LXR linux/kernel/rcutree.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, write to the Free Software
  17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  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/threads.h>
  28#include <linux/cpumask.h>
  29#include <linux/seqlock.h>
  30
  31/*
  32 * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
  33 * In theory, it should be possible to add more levels straightforwardly.
  34 * In practice, this did work well going from three levels to four.
  35 * Of course, your mileage may vary.
  36 */
  37#define MAX_RCU_LVLS 4
  38#if CONFIG_RCU_FANOUT > 16
  39#define RCU_FANOUT_LEAF       16
  40#else /* #if CONFIG_RCU_FANOUT > 16 */
  41#define RCU_FANOUT_LEAF       (CONFIG_RCU_FANOUT)
  42#endif /* #else #if CONFIG_RCU_FANOUT > 16 */
  43#define RCU_FANOUT_1          (RCU_FANOUT_LEAF)
  44#define RCU_FANOUT_2          (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)
  45#define RCU_FANOUT_3          (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)
  46#define RCU_FANOUT_4          (RCU_FANOUT_3 * CONFIG_RCU_FANOUT)
  47
  48#if NR_CPUS <= RCU_FANOUT_1
  49#  define NUM_RCU_LVLS        1
  50#  define NUM_RCU_LVL_0       1
  51#  define NUM_RCU_LVL_1       (NR_CPUS)
  52#  define NUM_RCU_LVL_2       0
  53#  define NUM_RCU_LVL_3       0
  54#  define NUM_RCU_LVL_4       0
  55#elif NR_CPUS <= RCU_FANOUT_2
  56#  define NUM_RCU_LVLS        2
  57#  define NUM_RCU_LVL_0       1
  58#  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  59#  define NUM_RCU_LVL_2       (NR_CPUS)
  60#  define NUM_RCU_LVL_3       0
  61#  define NUM_RCU_LVL_4       0
  62#elif NR_CPUS <= RCU_FANOUT_3
  63#  define NUM_RCU_LVLS        3
  64#  define NUM_RCU_LVL_0       1
  65#  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
  66#  define NUM_RCU_LVL_2       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  67#  define NUM_RCU_LVL_3       (NR_CPUS)
  68#  define NUM_RCU_LVL_4       0
  69#elif NR_CPUS <= RCU_FANOUT_4
  70#  define NUM_RCU_LVLS        4
  71#  define NUM_RCU_LVL_0       1
  72#  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
  73#  define NUM_RCU_LVL_2       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
  74#  define NUM_RCU_LVL_3       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  75#  define NUM_RCU_LVL_4       (NR_CPUS)
  76#else
  77# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
  78#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
  79
  80#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)
  81#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
  82
  83/*
  84 * Dynticks per-CPU state.
  85 */
  86struct rcu_dynticks {
  87        long long dynticks_nesting; /* Track irq/process nesting level. */
  88                                    /* Process level is worth LLONG_MAX/2. */
  89        int dynticks_nmi_nesting;   /* Track NMI nesting level. */
  90        atomic_t dynticks;          /* Even value for idle, else odd. */
  91};
  92
  93/* RCU's kthread states for tracing. */
  94#define RCU_KTHREAD_STOPPED  0
  95#define RCU_KTHREAD_RUNNING  1
  96#define RCU_KTHREAD_WAITING  2
  97#define RCU_KTHREAD_OFFCPU   3
  98#define RCU_KTHREAD_YIELDING 4
  99#define RCU_KTHREAD_MAX      4
 100
 101/*
 102 * Definition for node within the RCU grace-period-detection hierarchy.
