Home Home > GIT Browse
summaryrefslogtreecommitdiff
blob: 44d6606b83257acde72fe92435de6245fe77131e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
// SPDX-License-Identifier: GPL-2.0+
/*
 * Sleepable Read-Copy Update mechanism for mutual exclusion,
 *	tiny version for non-preemptible single-CPU use.
 *
 * Copyright (C) IBM Corporation, 2017
 *
 * Author: Paul McKenney <paulmck@linux.ibm.com>
 */

#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/preempt.h>
#include <linux/rcupdate_wait.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/srcu.h>

#include <linux/rcu_node_tree.h>
#include "rcu_segcblist.h"
#include "rcu.h"

int rcu_scheduler_active __read_mostly;
static LIST_HEAD(srcu_boot_list);
static bool srcu_init_done;

static int init_srcu_struct_fields(struct srcu_struct *ssp)
{
	ssp->srcu_lock_nesting[0] = 0;
	ssp->srcu_lock_nesting[1] = 0;
	init_swait_queue_head(&ssp->srcu_wq);
	ssp->srcu_cb_head = NULL;
	ssp->srcu_cb_tail = &ssp->srcu_cb_head;
	ssp->srcu_gp_running = false;
	ssp->srcu_gp_waiting = false;
	ssp->srcu_idx = 0;
	INIT_WORK(&ssp->srcu_work, srcu_drive_gp);
	INIT_LIST_HEAD(&ssp->srcu_work.entry);
	return 0;
}

#ifdef CONFIG_DEBUG_LOCK_ALLOC

int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
		       struct lock_class_key *key)
{
	/* Don't re-initialize a lock while it is held. */
	debug_check_no_locks_freed((void *)ssp, sizeof(*ssp));
	lockdep_init_map(&ssp->dep_map, name, key, 0);
	return init_srcu_struct_fields(ssp);
}
EXPORT_SYMBOL_GPL(__init_srcu_struct);

#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

/*
 * init_srcu_struct - initialize a sleep-RCU structure
 * @ssp: structure to initialize.
 *
 * Must invoke this on a given srcu_struct before passing that srcu_struct
 * to any other function.  Each srcu_struct represents a separate domain
 * of SRCU protection.
 */
int init_srcu_struct(struct srcu_struct *ssp)
{
	return init_srcu_struct_fields(ssp);
}
EXPORT_SYMBOL_GPL(init_srcu_struct);

#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

/*
 * cleanup_srcu_struct - deconstruct a sleep-RCU structure
 * @ssp: structure to clean up.
 *
 * Must invoke this after you are finished using a given srcu_struct that
 * was initialized via init_srcu_struct(), else you leak memory.
 */
void cleanup_srcu_struct(struct srcu_struct *ssp)
{
	WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]);
	flush_work(&ssp->srcu_work);
	WARN_ON(ssp->srcu_gp_running);
	WARN_ON(ssp->srcu_gp_waiting);
	WARN_ON(ssp->srcu_cb_head);
	WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail);
}
EXPORT_SYMBOL_GPL(cleanup_srcu_struct);

/*
 * Removes the count for the old reader from the appropriate element of
 * the srcu_struct.
 */
void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
	int newval = ssp->srcu_lock_nesting[idx] - 1;

	WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval);
	if (!newval && READ_ONCE(ssp->srcu_gp_waiting))
		swake_up_one(&ssp->srcu_wq);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);

/*
 * Workqueue handler to drive one grace period and invoke any callbacks
 * that become ready as a result.  Single-CPU and !PREEMPT operation
 * means that we get away with murder on synchronization.  ;-)
 */
void srcu_drive_gp(struct work_struct *wp)
{
	int idx;
	struct rcu_head *lh;
	struct rcu_head *rhp;
	struct srcu_struct *ssp;

	ssp = container_of(wp, struct srcu_struct, srcu_work);
	if (ssp->srcu_gp_running || !READ_ONCE(ssp->srcu_cb_head))
		return; /* Already running or nothing to do. */

	/* Remove recently arrived callbacks and wait for readers. */
	WRITE_ONCE(ssp->srcu_gp_running, true);
	local_irq_disable();
	lh = ssp->srcu_cb_head;
	ssp->srcu_cb_head = NULL;
	ssp->srcu_cb_tail = &ssp->srcu_cb_head;
	local_irq_enable();
	idx = ssp->srcu_idx;
	WRITE_ONCE(ssp->srcu_idx, !ssp->srcu_idx);
	WRITE_ONCE(ssp->srcu_gp_waiting, true);  /* srcu_read_unlock() wakes! */
	swait_event_exclusive(ssp->srcu_wq, !READ_ONCE(ssp->srcu_lock_nesting[idx]));
	WRITE_ONCE(ssp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */

	/* Invoke the callbacks we removed above. */
	while (lh) {
		rhp = lh;
		lh = lh->next;
		local_bh_disable();
		rhp->func(rhp);
		local_bh_enable();
	}

	/*
	 * Enable rescheduling, and if there are more callbacks,
	 * reschedule ourselves.  This can race with a call_srcu()
	 * at interrupt level, but the ->srcu_gp_running checks will
	 * straighten that out.
	 */
	WRITE_ONCE(ssp->srcu_gp_running, false);
	if (READ_ONCE(ssp->srcu_cb_head))
		schedule_work(&ssp->srcu_work);
}
EXPORT_SYMBOL_GPL(srcu_drive_gp);

/*
 * Enqueue an SRCU callback on the specified srcu_struct structure,
 * initiating grace-period processing if it is not already running.
 */
void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
	       rcu_callback_t func)
{
	unsigned long flags;

	rhp->func = func;
	rhp->next = NULL;
	local_irq_save(flags);
	*ssp->srcu_cb_tail = rhp;
	ssp->srcu_cb_tail = &rhp->next;
	local_irq_restore(flags);
	if (!READ_ONCE(ssp->srcu_gp_running)) {
		if (likely(srcu_init_done))
			schedule_work(&ssp->srcu_work);
		else if (list_empty(&ssp->srcu_work.entry))
			list_add(&ssp->srcu_work.entry, &srcu_boot_list);
	}
}
EXPORT_SYMBOL_GPL(call_srcu);

/*
 * synchronize_srcu - wait for prior SRCU read-side critical-section completion
 */
void synchronize_srcu(struct srcu_struct *ssp)
{
	struct rcu_synchronize rs;

	init_rcu_head_on_stack(&rs.head);
	init_completion(&rs.completion);
	call_srcu(ssp, &rs.head, wakeme_after_rcu);
	wait_for_completion(&rs.completion);
	destroy_rcu_head_on_stack(&rs.head);
}
EXPORT_SYMBOL_GPL(synchronize_srcu);

/* Lockdep diagnostics.  */
void __init rcu_scheduler_starting(void)
{
	rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
}

/*
 * Queue work for srcu_struct structures with early boot callbacks.
 * The work won't actually execute until the workqueue initialization
 * phase that takes place after the scheduler starts.
 */
void __init srcu_init(void)
{
	struct srcu_struct *ssp;

	srcu_init_done = true;
	while (!list_empty(&srcu_boot_list)) {
		ssp = list_first_entry(&srcu_boot_list,
				      struct srcu_struct, srcu_work.entry);
		list_del_init(&ssp->srcu_work.entry);
		schedule_work(&ssp->srcu_work);
	}
}