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9b1d82fa PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. | |
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 | * | |
18 | * Copyright IBM Corporation, 2008 | |
19 | * | |
20 | * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
21 | * | |
22 | * For detailed explanation of Read-Copy Update mechanism see - | |
4ce5b903 | 23 | * Documentation/RCU |
9b1d82fa | 24 | */ |
9b1d82fa | 25 | #include <linux/moduleparam.h> |
4ce5b903 IM |
26 | #include <linux/completion.h> |
27 | #include <linux/interrupt.h> | |
9b1d82fa | 28 | #include <linux/notifier.h> |
4ce5b903 IM |
29 | #include <linux/rcupdate.h> |
30 | #include <linux/kernel.h> | |
31 | #include <linux/module.h> | |
9b1d82fa | 32 | #include <linux/mutex.h> |
4ce5b903 IM |
33 | #include <linux/sched.h> |
34 | #include <linux/types.h> | |
35 | #include <linux/init.h> | |
9b1d82fa | 36 | #include <linux/time.h> |
4ce5b903 | 37 | #include <linux/cpu.h> |
9b1d82fa PM |
38 | |
39 | /* Global control variables for rcupdate callback mechanism. */ | |
40 | struct rcu_ctrlblk { | |
41 | struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ | |
42 | struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ | |
43 | struct rcu_head **curtail; /* ->next pointer of last CB. */ | |
44 | }; | |
45 | ||
46 | /* Definition for rcupdate control block. */ | |
99652b54 PM |
47 | static struct rcu_ctrlblk rcu_sched_ctrlblk = { |
48 | .donetail = &rcu_sched_ctrlblk.rcucblist, | |
49 | .curtail = &rcu_sched_ctrlblk.rcucblist, | |
9b1d82fa | 50 | }; |
4ce5b903 | 51 | |
9b1d82fa | 52 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { |
4ce5b903 IM |
53 | .donetail = &rcu_bh_ctrlblk.rcucblist, |
54 | .curtail = &rcu_bh_ctrlblk.rcucblist, | |
9b1d82fa PM |
55 | }; |
56 | ||
bbad9379 PM |
57 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
58 | int rcu_scheduler_active __read_mostly; | |
59 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
60 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
61 | ||
9b1d82fa PM |
62 | #ifdef CONFIG_NO_HZ |
63 | ||
64 | static long rcu_dynticks_nesting = 1; | |
65 | ||
66 | /* | |
67 | * Enter dynticks-idle mode, which is an extended quiescent state | |
68 | * if we have fully entered that mode (i.e., if the new value of | |
69 | * dynticks_nesting is zero). | |
70 | */ | |
71 | void rcu_enter_nohz(void) | |
72 | { | |
73 | if (--rcu_dynticks_nesting == 0) | |
74 | rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ | |
75 | } | |
76 | ||
77 | /* | |
78 | * Exit dynticks-idle mode, so that we are no longer in an extended | |
79 | * quiescent state. | |
80 | */ | |
81 | void rcu_exit_nohz(void) | |
82 | { | |
83 | rcu_dynticks_nesting++; | |
84 | } | |
85 | ||
86 | #endif /* #ifdef CONFIG_NO_HZ */ | |
87 | ||
88 | /* | |
89 | * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc(). | |
4ce5b903 IM |
90 | * Also disable irqs to avoid confusion due to interrupt handlers |
91 | * invoking call_rcu(). | |
9b1d82fa PM |
92 | */ |
93 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) | |
94 | { | |
95 | unsigned long flags; | |
96 | ||
97 | local_irq_save(flags); | |
98 | if (rcp->rcucblist != NULL && | |
99 | rcp->donetail != rcp->curtail) { | |
100 | rcp->donetail = rcp->curtail; | |
101 | local_irq_restore(flags); | |
102 | return 1; | |
103 | } | |
104 | local_irq_restore(flags); | |
