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 /* RCU's kthread states for tracing. */
  62 #define RCU_KTHREAD_STOPPED  0
  63 #define RCU_KTHREAD_RUNNING  1
  64 #define RCU_KTHREAD_WAITING  2
  65 #define RCU_KTHREAD_OFFCPU   3
  66 #define RCU_KTHREAD_YIELDING 4
  67 #define RCU_KTHREAD_MAX      4
  68
  69 /*
  70  * Definition for node within the RCU grace-period-detection hierarchy.
  71  */
  72 struct rcu_node {
  73         raw_spinlock_t __private lock;  /* Root rcu_node's lock protects */
  74                                         /*  some rcu_state fields as well as */
  75                                         /*  following. */
  76         unsigned long gpnum;    /* Current grace period for this node. */
  77                                 /*  This will either be equal to or one */
  78                                 /*  behind the root rcu_node's gpnum. */
  79         unsigned long completed; /* Last GP completed for this node. */
  80                                 /*  This will either be equal to or one */
  81                                 /*  behind the root rcu_node's gpnum. */
  82         unsigned long qsmask;   /* CPUs or groups that need to switch in */
  83                                 /*  order for current grace period to proceed.*/
  84                                 /*  In leaf rcu_node, each bit corresponds to */
  85                                 /*  an rcu_data structure, otherwise, each */
  86                                 /*  bit corresponds to a child rcu_node */
  87                                 /*  structure. */
  88         unsigned long qsmaskinit;
  89                                 /* Per-GP initial value for qsmask. */
  90                                 /*  Initialized from ->qsmaskinitnext at the */
  91                                 /*  beginning of each grace period. */
  92         unsigned long qsmaskinitnext;
  93                                 /* Online CPUs for next grace period. */
  94         unsigned long expmask;  /* CPUs or groups that need to check in */
  95                                 /*  to allow the current expedited GP */
  96                                 /*  to complete. */
  97         unsigned long expmaskinit;
  98                                 /* Per-GP initial values for expmask. */
  99                                 /*  Initialized from ->expmaskinitnext at the */
 100                                 /*  beginning of each expedited GP. */
 101         unsigned long expmaskinitnext;
 102                                 /* Online CPUs for next expedited GP. */
 103                                 /*  Any CPU that has ever been online will */
 104                                 /*  have its bit set. */
 105         unsigned long ffmask;   /* Fully functional CPUs. */
 106         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
 107                                 /*  Only one bit will be set in this mask. */
 108         int     grplo;          /* lowest-numbered CPU or group here. */
 109         int     grphi;          /* highest-numbered CPU or group here. */
 110         u8      grpnum;         /* CPU/group number for next level up. */
 111         u8      level;          /* root is at level 0. */
 112         bool    wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
 113                                 /*  exit RCU read-side critical sections */
 114                                 /*  before propagating offline up the */
 115                                 /*  rcu_node tree? */
 116         struct rcu_node *parent;
 117         struct list_head blkd_tasks;
 118                                 /* Tasks blocked in RCU read-side critical */
 119                                 /*  section.  Tasks are placed at the head */
 120                                 /*  of this list and age towards the tail. */
 121         struct list_head *gp_tasks;
 122                                 /* Pointer to the first task blocking the */
 123                                 /*  current grace period, or NULL if there */
 124                                 /*  is no such task. */
 125         struct list_head *exp_tasks;
 126                                 /* Pointer to the first task blocking the */
 127                                 /*  current expedited grace period, or NULL */
 128                                 /*  if there is no such task.  If there */
 129                                 /*  is no current expedited grace period, */
 130                                 /*  then there can cannot be any such task. */
 131         struct list_head *boost_tasks;
 132                                 /* Pointer to first task that needs to be */
 133                                 /*  priority boosted, or NULL if no priority */
 134                                 /*  boosting is needed for this rcu_node */
 135                                 /*  structure.  If there are no tasks */
 136                                 /*  queued on this rcu_node structure that */
 137                                 /*  are blocking the current grace period, */
 138                                 /*  there can be no such task. */
 139         struct rt_mutex boost_mtx;
 140                                 /* Used only for the priority-boosting */
 141                                 /*  side effect, not as a lock. */
 142         unsigned long boost_time;
 143                                 /* When to start boosting (jiffies). */
 144         struct task_struct *boost_kthread_task;
 145                                 /* kthread that takes care of priority */
 146                                 /*  boosting for this rcu_node structure. */
 147         unsigned int boost_kthread_status;
 148                                 /* State of boost_kthread_task for tracing. */
 149         unsigned long n_tasks_boosted;
 150                                 /* Total number of tasks boosted. */
 151         unsigned long n_exp_boosts;
 152                                 /* Number of tasks boosted for expedited GP. */
 153         unsigned long n_normal_boosts;
 154                                 /* Number of tasks boosted for normal GP. */
 155 #ifdef CONFIG_RCU_NOCB_CPU
 156         struct swait_queue_head nocb_gp_wq[2];
 157                                 /* Place for rcu_nocb_kthread() to wait GP. */
 158 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 159         int need_future_gp[2];
 160                                 /* Counts of upcoming no-CB GP requests. */
 161         raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
 162
 163         spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
 164         unsigned long exp_seq_rq;
 165         wait_queue_head_t exp_wq[4];
 166 } ____cacheline_internodealigned_in_smp;
 167
 168 /*
 169  * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
 170  * are indexed relative to this interval rather than the global CPU ID space.
