blob: 32dfd6522548507eef33b90fb2bb4befa118def6 [file] [log] [blame]
Paul E. McKenneyd8be8172017-03-25 09:59:38 -07001/*
2 * Sleepable Read-Copy Update mechanism for mutual exclusion,
3 * tiny version for non-preemptible single-CPU use.
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#include <linux/export.h>
25#include <linux/mutex.h>
26#include <linux/preempt.h>
27#include <linux/rcupdate_wait.h>
28#include <linux/sched.h>
29#include <linux/delay.h>
30#include <linux/srcu.h>
31
32#include <linux/rcu_node_tree.h>
Ingo Molnar45753c52017-05-02 10:31:18 +020033#include "rcu_segcblist.h"
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070034#include "rcu.h"
35
Paul E. McKenney825c5bd2017-05-26 16:16:40 -070036int rcu_scheduler_active __read_mostly;
Paul E. McKenneye0fcba92018-08-14 08:45:54 -070037static LIST_HEAD(srcu_boot_list);
38static bool srcu_init_done;
Paul E. McKenney825c5bd2017-05-26 16:16:40 -070039
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070040static int init_srcu_struct_fields(struct srcu_struct *ssp)
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070041{
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070042 ssp->srcu_lock_nesting[0] = 0;
43 ssp->srcu_lock_nesting[1] = 0;
44 init_swait_queue_head(&ssp->srcu_wq);
45 ssp->srcu_cb_head = NULL;
46 ssp->srcu_cb_tail = &ssp->srcu_cb_head;
47 ssp->srcu_gp_running = false;
48 ssp->srcu_gp_waiting = false;
49 ssp->srcu_idx = 0;
50 INIT_WORK(&ssp->srcu_work, srcu_drive_gp);
51 INIT_LIST_HEAD(&ssp->srcu_work.entry);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070052 return 0;
53}
54
55#ifdef CONFIG_DEBUG_LOCK_ALLOC
56
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070057int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070058 struct lock_class_key *key)
59{
60 /* Don't re-initialize a lock while it is held. */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070061 debug_check_no_locks_freed((void *)ssp, sizeof(*ssp));
62 lockdep_init_map(&ssp->dep_map, name, key, 0);
63 return init_srcu_struct_fields(ssp);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070064}
65EXPORT_SYMBOL_GPL(__init_srcu_struct);
66
67#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
68
69/*
70 * init_srcu_struct - initialize a sleep-RCU structure
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070071 * @ssp: structure to initialize.
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070072 *
73 * Must invoke this on a given srcu_struct before passing that srcu_struct
74 * to any other function. Each srcu_struct represents a separate domain
75 * of SRCU protection.
76 */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070077int init_srcu_struct(struct srcu_struct *ssp)
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070078{
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070079 return init_srcu_struct_fields(ssp);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070080}
81EXPORT_SYMBOL_GPL(init_srcu_struct);
82
83#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
84
85/*
86 * cleanup_srcu_struct - deconstruct a sleep-RCU structure
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070087 * @ssp: structure to clean up.
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070088 *
89 * Must invoke this after you are finished using a given srcu_struct that
90 * was initialized via init_srcu_struct(), else you leak memory.
91 */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070092void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced)
Paul E. McKenneyd8be8172017-03-25 09:59:38 -070093{
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070094 WARN_ON(ssp->srcu_lock_nesting[0] || ssp->srcu_lock_nesting[1]);
Paul E. McKenneyf7194ac2018-04-05 17:19:17 -070095 if (quiesced)
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070096 WARN_ON(work_pending(&ssp->srcu_work));
Paul E. McKenneyf7194ac2018-04-05 17:19:17 -070097 else
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -070098 flush_work(&ssp->srcu_work);
99 WARN_ON(ssp->srcu_gp_running);
100 WARN_ON(ssp->srcu_gp_waiting);
101 WARN_ON(ssp->srcu_cb_head);
102 WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700103}
Paul E. McKenneyf7194ac2018-04-05 17:19:17 -0700104EXPORT_SYMBOL_GPL(_cleanup_srcu_struct);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700105
106/*
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700107 * Removes the count for the old reader from the appropriate element of
Paolo Bonzinicdf7abc2017-05-31 14:03:10 +0200108 * the srcu_struct.
