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 #include <linux/irq_work.h>
  31
  32 /*
  33  * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
  34  * CONFIG_RCU_FANOUT_LEAF.
  35  * In theory, it should be possible to add more levels straightforwardly.
  36  * In practice, this did work well going from three levels to four.
  37  * Of course, your mileage may vary.
  38  */
  39 #define MAX_RCU_LVLS 4
  40 #define RCU_FANOUT_1          (CONFIG_RCU_FANOUT_LEAF)
  41 #define RCU_FANOUT_2          (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)
  42 #define RCU_FANOUT_3          (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)
  43 #define RCU_FANOUT_4          (RCU_FANOUT_3 * CONFIG_RCU_FANOUT)
  44
  45 #if NR_CPUS <= RCU_FANOUT_1
  46 #  define RCU_NUM_LVLS        1
  47 #  define NUM_RCU_LVL_0       1
  48 #  define NUM_RCU_LVL_1       (NR_CPUS)
  49 #  define NUM_RCU_LVL_2       0
  50 #  define NUM_RCU_LVL_3       0
  51 #  define NUM_RCU_LVL_4       0
  52 #elif NR_CPUS <= RCU_FANOUT_2
  53 #  define RCU_NUM_LVLS        2
  54 #  define NUM_RCU_LVL_0       1
  55 #  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  56 #  define NUM_RCU_LVL_2       (NR_CPUS)
  57 #  define NUM_RCU_LVL_3       0
  58 #  define NUM_RCU_LVL_4       0
  59 #elif NR_CPUS <= RCU_FANOUT_3
  60 #  define RCU_NUM_LVLS        3
  61 #  define NUM_RCU_LVL_0       1
  62 #  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
  63 #  define NUM_RCU_LVL_2       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  64 #  define NUM_RCU_LVL_3       (NR_CPUS)
  65 #  define NUM_RCU_LVL_4       0
  66 #elif NR_CPUS <= RCU_FANOUT_4
  67 #  define RCU_NUM_LVLS        4
  68 #  define NUM_RCU_LVL_0       1
  69 #  define NUM_RCU_LVL_1       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
  70 #  define NUM_RCU_LVL_2       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
  71 #  define NUM_RCU_LVL_3       DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
  72 #  define NUM_RCU_LVL_4       (NR_CPUS)
  73 #else
  74 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
  75 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
  76
  77 #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)
  78 #define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
  79
  80 extern int rcu_num_lvls;
  81 extern int rcu_num_nodes;
  82
  83 /*
  84  * Dynticks per-CPU state.
  85  */
  86 struct 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 #ifdef CONFIG_NO_HZ_FULL_SYSIDLE
  92         long long dynticks_idle_nesting;
  93                                     /* irq/process nesting level from idle. */
  94         atomic_t dynticks_idle;     /* Even value for idle, else odd. */
  95                                     /*  "Idle" excludes userspace execution. */
  96         unsigned long dynticks_idle_jiffies;
  97                                     /* End of last non-NMI non-idle period. */
  98 #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
  99 #ifdef CONFIG_RCU_FAST_NO_HZ
 100         bool all_lazy;              /* Are all CPU's CBs lazy? */
 101         unsigned long nonlazy_posted;
 102                                     /* # times non-lazy CBs posted to CPU. */
 103         unsigned long nonlazy_posted_snap;
 104                                     /* idle-period nonlazy_posted snapshot. */
 105         unsigned long last_accelerate;
 106                                     /* Last jiffy CBs were accelerated. */
 107         unsigned long last_advance_all;
 108                                     /* Last jiffy CBs were all advanced. */
 109         int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
 110 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 111 };
 112
 113 /* RCU's kthread states for tracing. */
 114 #define RCU_KTHREAD_STOPPED  0
 115 #define RCU_KTHREAD_RUNNING  1
 116 #define RCU_KTHREAD_WAITING  2
 117 #define RCU_KTHREAD_OFFCPU   3
 118 #define RCU_KTHREAD_YIELDING 4
 119 #define RCU_KTHREAD_MAX      4
 120
 121 /*
 122  * Definition for node within the RCU grace-period-detection hierarchy.