 171  * This generates the bit for a CPU in node-local masks.
 172  */
 173 #define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo))
 174
 175 /*
 176  * Union to allow "aggregate OR" operation on the need for a quiescent
 177  * state by the normal and expedited grace periods.
 178  */
 179 union rcu_noqs {
 180         struct {
 181                 u8 norm;
 182                 u8 exp;
 183         } b; /* Bits. */
 184         u16 s; /* Set of bits, aggregate OR here. */
 185 };
 186
 187 /* Index values for nxttail array in struct rcu_data. */
 188 #define RCU_DONE_TAIL           0       /* Also RCU_WAIT head. */
 189 #define RCU_WAIT_TAIL           1       /* Also RCU_NEXT_READY head. */
 190 #define RCU_NEXT_READY_TAIL     2       /* Also RCU_NEXT head. */
 191 #define RCU_NEXT_TAIL           3
 192 #define RCU_NEXT_SIZE           4
 193
 194 /* Per-CPU data for read-copy update. */
 195 struct rcu_data {
 196         /* 1) quiescent-state and grace-period handling : */
 197         unsigned long   completed;      /* Track rsp->completed gp number */
 198                                         /*  in order to detect GP end. */
 199         unsigned long   gpnum;          /* Highest gp number that this CPU */
 200                                         /*  is aware of having started. */
 201         unsigned long   rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
 202                                         /*  for rcu_all_qs() invocations. */
 203         union rcu_noqs  cpu_no_qs;      /* No QSes yet for this CPU. */
 204         bool            core_needs_qs;  /* Core waits for quiesc state. */
 205         bool            beenonline;     /* CPU online at least once. */
 206         bool            gpwrap;         /* Possible gpnum/completed wrap. */
 207         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 208         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 209         unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
 210                                         /*  ticks this CPU has handled */
 211                                         /*  during and after the last grace */
 212                                         /* period it is aware of. */
 213
 214         /* 2) batch handling */
 215         struct rcu_segcblist cblist;    /* Segmented callback list, with */
 216                                         /* different callbacks waiting for */
 217                                         /* different grace periods. */
 218         long            qlen_last_fqs_check;
 219                                         /* qlen at last check for QS forcing */
 220         unsigned long   n_cbs_invoked;  /* count of RCU cbs invoked. */
 221         unsigned long   n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
 222         unsigned long   n_force_qs_snap;
 223                                         /* did other CPU force QS recently? */
 224         long            blimit;         /* Upper limit on a processed batch */
 225
 226         /* 3) dynticks interface. */
 227         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
 228         int dynticks_snap;              /* Per-GP tracking for dynticks. */
 229
 230         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
 231         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
 232         unsigned long offline_fqs;      /* Kicked due to being offline. */
 233         unsigned long cond_resched_completed;
 234                                         /* Grace period that needs help */
 235                                         /*  from cond_resched(). */
 236
 237         /* 5) __rcu_pending() statistics. */
 238         unsigned long n_rcu_pending;    /* rcu_pending() calls since boot. */
 239         unsigned long n_rp_core_needs_qs;
 240         unsigned long n_rp_report_qs;
 241         unsigned long n_rp_cb_ready;
 242         unsigned long n_rp_cpu_needs_gp;
 243         unsigned long n_rp_gp_completed;
 244         unsigned long n_rp_gp_started;
 245         unsigned long n_rp_nocb_defer_wakeup;
 246         unsigned long n_rp_need_nothing;
 247
 248         /* 6) _rcu_barrier(), OOM callbacks, and expediting. */
 249         struct rcu_head barrier_head;
 250 #ifdef CONFIG_RCU_FAST_NO_HZ
 251         struct rcu_head oom_head;
 252 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 253         atomic_long_t exp_workdone0;    /* # done by workqueue. */
 254         atomic_long_t exp_workdone1;    /* # done by others #1. */
