu_func_t call;                   /* call_rcu() flavor. */
 337         int ncpus;                              /* # CPUs seen so far. */
 338
 339         /* The following fields are guarded by the root rcu_node's lock. */
 340
 341         u8      boost ____cacheline_internodealigned_in_smp;
 342                                                 /* Subject to priority boost. */
 343         unsigned long gpnum;                    /* Current gp number. */
 344         unsigned long completed;                /* # of last completed gp. */
 345         struct task_struct *gp_kthread;         /* Task for grace periods. */
 346         struct swait_queue_head gp_wq;          /* Where GP task waits. */
 347         short gp_flags;                         /* Commands for GP task. */
 348         short gp_state;                         /* GP kthread sleep state. */
 349
 350         /* End of fields guarded by root rcu_node's lock. */
 351
 352         struct mutex barrier_mutex;             /* Guards barrier fields. */
 353         atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
 354         struct completion barrier_completion;   /* Wake at barrier end. */
 355         unsigned long barrier_sequence;         /* ++ at start and end of */
 356                                                 /*  _rcu_barrier(). */
 357         /* End of fields guarded by barrier_mutex. */
 358
 359         struct mutex exp_mutex;                 /* Serialize expedited GP. */
 360         struct mutex exp_wake_mutex;            /* Serialize wakeup. */
 361         unsigned long expedited_sequence;       /* Take a ticket. */
 362         atomic_t expedited_need_qs;             /* # CPUs left to check in. */
 363         struct swait_queue_head expedited_wq;   /* Wait for check-ins. */
 364         int ncpus_snap;                         /* # CPUs seen last time. */
 365
 366         unsigned long jiffies_force_qs;         /* Time at which to invoke */
 367                                                 /*  force_quiescent_state(). */
 368         unsigned long jiffies_kick_kthreads;    /* Time at which to kick */
 369                                                 /*  kthreads, if configured. */
 370         unsigned long n_force_qs;               /* Number of calls to */
 371                                                 /*  force_quiescent_state(). */
 372         unsigned long gp_start;                 /* Time at which GP started, */
 373                                                 /*  but in jiffies. */
 374         unsigned long gp_activity;              /* Time of last GP kthread */
 375                                                 /*  activity in jiffies. */
 376         unsigned long jiffies_stall;            /* Time at which to check */
 377                                                 /*  for CPU stalls. */
 378         unsigned long jiffies_resched;          /* Time at which to resched */
 379                                                 /*  a reluctant CPU. */
 380         unsigned long n_force_qs_gpstart;       /* Snapshot of n_force_qs at */
 381                                                 /*  GP start. */
 382         unsigned long gp_max;                   /* Maximum GP duration in */
 383                                                 /*  jiffies. */
 384         const char *name;                       /* Name of structure. */
 385         char abbr;                              /* Abbreviated name. */
 386         struct list_head flavors;               /* List of RCU flavors. */
 387 };
 388
 389 /* Values for rcu_state structure's gp_flags field. */
 390 #define RCU_GP_FLAG_INIT 0x1    /* Need grace-period initialization. */
 391 #define RCU_GP_FLAG_FQS  0x2    /* Need grace-period quiescent-state forcing. */
 392
 393 /* Values for rcu_state structure's gp_state field. */
 394 #define RCU_GP_IDLE      0      /* Initial state and no GP in progress. */
 395 #define RCU_GP_WAIT_GPS  1      /* Wait for grace-period start. */
 396 #define RCU_GP_DONE_GPS  2      /* Wait done for grace-period start. */
 397 #define RCU_GP_WAIT_FQS  3      /* Wait for force-quiescent-state time. */
 398 #define RCU_GP_DOING_FQS 4      /* Wait done for force-quiescent-state time. */
 399 #define RCU_GP_CLEANUP   5      /* Grace-period cleanup started. */
 400 #define RCU_GP_CLEANED   6      /* Grace-period cleanup complete. */
 401
 402 #ifndef RCU_TREE_NONCORE
 403 static const char * const gp_state_names[] = {
 404         "RCU_GP_IDLE",
 405         "RCU_GP_WAIT_GPS",
 406         "RCU_GP_DONE_GPS",
