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