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TOMOYO Linux Cross Reference
Linux/include/linux/srcutree.h

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  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
146 

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