 255         atomic_long_t exp_workdone2;    /* # done by others #2. */
 256         atomic_long_t exp_workdone3;    /* # done by others #3. */
 257         int exp_dynticks_snap;          /* Double-check need for IPI. */
 258
 259         /* 7) Callback offloading. */
 260 #ifdef CONFIG_RCU_NOCB_CPU
 261         struct rcu_head *nocb_head;     /* CBs waiting for kthread. */
 262         struct rcu_head **nocb_tail;
 263         atomic_long_t nocb_q_count;     /* # CBs waiting for nocb */
 264         atomic_long_t nocb_q_count_lazy; /*  invocation (all stages). */
 265         struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
 266         struct rcu_head **nocb_follower_tail;
 267         struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
 268         struct task_struct *nocb_kthread;
 269         raw_spinlock_t nocb_lock;       /* Guard following pair of fields. */
 270         int nocb_defer_wakeup;          /* Defer wakeup of nocb_kthread. */
 271         struct timer_list nocb_timer;   /* Enforce finite deferral. */
 272
 273         /* The following fields are used by the leader, hence own cacheline. */
 274         struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
 275                                         /* CBs waiting for GP. */
 276         struct rcu_head **nocb_gp_tail;
 277         bool nocb_leader_sleep;         /* Is the nocb leader thread asleep? */
 278         struct rcu_data *nocb_next_follower;
 279                                         /* Next follower in wakeup chain. */
 280
 281         /* The following fields are used by the follower, hence new cachline. */
 282         struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
 283                                         /* Leader CPU takes GP-end wakeups. */
 284 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 285
 286         /* 8) RCU CPU stall data. */
 287         unsigned int softirq_snap;      /* Snapshot of softirq activity. */
 288         /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
 289         struct irq_work rcu_iw;         /* Check for non-irq activity. */
 290         bool rcu_iw_pending;            /* Is ->rcu_iw pending? */
 291         unsigned long rcu_iw_gpnum;     /* ->gpnum associated with ->rcu_iw. */
 292
 293         int cpu;
 294         struct rcu_state *rsp;
 295 };
 296
 297 /* Values for nocb_defer_wakeup field in struct rcu_data. */
 298 #define RCU_NOCB_WAKE_NOT       0
 299 #define RCU_NOCB_WAKE           1
 300 #define RCU_NOCB_WAKE_FORCE     2
 301
 302 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
 303                                         /* For jiffies_till_first_fqs and */
 304                                         /*  and jiffies_till_next_fqs. */
 305
 306 #define RCU_JIFFIES_FQS_DIV     256     /* Very large systems need more */
 307                                         /*  delay between bouts of */
 308                                         /*  quiescent-state forcing. */
 309
 310 #define RCU_STALL_RAT_DELAY     2       /* Allow other CPUs time to take */
 311                                         /*  at least one scheduling clock */
 312                                         /*  irq before ratting on them. */
 313
 314 #define rcu_wait(cond)                                                  \
 315 do {                                                                    \
 316         for (;;) {                                                      \
 317                 set_current_state(TASK_INTERRUPTIBLE);                  \
 318                 if (cond)                                               \
 319                         break;                                          \
 320                 schedule();                                             \
 321         }                                                               \
 322         __set_current_state(TASK_RUNNING);                              \
 323 } while (0)
 324
 325 /*
 326  * RCU global state, including node hierarchy.  This hierarchy is
 327  * represented in "heap" form in a dense array.  The root (first level)
 328  * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 329  * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 330  * and the third level in ->node[m+1] and following (->node[m+1] referenced
 331  * by ->level[2]).  The number of levels is determined by the number of
 332  * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 333  * consisting of a single rcu_node.