 123  */
 124 struct rcu_node {
 125         raw_spinlock_t lock;    /* Root rcu_node's lock protects some */
 126                                 /*  rcu_state fields as well as following. */
 127         unsigned long gpnum;    /* Current grace period for this node. */
 128                                 /*  This will either be equal to or one */
 129                                 /*  behind the root rcu_node's gpnum. */
 130         unsigned long completed; /* Last GP completed for this node. */
 131                                 /*  This will either be equal to or one */
 132                                 /*  behind the root rcu_node's gpnum. */
 133         unsigned long qsmask;   /* CPUs or groups that need to switch in */
 134                                 /*  order for current grace period to proceed.*/
 135                                 /*  In leaf rcu_node, each bit corresponds to */
 136                                 /*  an rcu_data structure, otherwise, each */
 137                                 /*  bit corresponds to a child rcu_node */
 138                                 /*  structure. */
 139         unsigned long expmask;  /* Groups that have ->blkd_tasks */
 140                                 /*  elements that need to drain to allow the */
 141                                 /*  current expedited grace period to */
 142                                 /*  complete (only for TREE_PREEMPT_RCU). */
 143         unsigned long qsmaskinit;
 144                                 /* Per-GP initial value for qsmask & expmask. */
 145         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
 146                                 /*  Only one bit will be set in this mask. */
 147         int     grplo;          /* lowest-numbered CPU or group here. */
 148         int     grphi;          /* highest-numbered CPU or group here. */
 149         u8      grpnum;         /* CPU/group number for next level up. */
 150         u8      level;          /* root is at level 0. */
 151         struct rcu_node *parent;
 152         struct list_head blkd_tasks;
 153                                 /* Tasks blocked in RCU read-side critical */
 154                                 /*  section.  Tasks are placed at the head */
 155                                 /*  of this list and age towards the tail. */
 156         struct list_head *gp_tasks;
 157                                 /* Pointer to the first task blocking the */
 158                                 /*  current grace period, or NULL if there */
 159                                 /*  is no such task. */
 160         struct list_head *exp_tasks;
 161                                 /* Pointer to the first task blocking the */
 162                                 /*  current expedited grace period, or NULL */
 163                                 /*  if there is no such task.  If there */
 164                                 /*  is no current expedited grace period, */
 165                                 /*  then there can cannot be any such task. */
 166 #ifdef CONFIG_RCU_BOOST
 167         struct list_head *boost_tasks;
 168                                 /* Pointer to first task that needs to be */
 169                                 /*  priority boosted, or NULL if no priority */
 170                                 /*  boosting is needed for this rcu_node */
 171                                 /*  structure.  If there are no tasks */
 172                                 /*  queued on this rcu_node structure that */
 173                                 /*  are blocking the current grace period, */
 174                                 /*  there can be no such task. */
 175         unsigned long boost_time;
 176                                 /* When to start boosting (jiffies). */
 177         struct task_struct *boost_kthread_task;
 178                                 /* kthread that takes care of priority */
 179                                 /*  boosting for this rcu_node structure. */
 180         unsigned int boost_kthread_status;
 181                                 /* State of boost_kthread_task for tracing. */
 182         unsigned long n_tasks_boosted;
 183                                 /* Total number of tasks boosted. */
 184         unsigned long n_exp_boosts;
 185                                 /* Number of tasks boosted for expedited GP. */
 186         unsigned long n_normal_boosts;
 187                                 /* Number of tasks boosted for normal GP. */
 188         unsigned long n_balk_blkd_tasks;
 189                                 /* Refused to boost: no blocked tasks. */
 190         unsigned long n_balk_exp_gp_tasks;
 191                                 /* Refused to boost: nothing blocking GP. */
 192         unsigned long n_balk_boost_tasks;
 193                                 /* Refused to boost: already boosting. */
 194         unsigned long n_balk_notblocked;
 195                                 /* Refused to boost: RCU RS CS still running. */
 196         unsigned long n_balk_notyet;
 197                                 /* Refused to boost: not yet time. */
 198         unsigned long n_balk_nos;
 199                                 /* Refused to boost: not sure why, though. */
 200                                 /*  This can happen due to race conditions. */
 201 #endif /* #ifdef CONFIG_RCU_BOOST */
 202 #ifdef CONFIG_RCU_NOCB_CPU
 203         wait_queue_head_t nocb_gp_wq[2];
 204                                 /* Place for rcu_nocb_kthread() to wait GP. */
 205 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 206         int need_future_gp[2];
 207                                 /* Counts of upcoming no-CB GP requests. */
 208         raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
 209 } ____cacheline_internodealigned_in_smp;
 210
 211 /*
 212  * Do a full breadth-first scan of the rcu_node structures for the
 213  * specified rcu_state structure.
