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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> |
268bb0ce | 38 | #include <linux/prefetch.h> |
9b1d82fa | 39 | |
29c00b4a | 40 | #ifdef CONFIG_RCU_TRACE |
29c00b4a | 41 | #include <trace/events/rcu.h> |
29c00b4a PM |
42 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
43 | ||
44 | #include "rcu.h" | |
45 | ||
a57eb940 | 46 | /* Forward declarations for rcutiny_plugin.h. */ |
24278d14 | 47 | struct rcu_ctrlblk; |
965a002b PM |
48 | static void invoke_rcu_callbacks(void); |
49 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); | |
50 | static void rcu_process_callbacks(struct softirq_action *unused); | |
a57eb940 PM |
51 | static void __call_rcu(struct rcu_head *head, |
52 | void (*func)(struct rcu_head *rcu), | |
53 | struct rcu_ctrlblk *rcp); | |
54 | ||
55 | #include "rcutiny_plugin.h" | |
56 | ||
9b1d82fa PM |
57 | #ifdef CONFIG_NO_HZ |
58 | ||
59 | static long rcu_dynticks_nesting = 1; | |
60 | ||
61 | /* | |
62 | * Enter dynticks-idle mode, which is an extended quiescent state | |
63 | * if we have fully entered that mode (i.e., if the new value of | |
64 | * dynticks_nesting is zero). | |
65 | */ | |
66 | void rcu_enter_nohz(void) | |
67 | { | |
68 | if (--rcu_dynticks_nesting == 0) | |
69 | rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ | |
70 | } | |
71 | ||
72 | /* | |
73 | * Exit dynticks-idle mode, so that we are no longer in an extended | |
74 | * quiescent state. | |
75 | */ | |
76 | void rcu_exit_nohz(void) | |
77 | { | |
78 | rcu_dynticks_nesting++; | |
79 | } | |
80 | ||
81 | #endif /* #ifdef CONFIG_NO_HZ */ | |
82 | ||
83 | /* | |
b554d7de ED |
84 | * Helper function for rcu_sched_qs() and rcu_bh_qs(). |
85 | * Also irqs are disabled to avoid confusion due to interrupt handlers | |
4ce5b903 | 86 | * invoking call_rcu(). |
9b1d82fa PM |
87 | */ |
88 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) | |
89 | { | |
9b1d82fa PM |
90 | if (rcp->rcucblist != NULL && |
91 | rcp->donetail != rcp->curtail) { | |
92 | rcp->donetail = rcp->curtail; | |
9b1d82fa PM |
93 | return 1; |
94 | } | |
4ce5b903 | 95 | |
9b1d82fa PM |
96 | return 0; |
97 | } | |
98 | ||
99 | /* | |
100 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we | |
101 | * are at it, given that any rcu quiescent state is also an rcu_bh | |
102 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. | |
103 | */ | |
104 | void rcu_sched_qs(int cpu) | |
105 | { | |
b554d7de ED |
106 | unsigned long flags; |
107 | ||
108 | local_irq_save(flags); | |
99652b54 PM |
109 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
110 | rcu_qsctr_help(&rcu_bh_ctrlblk)) | |
965a002b | 111 | invoke_rcu_callbacks(); |
b554d7de | 112 | local_irq_restore(flags); |
9b1d82fa PM |
113 | } |
114 | ||
115 | /* | |
116 | * Record an rcu_bh quiescent state. | |
117 | */ | |
118 | void rcu_bh_qs(int cpu) | |
119 | { | |
b554d7de ED |
120 | unsigned long flags; |
121 | ||
122 | local_irq_save(flags); | |
9b1d82fa | 123 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
965a002b | 124 | invoke_rcu_callbacks(); |
b554d7de | 125 | local_irq_restore(flags); |
9b1d82fa PM |
126 | } |
127 | ||
128 | /* | |
129 | * Check to see if the scheduling-clock interrupt came from an extended | |
130 | * quiescent state, and, if so, tell RCU about it. | |
131 | */ | |
132 | void rcu_check_callbacks(int cpu, int user) | |
133 | { | |
134 | if (user || | |
135 | (idle_cpu(cpu) && | |
136 | !in_softirq() && | |
137 | hardirq_count() <= (1 << HARDIRQ_SHIFT))) | |
138 | rcu_sched_qs(cpu); | |
139 | else if (!in_softirq()) | |
140 | rcu_bh_qs(cpu); | |
a57eb940 | 141 | rcu_preempt_check_callbacks(); |
9b1d82fa PM |
142 | } |
143 | ||
144 | /* | |
b2c0710c PM |
145 | * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure |
146 | * whose grace period has elapsed. | |
9b1d82fa | 147 | */ |
965a002b | 148 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
9b1d82fa | 149 | { |
d4c08f2a | 150 | char *rn = NULL; |
9b1d82fa | 151 | struct rcu_head *next, *list; |
4ce5b903 | 152 | unsigned long flags; |
9e571a82 | 153 | RCU_TRACE(int cb_count = 0); |
9b1d82fa PM |
