include/linux/srcutree.h

   1 /*
   2  * Sleepable Read-Copy Update mechanism for mutual exclusion,
   3  *      tree variant.
   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, you can access it online at
  17  * http://www.gnu.org/licenses/gpl-2.0.html.
  18  *
  19  * Copyright (C) IBM Corporation, 2017
  20  *
  21  * Author: Paul McKenney <paulmck@us.ibm.com>
  22  */
  23
  24 #ifndef _LINUX_SRCU_TREE_H
  25 #define _LINUX_SRCU_TREE_H
  26
  27 #include <linux/rcu_node_tree.h>
  28 #include <linux/completion.h>
  29
  30 struct srcu_node;
  31 struct srcu_struct;
  32
  33 /*
  34  * Per-CPU structure feeding into leaf srcu_node, similar in function
  35  * to rcu_node.
  36  */
  37 struct srcu_data {
  38         /* Read-side state. */
  39         unsigned long srcu_lock_count[2];       /* Locks per CPU. */
  40         unsigned long srcu_unlock_count[2];     /* Unlocks per CPU. */
  41
  42         /* Update-side state. */
  43         raw_spinlock_t __private lock ____cacheline_internodealigned_in_smp;
  44         struct rcu_segcblist srcu_cblist;       /* List of callbacks.*/
  45         unsigned long srcu_gp_seq_needed;       /* Furthest future GP needed. */
  46         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  47         bool srcu_cblist_invoking;              /* Invoking these CBs? */
  48         struct delayed_work work;               /* Context for CB invoking. */
  49         struct rcu_head srcu_barrier_head;      /* For srcu_barrier() use. */
  50         struct srcu_node *mynode;               /* Leaf srcu_node. */
  51         unsigned long grpmask;                  /* Mask for leaf srcu_node */
  52                                                 /*  ->srcu_data_have_cbs[]. */
  53         int cpu;
  54         struct srcu_struct *sp;
  55 };
  56
  57 /*
  58  * Node in SRCU combining tree, similar in function to rcu_data.
  59  */
  60 struct srcu_node {
  61         raw_spinlock_t __private lock;
  62         unsigned long srcu_have_cbs[4];         /* GP seq for children */
  63                                                 /*  having CBs, but only */
  64                                                 /*  is > ->srcu_gq_seq. */
  65         unsigned long srcu_data_have_cbs[4];    /* Which srcu_data structs */
  66                                                 /*  have CBs for given GP? */
  67         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  68         struct srcu_node *srcu_parent;          /* Next up in tree. */
  69         int grplo;                              /* Least CPU for node. */
  70         int grphi;                              /* Biggest CPU for node. */
  71 };
  72
  73 /*
  74  * Per-SRCU-domain structure, similar in function to rcu_state.
  75  */
  76 struct srcu_struct {
  77         struct srcu_node node[NUM_RCU_NODES];   /* Combining tree. */
  78         struct srcu_node *level[RCU_NUM_LVLS + 1];
  79                                                 /* First node at each level. */
  80         struct mutex srcu_cb_mutex;             /* Serialize CB preparation. */
  81         raw_spinlock_t __private lock;          /* Protect counters */
  82         struct mutex srcu_gp_mutex;             /* Serialize GP work. */
  83         unsigned int srcu_idx;                  /* Current rdr array element. */
  84         unsigned long srcu_gp_seq;              /* Grace-period seq #. */
  85         unsigned long srcu_gp_seq_needed;       /* Latest gp_seq needed. */
  86         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
  87         unsigned long srcu_last_gp_end;         /* Last GP end timestamp (ns) */
  88         struct srcu_data __percpu *sda;         /* Per-CPU srcu_data array. */
  89         unsigned long srcu_barrier_seq;         /* srcu_barrier seq #. */
  90         struct mutex srcu_barrier_mutex;        /* Serialize barrier ops. */
  91         struct completion srcu_barrier_completion;
  92                                                 /* Awaken barrier rq at end. */
  93         atomic_t srcu_barrier_cpu_cnt;          /* # CPUs not yet posting a */
  94                                                 /*  callback for the barrier */
  95                                                 /*  operation. */
  96         struct delayed_work work;
  97 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  98         struct lockdep_map dep_map;
  99 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 100 };
 101
 102 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
 103 #define SRCU_STATE_IDLE         0
 104 #define SRCU_STATE_SCAN1        1
 105 #define SRCU_STATE_SCAN2        2
 106
 107 void process_srcu(struct work_struct *work);
 108
 109 #define __SRCU_STRUCT_INIT(name)                                        \
 110         {                                                               \
 111                 .sda = &name##_srcu_data,                               \
 112                 .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock),            \
 113                 .srcu_gp_seq_needed = 0 - 1,                            \
 114                 __SRCU_DEP_MAP_INIT(name)                               \
 115         }
 116
 117 /*
 118  * Define and initialize a srcu struct at build time.
 119  * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
 120  *
 121  * Note that although DEFINE_STATIC_SRCU() hides the name from other
 122  * files, the per-CPU variable rules nevertheless require that the
 123  * chosen name be globally unique.  These rules also prohibit use of
 124  * DEFINE_STATIC_SRCU() within a function.  If these rules are too
 125  * restrictive, declare the srcu_struct manually.  For example, in
 126  * each file:
 127  *
 128  *      static struct srcu_struct my_srcu;
 129  *
 130  * Then, before the first use of each my_srcu, manually initialize it:
 131  *
 132  *      init_srcu_struct(&my_srcu);
 133  *
 134  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
 135  */
 136 #define __DEFINE_SRCU(name, is_static)                                  \
 137         static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\
 138         is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
 139 #define DEFINE_SRCU(name)               __DEFINE_SRCU(name, /* not static */)
 140 #define DEFINE_STATIC_SRCU(name)        __DEFINE_SRCU(name, static)
 141
 142 void synchronize_srcu_expedited(struct srcu_struct *sp);
 143 void srcu_barrier(struct srcu_struct *sp);
 144
 145 #endif