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700109 */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700110void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700111{
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700112 int newval = ssp->srcu_lock_nesting[idx] - 1;
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700113
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700114 WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval);
115 if (!newval && READ_ONCE(ssp->srcu_gp_waiting))
116 swake_up_one(&ssp->srcu_wq);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700117}
118EXPORT_SYMBOL_GPL(__srcu_read_unlock);
119
120/*
121 * Workqueue handler to drive one grace period and invoke any callbacks
122 * that become ready as a result. Single-CPU and !PREEMPT operation
123 * means that we get away with murder on synchronization. ;-)
124 */
125void srcu_drive_gp(struct work_struct *wp)
126{
127 int idx;
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700128 struct rcu_head *lh;
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700129 struct rcu_head *rhp;
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700130 struct srcu_struct *ssp;
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700131
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700132 ssp = container_of(wp, struct srcu_struct, srcu_work);
133 if (ssp->srcu_gp_running || !READ_ONCE(ssp->srcu_cb_head))
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700134 return; /* Already running or nothing to do. */
135
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700136 /* Remove recently arrived callbacks and wait for readers. */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700137 WRITE_ONCE(ssp->srcu_gp_running, true);
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700138 local_irq_disable();
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700139 lh = ssp->srcu_cb_head;
140 ssp->srcu_cb_head = NULL;
141 ssp->srcu_cb_tail = &ssp->srcu_cb_head;
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700142 local_irq_enable();
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700143 idx = ssp->srcu_idx;
144 WRITE_ONCE(ssp->srcu_idx, !ssp->srcu_idx);
145 WRITE_ONCE(ssp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */
146 swait_event_exclusive(ssp->srcu_wq, !READ_ONCE(ssp->srcu_lock_nesting[idx]));
147 WRITE_ONCE(ssp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700148
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700149 /* Invoke the callbacks we removed above. */
150 while (lh) {
151 rhp = lh;
152 lh = lh->next;
153 local_bh_disable();
154 rhp->func(rhp);
155 local_bh_enable();
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700156 }
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700157
158 /*
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700159 * Enable rescheduling, and if there are more callbacks,
160 * reschedule ourselves. This can race with a call_srcu()
161 * at interrupt level, but the ->srcu_gp_running checks will
162 * straighten that out.
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700163 */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700164 WRITE_ONCE(ssp->srcu_gp_running, false);
165 if (READ_ONCE(ssp->srcu_cb_head))
166 schedule_work(&ssp->srcu_work);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700167}
168EXPORT_SYMBOL_GPL(srcu_drive_gp);
169
170/*
171 * Enqueue an SRCU callback on the specified srcu_struct structure,
172 * initiating grace-period processing if it is not already running.
173 */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700174void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700175 rcu_callback_t func)
176{
177 unsigned long flags;
178
Paul E. McKenney2464dd92017-05-04 14:29:16 -0700179 rhp->func = func;
180 rhp->next = NULL;
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700181 local_irq_save(flags);
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700182 *ssp->srcu_cb_tail = rhp;
183 ssp->srcu_cb_tail = &rhp->next;
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700184 local_irq_restore(flags);
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700185 if (!READ_ONCE(ssp->srcu_gp_running)) {
Paul E. McKenneye0fcba92018-08-14 08:45:54 -0700186 if (likely(srcu_init_done))
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700187 schedule_work(&ssp->srcu_work);
188 else if (list_empty(&ssp->srcu_work.entry))
189 list_add(&ssp->srcu_work.entry, &srcu_boot_list);
Paul E. McKenneye0fcba92018-08-14 08:45:54 -0700190 }
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700191}
192EXPORT_SYMBOL_GPL(call_srcu);
193
194/*
195 * synchronize_srcu - wait for prior SRCU read-side critical-section completion
196 */
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700197void synchronize_srcu(struct srcu_struct *ssp)
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700198{
199 struct rcu_synchronize rs;
200
201 init_rcu_head_on_stack(&rs.head);
202 init_completion(&rs.completion);
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700203 call_srcu(ssp, &rs.head, wakeme_after_rcu);
Paul E. McKenneyd8be8172017-03-25 09:59:38 -0700204 wait_for_completion(&rs.completion);
205 destroy_rcu_head_on_stack(&rs.head);
206}
207EXPORT_SYMBOL_GPL(synchronize_srcu);
Paul E. McKenney825c5bd2017-05-26 16:16:40 -0700208
209/* Lockdep diagnostics. */
210void __init rcu_scheduler_starting(void)
211{
212 rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
213}
Paul E. McKenneye0fcba92018-08-14 08:45:54 -0700214
215/*
216 * Queue work for srcu_struct structures with early boot callbacks.
217 * The work won't actually execute until the workqueue initialization
218 * phase that takes place after the scheduler starts.
219 */
220void __init srcu_init(void)
221{
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700222 struct srcu_struct *ssp;
Paul E. McKenneye0fcba92018-08-14 08:45:54 -0700223
224 srcu_init_done = true;
225 while (!list_empty(&srcu_boot_list)) {
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700226 ssp = list_first_entry(&srcu_boot_list,
Paul E. McKenney4e6ea4e2018-08-14 14:41:49 -0700227 struct srcu_struct, srcu_work.entry);
Paul E. McKenneyaacb5d92018-10-28 10:32:51 -0700228 list_del_init(&ssp->srcu_work.entry);
229 schedule_work(&ssp->srcu_work);
Paul E. McKenneye0fcba92018-08-14 08:45:54 -0700230 }
231}