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