 214  */
 215 #define rcu_for_each_node_breadth_first(rsp, rnp) \
 216         for ((rnp) = &(rsp)->node[0]; \
 217              (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
 218
 219 /*
 220  * Do a breadth-first scan of the non-leaf rcu_node structures for the
 221  * specified rcu_state structure.  Note that if there is a singleton
 222  * rcu_node tree with but one rcu_node structure, this loop is a no-op.
 223  */
 224 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
 225         for ((rnp) = &(rsp)->node[0]; \
 226              (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)
 227
 228 /*
 229  * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
 230  * structure.  Note that if there is a singleton rcu_node tree with but
 231  * one rcu_node structure, this loop -will- visit the rcu_node structure.
 232  * It is still a leaf node, even if it is also the root node.
 233  */
 234 #define rcu_for_each_leaf_node(rsp, rnp) \
 235         for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
 236              (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
 237
 238 /* Index values for nxttail array in struct rcu_data. */
 239 #define RCU_DONE_TAIL           0       /* Also RCU_WAIT head. */
 240 #define RCU_WAIT_TAIL           1       /* Also RCU_NEXT_READY head. */
 241 #define RCU_NEXT_READY_TAIL     2       /* Also RCU_NEXT head. */
 242 #define RCU_NEXT_TAIL           3
 243 #define RCU_NEXT_SIZE           4
 244
 245 /* Per-CPU data for read-copy update. */
 246 struct rcu_data {
 247         /* 1) quiescent-state and grace-period handling : */
 248         unsigned long   completed;      /* Track rsp->completed gp number */
 249                                         /*  in order to detect GP end. */
 250         unsigned long   gpnum;          /* Highest gp number that this CPU */
 251                                         /*  is aware of having started. */
 252         bool            passed_quiesce; /* User-mode/idle loop etc. */
 253         bool            qs_pending;     /* Core waits for quiesc state. */
 254         bool            beenonline;     /* CPU online at least once. */
 255         bool            preemptible;    /* Preemptible RCU? */
 256         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 257         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 258 #ifdef CONFIG_RCU_CPU_STALL_INFO
 259         unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
 260                                         /*  ticks this CPU has handled */
 261                                         /*  during and after the last grace */
 262                                         /* period it is aware of. */
 263 #endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
 264
 265         /* 2) batch handling */
 266         /*
 267          * If nxtlist is not NULL, it is partitioned as follows.
 268          * Any of the partitions might be empty, in which case the
 269          * pointer to that partition will be equal to the pointer for
 270          * the following partition.  When the list is empty, all of
 271          * the nxttail elements point to the ->nxtlist pointer itself,
 272          * which in that case is NULL.
 273          *
 274          * [nxtlist, *nxttail[RCU_DONE_TAIL]):
 275          *      Entries that batch # <= ->completed
 276          *      The grace period for these entries has completed, and
 277          *      the other grace-period-completed entries may be moved
 278          *      here temporarily in rcu_process_callbacks().
 279          * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
 280          *      Entries that batch # <= ->completed - 1: waiting for current GP
 281          * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
 282          *      Entries known to have arrived before current GP ended
 283          * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
 284          *      Entries that might have arrived after current GP ended
 285          *      Note that the value of *nxttail[RCU_NEXT_TAIL] will
 286          *      always be NULL, as this is the end of the list.
