Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * Sleepable Read-Copy Update mechanism for mutual exclusion,
4 * tiny variant.
5 *
6 * Copyright (C) IBM Corporation, 2017
7 *
8 * Author: Paul McKenney <paulmck@linux.ibm.com>
9 */
10
11#ifndef _LINUX_SRCU_TINY_H
12#define _LINUX_SRCU_TINY_H
13
14#include <linux/swait.h>
15
16struct srcu_struct {
17 short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */
18 u8 srcu_gp_running; /* GP workqueue running? */
19 u8 srcu_gp_waiting; /* GP waiting for readers? */
20 unsigned long srcu_idx; /* Current reader array element in bit 0x2. */
21 unsigned long srcu_idx_max; /* Furthest future srcu_idx request. */
22 struct swait_queue_head srcu_wq;
23 /* Last srcu_read_unlock() wakes GP. */
24 struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */
25 struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */
26 struct work_struct srcu_work; /* For driving grace periods. */
27#ifdef CONFIG_DEBUG_LOCK_ALLOC
28 struct lockdep_map dep_map;
29#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
30};
31
32void srcu_drive_gp(struct work_struct *wp);
33
34#define __SRCU_STRUCT_INIT(name, __ignored, ___ignored) \
35{ \
36 .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
37 .srcu_cb_tail = &name.srcu_cb_head, \
38 .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \
39 __SRCU_DEP_MAP_INIT(name) \
40}
41
42/*
43 * This odd _STATIC_ arrangement is needed for API compatibility with
44 * Tree SRCU, which needs some per-CPU data.
45 */
46#define DEFINE_SRCU(name) \
47 struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
48#define DEFINE_STATIC_SRCU(name) \
49 static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
50
51// Dummy structure for srcu_notifier_head.
52struct srcu_usage { };
53#define __SRCU_USAGE_INIT(name) { }
54
55void synchronize_srcu(struct srcu_struct *ssp);
56
57/*
58 * Counts the new reader in the appropriate per-CPU element of the
59 * srcu_struct. Can be invoked from irq/bh handlers, but the matching
60 * __srcu_read_unlock() must be in the same handler instance. Returns an
61 * index that must be passed to the matching srcu_read_unlock().
62 */
63static inline int __srcu_read_lock(struct srcu_struct *ssp)
64{
65 int idx;
66
67 preempt_disable(); // Needed for PREEMPT_LAZY
68 idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
69 WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
70 preempt_enable();
71 return idx;
72}
73
74struct srcu_ctr;
75
76static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __percpu *scpp)
77{
78 return (int)(intptr_t)(struct srcu_ctr __force __kernel *)scpp;
79}
80
81static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ssp, int idx)
82{
83 return (struct srcu_ctr __percpu *)(intptr_t)idx;
84}
85
86static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp)
87{
88 return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp));
89}
90
91static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp)
92{
93 __srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp));
94}
95
96#define __srcu_read_lock_lite __srcu_read_lock
97#define __srcu_read_unlock_lite __srcu_read_unlock
98
99static inline void synchronize_srcu_expedited(struct srcu_struct *ssp)
100{
101 synchronize_srcu(ssp);
102}
103
104static inline void srcu_barrier(struct srcu_struct *ssp)
105{
106 synchronize_srcu(ssp);
107}
108
109#define srcu_check_read_flavor(ssp, read_flavor) do { } while (0)
110#define srcu_check_read_flavor_force(ssp, read_flavor) do { } while (0)
111
112/* Defined here to avoid size increase for non-torture kernels. */
113static inline void srcu_torture_stats_print(struct srcu_struct *ssp,
114 char *tt, char *tf)
115{
116 int idx;
117
118 idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1;
119 pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd) gp: %lu->%lu\n",
120 tt, tf, idx,
121 data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])),
122 data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])),
123 data_race(READ_ONCE(ssp->srcu_idx)),
124 data_race(READ_ONCE(ssp->srcu_idx_max)));
125}
126
127#endif