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