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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 | |
87de1cfd PM |
15 | * along with this program; if not, you can access it online at |
16 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
9b1d82fa PM |
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 | */ |
4ce5b903 IM |
25 | #include <linux/completion.h> |
26 | #include <linux/interrupt.h> | |
9b1d82fa | 27 | #include <linux/notifier.h> |
f9411ebe | 28 | #include <linux/rcupdate_wait.h> |
4ce5b903 | 29 | #include <linux/kernel.h> |
9984de1a | 30 | #include <linux/export.h> |
9b1d82fa | 31 | #include <linux/mutex.h> |
4ce5b903 IM |
32 | #include <linux/sched.h> |
33 | #include <linux/types.h> | |
34 | #include <linux/init.h> | |
9b1d82fa | 35 | #include <linux/time.h> |
4ce5b903 | 36 | #include <linux/cpu.h> |
268bb0ce | 37 | #include <linux/prefetch.h> |
af658dca | 38 | #include <linux/trace_events.h> |
9b1d82fa | 39 | |
29c00b4a PM |
40 | #include "rcu.h" |
41 | ||
4102adab | 42 | /* Forward declarations for tiny_plugin.h. */ |
24278d14 | 43 | struct rcu_ctrlblk; |
a57eb940 | 44 | static void __call_rcu(struct rcu_head *head, |
b6a4ae76 | 45 | rcu_callback_t func, |
a57eb940 PM |
46 | struct rcu_ctrlblk *rcp); |
47 | ||
4102adab | 48 | #include "tiny_plugin.h" |
6bfc09e2 | 49 | |
f9411ebe IM |
50 | void rcu_barrier_bh(void) |
51 | { | |
52 | wait_rcu_gp(call_rcu_bh); | |
53 | } | |
54 | EXPORT_SYMBOL(rcu_barrier_bh); | |
55 | ||
56 | void rcu_barrier_sched(void) | |
57 | { | |
58 | wait_rcu_gp(call_rcu_sched); | |
59 | } | |
60 | EXPORT_SYMBOL(rcu_barrier_sched); | |
61 | ||
cc6783f7 | 62 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) |
9b2e4f18 PM |
63 | |
64 | /* | |
65 | * Test whether RCU thinks that the current CPU is idle. | |
66 | */ | |
9418fb20 | 67 | bool notrace __rcu_is_watching(void) |
9b2e4f18 | 68 | { |
5f6130fa | 69 | return true; |
9b2e4f18 | 70 | } |
5c173eb8 | 71 | EXPORT_SYMBOL(__rcu_is_watching); |
9b2e4f18 | 72 | |
cc6783f7 | 73 | #endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */ |
9b2e4f18 | 74 | |
9b1d82fa | 75 | /* |
b554d7de ED |
76 | * Helper function for rcu_sched_qs() and rcu_bh_qs(). |
77 | * Also irqs are disabled to avoid confusion due to interrupt handlers | |
4ce5b903 | 78 | * invoking call_rcu(). |
9b1d82fa PM |
79 | */ |
80 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) | |
81 | { | |
14961444 | 82 | RCU_TRACE(reset_cpu_stall_ticks(rcp)); |
27153acb | 83 | if (rcp->donetail != rcp->curtail) { |
9b1d82fa | 84 | rcp->donetail = rcp->curtail; |
9b1d82fa PM |
85 | return 1; |
86 | } | |
4ce5b903 | 87 | |
9b1d82fa PM |
88 | return 0; |
89 | } | |
90 | ||
91 | /* | |
92 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we | |
93 | * are at it, given that any rcu quiescent state is also an rcu_bh | |
94 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. | |
95 | */ | |
284a8c93 | 96 | void rcu_sched_qs(void) |
9b1d82fa | 97 | { |
b554d7de ED |
98 | unsigned long flags; |
99 | ||
100 | local_irq_save(flags); | |
99652b54 PM |
101 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
102 | rcu_qsctr_help(&rcu_bh_ctrlblk)) | |
9dc5ad32 | 103 | raise_softirq(RCU_SOFTIRQ); |
b554d7de | 104 | local_irq_restore(flags); |
9b1d82fa PM |
105 | } |
106 | ||
107 | /* | |
108 | * Record an rcu_bh quiescent state. | |
109 | */ | |
284a8c93 | 110 | void rcu_bh_qs(void) |
9b1d82fa | 111 | { |
b554d7de ED |
112 | unsigned long flags; |
113 | ||
114 | local_irq_save(flags); | |
9b1d82fa | 115 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
9dc5ad32 | 116 | raise_softirq(RCU_SOFTIRQ); |
b554d7de | 117 | local_irq_restore(flags); |
9b1d82fa PM |
118 | } |
119 | ||
120 | /* | |
121 | * Check to see if the scheduling-clock interrupt came from an extended | |
9b2e4f18 PM |
122 | * quiescent state, and, if so, tell RCU about it. This function must |
123 | * be called from hardirq context. It is normally called from the | |
124 | * scheduling-clock interrupt. | |
9b1d82fa | 125 | */ |
c3377c2d | 126 | void rcu_check_callbacks(int user) |
9b1d82fa | 127 | { |
14961444 | 128 | RCU_TRACE(check_cpu_stalls()); |
ca9558a3 | 129 | if (user) |
284a8c93 | 130 | rcu_sched_qs(); |
9b1d82fa | 131 | else if (!in_softirq()) |
284a8c93 | 132 | rcu_bh_qs(); |
8315f422 PM |
133 | if (user) |
134 | rcu_note_voluntary_context_switch(current); | |
9b1d82fa PM |
135 | } |
136 | ||
137 | /* | |
b2c0710c PM |
138 | * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure |
139 | * whose grace period has elapsed. | |
9b1d82fa | 140 | */ |
965a002b | 141 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
9b1d82fa | 142 | { |
e66c33d5 | 143 | const char *rn = NULL; |
9b1d82fa | 144 | struct rcu_head *next, *list; |