 103 */
 104struct rcu_node {
 105        raw_spinlock_t lock;    /* Root rcu_node's lock protects some */
 106                                /*  rcu_state fields as well as following. */
 107        unsigned long gpnum;    /* Current grace period for this node. */
 108                                /*  This will either be equal to or one */
 109                                /*  behind the root rcu_node's gpnum. */
 110        unsigned long completed; /* Last GP completed for this node. */
 111                                /*  This will either be equal to or one */
 112                                /*  behind the root rcu_node's gpnum. */
 113        unsigned long qsmask;   /* CPUs or groups that need to switch in */
 114                                /*  order for current grace period to proceed.*/
 115                                /*  In leaf rcu_node, each bit corresponds to */
 116                                /*  an rcu_data structure, otherwise, each */
 117                                /*  bit corresponds to a child rcu_node */
 118                                /*  structure. */
 119        unsigned long expmask;  /* Groups that have ->blkd_tasks */
 120                                /*  elements that need to drain to allow the */
 121                                /*  current expedited grace period to */
 122                                /*  complete (only for TREE_PREEMPT_RCU). */
 123        atomic_t wakemask;      /* CPUs whose kthread needs to be awakened. */
 124                                /*  Since this has meaning only for leaf */
 125                                /*  rcu_node structures, 32 bits suffices. */
 126        unsigned long qsmaskinit;
 127                                /* Per-GP initial value for qsmask & expmask. */
 128        unsigned long grpmask;  /* Mask to apply to parent qsmask. */
 129                                /*  Only one bit will be set in this mask. */
 130        int     grplo;          /* lowest-numbered CPU or group here. */
 131        int     grphi;          /* highest-numbered CPU or group here. */
 132        u8      grpnum;         /* CPU/group number for next level up. */
 133        u8      level;          /* root is at level 0. */
 134        struct rcu_node *parent;
 135        struct list_head blkd_tasks;
 136                                /* Tasks blocked in RCU read-side critical */
 137                                /*  section.  Tasks are placed at the head */
 138                                /*  of this list and age towards the tail. */
 139        struct list_head *gp_tasks;
 140                                /* Pointer to the first task blocking the */
 141                                /*  current grace period, or NULL if there */
 142                                /*  is no such task. */
 143        struct list_head *exp_tasks;
 144                                /* Pointer to the first task blocking the */
 145                                /*  current expedited grace period, or NULL */
 146                                /*  if there is no such task.  If there */
 147                                /*  is no current expedited grace period, */
 148                                /*  then there can cannot be any such task. */
 149#ifdef CONFIG_RCU_BOOST
 150        struct list_head *boost_tasks;
 151                                /* Pointer to first task that needs to be */
 152                                /*  priority boosted, or NULL if no priority */
 153                                /*  boosting is needed for this rcu_node */
 154                                /*  structure.  If there are no tasks */
 155                                /*  queued on this rcu_node structure that */
 156                                /*  are blocking the current grace period, */
 157                                /*  there can be no such task. */
 158        unsigned long boost_time;
 159                                /* When to start boosting (jiffies). */
 160        struct task_struct *boost_kthread_task;
 161                                /* kthread that takes care of priority */
 162                                /*  boosting for this rcu_node structure. */
 163        unsigned int boost_kthread_status;
 164                                /* State of boost_kthread_task for tracing. */
 165        unsigned long n_tasks_boosted;
 166                                /* Total number of tasks boosted. */
 167        unsigned long n_exp_boosts;
 168                                /* Number of tasks boosted for expedited GP. */
 169        unsigned long n_normal_boosts;
 170                                /* Number of tasks boosted for normal GP. */
 171        unsigned long n_balk_blkd_tasks;
 172                                /* Refused to boost: no blocked tasks. */
 173        unsigned long n_balk_exp_gp_tasks;
 174                                /* Refused to boost: nothing blocking GP. */
 175        unsigned long n_balk_boost_tasks;
 176                                /* Refused to boost: already boosting. */
 177        unsigned long n_balk_notblocked;
 178                                /* Refused to boost: RCU RS CS still running. */
 179        unsigned long n_balk_notyet;
 180                                /* Refused to boost: not yet time. */
 181        unsigned long n_balk_nos;
 182                                /* Refused to boost: not sure why, though. */
 183                                /*  This can happen due to race conditions. */
 184#endif /* #ifdef CONFIG_RCU_BOOST */
 185        struct task_struct *node_kthread_task;
 186                                /* kthread that takes care of this rcu_node */
 187                                /*  structure, for example, awakening the */
 188                                /*  per-CPU kthreads as needed. */
 189        unsigned int node_kthread_status;
 190                                /* State of node_kthread_task for tracing. */
 191} ____cacheline_internodealigned_in_smp;
 192
 193/*
 194 * Do a full breadth-first scan of the rcu_node structures for the
 195 * specified rcu_state structure.
