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1da177e4 LT |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
01c1c660 | 18 | * Copyright IBM Corporation, 2001 |
1da177e4 LT |
19 | * |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
a71fca58 | 22 | * |
1da177e4 LT |
23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
25 | * Papers: | |
26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf | |
27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) | |
28 | * | |
29 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
31 | * |
32 | */ | |
33 | #include <linux/types.h> | |
34 | #include <linux/kernel.h> | |
35 | #include <linux/init.h> | |
36 | #include <linux/spinlock.h> | |
37 | #include <linux/smp.h> | |
38 | #include <linux/interrupt.h> | |
39 | #include <linux/sched.h> | |
40 | #include <asm/atomic.h> | |
41 | #include <linux/bitops.h> | |
1da177e4 LT |
42 | #include <linux/percpu.h> |
43 | #include <linux/notifier.h> | |
1da177e4 | 44 | #include <linux/cpu.h> |
9331b315 | 45 | #include <linux/mutex.h> |
01c1c660 | 46 | #include <linux/module.h> |
a6826048 | 47 | #include <linux/kernel_stat.h> |
1da177e4 | 48 | |
162cc279 PM |
49 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
50 | static struct lock_class_key rcu_lock_key; | |
51 | struct lockdep_map rcu_lock_map = | |
52 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); | |
53 | EXPORT_SYMBOL_GPL(rcu_lock_map); | |
54 | #endif | |
55 | ||
a6826048 | 56 | int rcu_scheduler_active __read_mostly; |
21a1ea9e | 57 | |
fbf6bfca PM |
58 | /* |
59 | * Awaken the corresponding synchronize_rcu() instance now that a | |
60 | * grace period has elapsed. | |
61 | */ | |
4446a36f | 62 | void wakeme_after_rcu(struct rcu_head *head) |
21a1ea9e | 63 | { |
01c1c660 PM |
64 | struct rcu_synchronize *rcu; |
65 | ||
66 | rcu = container_of(head, struct rcu_synchronize, head); | |
67 | complete(&rcu->completion); | |
21a1ea9e | 68 | } |
1da177e4 | 69 | |
9b1d82fa PM |
70 | #ifndef CONFIG_TINY_RCU |
71 | ||
16e30811 PM |
72 | #ifdef CONFIG_TREE_PREEMPT_RCU |
73 | ||
1da177e4 | 74 | /** |
01c1c660 | 75 | * synchronize_rcu - wait until a grace period has elapsed. |
1da177e4 | 76 | * |
01c1c660 PM |
77 | * Control will return to the caller some time after a full grace |
78 | * period has elapsed, in other words after all currently executing RCU | |
1da177e4 LT |
79 | * read-side critical sections have completed. RCU read-side critical |
80 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
81 | * and may be nested. | |
82 | */ | |
ea7d3fef PM |
83 | void synchronize_rcu(void) |
84 | { | |
85 | struct rcu_synchronize rcu; | |
a6826048 | 86 | |
16e30811 | 87 | if (!rcu_scheduler_active) |
a6826048 PM |
88 | return; |
89 | ||
ea7d3fef PM |
90 | init_completion(&rcu.completion); |
91 | /* Will wake me after RCU finished. */ | |
92 | call_rcu(&rcu.head, wakeme_after_rcu); | |
93 | /* Wait for it. */ | |
94 | wait_for_completion(&rcu.completion); | |
95 | } | |
01c1c660 | 96 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
c32e0660 | 97 | |
16e30811 PM |
98 | #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
99 | ||
100 | /** | |
101 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. | |
102 | * | |
103 | * Control will return to the caller some time after a full rcu-sched | |
104 | * grace period has elapsed, in other words after all currently executing | |
105 | * rcu-sched read-side critical sections have completed. These read-side | |
106 | * critical sections are delimited by rcu_read_lock_sched() and | |
107 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), | |
108 | * local_irq_disable(), and so on may be used in place of | |
109 | * rcu_read_lock_sched(). | |
110 | * | |
111 | * This means that all preempt_disable code sequences, including NMI and | |
112 | * hardware-interrupt handlers, in progress on entry will have completed | |
113 | * before this primitive returns. However, this does not guarantee that | |
114 | * softirq handlers will have completed, since in some kernels, these | |
115 | * handlers can run in process context, and can block. | |
116 | * | |
117 | * This primitive provides the guarantees made by the (now removed) | |
118 | * synchronize_kernel() API. In contrast, synchronize_rcu() only | |
119 | * guarantees that rcu_read_lock() sections will have completed. | |
120 | * In "classic RCU", these two guarantees happen to be one and | |
121 | * the same, but can differ in realtime RCU implementations. | |
122 | */ | |
123 | void synchronize_sched(void) | |
124 | { | |
125 | struct rcu_synchronize rcu; | |
126 | ||
127 | if (rcu_blocking_is_gp()) | |
128 | return; | |
129 | ||
130 | init_completion(&rcu.completion); | |
131 | /* Will wake me after RCU finished. */ | |
132 | call_rcu_sched(&rcu.head, wakeme_after_rcu); | |
133 | /* Wait for it. */ | |
134 | wait_for_completion(&rcu.completion); | |
135 | } | |
136 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
137 | ||
03b042bf PM |
138 | /** |
139 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. | |
140 | * | |
141 | * Control will return to the caller some time after a full rcu_bh grace | |
142 | * period has elapsed, in other words after all currently executing rcu_bh | |
143 | * read-side critical sections have completed. RCU read-side critical | |
144 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), | |
145 | * and may be nested. | |
146 | */ | |
147 | void synchronize_rcu_bh(void) | |
148 | { | |
149 | struct rcu_synchronize rcu; | |
150 | ||
151 | if (rcu_blocking_is_gp()) | |
152 | return; | |
153 | ||
154 | init_completion(&rcu.completion); | |
155 | /* Will wake me after RCU finished. */ | |
156 | call_rcu_bh(&rcu.head, wakeme_after_rcu); | |
157 | /* Wait for it. */ | |
158 | wait_for_completion(&rcu.completion); | |
159 | } | |
160 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); | |
161 | ||
9b1d82fa PM |
162 | #endif /* #ifndef CONFIG_TINY_RCU */ |
163 | ||
f69b17d7 LJ |
164 | static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, |
165 | unsigned long action, void *hcpu) | |
166 | { | |
d0ec774c | 167 | return rcu_cpu_notify(self, action, hcpu); |
f69b17d7 LJ |
168 | } |
169 | ||
1da177e4 LT |
170 | void __init rcu_init(void) |
171 | { | |
2e597558 PM |
172 | int i; |
173 | ||
01c1c660 | 174 | __rcu_init(); |
2e597558 PM |
175 | cpu_notifier(rcu_barrier_cpu_hotplug, 0); |
176 | ||
177 | /* | |
178 | * We don't need protection against CPU-hotplug here because | |
179 | * this is called early in boot, before either interrupts | |
180 | * or the scheduler are operational. | |
181 | */ | |
182 | for_each_online_cpu(i) | |
183 | rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i); | |
1da177e4 LT |
184 | } |
185 | ||
a6826048 PM |
186 | void rcu_scheduler_starting(void) |
187 | { | |
188 | WARN_ON(num_online_cpus() != 1); | |
189 | WARN_ON(nr_context_switches() > 0); | |
190 | rcu_scheduler_active = 1; | |
191 | } |