 334  */
 335 struct rcu_state {
 336         struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 337         struct rcu_node *level[RCU_NUM_LVLS + 1];
 338                                                 /* Hierarchy levels (+1 to */
 339                                                 /*  shut bogus gcc warning) */
 340         struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
 341         call_rcu_func_t call;                   /* call_rcu() flavor. */
 342         int ncpus;                              /* # CPUs seen so far. */
 343
 344         /* The following fields are guarded by the root rcu_node's lock. */
 345
 346         u8      boost ____cacheline_internodealigned_in_smp;
 347                                                 /* Subject to priority boost. */
 348         unsigned long gpnum;                    /* Current gp number. */
 349         unsigned long completed;                /* # of last completed gp. */
 350         struct task_struct *gp_kthread;         /* Task for grace periods. */
 351         struct swait_queue_head gp_wq;          /* Where GP task waits. */
 352         short gp_flags;                         /* Commands for GP task. */
 353         short gp_state;                         /* GP kthread sleep state. */
 354
 355         /* End of fields guarded by root rcu_node's lock. */
 356
 357         struct mutex barrier_mutex;             /* Guards barrier fields. */
 358         atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
 359         struct completion barrier_completion;   /* Wake at barrier end. */
 360         unsigned long barrier_sequence;         /* ++ at start and end of */
 361                                                 /*  _rcu_barrier(). */
 362         /* End of fields guarded by barrier_mutex. */
 363
 364         struct mutex exp_mutex;                 /* Serialize expedited GP. */
 365         struct mutex exp_wake_mutex;            /* Serialize wakeup. */
 366         unsigned long expedited_sequence;       /* Take a ticket. */
 367         atomic_t expedited_need_qs;             /* # CPUs left to check in. */
 368         struct swait_queue_head expedited_wq;   /* Wait for check-ins. */
 369         int ncpus_snap;                         /* # CPUs seen last time. */
 370
 371         unsigned long jiffies_force_qs;         /* Time at which to invoke */
 372                                                 /*  force_quiescent_state(). */
 373         unsigned long jiffies_kick_kthreads;    /* Time at which to kick */
 374                                                 /*  kthreads, if configured. */
 375         unsigned long n_force_qs;               /* Number of calls to */
 376                                                 /*  force_quiescent_state(). */
 377         unsigned long n_force_qs_lh;            /* ~Number of calls leaving */
 378                                                 /*  due to lock unavailable. */
 379         unsigned long n_force_qs_ngp;           /* Number of calls leaving */
 380                                                 /*  due to no GP active. */
 381         unsigned long gp_start;                 /* Time at which GP started, */
 382                                                 /*  but in jiffies. */
 383         unsigned long gp_activity;              /* Time of last GP kthread */
 384                                                 /*  activity in jiffies. */
 385         unsigned long jiffies_stall;            /* Time at which to check */
 386                                                 /*  for CPU stalls. */
 387         unsigned long jiffies_resched;          /* Time at which to resched */
 388                                                 /*  a reluctant CPU. */
 389         unsigned long n_force_qs_gpstart;       /* Snapshot of n_force_qs at */
 390                                                 /*  GP start. */
 391         unsigned long gp_max;                   /* Maximum GP duration in */
 392                                                 /*  jiffies. */
 393         const char *name;                       /* Name of structure. */
 394         char abbr;                              /* Abbreviated name. */
 395         struct list_head flavors;               /* List of RCU flavors. */
 396 };
 397
 398 /* Values for rcu_state structure's gp_flags field. */
 399 #define RCU_GP_FLAG_INIT 0x1    /* Need grace-period initialization. */
 400 #define RCU_GP_FLAG_FQS  0x2    /* Need grace-period quiescent-state forcing. */
 401
 402 /* Values for rcu_state structure's gp_state field. */
 403 #define RCU_GP_IDLE      0      /* Initial state and no GP in progress. */
 404 #define RCU_GP_WAIT_GPS  1      /* Wait for grace-period start. */
 405 #define RCU_GP_DONE_GPS  2      /* Wait done for grace-period start. */
 406 #define RCU_GP_WAIT_FQS  3      /* Wait for force-quiescent-state time. */
 407 #define RCU_GP_DOING_FQS 4      /* Wait done for force-quiescent-state time. */