 196 */
 197#define rcu_for_each_node_breadth_first(rsp, rnp) \
 198        for ((rnp) = &(rsp)->node[0]; \
 199             (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
 200
 201/*
 202 * Do a breadth-first scan of the non-leaf rcu_node structures for the
 203 * specified rcu_state structure.  Note that if there is a singleton
 204 * rcu_node tree with but one rcu_node structure, this loop is a no-op.
 205 */
 206#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
 207        for ((rnp) = &(rsp)->node[0]; \
 208             (rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++)
 209
 210/*
 211 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
 212 * structure.  Note that if there is a singleton rcu_node tree with but
 213 * one rcu_node structure, this loop -will- visit the rcu_node structure.
 214 * It is still a leaf node, even if it is also the root node.
 215 */
 216#define rcu_for_each_leaf_node(rsp, rnp) \
 217        for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \
 218             (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
 219
 220/* Index values for nxttail array in struct rcu_data. */
 221#define RCU_DONE_TAIL           0       /* Also RCU_WAIT head. */
 222#define RCU_WAIT_TAIL           1       /* Also RCU_NEXT_READY head. */
 223#define RCU_NEXT_READY_TAIL     2       /* Also RCU_NEXT head. */
 224#define RCU_NEXT_TAIL           3
 225#define RCU_NEXT_SIZE           4
 226
 227/* Per-CPU data for read-copy update. */
 228struct rcu_data {
 229        /* 1) quiescent-state and grace-period handling : */
 230        unsigned long   completed;      /* Track rsp->completed gp number */
 231                                        /*  in order to detect GP end. */
 232        unsigned long   gpnum;          /* Highest gp number that this CPU */
 233                                        /*  is aware of having started. */
 234        unsigned long   passed_quiesce_gpnum;
 235                                        /* gpnum at time of quiescent state. */
 236        bool            passed_quiesce; /* User-mode/idle loop etc. */
 237        bool            qs_pending;     /* Core waits for quiesc state. */
 238        bool            beenonline;     /* CPU online at least once. */
 239        bool            preemptible;    /* Preemptible RCU? */
 240        struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 241        unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 242
 243        /* 2) batch handling */
 244        /*
 245         * If nxtlist is not NULL, it is partitioned as follows.
 246         * Any of the partitions might be empty, in which case the
 247         * pointer to that partition will be equal to the pointer for
 248         * the following partition.  When the list is empty, all of
 249         * the nxttail elements point to the ->nxtlist pointer itself,
 250         * which in that case is NULL.
 251         *
 252         * [nxtlist, *nxttail[RCU_DONE_TAIL]):
 253         *      Entries that batch # <= ->completed
 254         *      The grace period for these entries has completed, and
 255         *      the other grace-period-completed entries may be moved
 256         *      here temporarily in rcu_process_callbacks().
 257         * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
 258         *      Entries that batch # <= ->completed - 1: waiting for current GP
 259         * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
 260         *      Entries known to have arrived before current GP ended
 261         * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
 262         *      Entries that might have arrived after current GP ended
 263         *      Note that the value of *nxttail[RCU_NEXT_TAIL] will
 264         *      always be NULL, as this is the end of the list.