 287          */
 288         struct rcu_head *nxtlist;
 289         struct rcu_head **nxttail[RCU_NEXT_SIZE];
 290         unsigned long   nxtcompleted[RCU_NEXT_SIZE];
 291                                         /* grace periods for sublists. */
 292         long            qlen_lazy;      /* # of lazy queued callbacks */
 293         long            qlen;           /* # of queued callbacks, incl lazy */
 294         long            qlen_last_fqs_check;
 295                                         /* qlen at last check for QS forcing */
 296         unsigned long   n_cbs_invoked;  /* count of RCU cbs invoked. */
 297         unsigned long   n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
 298         unsigned long   n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
 299         unsigned long   n_cbs_adopted;  /* RCU cbs adopted from dying CPU */
 300         unsigned long   n_force_qs_snap;
 301                                         /* did other CPU force QS recently? */
 302         long            blimit;         /* Upper limit on a processed batch */
 303
 304         /* 3) dynticks interface. */
 305         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
 306         int dynticks_snap;              /* Per-GP tracking for dynticks. */
 307
 308         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
 309         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
 310         unsigned long offline_fqs;      /* Kicked due to being offline. */
 311
 312         /* 5) __rcu_pending() statistics. */
 313         unsigned long n_rcu_pending;    /* rcu_pending() calls since boot. */
 314         unsigned long n_rp_qs_pending;
 315         unsigned long n_rp_report_qs;
 316         unsigned long n_rp_cb_ready;
 317         unsigned long n_rp_cpu_needs_gp;
 318         unsigned long n_rp_gp_completed;
 319         unsigned long n_rp_gp_started;
 320         unsigned long n_rp_need_nothing;
 321
 322         /* 6) _rcu_barrier() and OOM callbacks. */
 323         struct rcu_head barrier_head;
 324 #ifdef CONFIG_RCU_FAST_NO_HZ
 325         struct rcu_head oom_head;
 326 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 327
 328         /* 7) Callback offloading. */
 329 #ifdef CONFIG_RCU_NOCB_CPU
 330         struct rcu_head *nocb_head;     /* CBs waiting for kthread. */
 331         struct rcu_head **nocb_tail;
 332         atomic_long_t nocb_q_count;     /* # CBs waiting for kthread */
 333         atomic_long_t nocb_q_count_lazy; /*  (approximate). */
 334         int nocb_p_count;               /* # CBs being invoked by kthread */
 335         int nocb_p_count_lazy;          /*  (approximate). */
 336         wait_queue_head_t nocb_wq;      /* For nocb kthreads to sleep on. */
 337         struct task_struct *nocb_kthread;
 338 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 339
 340         /* 8) RCU CPU stall data. */
 341 #ifdef CONFIG_RCU_CPU_STALL_INFO
 342         unsigned int softirq_snap;      /* Snapshot of softirq activity. */
 343 #endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
 344
 345         int cpu;
 346         struct rcu_state *rsp;
 347 };
 348
 349 /* Values for fqs_state field in struct rcu_state. */
 350 #define RCU_GP_IDLE             0       /* No grace period in progress. */
 351 #define RCU_GP_INIT             1       /* Grace period being initialized. */
 352 #define RCU_SAVE_DYNTICK        2       /* Need to scan dyntick state. */
 353 #define RCU_FORCE_QS            3       /* Need to force quiescent state. */
 354 #define RCU_SIGNAL_INIT         RCU_SAVE_DYNTICK
 355
 356 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
 357                                         /* For jiffies_till_first_fqs and */
 358                                         /*  and jiffies_till_next_fqs. */
 359
 360 #define RCU_JIFFIES_FQS_DIV     256     /* Very large systems need more */
 361                                         /*  delay between bouts of */
 362                                         /*  quiescent-state forcing. */
 363
 364 #define RCU_STALL_RAT_DELAY     2       /* Allow other CPUs time to take */
 365                                         /*  at least one scheduling clock */
 366                                         /*  irq before ratting on them. */
 367
 368 #define rcu_wait(cond)                                                  \
 369 do {                                                                    \
 370         for (;;) {                                                      \
 371                 set_current_state(TASK_INTERRUPTIBLE);                  \
 372                 if (cond)                                               \
 373                         break;                                          \
 374                 schedule();                                             \
 375         }                                                               \
 376         __set_current_state(TASK_RUNNING);                              \
 377 } while (0)
 378
 379 /*
 380  * RCU global state, including node hierarchy.  This hierarchy is
 381  * represented in "heap" form in a dense array.  The root (first level)
 382  * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 383  * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 384  * and the third level in ->node[m+1] and following (->node[m+1] referenced
 385  * by ->level[2]).  The number of levels is determined by the number of
 386  * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 387  * consisting of a single rcu_node.