 408 #define RCU_GP_CLEANUP   5      /* Grace-period cleanup started. */
 409 #define RCU_GP_CLEANED   6      /* Grace-period cleanup complete. */
 410
 411 #ifndef RCU_TREE_NONCORE
 412 static const char * const gp_state_names[] = {
 413         "RCU_GP_IDLE",
 414         "RCU_GP_WAIT_GPS",
 415         "RCU_GP_DONE_GPS",
 416         "RCU_GP_WAIT_FQS",
 417         "RCU_GP_DOING_FQS",
 418         "RCU_GP_CLEANUP",
 419         "RCU_GP_CLEANED",
 420 };
 421 #endif /* #ifndef RCU_TREE_NONCORE */
 422
 423 extern struct list_head rcu_struct_flavors;
 424
 425 /* Sequence through rcu_state structures for each RCU flavor. */
 426 #define for_each_rcu_flavor(rsp) \
 427         list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
 428
 429 /*
 430  * RCU implementation internal declarations:
 431  */
 432 extern struct rcu_state rcu_sched_state;
 433
 434 extern struct rcu_state rcu_bh_state;
 435
 436 #ifdef CONFIG_PREEMPT_RCU
 437 extern struct rcu_state rcu_preempt_state;
 438 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 439
 440 int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
 441 bool rcu_eqs_special_set(int cpu);
 442
 443 #ifdef CONFIG_RCU_BOOST
 444 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 445 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
 446 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 447 DECLARE_PER_CPU(char, rcu_cpu_has_work);
 448 #endif /* #ifdef CONFIG_RCU_BOOST */
 449
 450 #ifndef RCU_TREE_NONCORE
 451
 452 /* Forward declarations for rcutree_plugin.h */
 453 static void rcu_bootup_announce(void);
 454 static void rcu_preempt_note_context_switch(bool preempt);
 455 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 456 #ifdef CONFIG_HOTPLUG_CPU
 457 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 458 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 459 static void rcu_print_detail_task_stall(struct rcu_state *rsp);
 460 static int rcu_print_task_stall(struct rcu_node *rnp);
 461 static int rcu_print_task_exp_stall(struct rcu_node *rnp);
 462 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 463 static void rcu_preempt_check_callbacks(void);
 464 void call_rcu(struct rcu_head *head, rcu_callback_t func);
 465 static void __init __rcu_init_preempt(void);
 466 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 467 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 468 static void invoke_rcu_callbacks_kthread(void);
 469 static bool rcu_is_callbacks_kthread(void);
 470 #ifdef CONFIG_RCU_BOOST
 471 static void rcu_preempt_do_callbacks(void);
 472 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 473                                                  struct rcu_node *rnp);
 474 #endif /* #ifdef CONFIG_RCU_BOOST */
 475 static void __init rcu_spawn_boost_kthreads(void);
 476 static void rcu_prepare_kthreads(int cpu);
 477 static void rcu_cleanup_after_idle(void);
 478 static void rcu_prepare_for_idle(void);
 479 static void rcu_idle_count_callbacks_posted(void);
 480 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 481 static void print_cpu_stall_info_begin(void);
 482 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
 483 static void print_cpu_stall_info_end(void);
 484 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 485 static void increment_cpu_stall_ticks(void);
 486 static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
 487 static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
 488 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
 489 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
 490 static void rcu_init_one_nocb(struct rcu_node *rnp);
 491 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
 492                             bool lazy, unsigned long flags);
 493 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
 494                                       struct rcu_data *rdp,
 495                                       unsigned long flags);
 496 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
 497 static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
 498 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 499 static void rcu_spawn_all_nocb_kthreads(int cpu);
 500 static void __init rcu_spawn_nocb_kthreads(void);
 501 #ifdef CONFIG_RCU_NOCB_CPU
 502 static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
 503 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 504 static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
 505 static bool init_nocb_callback_list(struct rcu_data *rdp);
 506 static void rcu_bind_gp_kthread(void);
 507 static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
 508 static void rcu_dynticks_task_enter(void);
 509 static void rcu_dynticks_task_exit(void);
 510
 511 #ifdef CONFIG_SRCU
 512 void srcu_online_cpu(unsigned int cpu);
 513 void srcu_offline_cpu(unsigned int cpu);
 514 #else /* #ifdef CONFIG_SRCU */
 515 void srcu_online_cpu(unsigned int cpu) { }
 516 void srcu_offline_cpu(unsigned int cpu) { }
 517 #endif /* #else #ifdef CONFIG_SRCU */
 518
 519 #endif /* #ifndef RCU_TREE_NONCORE */