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 has not been tested, so there is probably some
  35  * bug somewhere.
  36  */
  37 #define MAX_RCU_LVLS 3
  38 #define RCU_FANOUT            (CONFIG_RCU_FANOUT)
  39 #define RCU_FANOUT_SQ         (RCU_FANOUT * RCU_FANOUT)
  40 #define RCU_FANOUT_CUBE       (RCU_FANOUT_SQ * RCU_FANOUT)
  41
  42 #if NR_CPUS <= RCU_FANOUT
  43 #  define NUM_RCU_LVLS        1
  44 #  define NUM_RCU_LVL_0       1
  45 #  define NUM_RCU_LVL_1       (NR_CPUS)
  46 #  define NUM_RCU_LVL_2       0
  47 #  define NUM_RCU_LVL_3       0
  48 #elif NR_CPUS <= RCU_FANOUT_SQ
  49 #  define NUM_RCU_LVLS        2
  50 #  define NUM_RCU_LVL_0       1
  51 #  define NUM_RCU_LVL_1       (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT)
  52 #  define NUM_RCU_LVL_2       (NR_CPUS)
  53 #  define NUM_RCU_LVL_3       0
  54 #elif NR_CPUS <= RCU_FANOUT_CUBE
  55 #  define NUM_RCU_LVLS        3
  56 #  define NUM_RCU_LVL_0       1
  57 #  define NUM_RCU_LVL_1       (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ)
  58 #  define NUM_RCU_LVL_2       (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT))
  59 #  define NUM_RCU_LVL_3       NR_CPUS
  60 #else
  61 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
  62 #endif /* #if (NR_CPUS) <= RCU_FANOUT */
  63
  64 #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
  65 #define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
  66
  67 /*
  68  * Dynticks per-CPU state.
  69  */
  70 struct rcu_dynticks {
  71         int dynticks_nesting;   /* Track nesting level, sort of. */
  72         int dynticks;           /* Even value for dynticks-idle, else odd. */
  73         int dynticks_nmi;       /* Even value for either dynticks-idle or */
  74                                 /*  not in nmi handler, else odd.  So this */
  75                                 /*  remains even for nmi from irq handler. */
  76 };
  77
  78 /*
  79  * Definition for node within the RCU grace-period-detection hierarchy.
  80  */
  81 struct rcu_node {
  82         spinlock_t lock;
  83         long    gpnum;          /* Current grace period for this node. */
  84                                 /*  This will either be equal to or one */
  85                                 /*  behind the root rcu_node's gpnum. */
  86         unsigned long qsmask;   /* CPUs or groups that need to switch in */
  87                                 /*  order for current grace period to proceed.*/
  88         unsigned long qsmaskinit;
  89                                 /* Per-GP initialization for qsmask. */
  90         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
  91         int     grplo;          /* lowest-numbered CPU or group here. */
  92         int     grphi;          /* highest-numbered CPU or group here. */
  93         u8      grpnum;         /* CPU/group number for next level up. */
  94         u8      level;          /* root is at level 0. */
  95         struct rcu_node *parent;
  96         struct list_head blocked_tasks[2];
  97                                 /* Tasks blocked in RCU read-side critsect. */
  98 } ____cacheline_internodealigned_in_smp;
  99
 100 /* Index values for nxttail array in struct rcu_data. */
 101 #define RCU_DONE_TAIL           0       /* Also RCU_WAIT head. */
 102 #define RCU_WAIT_TAIL           1       /* Also RCU_NEXT_READY head. */
 103 #define RCU_NEXT_READY_TAIL     2       /* Also RCU_NEXT head. */
 104 #define RCU_NEXT_TAIL           3
 105 #define RCU_NEXT_SIZE           4
 106
 107 /* Per-CPU data for read-copy update. */
 108 struct rcu_data {
 109         /* 1) quiescent-state and grace-period handling : */
 110         long            completed;      /* Track rsp->completed gp number */
 111                                         /*  in order to detect GP end. */
 112         long            gpnum;          /* Highest gp number that this CPU */
 113                                         /*  is aware of having started. */
 114         long            passed_quiesc_completed;
 115                                         /* Value of completed at time of qs. */
 116         bool            passed_quiesc;  /* User-mode/idle loop etc. */
 117         bool            qs_pending;     /* Core waits for quiesc state. */
 118         bool            beenonline;     /* CPU online at least once. */
 119         bool            preemptable;    /* Preemptable RCU? */
 120         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 121         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 122
 123         /* 2) batch handling */
 124         /*
 125          * If nxtlist is not NULL, it is partitioned as follows.
 126          * Any of the partitions might be empty, in which case the
 127          * pointer to that partition will be equal to the pointer for
 128          * the following partition.  When the list is empty, all of
 129          * the nxttail elements point to nxtlist, which is NULL.
 130          *
 131          * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]):
 132          *      Entries that might have arrived after current GP ended
 133          * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
 134          *      Entries known to have arrived before current GP ended
 135          * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
 136          *      Entries that batch # <= ->completed - 1: waiting for current GP
 137          * [nxtlist, *nxttail[RCU_DONE_TAIL]):
 138          *      Entries that batch # <= ->completed
 139          *      The grace period for these entries has completed, and
 140          *      the other grace-period-completed entries may be moved
 141          *      here temporarily in rcu_process_callbacks().