 265         */
 266        struct rcu_head *nxtlist;
 267        struct rcu_head **nxttail[RCU_NEXT_SIZE];
 268        long            qlen;           /* # of queued callbacks */
 269        long            qlen_last_fqs_check;
 270                                        /* qlen at last check for QS forcing */
 271        unsigned long   n_cbs_invoked;  /* count of RCU cbs invoked. */
 272        unsigned long   n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
 273        unsigned long   n_cbs_adopted;  /* RCU cbs adopted from dying CPU */
 274        unsigned long   n_force_qs_snap;
 275                                        /* did other CPU force QS recently? */
 276        long            blimit;         /* Upper limit on a processed batch */
 277
 278        /* 3) dynticks interface. */
 279        struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
 280        int dynticks_snap;              /* Per-GP tracking for dynticks. */
 281
 282        /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
 283        unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
 284        unsigned long offline_fqs;      /* Kicked due to being offline. */
 285        unsigned long resched_ipi;      /* Sent a resched IPI. */
 286
 287        /* 5) __rcu_pending() statistics. */
 288        unsigned long n_rcu_pending;    /* rcu_pending() calls since boot. */
 289        unsigned long n_rp_qs_pending;
 290        unsigned long n_rp_report_qs;
 291        unsigned long n_rp_cb_ready;
 292        unsigned long n_rp_cpu_needs_gp;
 293        unsigned long n_rp_gp_completed;
 294        unsigned long n_rp_gp_started;
 295        unsigned long n_rp_need_fqs;
 296        unsigned long n_rp_need_nothing;
 297
 298        int cpu;
 299        struct rcu_state *rsp;
 300};
 301
 302/* Values for fqs_state field in struct rcu_state. */
 303#define RCU_GP_IDLE             0       /* No grace period in progress. */
 304#define RCU_GP_INIT             1       /* Grace period being initialized. */
 305#define RCU_SAVE_DYNTICK        2       /* Need to scan dyntick state. */
 306#define RCU_FORCE_QS            3       /* Need to force quiescent state. */
 307#define RCU_SIGNAL_INIT         RCU_SAVE_DYNTICK
 308
 309#define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
 310
 311#ifdef CONFIG_PROVE_RCU
 312#define RCU_STALL_DELAY_DELTA          (5 * HZ)
 313#else
 314#define RCU_STALL_DELAY_DELTA          0
 315#endif
 316
 317#define RCU_SECONDS_TILL_STALL_CHECK   (CONFIG_RCU_CPU_STALL_TIMEOUT * HZ + \
 318                                        RCU_STALL_DELAY_DELTA)
 319                                                /* for rsp->jiffies_stall */
 320#define RCU_SECONDS_TILL_STALL_RECHECK (3 * RCU_SECONDS_TILL_STALL_CHECK + 30)
 321                                                /* for rsp->jiffies_stall */
 322#define RCU_STALL_RAT_DELAY             2       /* Allow other CPUs time */
 323                                                /*  to take at least one */
 324                                                /*  scheduling clock irq */
 325                                                /*  before ratting on them. */
 326
 327#define rcu_wait(cond)                                                  \
 328do {                                                                    \
 329        for (;;) {                                                      \
 330                set_current_state(TASK_INTERRUPTIBLE);                  \
 331                if (cond)                                               \
 332                        break;                                          \
 333                schedule();                                             \
 334        }                                                               \
 335        __set_current_state(TASK_RUNNING);                              \
 336} while (0)
 337
 338/*
 339 * RCU global state, including node hierarchy.  This hierarchy is
 340 * represented in "heap" form in a dense array.  The root (first level)
 341 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 342 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 343 * and the third level in ->node[m+1] and following (->node[m+1] referenced
 344 * by ->level[2]).  The number of levels is determined by the number of
 345 * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 346 * consisting of a single rcu_node.
 347 */
 348struct rcu_state {
 349        struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 350        struct rcu_node *level[NUM_RCU_LVLS];   /* Hierarchy levels. */
 351        u32 levelcnt[MAX_RCU_LVLS + 1];         /* # nodes in each level. */
 352        u8 levelspread[NUM_RCU_LVLS];           /* kids/node in each level. */
 353        struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
 354
 355        /* The following fields are guarded by the root rcu_node's lock. */
 356
 357        u8      fqs_state ____cacheline_internodealigned_in_smp;
 358                                                /* Force QS state. */
 359        u8      fqs_active;                     /* force_quiescent_state() */
 360                                                /*  is running. */
 361        u8      fqs_need_gp;                    /* A CPU was prevented from */
 362                                                /*  starting a new grace */
 363                                                /*  period because */
 364                                                /*  force_quiescent_state() */
 365                                                /*  was running. */
 366        u8      boost;                          /* Subject to priority boost. */
 367        unsigned long gpnum;                    /* Current gp number. */