154 | |
155 | /* If no RCU callbacks ready to invoke, just return. */ | |
29c00b4a | 156 | if (&rcp->rcucblist == rcp->donetail) { |
72fe701b PM |
157 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); |
158 | RCU_TRACE(trace_rcu_batch_end(rcp->name, 0)); | |
9b1d82fa | 159 | return; |
29c00b4a | 160 | } |
9b1d82fa PM |
161 | |
162 | /* Move the ready-to-invoke callbacks to a local list. */ | |
163 | local_irq_save(flags); | |
72fe701b | 164 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); |
9b1d82fa PM |
165 | list = rcp->rcucblist; |
166 | rcp->rcucblist = *rcp->donetail; | |
167 | *rcp->donetail = NULL; | |
168 | if (rcp->curtail == rcp->donetail) | |
169 | rcp->curtail = &rcp->rcucblist; | |
a57eb940 | 170 | rcu_preempt_remove_callbacks(rcp); |
9b1d82fa PM |
171 | rcp->donetail = &rcp->rcucblist; |
172 | local_irq_restore(flags); | |
173 | ||
174 | /* Invoke the callbacks on the local list. */ | |
d4c08f2a | 175 | RCU_TRACE(rn = rcp->name); |
9b1d82fa PM |
176 | while (list) { |
177 | next = list->next; | |
178 | prefetch(next); | |
551d55a9 | 179 | debug_rcu_head_unqueue(list); |
b2c0710c | 180 | local_bh_disable(); |
d4c08f2a | 181 | __rcu_reclaim(rn, list); |
b2c0710c | 182 | local_bh_enable(); |
9b1d82fa | 183 | list = next; |
9e571a82 | 184 | RCU_TRACE(cb_count++); |
9b1d82fa | 185 | } |
9e571a82 | 186 | RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
72fe701b | 187 | RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count)); |
9b1d82fa PM |
188 | } |
189 | ||
965a002b | 190 | static void rcu_process_callbacks(struct softirq_action *unused) |
b2c0710c | 191 | { |
965a002b PM |
192 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
193 | __rcu_process_callbacks(&rcu_bh_ctrlblk); | |
194 | rcu_preempt_process_callbacks(); | |
b2c0710c PM |
195 | } |
196 | ||
9b1d82fa PM |
197 | /* |
198 | * Wait for a grace period to elapse. But it is illegal to invoke | |
199 | * synchronize_sched() from within an RCU read-side critical section. | |
200 | * Therefore, any legal call to synchronize_sched() is a quiescent | |
201 | * state, and so on a UP system, synchronize_sched() need do nothing. | |
202 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the | |
203 | * benefits of doing might_sleep() to reduce latency.) | |
204 | * | |
205 | * Cool, huh? (Due to Josh Triplett.) | |
206 | * | |
da848c47 PM |
207 | * But we want to make this a static inline later. The cond_resched() |
208 | * currently makes this problematic. | |
9b1d82fa PM |
209 | */ |
210 | void synchronize_sched(void) | |
211 | { | |
212 | cond_resched(); | |
213 | } | |
214 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
215 | ||
9b1d82fa PM |
216 | /* |
217 | * Helper function for call_rcu() and call_rcu_bh(). | |
218 | */ | |
219 | static void __call_rcu(struct rcu_head *head, | |
220 | void (*func)(struct rcu_head *rcu), | |
221 | struct rcu_ctrlblk *rcp) | |
222 | { | |
223 | unsigned long flags; | |
224 | ||
551d55a9 | 225 | debug_rcu_head_queue(head); |
9b1d82fa PM |
226 | head->func = func; |
227 | head->next = NULL; | |
4ce5b903 | 228 | |
9b1d82fa PM |
229 | local_irq_save(flags); |
230 | *rcp->curtail = head; | |
231 | rcp->curtail = &head->next; | |
9e571a82 | 232 | RCU_TRACE(rcp->qlen++); |
9b1d82fa PM |
233 | local_irq_restore(flags); |
234 | } | |
235 | ||
236 | /* | |
a57eb940 | 237 | * Post an RCU callback to be invoked after the end of an RCU-sched grace |
9b1d82fa PM |
238 | * period. But since we have but one CPU, that would be after any |
239 | * quiescent state. | |
240 | */ | |
a57eb940 | 241 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa | 242 | { |
99652b54 | 243 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
9b1d82fa | 244 | } |
a57eb940 | 245 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
9b1d82fa PM |
246 | |
247 | /* | |
248 | * Post an RCU bottom-half callback to be invoked after any subsequent | |
249 | * quiescent state. | |
250 | */ | |
4ce5b903 | 251 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa PM |
252 | { |
253 | __call_rcu(head, func, &rcu_bh_ctrlblk); | |
254 | } | |
255 | EXPORT_SYMBOL_GPL(call_rcu_bh); |