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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> | |
22 | * | |
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 - | |
30 | * http://lse.sourceforge.net/locking/rcupdate.html | |
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> |
1da177e4 | 47 | |
70f12f84 PM |
48 | enum rcu_barrier { |
49 | RCU_BARRIER_STD, | |
50 | RCU_BARRIER_BH, | |
51 | RCU_BARRIER_SCHED, | |
52 | }; | |
53 | ||
01c1c660 | 54 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
21a1ea9e | 55 | static atomic_t rcu_barrier_cpu_count; |
9331b315 | 56 | static DEFINE_MUTEX(rcu_barrier_mutex); |
21a1ea9e DS |
57 | static struct completion rcu_barrier_completion; |
58 | ||
fbf6bfca PM |
59 | /* |
60 | * Awaken the corresponding synchronize_rcu() instance now that a | |
61 | * grace period has elapsed. | |
62 | */ | |
4446a36f | 63 | void wakeme_after_rcu(struct rcu_head *head) |
21a1ea9e | 64 | { |
01c1c660 PM |
65 | struct rcu_synchronize *rcu; |
66 | ||
67 | rcu = container_of(head, struct rcu_synchronize, head); | |
68 | complete(&rcu->completion); | |
21a1ea9e | 69 | } |
1da177e4 LT |
70 | |
71 | /** | |
01c1c660 | 72 | * synchronize_rcu - wait until a grace period has elapsed. |
1da177e4 | 73 | * |
01c1c660 PM |
74 | * Control will return to the caller some time after a full grace |
75 | * period has elapsed, in other words after all currently executing RCU | |
1da177e4 LT |
76 | * read-side critical sections have completed. RCU read-side critical |
77 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
78 | * and may be nested. | |
79 | */ | |
01dcb044 | 80 | void synchronize_rcu(void); /* Makes kernel-doc tools happy */ |
4446a36f | 81 | synchronize_rcu_xxx(synchronize_rcu, call_rcu) |
01c1c660 | 82 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
c32e0660 | 83 | |
ab4720ec DS |
84 | static void rcu_barrier_callback(struct rcu_head *notused) |
85 | { | |
86 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) | |
87 | complete(&rcu_barrier_completion); | |
88 | } | |
89 | ||
90 | /* | |
91 | * Called with preemption disabled, and from cross-cpu IRQ context. | |
92 | */ | |
70f12f84 | 93 | static void rcu_barrier_func(void *type) |
ab4720ec DS |
94 | { |
95 | int cpu = smp_processor_id(); | |
01c1c660 | 96 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
ab4720ec | 97 | |
ab4720ec | 98 | atomic_inc(&rcu_barrier_cpu_count); |
70f12f84 PM |
99 | switch ((enum rcu_barrier)type) { |
100 | case RCU_BARRIER_STD: | |
101 | call_rcu(head, rcu_barrier_callback); | |
102 | break; | |
103 | case RCU_BARRIER_BH: | |
104 | call_rcu_bh(head, rcu_barrier_callback); | |
105 | break; | |
106 | case RCU_BARRIER_SCHED: | |
107 | call_rcu_sched(head, rcu_barrier_callback); | |
108 | break; | |
109 | } | |
ab4720ec DS |
110 | } |
111 | ||
70f12f84 PM |
112 | /* |
113 | * Orchestrate the specified type of RCU barrier, waiting for all | |
114 | * RCU callbacks of the specified type to complete. | |
ab4720ec | 115 | */ |
70f12f84 | 116 | static void _rcu_barrier(enum rcu_barrier type) |
ab4720ec DS |
117 | { |
118 | BUG_ON(in_interrupt()); | |
9331b315 IM |
119 | /* Take cpucontrol mutex to protect against CPU hotplug */ |
120 | mutex_lock(&rcu_barrier_mutex); | |
ab4720ec DS |
121 | init_completion(&rcu_barrier_completion); |
122 | atomic_set(&rcu_barrier_cpu_count, 0); | |
e0ecfa79 PM |
123 | /* |
124 | * The queueing of callbacks in all CPUs must be atomic with | |
125 | * respect to RCU, otherwise one CPU may queue a callback, | |
126 | * wait for a grace period, decrement barrier count and call | |
127 | * complete(), while other CPUs have not yet queued anything. | |
128 | * So, we need to make sure that grace periods cannot complete | |
129 | * until all the callbacks are queued. | |
130 | */ | |
131 | rcu_read_lock(); | |
59190f42 | 132 | on_each_cpu(rcu_barrier_func, (void *)type, 1); |
e0ecfa79 | 133 | rcu_read_unlock(); |
ab4720ec | 134 | wait_for_completion(&rcu_barrier_completion); |
9331b315 | 135 | mutex_unlock(&rcu_barrier_mutex); |
ab4720ec | 136 | } |
70f12f84 PM |
137 | |
138 | /** | |
139 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. | |
140 | */ | |
141 | void rcu_barrier(void) | |
142 | { | |
143 | _rcu_barrier(RCU_BARRIER_STD); | |
144 | } | |
ab4720ec DS |
145 | EXPORT_SYMBOL_GPL(rcu_barrier); |
146 | ||
70f12f84 PM |
147 | /** |
148 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. | |
149 | */ | |
150 | void rcu_barrier_bh(void) | |
151 | { | |
152 | _rcu_barrier(RCU_BARRIER_BH); | |
153 | } | |
154 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
155 | ||
156 | /** | |
157 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. | |
158 | */ | |
159 | void rcu_barrier_sched(void) | |
160 | { | |
161 | _rcu_barrier(RCU_BARRIER_SCHED); | |
162 | } | |
163 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
164 | ||
1da177e4 LT |
165 | void __init rcu_init(void) |
166 | { | |
01c1c660 | 167 | __rcu_init(); |
1da177e4 LT |
168 | } |
169 |