4ce5b903 | 145 | unsigned long flags; |
9e571a82 | 146 | RCU_TRACE(int cb_count = 0); |
9b1d82fa | 147 | |
9b1d82fa PM |
148 | /* Move the ready-to-invoke callbacks to a local list. */ |
149 | local_irq_save(flags); | |
6e91f8cb PM |
150 | if (rcp->donetail == &rcp->rcucblist) { |
151 | /* No callbacks ready, so just leave. */ | |
152 | local_irq_restore(flags); | |
153 | return; | |
154 | } | |
486e2593 | 155 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1)); |
9b1d82fa PM |
156 | list = rcp->rcucblist; |
157 | rcp->rcucblist = *rcp->donetail; | |
158 | *rcp->donetail = NULL; | |
159 | if (rcp->curtail == rcp->donetail) | |
160 | rcp->curtail = &rcp->rcucblist; | |
161 | rcp->donetail = &rcp->rcucblist; | |
162 | local_irq_restore(flags); | |
163 | ||
164 | /* Invoke the callbacks on the local list. */ | |
d4c08f2a | 165 | RCU_TRACE(rn = rcp->name); |
9b1d82fa PM |
166 | while (list) { |
167 | next = list->next; | |
168 | prefetch(next); | |
551d55a9 | 169 | debug_rcu_head_unqueue(list); |
b2c0710c | 170 | local_bh_disable(); |
d4c08f2a | 171 | __rcu_reclaim(rn, list); |
b2c0710c | 172 | local_bh_enable(); |
9b1d82fa | 173 | list = next; |
9e571a82 | 174 | RCU_TRACE(cb_count++); |
9b1d82fa | 175 | } |
9e571a82 | 176 | RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
0d752924 PM |
177 | RCU_TRACE(trace_rcu_batch_end(rcp->name, |
178 | cb_count, 0, need_resched(), | |
4968c300 | 179 | is_idle_task(current), |
9dc5ad32 | 180 | false)); |
9b1d82fa PM |
181 | } |
182 | ||
0766f788 | 183 | static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) |
b2c0710c | 184 | { |
965a002b PM |
185 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
186 | __rcu_process_callbacks(&rcu_bh_ctrlblk); | |
b2c0710c PM |
187 | } |
188 | ||
9b1d82fa PM |
189 | /* |
190 | * Wait for a grace period to elapse. But it is illegal to invoke | |
191 | * synchronize_sched() from within an RCU read-side critical section. | |
192 | * Therefore, any legal call to synchronize_sched() is a quiescent | |
193 | * state, and so on a UP system, synchronize_sched() need do nothing. | |
194 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the | |
195 | * benefits of doing might_sleep() to reduce latency.) | |
196 | * | |
197 | * Cool, huh? (Due to Josh Triplett.) | |
9b1d82fa PM |
198 | */ |
199 | void synchronize_sched(void) | |
200 | { | |
f78f5b90 PM |
201 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
202 | lock_is_held(&rcu_lock_map) || | |
203 | lock_is_held(&rcu_sched_lock_map), | |
204 | "Illegal synchronize_sched() in RCU read-side critical section"); | |
9b1d82fa PM |
205 | } |
206 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
207 | ||
9b1d82fa PM |
208 | /* |
209 | * Helper function for call_rcu() and call_rcu_bh(). | |
210 | */ | |
211 | static void __call_rcu(struct rcu_head *head, | |
b6a4ae76 | 212 | rcu_callback_t func, |
9b1d82fa PM |
213 | struct rcu_ctrlblk *rcp) |
214 | { | |
215 | unsigned long flags; | |
216 | ||
551d55a9 | 217 | debug_rcu_head_queue(head); |
9b1d82fa PM |
218 | head->func = func; |
219 | head->next = NULL; | |
4ce5b903 | 220 | |
9b1d82fa PM |
221 | local_irq_save(flags); |
222 | *rcp->curtail = head; | |
223 | rcp->curtail = &head->next; | |
9e571a82 | 224 | RCU_TRACE(rcp->qlen++); |
9b1d82fa | 225 | local_irq_restore(flags); |
5f6130fa LJ |
226 | |
227 | if (unlikely(is_idle_task(current))) { | |
228 | /* force scheduling for rcu_sched_qs() */ | |
229 | resched_cpu(0); | |
230 | } | |
9b1d82fa PM |
231 | } |
232 | ||
233 | /* | |
a57eb940 | 234 | * Post an RCU callback to be invoked after the end of an RCU-sched grace |
9b1d82fa PM |
235 | * period. But since we have but one CPU, that would be after any |
236 | * quiescent state. | |
237 | */ | |
b6a4ae76 | 238 | void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) |
9b1d82fa | 239 | { |
99652b54 | 240 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
9b1d82fa | 241 | } |
a57eb940 | 242 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
9b1d82fa PM |
243 | |
244 | /* | |
245 | * Post an RCU bottom-half callback to be invoked after any subsequent | |
246 | * quiescent state. | |
247 | */ | |
b6a4ae76 | 248 | void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) |
9b1d82fa PM |
249 | { |
250 | __call_rcu(head, func, &rcu_bh_ctrlblk); | |
251 | } | |
252 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
9dc5ad32 | 253 | |
aa23c6fb | 254 | void __init rcu_init(void) |
9dc5ad32 PM |
255 | { |
256 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); | |
630181c4 PM |
257 | RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk)); |
258 | RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk)); | |
aa23c6fb PK |
259 | |
260 | rcu_early_boot_tests(); | |
9dc5ad32 | 261 | } |