4ce5b903 | 105 | |
9b1d82fa PM |
106 | return 0; |
107 | } | |
108 | ||
109 | /* | |
110 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we | |
111 | * are at it, given that any rcu quiescent state is also an rcu_bh | |
112 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. | |
113 | */ | |
114 | void rcu_sched_qs(int cpu) | |
115 | { | |
99652b54 PM |
116 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
117 | rcu_qsctr_help(&rcu_bh_ctrlblk)) | |
9b1d82fa PM |
118 | raise_softirq(RCU_SOFTIRQ); |
119 | } | |
120 | ||
121 | /* | |
122 | * Record an rcu_bh quiescent state. | |
123 | */ | |
124 | void rcu_bh_qs(int cpu) | |
125 | { | |
126 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) | |
127 | raise_softirq(RCU_SOFTIRQ); | |
128 | } | |
129 | ||
130 | /* | |
131 | * Check to see if the scheduling-clock interrupt came from an extended | |
132 | * quiescent state, and, if so, tell RCU about it. | |
133 | */ | |
134 | void rcu_check_callbacks(int cpu, int user) | |
135 | { | |
136 | if (user || | |
137 | (idle_cpu(cpu) && | |
138 | !in_softirq() && | |
139 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) | |
140 | rcu_sched_qs(cpu); | |
141 | else if (!in_softirq()) | |
142 | rcu_bh_qs(cpu); | |
143 | } | |
144 | ||
145 | /* | |
146 | * Helper function for rcu_process_callbacks() that operates on the | |
147 | * specified rcu_ctrlkblk structure. | |
148 | */ | |
149 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) | |
150 | { | |
9b1d82fa | 151 | struct rcu_head *next, *list; |
4ce5b903 | 152 | unsigned long flags; |
9b1d82fa PM |
153 | |
154 | /* If no RCU callbacks ready to invoke, just return. */ | |
155 | if (&rcp->rcucblist == rcp->donetail) | |
156 | return; | |
157 | ||
158 | /* Move the ready-to-invoke callbacks to a local list. */ | |
159 | local_irq_save(flags); | |
160 | list = rcp->rcucblist; | |
161 | rcp->rcucblist = *rcp->donetail; | |
162 | *rcp->donetail = NULL; | |
163 | if (rcp->curtail == rcp->donetail) | |
164 | rcp->curtail = &rcp->rcucblist; | |
165 | rcp->donetail = &rcp->rcucblist; | |
166 | local_irq_restore(flags); | |
167 | ||
168 | /* Invoke the callbacks on the local list. */ | |
169 | while (list) { | |
170 | next = list->next; | |
171 | prefetch(next); | |
551d55a9 | 172 | debug_rcu_head_unqueue(list); |
9b1d82fa PM |
173 | list->func(list); |
174 | list = next; | |
175 | } | |
176 | } | |
177 | ||
178 | /* | |
179 | * Invoke any callbacks whose grace period has completed. | |
180 | */ | |
181 | static void rcu_process_callbacks(struct softirq_action *unused) | |
182 | { | |
99652b54 | 183 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
9b1d82fa PM |
184 | __rcu_process_callbacks(&rcu_bh_ctrlblk); |
185 | } | |
186 | ||
9b1d82fa PM |
187 | /* |
188 | * Wait for a grace period to elapse. But it is illegal to invoke | |
189 | * synchronize_sched() from within an RCU read-side critical section. | |
190 | * Therefore, any legal call to synchronize_sched() is a quiescent | |
191 | * state, and so on a UP system, synchronize_sched() need do nothing. | |
192 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the | |
193 | * benefits of doing might_sleep() to reduce latency.) | |
194 | * | |
195 | * Cool, huh? (Due to Josh Triplett.) | |
196 | * | |
da848c47 PM |
197 | * But we want to make this a static inline later. The cond_resched() |