 388  */
 389 struct rcu_state {
 390         struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 391         struct rcu_node *level[RCU_NUM_LVLS];   /* Hierarchy levels. */
 392         u32 levelcnt[MAX_RCU_LVLS + 1];         /* # nodes in each level. */
 393         u8 levelspread[RCU_NUM_LVLS];           /* kids/node in each level. */
 394         struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
 395         void (*call)(struct rcu_head *head,     /* call_rcu() flavor. */
 396                      void (*func)(struct rcu_head *head));
 397
 398         /* The following fields are guarded by the root rcu_node's lock. */
 399
 400         u8      fqs_state ____cacheline_internodealigned_in_smp;
 401                                                 /* Force QS state. */
 402         u8      boost;                          /* Subject to priority boost. */
 403         unsigned long gpnum;                    /* Current gp number. */
 404         unsigned long completed;                /* # of last completed gp. */
 405         struct task_struct *gp_kthread;         /* Task for grace periods. */
 406         wait_queue_head_t gp_wq;                /* Where GP task waits. */
 407         int gp_flags;                           /* Commands for GP task. */
 408
 409         /* End of fields guarded by root rcu_node's lock. */
 410
 411         raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;
 412                                                 /* Protect following fields. */
 413         struct rcu_head *orphan_nxtlist;        /* Orphaned callbacks that */
 414                                                 /*  need a grace period. */
 415         struct rcu_head **orphan_nxttail;       /* Tail of above. */
 416         struct rcu_head *orphan_donelist;       /* Orphaned callbacks that */
 417                                                 /*  are ready to invoke. */
 418         struct rcu_head **orphan_donetail;      /* Tail of above. */
 419         long qlen_lazy;                         /* Number of lazy callbacks. */
 420         long qlen;                              /* Total number of callbacks. */
 421         /* End of fields guarded by orphan_lock. */
 422
 423         struct mutex onoff_mutex;               /* Coordinate hotplug & GPs. */
 424
 425         struct mutex barrier_mutex;             /* Guards barrier fields. */
 426         atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
 427         struct completion barrier_completion;   /* Wake at barrier end. */
 428         unsigned long n_barrier_done;           /* ++ at start and end of */
 429                                                 /*  _rcu_barrier(). */
 430         /* End of fields guarded by barrier_mutex. */
 431
 432         atomic_long_t expedited_start;          /* Starting ticket. */
 433         atomic_long_t expedited_done;           /* Done ticket. */
 434         atomic_long_t expedited_wrap;           /* # near-wrap incidents. */
 435         atomic_long_t expedited_tryfail;        /* # acquisition failures. */
 436         atomic_long_t expedited_workdone1;      /* # done by others #1. */
 437         atomic_long_t expedited_workdone2;      /* # done by others #2. */
 438         atomic_long_t expedited_normal;         /* # fallbacks to normal. */
 439         atomic_long_t expedited_stoppedcpus;    /* # successful stop_cpus. */
 440         atomic_long_t expedited_done_tries;     /* # tries to update _done. */
 441         atomic_long_t expedited_done_lost;      /* # times beaten to _done. */
 442         atomic_long_t expedited_done_exit;      /* # times exited _done loop. */
 443
 444         unsigned long jiffies_force_qs;         /* Time at which to invoke */
 445                                                 /*  force_quiescent_state(). */
 446         unsigned long n_force_qs;               /* Number of calls to */
 447                                                 /*  force_quiescent_state(). */
 448         unsigned long n_force_qs_lh;            /* ~Number of calls leaving */
 449                                                 /*  due to lock unavailable. */
 450         unsigned long n_force_qs_ngp;           /* Number of calls leaving */
 451                                                 /*  due to no GP active. */
 452         unsigned long gp_start;                 /* Time at which GP started, */
 453                                                 /*  but in jiffies. */
 454         unsigned long jiffies_stall;            /* Time at which to check */
 455                                                 /*  for CPU stalls. */
 456         unsigned long gp_max;                   /* Maximum GP duration in */
 457                                                 /*  jiffies. */
 458         const char *name;                       /* Name of structure. */
 459         char abbr;                              /* Abbreviated name. */
 460         struct list_head flavors;               /* List of RCU flavors. */
 461         struct irq_work wakeup_work;            /* Postponed wakeups */
 462 };
 463
 464 /* Values for rcu_state structure's gp_flags field. */
 465 #define RCU_GP_FLAG_INIT 0x1    /* Need grace-period initialization. */
 466 #define RCU_GP_FLAG_FQS  0x2    /* Need grace-period quiescent-state forcing. */
 467
 468 extern struct list_head rcu_struct_flavors;
 469
 470 /* Sequence through rcu_state structures for each RCU flavor. */
 471 #define for_each_rcu_flavor(rsp) \