 368        unsigned long completed;                /* # of last completed gp. */
 369
 370        /* End of fields guarded by root rcu_node's lock. */
 371
 372        raw_spinlock_t onofflock;               /* exclude on/offline and */
 373                                                /*  starting new GP. */
 374        raw_spinlock_t fqslock;                 /* Only one task forcing */
 375                                                /*  quiescent states. */
 376        unsigned long jiffies_force_qs;         /* Time at which to invoke */
 377                                                /*  force_quiescent_state(). */
 378        unsigned long n_force_qs;               /* Number of calls to */
 379                                                /*  force_quiescent_state(). */
 380        unsigned long n_force_qs_lh;            /* ~Number of calls leaving */
 381                                                /*  due to lock unavailable. */
 382        unsigned long n_force_qs_ngp;           /* Number of calls leaving */
 383                                                /*  due to no GP active. */
 384        unsigned long gp_start;                 /* Time at which GP started, */
 385                                                /*  but in jiffies. */
 386        unsigned long jiffies_stall;            /* Time at which to check */
 387                                                /*  for CPU stalls. */
 388        unsigned long gp_max;                   /* Maximum GP duration in */
 389                                                /*  jiffies. */
 390        char *name;                             /* Name of structure. */
 391};
 392
 393/* Return values for rcu_preempt_offline_tasks(). */
 394
 395#define RCU_OFL_TASKS_NORM_GP   0x1             /* Tasks blocking normal */
 396                                                /*  GP were moved to root. */
 397#define RCU_OFL_TASKS_EXP_GP    0x2             /* Tasks blocking expedited */
 398                                                /*  GP were moved to root. */
 399
 400/*
 401 * RCU implementation internal declarations:
 402 */
 403extern struct rcu_state rcu_sched_state;
 404DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 405
 406extern struct rcu_state rcu_bh_state;
 407DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 408
 409#ifdef CONFIG_TREE_PREEMPT_RCU
 410extern struct rcu_state rcu_preempt_state;
 411DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 412#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 413
 414#ifdef CONFIG_RCU_BOOST
 415DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 416DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
 417DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 418DECLARE_PER_CPU(char, rcu_cpu_has_work);
 419#endif /* #ifdef CONFIG_RCU_BOOST */
 420
 421#ifndef RCU_TREE_NONCORE
 422
 423/* Forward declarations for rcutree_plugin.h */
 424static void rcu_bootup_announce(void);
 425long rcu_batches_completed(void);
 426static void rcu_preempt_note_context_switch(int cpu);
 427static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 428#ifdef CONFIG_HOTPLUG_CPU
 429static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
 430                                      unsigned long flags);
 431static void rcu_stop_cpu_kthread(int cpu);
 432#endif /* #ifdef CONFIG_HOTPLUG_CPU */
 433static void rcu_print_detail_task_stall(struct rcu_state *rsp);
 434static int rcu_print_task_stall(struct rcu_node *rnp);
 435static void rcu_preempt_stall_reset(void);
 436static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 437#ifdef CONFIG_HOTPLUG_CPU
 438static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 439                                     struct rcu_node *rnp,
 440                                     struct rcu_data *rdp);
 441static void rcu_preempt_offline_cpu(int cpu);
 442#endif /* #ifdef CONFIG_HOTPLUG_CPU */
 443static void rcu_preempt_check_callbacks(int cpu);
 444static void rcu_preempt_process_callbacks(void);
 445void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
 446#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
 447static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 448                               bool wake);
 449#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
 450static int rcu_preempt_pending(int cpu);
 451static int rcu_preempt_needs_cpu(int cpu);
 452static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
 453static void rcu_preempt_send_cbs_to_online(void);
 454static void __init __rcu_init_preempt(void);
 455static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 456static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 457static void invoke_rcu_callbacks_kthread(void);
 458static bool rcu_is_callbacks_kthread(void);
 459#ifdef CONFIG_RCU_BOOST
 460static void rcu_preempt_do_callbacks(void);
 461static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
 462                                          cpumask_var_t cm);
 463static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 464                                                 struct rcu_node *rnp,
 465                                                 int rnp_index);
 466static void invoke_rcu_node_kthread(struct rcu_node *rnp);
 467static void rcu_yield(void (*f)(unsigned long), unsigned long arg);
 468#endif /* #ifdef CONFIG_RCU_BOOST */
 469static void rcu_cpu_kthread_setrt(int cpu, int to_rt);
 470static void __cpuinit rcu_prepare_kthreads(int cpu);
 471static void rcu_prepare_for_idle_init(int cpu);
 472static void rcu_cleanup_after_idle(int cpu);
 473static void rcu_prepare_for_idle(int cpu);
 474
 475#endif /* #ifndef RCU_TREE_NONCORE */
 476