198 | * currently makes this problematic. | |
9b1d82fa PM |
199 | */ |
200 | void synchronize_sched(void) | |
201 | { | |
202 | cond_resched(); | |
203 | } | |
204 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
205 | ||
9b1d82fa PM |
206 | /* |
207 | * Helper function for call_rcu() and call_rcu_bh(). | |
208 | */ | |
209 | static void __call_rcu(struct rcu_head *head, | |
210 | void (*func)(struct rcu_head *rcu), | |
211 | struct rcu_ctrlblk *rcp) | |
212 | { | |
213 | unsigned long flags; | |
214 | ||
551d55a9 | 215 | debug_rcu_head_queue(head); |
9b1d82fa PM |
216 | head->func = func; |
217 | head->next = NULL; | |
4ce5b903 | 218 | |
9b1d82fa PM |
219 | local_irq_save(flags); |
220 | *rcp->curtail = head; | |
221 | rcp->curtail = &head->next; | |
222 | local_irq_restore(flags); | |
223 | } | |
224 | ||
225 | /* | |
226 | * Post an RCU callback to be invoked after the end of an RCU grace | |
227 | * period. But since we have but one CPU, that would be after any | |
228 | * quiescent state. | |
229 | */ | |
4ce5b903 | 230 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa | 231 | { |
99652b54 | 232 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
9b1d82fa PM |
233 | } |
234 | EXPORT_SYMBOL_GPL(call_rcu); | |
235 | ||
236 | /* | |
237 | * Post an RCU bottom-half callback to be invoked after any subsequent | |
238 | * quiescent state. | |
239 | */ | |
4ce5b903 | 240 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa PM |
241 | { |
242 | __call_rcu(head, func, &rcu_bh_ctrlblk); | |
243 | } | |
244 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
245 | ||
246 | void rcu_barrier(void) | |
247 | { | |
248 | struct rcu_synchronize rcu; | |
249 | ||
72d5a9f7 | 250 | init_rcu_head_on_stack(&rcu.head); |
9b1d82fa PM |
251 | init_completion(&rcu.completion); |
252 | /* Will wake me after RCU finished. */ | |
253 | call_rcu(&rcu.head, wakeme_after_rcu); | |
254 | /* Wait for it. */ | |
255 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 256 | destroy_rcu_head_on_stack(&rcu.head); |
9b1d82fa PM |
257 | } |
258 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
259 | ||
260 | void rcu_barrier_bh(void) | |
261 | { | |
262 | struct rcu_synchronize rcu; | |
263 | ||
72d5a9f7 | 264 | init_rcu_head_on_stack(&rcu.head); |
9b1d82fa PM |
265 | init_completion(&rcu.completion); |
266 | /* Will wake me after RCU finished. */ | |
267 | call_rcu_bh(&rcu.head, wakeme_after_rcu); | |
268 | /* Wait for it. */ | |
269 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 270 | destroy_rcu_head_on_stack(&rcu.head); |
9b1d82fa PM |
271 | } |
272 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); | |
273 | ||
274 | void rcu_barrier_sched(void) | |
275 | { | |
276 | struct rcu_synchronize rcu; | |
277 | ||
72d5a9f7 | 278 | init_rcu_head_on_stack(&rcu.head); |
9b1d82fa PM |
279 | init_completion(&rcu.completion); |
280 | /* Will wake me after RCU finished. */ | |
281 | call_rcu_sched(&rcu.head, wakeme_after_rcu); | |
282 | /* Wait for it. */ | |
283 | wait_for_completion(&rcu.completion); | |
72d5a9f7 | 284 | destroy_rcu_head_on_stack(&rcu.head); |
9b1d82fa PM |
285 | } |
286 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); | |
287 | ||
9f680ab4 | 288 | void __init rcu_init(void) |
9b1d82fa PM |
289 | { |
290 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); | |
291 | } | |
bbad9379 PM |
292 | |
293 | #include "rcutiny_plugin.h" |