Linux kernel mirror (for testing)
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1/*
2 * Sleepable Read-Copy Update mechanism for mutual exclusion,
3 * tiny 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_TINY_H
25#define _LINUX_SRCU_TINY_H
26
27#include <linux/swait.h>
28
29struct srcu_struct {
30 short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */
31 short srcu_idx; /* Current reader array element. */
32 u8 srcu_gp_running; /* GP workqueue running? */
33 u8 srcu_gp_waiting; /* GP waiting for readers? */
34 struct swait_queue_head srcu_wq;
35 /* Last srcu_read_unlock() wakes GP. */
36 struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */
37 struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */
38 struct work_struct srcu_work; /* For driving grace periods. */
39#ifdef CONFIG_DEBUG_LOCK_ALLOC
40 struct lockdep_map dep_map;
41#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
42};
43
44void srcu_drive_gp(struct work_struct *wp);
45
46#define __SRCU_STRUCT_INIT(name) \
47{ \
48 .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
49 .srcu_cb_tail = &name.srcu_cb_head, \
50 .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \
51 __SRCU_DEP_MAP_INIT(name) \
52}
53
54/*
55 * This odd _STATIC_ arrangement is needed for API compatibility with
56 * Tree SRCU, which needs some per-CPU data.
57 */
58#define DEFINE_SRCU(name) \
59 struct srcu_struct name = __SRCU_STRUCT_INIT(name)
60#define DEFINE_STATIC_SRCU(name) \
61 static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
62
63void synchronize_srcu(struct srcu_struct *sp);
64
65/*
66 * Counts the new reader in the appropriate per-CPU element of the
67 * srcu_struct. Can be invoked from irq/bh handlers, but the matching
68 * __srcu_read_unlock() must be in the same handler instance. Returns an
69 * index that must be passed to the matching srcu_read_unlock().
70 */
71static inline int __srcu_read_lock(struct srcu_struct *sp)
72{
73 int idx;
74
75 idx = READ_ONCE(sp->srcu_idx);
76 WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1);
77 return idx;
78}
79
80static inline void synchronize_srcu_expedited(struct srcu_struct *sp)
81{
82 synchronize_srcu(sp);
83}
84
85static inline void srcu_barrier(struct srcu_struct *sp)
86{
87 synchronize_srcu(sp);
88}
89
90/* Defined here to avoid size increase for non-torture kernels. */
91static inline void srcu_torture_stats_print(struct srcu_struct *sp,
92 char *tt, char *tf)
93{
94 int idx;
95
96 idx = READ_ONCE(sp->srcu_idx) & 0x1;
97 pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
98 tt, tf, idx,
99 READ_ONCE(sp->srcu_lock_nesting[!idx]),
100 READ_ONCE(sp->srcu_lock_nesting[idx]));
101}
102
103#endif