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, CONFIG_RCU_FANOUT, and
  33  * CONFIG_RCU_FANOUT_LEAF.
  34  * In theory, it should be possible to add more levels straightforwardly.
  35  * In practice, this did work well going from three levels to four.
  36  * Of course, your mileage may vary.
  37  */
  38 #define MAX_RCU_LVLS 4
  39 #define RCU_FANOUT_1          (CONFIG_RCU_FANOUT_LEAF)
  40 #define RCU_FANOUT_2          (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)
  41 #define RCU_FANOUT_3          (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)
  42 #define RCU_FANOUT_4          (RCU_FANOUT_3 * CONFIG_RCU_FANOUT)
  43
  44 #if NR_CPUS <= RCU_FANOUT_1
  45 #  define RCU_NUM_LVLS        1
  46 #  define NUM_RCU_LVL_0       1
  47 #  define NUM_RCU_LVL_1       (NR_CPUS)
  48 #  define NUM_RCU_LVL_2       0
  49 #  define NUM_RCU_LVL_3       0
  50 #  define NUM_RCU_LVL_4       0
  51 #elif NR_CPUS <= RCU_FANOUT_2
  52 #  define RCU_NUM_LVLS        2
  53 #  define NUM_RCU_LVL_0       1
  54 #  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  55 #  define NUM_RCU_LVL_2       (NR_CPUS)
  56 #  define NUM_RCU_LVL_3       0
  57 #  define NUM_RCU_LVL_4       0
  58 #elif NR_CPUS <= RCU_FANOUT_3
  59 #  define RCU_NUM_LVLS        3
  60 #  define NUM_RCU_LVL_0       1
  61 #  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
  62 #  define NUM_RCU_LVL_2       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  63 #  define NUM_RCU_LVL_3       (NR_CPUS)
  64 #  define NUM_RCU_LVL_4       0
  65 #elif NR_CPUS <= RCU_FANOUT_4
  66 #  define RCU_NUM_LVLS        4
  67 #  define NUM_RCU_LVL_0       1
  68 #  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
  69 #  define NUM_RCU_LVL_2       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
  70 #  define NUM_RCU_LVL_3       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  71 #  define NUM_RCU_LVL_4       (NR_CPUS)
  72 #else
  73 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
  74 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
  75
  76 #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)
  77 #define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
  78
  79 extern int rcu_num_lvls;
  80 extern int rcu_num_nodes;
  81
  82 /*
  83  * Dynticks per-CPU state.
  84  */
  85 struct rcu_dynticks {
  86         long long dynticks_nesting; /* Track irq/process nesting level. */
  87                                     /* Process level is worth LLONG_MAX/2. */
  88         int dynticks_nmi_nesting;   /* Track NMI nesting level. */
  89         atomic_t dynticks;          /* Even value for idle, else odd. */
  90 #ifdef CONFIG_RCU_FAST_NO_HZ
  91         int dyntick_drain;          /* Prepare-for-idle state variable. */
  92         unsigned long dyntick_holdoff;
  93                                     /* No retries for the jiffy of failure. */
  94         struct timer_list idle_gp_timer;
  95                                     /* Wake up CPU sleeping with callbacks. */
  96         unsigned long idle_gp_timer_expires;
  97                                     /* When to wake up CPU (for repost). */
  98         bool idle_first_pass;       /* First pass of attempt to go idle? */
  99         unsigned long nonlazy_posted;
 100                                     /* # times non-lazy CBs posted to CPU. */
 101         unsigned long nonlazy_posted_snap;
 102                                     /* idle-period nonlazy_posted snapshot. */
 103         int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
 104 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 105 };
 106
 107 /* RCU's kthread states for tracing. */
 108 #define RCU_KTHREAD_STOPPED  0
 109 #define RCU_KTHREAD_RUNNING  1
 110 #define RCU_KTHREAD_WAITING  2
 111 #define RCU_KTHREAD_OFFCPU   3
 112 #define RCU_KTHREAD_YIELDING 4
 113 #define RCU_KTHREAD_MAX      4
 114
 115 /*
 116  * Definition for node within the RCU grace-period-detection hierarchy.
