LXR linux/include/linux/srcutree.h

   1/* SPDX-License-Identifier: GPL-2.0+ */
   2/*
   3 * Sleepable Read-Copy Update mechanism for mutual exclusion,
   4 *      tree variant.
   5 *
   6 * Copyright (C) IBM Corporation, 2017
   7 *
   8 * Author: Paul McKenney <paulmck@linux.ibm.com>
   9 */
  10
  11#ifndef _LINUX_SRCU_TREE_H
  12#define _LINUX_SRCU_TREE_H
  13
  14#include <linux/rcu_node_tree.h>
  15#include <linux/completion.h>
  16
  17struct srcu_node;
  18struct srcu_struct;
  19
  20/*
  21 * Per-CPU structure feeding into leaf srcu_node, similar in function
  22 * to rcu_node.
  23 */
  24struct srcu_data {
  25        /* Read-side state. */
  26        unsigned long srcu_lock_count[2];       /* Locks per CPU. */
  27        unsigned long srcu_unlock_count[2];     /* Unlocks per CPU. */
  28
  29        /* Update-side state. */
  30        spinlock_t __private lock ____cacheline_internodealigned_in_smp;
  31        struct rcu_segcblist srcu_cblist;       /* List of callbacks.*/
  32        unsigned long srcu_gp_seq_needed;       /* Furthest future GP needed. */
  33        unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  34        bool srcu_cblist_invoking;              /* Invoking these CBs? */
  35        struct timer_list delay_work;           /* Delay for CB invoking */
  36        struct work_struct work;                /* Context for CB invoking. */
  37        struct rcu_head srcu_barrier_head;      /* For srcu_barrier() use. */
  38        struct srcu_node *mynode;               /* Leaf srcu_node. */
  39        unsigned long grpmask;                  /* Mask for leaf srcu_node */
  40                                                /*  ->srcu_data_have_cbs[]. */
  41        int cpu;
  42        struct srcu_struct *ssp;
  43};
  44
  45/*
  46 * Node in SRCU combining tree, similar in function to rcu_data.
  47 */
  48struct srcu_node {
  49        spinlock_t __private lock;
  50        unsigned long srcu_have_cbs[4];         /* GP seq for children having CBs, but only */
  51                                                /*  if greater than ->srcu_gq_seq. */
  52        unsigned long srcu_data_have_cbs[4];    /* Which srcu_data structs have CBs for given GP? */
  53        unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  54        struct srcu_node *srcu_parent;          /* Next up in tree. */
  55        int grplo;                              /* Least CPU for node. */
  56        int grphi;                              /* Biggest CPU for node. */
  57};
  58
  59/*
  60 * Per-SRCU-domain structure, similar in function to rcu_state.
  61 */
  62struct srcu_struct {
  63        struct srcu_node *node;                 /* Combining tree. */
  64        struct srcu_node *level[RCU_NUM_LVLS + 1];
  65                                                /* First node at each level. */
  66        int srcu_size_state;                    /* Small-to-big transition state. */
  67        struct mutex srcu_cb_mutex;             /* Serialize CB preparation. */
  68        spinlock_t __private lock;              /* Protect counters and size state. */
  69        struct mutex srcu_gp_mutex;             /* Serialize GP work. */
  70        unsigned int srcu_idx;                  /* Current rdr array element. */
  71        unsigned long srcu_gp_seq;              /* Grace-period seq #. */
  72        unsigned long srcu_gp_seq_needed;       /* Latest gp_seq needed. */
  73        unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  74        unsigned long srcu_gp_start;            /* Last GP start timestamp (jiffies) */
  75        unsigned long srcu_last_gp_end;         /* Last GP end timestamp (ns) */
  76        unsigned long srcu_size_jiffies;        /* Current contention-measurement interval. */
  77        unsigned long srcu_n_lock_retries;      /* Contention events in current interval. */
  78        unsigned long srcu_n_exp_nodelay;       /* # expedited no-delays in current GP phase. */
