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