 117  */
 118 struct rcu_node {
 119         raw_spinlock_t lock;    /* Root rcu_node's lock protects some */
 120                                 /*  rcu_state fields as well as following. */
 121         unsigned long gpnum;    /* Current grace period for this node. */
 122                                 /*  This will either be equal to or one */
 123                                 /*  behind the root rcu_node's gpnum. */
 124         unsigned long completed; /* Last GP completed for this node. */
 125                                 /*  This will either be equal to or one */
 126                                 /*  behind the root rcu_node's gpnum. */
 127         unsigned long qsmask;   /* CPUs or groups that need to switch in */
 128                                 /*  order for current grace period to proceed.*/
 129                                 /*  In leaf rcu_node, each bit corresponds to */
 130                                 /*  an rcu_data structure, otherwise, each */
 131                                 /*  bit corresponds to a child rcu_node */
 132                                 /*  structure. */
 133         unsigned long expmask;  /* Groups that have ->blkd_tasks */
 134                                 /*  elements that need to drain to allow the */
 135                                 /*  current expedited grace period to */
 136                                 /*  complete (only for TREE_PREEMPT_RCU). */
 137         atomic_t wakemask;      /* CPUs whose kthread needs to be awakened. */
 138                                 /*  Since this has meaning only for leaf */
 139                                 /*  rcu_node structures, 32 bits suffices. */
 140         unsigned long qsmaskinit;
 141                                 /* Per-GP initial value for qsmask & expmask. */
 142         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
 143                                 /*  Only one bit will be set in this mask. */
 144         int     grplo;          /* lowest-numbered CPU or group here. */
 145         int     grphi;          /* highest-numbered CPU or group here. */
 146         u8      grpnum;         /* CPU/group number for next level up. */
 147         u8      level;          /* root is at level 0. */
 148         struct rcu_node *parent;
 149         struct list_head blkd_tasks;
 150                                 /* Tasks blocked in RCU read-side critical */
 151                                 /*  section.  Tasks are placed at the head */
 152                                 /*  of this list and age towards the tail. */
 153         struct list_head *gp_tasks;
 154                                 /* Pointer to the first task blocking the */
 155                                 /*  current grace period, or NULL if there */
 156                                 /*  is no such task. */
 157         struct list_head *exp_tasks;
 158                                 /* Pointer to the first task blocking the */
 159                                 /*  current expedited grace period, or NULL */
 160                                 /*  if there is no such task.  If there */
 161                                 /*  is no current expedited grace period, */
 162                                 /*  then there can cannot be any such task. */
 163 #ifdef CONFIG_RCU_BOOST
 164         struct list_head *boost_tasks;
 165                                 /* Pointer to first task that needs to be */
 166                                 /*  priority boosted, or NULL if no priority */
 167                                 /*  boosting is needed for this rcu_node */
 168                                 /*  structure.  If there are no tasks */
 169                                 /*  queued on this rcu_node structure that */
 170                                 /*  are blocking the current grace period, */
 171                                 /*  there can be no such task. */
 172         unsigned long boost_time;
 173                                 /* When to start boosting (jiffies). */
 174         struct task_struct *boost_kthread_task;
 175                                 /* kthread that takes care of priority */
 176                                 /*  boosting for this rcu_node structure. */
 177         unsigned int boost_kthread_status;
 178                                 /* State of boost_kthread_task for tracing. */
 179         unsigned long n_tasks_boosted;
 180                                 /* Total number of tasks boosted. */
 181         unsigned long n_exp_boosts;
 182                                 /* Number of tasks boosted for expedited GP. */
 183         unsigned long n_normal_boosts;
 184                                 /* Number of tasks boosted for normal GP. */
 185         unsigned long n_balk_blkd_tasks;
 186                                 /* Refused to boost: no blocked tasks. */
 187         unsigned long n_balk_exp_gp_tasks;
 188                                 /* Refused to boost: nothing blocking GP. */
 189         unsigned long n_balk_boost_tasks;
 190                                 /* Refused to boost: already boosting. */
 191         unsigned long n_balk_notblocked;
 192                                 /* Refused to boost: RCU RS CS still running. */
 193         unsigned long n_balk_notyet;
 194                                 /* Refused to boost: not yet time. */
 195         unsigned long n_balk_nos;
 196                                 /* Refused to boost: not sure why, though. */
 197                                 /*  This can happen due to race conditions. */
 198 #endif /* #ifdef CONFIG_RCU_BOOST */
 199         struct task_struct *node_kthread_task;
 200                                 /* kthread that takes care of this rcu_node */
 201                                 /*  structure, for example, awakening the */
 202                                 /*  per-CPU kthreads as needed. */
 203         unsigned int node_kthread_status;
 204                                 /* State of node_kthread_task for tracing. */
 205 } ____cacheline_internodealigned_in_smp;
 206
 207 /*
 208  * Do a full breadth-first scan of the rcu_node structures for the
 209  * specified rcu_state structure.
