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Linux/include/linux/srcutree.h

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  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 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 86         struct lockdep_map dep_map;
 87 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 88 };
 89 
 90 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
 91 #define SRCU_STATE_IDLE         0
 92 #define SRCU_STATE_SCAN1        1
 93 #define SRCU_STATE_SCAN2        2
 94 
 95 #define __SRCU_STRUCT_INIT(name, pcpu_name)                             \
 96 {                                                                       \
 97         .sda = &pcpu_name,                                              \
 98         .lock = __SPIN_LOCK_UNLOCKED(name.lock),                        \
 99         .srcu_gp_seq_needed = -1UL,                                     \
100         .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),         \
101         __SRCU_DEP_MAP_INIT(name)                                       \
102 }
103 
104 /*
105  * Define and initialize a srcu struct at build time.
106  * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
107  *
108  * Note that although DEFINE_STATIC_SRCU() hides the name from other
109  * files, the per-CPU variable rules nevertheless require that the
110  * chosen name be globally unique.  These rules also prohibit use of
111  * DEFINE_STATIC_SRCU() within a function.  If these rules are too
112  * restrictive, declare the srcu_struct manually.  For example, in
113  * each file:
114  *
115  *      static struct srcu_struct my_srcu;
116  *
117  * Then, before the first use of each my_srcu, manually initialize it:
118  *
119  *      init_srcu_struct(&my_srcu);
120  *
121  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
122  */
123 #ifdef MODULE
124 # define __DEFINE_SRCU(name, is_static)                                 \
125         is_static struct srcu_struct name;                              \
126         struct srcu_struct * const __srcu_struct_##name                 \
127                 __section("___srcu_struct_ptrs") = &name
128 #else
129 # define __DEFINE_SRCU(name, is_static)                                 \
130         static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);      \
131         is_static struct srcu_struct name =                             \
132                 __SRCU_STRUCT_INIT(name, name##_srcu_data)
133 #endif
134 #define DEFINE_SRCU(name)               __DEFINE_SRCU(name, /* not static */)
135 #define DEFINE_STATIC_SRCU(name)        __DEFINE_SRCU(name, static)
136 
137 void synchronize_srcu_expedited(struct srcu_struct *ssp);
138 void srcu_barrier(struct srcu_struct *ssp);
139 void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
140 
141 #endif
142 

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