 407         "RCU_GP_WAIT_FQS",
 408         "RCU_GP_DOING_FQS",
 409         "RCU_GP_CLEANUP",
 410         "RCU_GP_CLEANED",
 411 };
 412 #endif /* #ifndef RCU_TREE_NONCORE */
 413
 414 extern struct list_head rcu_struct_flavors;
 415
 416 /* Sequence through rcu_state structures for each RCU flavor. */
 417 #define for_each_rcu_flavor(rsp) \
 418         list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
 419
 420 /*
 421  * RCU implementation internal declarations:
 422  */
 423 extern struct rcu_state rcu_sched_state;
 424
 425 extern struct rcu_state rcu_bh_state;
 426
 427 #ifdef CONFIG_PREEMPT_RCU
 428 extern struct rcu_state rcu_preempt_state;
 429 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 430
 431 int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
 432
 433 #ifdef CONFIG_RCU_BOOST
 434 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 435 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
 436 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 437 DECLARE_PER_CPU(char, rcu_cpu_has_work);
 438 #endif /* #ifdef CONFIG_RCU_BOOST */
 439
 440 #ifndef RCU_TREE_NONCORE
 441
 442 /* Forward declarations for rcutree_plugin.h */
 443 static void rcu_bootup_announce(void);
 444 static void rcu_preempt_note_context_switch(bool preempt);
 445 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 446 #ifdef CONFIG_HOTPLUG_CPU
 447 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 448 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 449 static void rcu_print_detail_task_stall(struct rcu_state *rsp);
 450 static int rcu_print_task_stall(struct rcu_node *rnp);
 451 static int rcu_print_task_exp_stall(struct rcu_node *rnp);
 452 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 453 static void rcu_preempt_check_callbacks(void);
 454 void call_rcu(struct rcu_head *head, rcu_callback_t func);
 455 static void __init __rcu_init_preempt(void);
 456 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 457 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 458 static void invoke_rcu_callbacks_kthread(void);
 459 static bool rcu_is_callbacks_kthread(void);
 460 #ifdef CONFIG_RCU_BOOST
 461 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 462                                                  struct rcu_node *rnp);
 463 #endif /* #ifdef CONFIG_RCU_BOOST */
 464 static void __init rcu_spawn_boost_kthreads(void);
 465 static void rcu_prepare_kthreads(int cpu);
 466 static void rcu_cleanup_after_idle(void);
 467 static void rcu_prepare_for_idle(void);
 468 static void rcu_idle_count_callbacks_posted(void);
 469 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 470 static void print_cpu_stall_info_begin(void);
 471 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
 472 static void print_cpu_stall_info_end(void);
 473 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 474 static void increment_cpu_stall_ticks(void);
 475 static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
 476 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
 477 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
 478 static void rcu_init_one_nocb(struct rcu_node *rnp);
 479 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
 480                             bool lazy, unsigned long flags);
 481 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
 482                                       struct rcu_data *rdp,
 483                                       unsigned long flags);
 484 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
 485 static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
 486 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 487 static void rcu_spawn_all_nocb_kthreads(int cpu);
 488 static void __init rcu_spawn_nocb_kthreads(void);
 489 #ifdef CONFIG_RCU_NOCB_CPU
 490 static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
 491 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 492 static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
 493 static bool init_nocb_callback_list(struct rcu_data *rdp);
 494 static void rcu_bind_gp_kthread(void);
 495 static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
 496 static void rcu_dynticks_task_enter(void);
 497 static void rcu_dynticks_task_exit(void);
 498
 499 #ifdef CONFIG_SRCU
 500 void srcu_online_cpu(unsigned int cpu);
 501 void srcu_offline_cpu(unsigned int cpu);
 502 #else /* #ifdef CONFIG_SRCU */
 503 void srcu_online_cpu(unsigned int cpu) { }
 504 void srcu_offline_cpu(unsigned int cpu) { }
 505 #endif /* #else #ifdef CONFIG_SRCU */
 506
 507 #endif /* #ifndef RCU_TREE_NONCORE */