 210  */
 211 #define rcu_for_each_node_breadth_first(rsp, rnp) \
 212         for ((rnp) = &(rsp)->node[0]; \
 213              (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
 214
 215 /*
 216  * Do a breadth-first scan of the non-leaf rcu_node structures for the
 217  * specified rcu_state structure.  Note that if there is a singleton
 218  * rcu_node tree with but one rcu_node structure, this loop is a no-op.
 219  */
 220 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
 221         for ((rnp) = &(rsp)->node[0]; \
 222              (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)
 223
 224 /*
 225  * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
 226  * structure.  Note that if there is a singleton rcu_node tree with but
 227  * one rcu_node structure, this loop -will- visit the rcu_node structure.
 228  * It is still a leaf node, even if it is also the root node.
 229  */
 230 #define rcu_for_each_leaf_node(rsp, rnp) \
 231         for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
 232              (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
 233
 234 /* Index values for nxttail array in struct rcu_data. */
 235 #define RCU_DONE_TAIL           0       /* Also RCU_WAIT head. */
 236 #define RCU_WAIT_TAIL           1       /* Also RCU_NEXT_READY head. */
 237 #define RCU_NEXT_READY_TAIL     2       /* Also RCU_NEXT head. */
 238 #define RCU_NEXT_TAIL           3
 239 #define RCU_NEXT_SIZE           4
 240
 241 /* Per-CPU data for read-copy update. */
 242 struct rcu_data {
 243         /* 1) quiescent-state and grace-period handling : */
 244         unsigned long   completed;      /* Track rsp->completed gp number */
 245                                         /*  in order to detect GP end. */
 246         unsigned long   gpnum;          /* Highest gp number that this CPU */
 247                                         /*  is aware of having started. */
 248         unsigned long   passed_quiesce_gpnum;
 249                                         /* gpnum at time of quiescent state. */
 250         bool            passed_quiesce; /* User-mode/idle loop etc. */
 251         bool            qs_pending;     /* Core waits for quiesc state. */
 252         bool            beenonline;     /* CPU online at least once. */
 253         bool            preemptible;    /* Preemptible RCU? */
 254         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 255         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 256 #ifdef CONFIG_RCU_CPU_STALL_INFO
 257         unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
 258                                         /*  ticks this CPU has handled */
 259                                         /*  during and after the last grace */
 260                                         /* period it is aware of. */
 261 #endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
 262
 263         /* 2) batch handling */
 264         /*
 265          * If nxtlist is not NULL, it is partitioned as follows.
 266          * Any of the partitions might be empty, in which case the
 267          * pointer to that partition will be equal to the pointer for
 268          * the following partition.  When the list is empty, all of
 269          * the nxttail elements point to the ->nxtlist pointer itself,
 270          * which in that case is NULL.
 271          *
 272          * [nxtlist, *nxttail[RCU_DONE_TAIL]):
 273          *      Entries that batch # <= ->completed
 274          *      The grace period for these entries has completed, and
 275          *      the other grace-period-completed entries may be moved
 276          *      here temporarily in rcu_process_callbacks().
 277          * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
 278          *      Entries that batch # <= ->completed - 1: waiting for current GP
 279          * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
 280          *      Entries known to have arrived before current GP ended
 281          * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
 282          *      Entries that might have arrived after current GP ended
 283          *      Note that the value of *nxttail[RCU_NEXT_TAIL] will
 284          *      always be NULL, as this is the end of the list.