 472         list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
 473
 474 /* Return values for rcu_preempt_offline_tasks(). */
 475
 476 #define RCU_OFL_TASKS_NORM_GP   0x1             /* Tasks blocking normal */
 477                                                 /*  GP were moved to root. */
 478 #define RCU_OFL_TASKS_EXP_GP    0x2             /* Tasks blocking expedited */
 479                                                 /*  GP were moved to root. */
 480
 481 /*
 482  * RCU implementation internal declarations:
 483  */
 484 extern struct rcu_state rcu_sched_state;
 485 DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 486
 487 extern struct rcu_state rcu_bh_state;
 488 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 489
 490 #ifdef CONFIG_TREE_PREEMPT_RCU
 491 extern struct rcu_state rcu_preempt_state;
 492 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 493 #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 494
 495 #ifdef CONFIG_RCU_BOOST
 496 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 497 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
 498 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 499 DECLARE_PER_CPU(char, rcu_cpu_has_work);
 500 #endif /* #ifdef CONFIG_RCU_BOOST */
 501
 502 #ifndef RCU_TREE_NONCORE
 503
 504 /* Forward declarations for rcutree_plugin.h */
 505 static void rcu_bootup_announce(void);
 506 long rcu_batches_completed(void);
 507 static void rcu_preempt_note_context_switch(int cpu);
 508 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 509 #ifdef CONFIG_HOTPLUG_CPU
 510 static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
 511                                       unsigned long flags);
 512 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 513 static void rcu_print_detail_task_stall(struct rcu_state *rsp);
 514 static int rcu_print_task_stall(struct rcu_node *rnp);
 515 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 516 #ifdef CONFIG_HOTPLUG_CPU
 517 static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 518                                      struct rcu_node *rnp,
 519                                      struct rcu_data *rdp);
 520 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 521 static void rcu_preempt_check_callbacks(int cpu);
 522 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
 523 #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
 524 static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 525                                bool wake);
 526 #endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
 527 static void __init __rcu_init_preempt(void);
 528 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 529 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 530 static void invoke_rcu_callbacks_kthread(void);
 531 static bool rcu_is_callbacks_kthread(void);
 532 #ifdef CONFIG_RCU_BOOST
 533 static void rcu_preempt_do_callbacks(void);
 534 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 535                                                  struct rcu_node *rnp);
 536 #endif /* #ifdef CONFIG_RCU_BOOST */
 537 static void rcu_prepare_kthreads(int cpu);
 538 static void rcu_cleanup_after_idle(int cpu);
 539 static void rcu_prepare_for_idle(int cpu);
 540 static void rcu_idle_count_callbacks_posted(void);
 541 static void print_cpu_stall_info_begin(void);
 542 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
 543 static void print_cpu_stall_info_end(void);
 544 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 545 static void increment_cpu_stall_ticks(void);
 546 static int rcu_nocb_needs_gp(struct rcu_state *rsp);
 547 static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
 548 static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp);
 549 static void rcu_init_one_nocb(struct rcu_node *rnp);
 550 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
 551                             bool lazy);
 552 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
 553                                       struct rcu_data *rdp);
 554 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 555 static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp);
 556 static void rcu_kick_nohz_cpu(int cpu);
 557 static bool init_nocb_callback_list(struct rcu_data *rdp);
 558 static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq);
 559 static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq);
 560 static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
 561                                   unsigned long *maxj);
 562 static bool is_sysidle_rcu_state(struct rcu_state *rsp);
 563 static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
 564                                   unsigned long maxj);
 565 static void rcu_bind_gp_kthread(void);
 566 static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp);
 567
 568 #endif /* #ifndef RCU_TREE_NONCORE */
 569
 570 #ifdef CONFIG_RCU_TRACE
 571 #ifdef CONFIG_RCU_NOCB_CPU
 572 /* Sum up queue lengths for tracing. */
 573 static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
 574 {
 575         *ql = atomic_long_read(&rdp->nocb_q_count) + rdp->nocb_p_count;
 576         *qll = atomic_long_read(&rdp->nocb_q_count_lazy) + rdp->nocb_p_count_lazy;
 577 }
 578 #else /* #ifdef CONFIG_RCU_NOCB_CPU */
 579 static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
 580 {
 581         *ql = 0;
 582         *qll = 0;
 583 }
 584 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
 585 #endif /* #ifdef CONFIG_RCU_TRACE */