 142          */
 143         struct rcu_head *nxtlist;
 144         struct rcu_head **nxttail[RCU_NEXT_SIZE];
 145         long            qlen;           /* # of queued callbacks */
 146         long            blimit;         /* Upper limit on a processed batch */
 147
 148 #ifdef CONFIG_NO_HZ
 149         /* 3) dynticks interface. */
 150         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
 151         int dynticks_snap;              /* Per-GP tracking for dynticks. */
 152         int dynticks_nmi_snap;          /* Per-GP tracking for dynticks_nmi. */
 153 #endif /* #ifdef CONFIG_NO_HZ */
 154
 155         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
 156 #ifdef CONFIG_NO_HZ
 157         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
 158 #endif /* #ifdef CONFIG_NO_HZ */
 159         unsigned long offline_fqs;      /* Kicked due to being offline. */
 160         unsigned long resched_ipi;      /* Sent a resched IPI. */
 161
 162         /* 5) __rcu_pending() statistics. */
 163         long n_rcu_pending;             /* rcu_pending() calls since boot. */
 164         long n_rp_qs_pending;
 165         long n_rp_cb_ready;
 166         long n_rp_cpu_needs_gp;
 167         long n_rp_gp_completed;
 168         long n_rp_gp_started;
 169         long n_rp_need_fqs;
 170         long n_rp_need_nothing;
 171
 172         int cpu;
 173 };
 174
 175 /* Values for signaled field in struct rcu_state. */
 176 #define RCU_GP_INIT             0       /* Grace period being initialized. */
 177 #define RCU_SAVE_DYNTICK        1       /* Need to scan dyntick state. */
 178 #define RCU_FORCE_QS            2       /* Need to force quiescent state. */
 179 #ifdef CONFIG_NO_HZ
 180 #define RCU_SIGNAL_INIT         RCU_SAVE_DYNTICK
 181 #else /* #ifdef CONFIG_NO_HZ */
 182 #define RCU_SIGNAL_INIT         RCU_FORCE_QS
 183 #endif /* #else #ifdef CONFIG_NO_HZ */
 184
 185 #define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
 186 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
 187 #define RCU_SECONDS_TILL_STALL_CHECK   (10 * HZ)  /* for rsp->jiffies_stall */
 188 #define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ)  /* for rsp->jiffies_stall */
 189 #define RCU_STALL_RAT_DELAY             2         /* Allow other CPUs time */
 190                                                   /*  to take at least one */
 191                                                   /*  scheduling clock irq */
 192                                                   /*  before ratting on them. */
 193
 194 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
 195
 196 /*
 197  * RCU global state, including node hierarchy.  This hierarchy is
 198  * represented in "heap" form in a dense array.  The root (first level)
 199  * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 200  * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 201  * and the third level in ->node[m+1] and following (->node[m+1] referenced
 202  * by ->level[2]).  The number of levels is determined by the number of
 203  * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 204  * consisting of a single rcu_node.
 205  */
 206 struct rcu_state {
 207         struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 208         struct rcu_node *level[NUM_RCU_LVLS];   /* Hierarchy levels. */
 209         u32 levelcnt[MAX_RCU_LVLS + 1];         /* # nodes in each level. */
 210         u8 levelspread[NUM_RCU_LVLS];           /* kids/node in each level. */
 211         struct rcu_data *rda[NR_CPUS];          /* array of rdp pointers. */
 212
 213         /* The following fields are guarded by the root rcu_node's lock. */
 214
 215         u8      signaled ____cacheline_internodealigned_in_smp;
 216                                                 /* Force QS state. */
 217         long    gpnum;                          /* Current gp number. */
 218         long    completed;                      /* # of last completed gp. */
 219         spinlock_t onofflock;                   /* exclude on/offline and */
 220                                                 /*  starting new GP. */
 221         spinlock_t fqslock;                     /* Only one task forcing */
 222                                                 /*  quiescent states. */
 223         unsigned long jiffies_force_qs;         /* Time at which to invoke */
 224                                                 /*  force_quiescent_state(). */
 225         unsigned long n_force_qs;               /* Number of calls to */
 226                                                 /*  force_quiescent_state(). */
 227         unsigned long n_force_qs_lh;            /* ~Number of calls leaving */
 228                                                 /*  due to lock unavailable. */
 229         unsigned long n_force_qs_ngp;           /* Number of calls leaving */
 230                                                 /*  due to no GP active. */
 231 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
 232         unsigned long gp_start;                 /* Time at which GP started, */
 233                                                 /*  but in jiffies. */
 234         unsigned long jiffies_stall;            /* Time at which to check */
 235                                                 /*  for CPU stalls. */
 236 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
 237 #ifdef CONFIG_NO_HZ
 238         long dynticks_completed;                /* Value of completed @ snap. */
 239 #endif /* #ifdef CONFIG_NO_HZ */
 240 };
 241
 242 #ifdef RCU_TREE_NONCORE
 243
 244 /*
 245  * RCU implementation internal declarations:
 246  */
 247 extern struct rcu_state rcu_sched_state;
 248 DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 249
 250 extern struct rcu_state rcu_bh_state;
 251 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 252
 253 #ifdef CONFIG_TREE_PREEMPT_RCU
 254 extern struct rcu_state rcu_preempt_state;
 255 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 256 #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 257
 258 #endif /* #ifdef RCU_TREE_NONCORE */
 259