 285          */
 286         struct rcu_head *nxtlist;
 287         struct rcu_head **nxttail[RCU_NEXT_SIZE];
 288         long            qlen_lazy;      /* # of lazy queued callbacks */
 289         long            qlen;           /* # of queued callbacks, incl lazy */
 290         long            qlen_last_fqs_check;
 291                                         /* qlen at last check for QS forcing */
 292         unsigned long   n_cbs_invoked;  /* count of RCU cbs invoked. */
 293         unsigned long   n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
 294         unsigned long   n_cbs_adopted;  /* RCU cbs adopted from dying CPU */
 295         unsigned long   n_force_qs_snap;
 296                                         /* did other CPU force QS recently? */
 297         long            blimit;         /* Upper limit on a processed batch */
 298
 299         /* 3) dynticks interface. */
 300         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
 301         int dynticks_snap;              /* Per-GP tracking for dynticks. */
 302
 303         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
 304         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
 305         unsigned long offline_fqs;      /* Kicked due to being offline. */
 306
 307         /* 5) __rcu_pending() statistics. */
 308         unsigned long n_rcu_pending;    /* rcu_pending() calls since boot. */
 309         unsigned long n_rp_qs_pending;
 310         unsigned long n_rp_report_qs;
 311         unsigned long n_rp_cb_ready;
 312         unsigned long n_rp_cpu_needs_gp;
 313         unsigned long n_rp_gp_completed;
 314         unsigned long n_rp_gp_started;
 315         unsigned long n_rp_need_fqs;
 316         unsigned long n_rp_need_nothing;
 317
 318         /* 6) _rcu_barrier() callback. */
 319         struct rcu_head barrier_head;
 320
 321         int cpu;
 322         struct rcu_state *rsp;
 323 };
 324
 325 /* Values for fqs_state field in struct rcu_state. */
 326 #define RCU_GP_IDLE             0       /* No grace period in progress. */
 327 #define RCU_GP_INIT             1       /* Grace period being initialized. */
 328 #define RCU_SAVE_DYNTICK        2       /* Need to scan dyntick state. */
 329 #define RCU_FORCE_QS            3       /* Need to force quiescent state. */
 330 #define RCU_SIGNAL_INIT         RCU_SAVE_DYNTICK
 331
 332 #define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
 333
 334 #ifdef CONFIG_PROVE_RCU
 335 #define RCU_STALL_DELAY_DELTA          (5 * HZ)
 336 #else
 337 #define RCU_STALL_DELAY_DELTA          0
 338 #endif
 339 #define RCU_STALL_RAT_DELAY             2       /* Allow other CPUs time */
 340                                                 /*  to take at least one */
 341                                                 /*  scheduling clock irq */
 342                                                 /*  before ratting on them. */
 343
 344 #define rcu_wait(cond)                                                  \
 345 do {                                                                    \
 346         for (;;) {                                                      \
 347                 set_current_state(TASK_INTERRUPTIBLE);                  \
 348                 if (cond)                                               \
 349                         break;                                          \
 350                 schedule();                                             \
 351         }                                                               \
 352         __set_current_state(TASK_RUNNING);                              \
 353 } while (0)
 354
 355 /*
 356  * RCU global state, including node hierarchy.  This hierarchy is
 357  * represented in "heap" form in a dense array.  The root (first level)
 358  * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 359  * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 360  * and the third level in ->node[m+1] and following (->node[m+1] referenced
 361  * by ->level[2]).  The number of levels is determined by the number of
 362  * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 363  * consisting of a single rcu_node.
 364  */
 365 struct rcu_state {
 366         struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 367         struct rcu_node *level[RCU_NUM_LVLS];   /* Hierarchy levels. */
 368         u32 levelcnt[MAX_RCU_LVLS + 1];         /* # nodes in each level. */
 369         u8 levelspread[RCU_NUM_LVLS];           /* kids/node in each level. */
 370         struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
 371         void (*call)(struct rcu_head *head,     /* call_rcu() flavor. */
 372                      void (*func)(struct rcu_head *head));
 373
 374         /* The following fields are guarded by the root rcu_node's lock. */
 375
 376         u8      fqs_state ____cacheline_internodealigned_in_smp;
 377                                                 /* Force QS state. */
 378         u8      fqs_active;                     /* force_quiescent_state() */
 379                                                 /*  is running. */
 380         u8      fqs_need_gp;                    /* A CPU was prevented from */
 381                                                 /*  starting a new grace */
 382                                                 /*  period because */
 383                                                 /*  force_quiescent_state() */
 384                                                 /*  was running. */
 385         u8      boost;                          /* Subject to priority boost. */
 386         unsigned long gpnum;                    /* Current gp number. */
 387         unsigned long completed;                /* # of last completed gp. */
 388
 389         /* End of fields guarded by root rcu_node's lock. */
 390
 391         raw_spinlock_t onofflock;               /* exclude on/offline and */
 392                                                 /*  starting new GP. */
 393         struct rcu_head *orphan_nxtlist;        /* Orphaned callbacks that */
 394                                                 /*  need a grace period. */
 395         struct rcu_head **orphan_nxttail;       /* Tail of above. */
 396         struct rcu_head *orphan_donelist;       /* Orphaned callbacks that */
 397                                                 /*  are ready to invoke. */
 398         struct rcu_head **orphan_donetail;      /* Tail of above. */
