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
  17 struct srcu_node;
  18 struct srcu_struct;
  19
  20 /*
  21  * Per-CPU structure feeding into leaf srcu_node, similar in function
  22  * to rcu_node.
  23  */
  24 struct 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  */
  48 struct srcu_node {
  49         spinlock_t __private lock;
  50         unsigned long srcu_have_cbs[4];         /* GP seq for children */
  51                                                 /*  having CBs, but only */
  52                                                 /*  is > ->srcu_gq_seq. */
  53         unsigned long srcu_data_have_cbs[4];    /* Which srcu_data structs */
  54                                                 /*  have CBs for given GP? */
  55         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  56         struct srcu_node *srcu_parent;          /* Next up in tree. */
  57         int grplo;                              /* Least CPU for node. */
  58         int grphi;                              /* Biggest CPU for node. */
  59 };
  60
  61 /*
  62  * Per-SRCU-domain structure, similar in function to rcu_state.
  63  */
  64 struct srcu_struct {
  65         struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
  66         struct srcu_node *level[RCU_NUM_LVLS + 1];
  67                                                 /* First node at each level. */
  68         struct mutex srcu_cb_mutex;             /* Serialize CB preparation. */
  69         spinlock_t __private lock;              /* Protect counters */
  70         struct mutex srcu_gp_mutex;             /* Serialize GP work. */
  71         unsigned int srcu_idx;                  /* Current rdr array element. */
  72         unsigned long srcu_gp_seq;              /* Grace-period seq #. */
  73         unsigned long srcu_gp_seq_needed;       /* Latest gp_seq needed. */
  74         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  75         unsigned long srcu_last_gp_end;         /* Last GP end timestamp (ns) */
  76         struct srcu_data __percpu *sda;         /* Per-CPU srcu_data array. */
  77         unsigned long srcu_barrier_seq;         /* srcu_barrier seq #. */
  78         struct mutex srcu_barrier_mutex;        /* Serialize barrier ops. */
  79         struct completion srcu_barrier_completion;
  80                                                 /* Awaken barrier rq at end. */
  81         atomic_t srcu_barrier_cpu_cnt;          /* # CPUs not yet posting a */
  82                                                 /*  callback for the barrier */
  83                                                 /*  operation. */
  84         struct delayed_work work;
  85         struct lockdep_map dep_map;
  86 };
  87
  88 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
  89 #define SRCU_STATE_IDLE         0
  90 #define SRCU_STATE_SCAN1        1
  91 #define SRCU_STATE_SCAN2        2
  92
  93 #define __SRCU_STRUCT_INIT(name, pcpu_name)                             \
  94 {                                                                       \
  95         .sda = &pcpu_name,                                              \
  96         .lock = __SPIN_LOCK_UNLOCKED(name.lock),                        \
  97         .srcu_gp_seq_needed = -1UL,                                     \
  98         .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),         \
  99         __SRCU_DEP_MAP_INIT(name)                                       \
 100 }
 101
 102 /*
 103  * Define and initialize a srcu struct at build time.
 104  * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
 105  *
 106  * Note that although DEFINE_STATIC_SRCU() hides the name from other
 107  * files, the per-CPU variable rules nevertheless require that the
 108  * chosen name be globally unique.  These rules also prohibit use of
 109  * DEFINE_STATIC_SRCU() within a function.  If these rules are too
 110  * restrictive, declare the srcu_struct manually.  For example, in
 111  * each file:
 112  *
 113  *      static struct srcu_struct my_srcu;
 114  *
 115  * Then, before the first use of each my_srcu, manually initialize it:
 116  *
 117  *      init_srcu_struct(&my_srcu);
 118  *
 119  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
 120  */
 121 #ifdef MODULE
 122 # define __DEFINE_SRCU(name, is_static)                                 \
 123         is_static struct srcu_struct name;                              \
 124         struct srcu_struct * const __srcu_struct_##name                 \
 125                 __section("___srcu_struct_ptrs") = &name
 126 #else
 127 # define __DEFINE_SRCU(name, is_static)                                 \
 128         static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);      \
 129         is_static struct srcu_struct name =                             \
 130                 __SRCU_STRUCT_INIT(name, name##_srcu_data)
 131 #endif
 132 #define DEFINE_SRCU(name)               __DEFINE_SRCU(name, /* not static */)
 133 #define DEFINE_STATIC_SRCU(name)        __DEFINE_SRCU(name, static)
 134
 135 void synchronize_srcu_expedited(struct srcu_struct *ssp);
 136 void srcu_barrier(struct srcu_struct *ssp);
 137 void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
 138
 139 #endif