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