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 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 */
48struct 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 */
64struct 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#define __DEFINE_SRCU(name, is_static) \
124 static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\
125 is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name##_srcu_data)
126#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
127#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
128
129void synchronize_srcu_expedited(struct srcu_struct *ssp);
130void srcu_barrier(struct srcu_struct *ssp);
131void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
132
133#endif
134