 399         long qlen_lazy;                         /* Number of lazy callbacks. */
 400         long qlen;                              /* Total number of callbacks. */
 401         struct task_struct *rcu_barrier_in_progress;
 402                                                 /* Task doing rcu_barrier(), */
 403                                                 /*  or NULL if no barrier. */
 404         struct mutex barrier_mutex;             /* Guards barrier fields. */
 405         atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
 406         struct completion barrier_completion;   /* Wake at barrier end. */
 407         unsigned long n_barrier_done;           /* ++ at start and end of */
 408                                                 /*  _rcu_barrier(). */
 409         raw_spinlock_t fqslock;                 /* Only one task forcing */
 410                                                 /*  quiescent states. */
 411         unsigned long jiffies_force_qs;         /* Time at which to invoke */
 412                                                 /*  force_quiescent_state(). */
 413         unsigned long n_force_qs;               /* Number of calls to */
 414                                                 /*  force_quiescent_state(). */
 415         unsigned long n_force_qs_lh;            /* ~Number of calls leaving */
 416                                                 /*  due to lock unavailable. */
 417         unsigned long n_force_qs_ngp;           /* Number of calls leaving */
 418                                                 /*  due to no GP active. */
 419         unsigned long gp_start;                 /* Time at which GP started, */
 420                                                 /*  but in jiffies. */
 421         unsigned long jiffies_stall;            /* Time at which to check */
 422                                                 /*  for CPU stalls. */
 423         unsigned long gp_max;                   /* Maximum GP duration in */
 424                                                 /*  jiffies. */
 425         char *name;                             /* Name of structure. */
 426         struct list_head flavors;               /* List of RCU flavors. */
 427 };
 428
 429 extern struct list_head rcu_struct_flavors;
 430 #define for_each_rcu_flavor(rsp) \
 431         list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
 432
 433 /* Return values for rcu_preempt_offline_tasks(). */
 434
 435 #define RCU_OFL_TASKS_NORM_GP   0x1             /* Tasks blocking normal */
 436                                                 /*  GP were moved to root. */
 437 #define RCU_OFL_TASKS_EXP_GP    0x2             /* Tasks blocking expedited */
 438                                                 /*  GP were moved to root. */
 439
 440 /*
 441  * RCU implementation internal declarations:
 442  */
 443 extern struct rcu_state rcu_sched_state;
 444 DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 445
 446 extern struct rcu_state rcu_bh_state;
 447 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 448
 449 #ifdef CONFIG_TREE_PREEMPT_RCU
 450 extern struct rcu_state rcu_preempt_state;
 451 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 452 #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 453
 454 #ifdef CONFIG_RCU_BOOST
 455 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 456 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
 457 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 458 DECLARE_PER_CPU(char, rcu_cpu_has_work);
 459 #endif /* #ifdef CONFIG_RCU_BOOST */
 460
 461 #ifndef RCU_TREE_NONCORE
 462
 463 /* Forward declarations for rcutree_plugin.h */
 464 static void rcu_bootup_announce(void);
 465 long rcu_batches_completed(void);
 466 static void rcu_preempt_note_context_switch(int cpu);
 467 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 468 #ifdef CONFIG_HOTPLUG_CPU
 469 static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
 470                                       unsigned long flags);
 471 static void rcu_stop_cpu_kthread(int cpu);
 472 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 473 static void rcu_print_detail_task_stall(struct rcu_state *rsp);
 474 static int rcu_print_task_stall(struct rcu_node *rnp);
 475 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 476 #ifdef CONFIG_HOTPLUG_CPU
 477 static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 478                                      struct rcu_node *rnp,
 479                                      struct rcu_data *rdp);
 480 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 481 static void rcu_preempt_check_callbacks(int cpu);
 482 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
 483 #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
 484 static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 485                                bool wake);
 486 #endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
 487 static void __init __rcu_init_preempt(void);
 488 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 489 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 490 static void invoke_rcu_callbacks_kthread(void);
 491 static bool rcu_is_callbacks_kthread(void);
 492 #ifdef CONFIG_RCU_BOOST
 493 static void rcu_preempt_do_callbacks(void);
 494 static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
 495                                           cpumask_var_t cm);
 496 static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 497                                                  struct rcu_node *rnp,
 498                                                  int rnp_index);
 499 static void invoke_rcu_node_kthread(struct rcu_node *rnp);
 500 static void rcu_yield(void (*f)(unsigned long), unsigned long arg);
 501 #endif /* #ifdef CONFIG_RCU_BOOST */
 502 static void rcu_cpu_kthread_setrt(int cpu, int to_rt);
 503 static void __cpuinit rcu_prepare_kthreads(int cpu);
 504 static void rcu_prepare_for_idle_init(int cpu);
 505 static void rcu_cleanup_after_idle(int cpu);
 506 static void rcu_prepare_for_idle(int cpu);
 507 static void rcu_idle_count_callbacks_posted(void);
 508 static void print_cpu_stall_info_begin(void);
 509 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
 510 static void print_cpu_stall_info_end(void);
 511 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 512 static void increment_cpu_stall_ticks(void);
 513
 514 #endif /* #ifndef RCU_TREE_NONCORE */