  79        struct srcu_data __percpu *sda;         /* Per-CPU srcu_data array. */
  80        bool sda_is_static;                     /* May ->sda be passed to free_percpu()? */
  81        unsigned long srcu_barrier_seq;         /* srcu_barrier seq #. */
  82        struct mutex srcu_barrier_mutex;        /* Serialize barrier ops. */
  83        struct completion srcu_barrier_completion;
  84                                                /* Awaken barrier rq at end. */
  85        atomic_t srcu_barrier_cpu_cnt;          /* # CPUs not yet posting a */
  86                                                /*  callback for the barrier */
  87                                                /*  operation. */
  88        unsigned long reschedule_jiffies;
  89        unsigned long reschedule_count;
  90        struct delayed_work work;
  91        struct lockdep_map dep_map;
  92};
  93
  94/* Values for size state variable (->srcu_size_state). */
  95#define SRCU_SIZE_SMALL         0
  96#define SRCU_SIZE_ALLOC         1
  97#define SRCU_SIZE_WAIT_BARRIER  2
  98#define SRCU_SIZE_WAIT_CALL     3
  99#define SRCU_SIZE_WAIT_CBS1     4
 100#define SRCU_SIZE_WAIT_CBS2     5
 101#define SRCU_SIZE_WAIT_CBS3     6
 102#define SRCU_SIZE_WAIT_CBS4     7
 103#define SRCU_SIZE_BIG           8
 104
 105/* Values for state variable (bottom bits of ->srcu_gp_seq). */
 106#define SRCU_STATE_IDLE         0
 107#define SRCU_STATE_SCAN1        1
 108#define SRCU_STATE_SCAN2        2
 109
 110#define __SRCU_STRUCT_INIT(name, pcpu_name)                             \
 111{                                                                       \
 112        .sda = &pcpu_name,                                              \
 113        .lock = __SPIN_LOCK_UNLOCKED(name.lock),                        \
 114        .srcu_gp_seq_needed = -1UL,                                     \
 115        .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),         \
 116        __SRCU_DEP_MAP_INIT(name)                                       \
 117}
 118
 119/*
 120 * Define and initialize a srcu struct at build time.
 121 * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
 122 *
 123 * Note that although DEFINE_STATIC_SRCU() hides the name from other
 124 * files, the per-CPU variable rules nevertheless require that the
 125 * chosen name be globally unique.  These rules also prohibit use of
 126 * DEFINE_STATIC_SRCU() within a function.  If these rules are too
 127 * restrictive, declare the srcu_struct manually.  For example, in
 128 * each file:
 129 *
 130 *      static struct srcu_struct my_srcu;
 131 *
 132 * Then, before the first use of each my_srcu, manually initialize it:
 133 *
 134 *      init_srcu_struct(&my_srcu);
 135 *
 136 * See include/linux/percpu-defs.h for the rules on per-CPU variables.
 137 */
 138#ifdef MODULE
 139# define __DEFINE_SRCU(name, is_static)                                 \
 140        is_static struct srcu_struct name;                              \
 141        extern struct srcu_struct * const __srcu_struct_##name;         \
 142        struct srcu_struct * const __srcu_struct_##name                 \
 143                __section("___srcu_struct_ptrs") = &name
 144#else
 145# define __DEFINE_SRCU(name, is_static)                                 \
 146        static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);      \
 147        is_static struct srcu_struct name =                             \
 148                __SRCU_STRUCT_INIT(name, name##_srcu_data)
 149#endif
 150#define DEFINE_SRCU(name)               __DEFINE_SRCU(name, /* not static */)
 151#define DEFINE_STATIC_SRCU(name)        __DEFINE_SRCU(name, static)
 152
 153void synchronize_srcu_expedited(struct srcu_struct *ssp);
 154void srcu_barrier(struct srcu_struct *ssp);
 155void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
 156
 157#endif
 158