Commit | Line | Data |
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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> |
4ce5b903 IM |
28 | #include <linux/rcupdate.h> |
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; |
965a002b PM |
44 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); |
45 | static void rcu_process_callbacks(struct softirq_action *unused); | |
a57eb940 PM |
46 | static void __call_rcu(struct rcu_head *head, |
47 | void (*func)(struct rcu_head *rcu), | |
48 | struct rcu_ctrlblk *rcp); | |
49 | ||
4102adab | 50 | #include "tiny_plugin.h" |
6bfc09e2 | 51 | |
cc6783f7 | 52 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) |
9b2e4f18 PM |
53 | |
54 | /* | |
55 | * Test whether RCU thinks that the current CPU is idle. | |
56 | */ | |
9418fb20 | 57 | bool notrace __rcu_is_watching(void) |
9b2e4f18 | 58 | { |
5f6130fa | 59 | return true; |
9b2e4f18 | 60 | } |
5c173eb8 | 61 | EXPORT_SYMBOL(__rcu_is_watching); |
9b2e4f18 | 62 | |
cc6783f7 | 63 | #endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */ |
9b2e4f18 | 64 | |
9b1d82fa | 65 | /* |
b554d7de ED |
66 | * Helper function for rcu_sched_qs() and rcu_bh_qs(). |
67 | * Also irqs are disabled to avoid confusion due to interrupt handlers | |
4ce5b903 | 68 | * invoking call_rcu(). |
9b1d82fa PM |
69 | */ |
70 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) | |
71 | { | |
14961444 | 72 | RCU_TRACE(reset_cpu_stall_ticks(rcp)); |
27153acb | 73 | if (rcp->donetail != rcp->curtail) { |
9b1d82fa | 74 | rcp->donetail = rcp->curtail; |
9b1d82fa PM |
75 | return 1; |
76 | } | |
4ce5b903 | 77 | |
9b1d82fa PM |
78 | return 0; |
79 | } | |
80 | ||
81 | /* | |
82 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we | |
83 | * are at it, given that any rcu quiescent state is also an rcu_bh | |
84 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. | |
85 | */ | |
284a8c93 | 86 | void rcu_sched_qs(void) |
9b1d82fa | 87 | { |
b554d7de ED |
88 | unsigned long flags; |
89 | ||
90 | local_irq_save(flags); | |
99652b54 PM |
91 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
92 | rcu_qsctr_help(&rcu_bh_ctrlblk)) | |
9dc5ad32 | 93 | raise_softirq(RCU_SOFTIRQ); |
b554d7de | 94 | local_irq_restore(flags); |
9b1d82fa PM |
95 | } |
96 | ||
97 | /* | |
98 | * Record an rcu_bh quiescent state. | |
99 | */ | |
284a8c93 | 100 | void rcu_bh_qs(void) |
9b1d82fa | 101 | { |
b554d7de ED |
102 | unsigned long flags; |
103 | ||
104 | local_irq_save(flags); | |
9b1d82fa | 105 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
9dc5ad32 | 106 | raise_softirq(RCU_SOFTIRQ); |
b554d7de | 107 | local_irq_restore(flags); |
9b1d82fa PM |
108 | } |
109 | ||
110 | /* | |
111 | * Check to see if the scheduling-clock interrupt came from an extended | |
9b2e4f18 PM |
112 | * quiescent state, and, if so, tell RCU about it. This function must |
113 | * be called from hardirq context. It is normally called from the | |
114 | * scheduling-clock interrupt. | |
9b1d82fa | 115 | */ |
c3377c2d | 116 | void rcu_check_callbacks(int user) |
9b1d82fa | 117 | { |
14961444 | 118 | RCU_TRACE(check_cpu_stalls()); |
ca9558a3 | 119 | if (user) |
284a8c93 | 120 | rcu_sched_qs(); |
9b1d82fa | 121 | else if (!in_softirq()) |
284a8c93 | 122 | rcu_bh_qs(); |
8315f422 PM |
123 | if (user) |
124 | rcu_note_voluntary_context_switch(current); | |
9b1d82fa PM |
125 | } |
126 | ||
127 | /* | |
b2c0710c PM |
128 | * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure |
129 | * whose grace period has elapsed. | |
9b1d82fa | 130 | */ |
965a002b | 131 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
9b1d82fa | 132 | { |
e66c33d5 | 133 | const char *rn = NULL; |
9b1d82fa | 134 | struct rcu_head *next, *list; |
4ce5b903 | 135 | unsigned long flags; |
9e571a82 | 136 | RCU_TRACE(int cb_count = 0); |
9b1d82fa | 137 | |
9b1d82fa PM |
138 | /* Move the ready-to-invoke callbacks to a local list. */ |
139 | local_irq_save(flags); | |
6e91f8cb PM |
140 | if (rcp->donetail == &rcp->rcucblist) { |
141 | /* No callbacks ready, so just leave. */ | |
142 | local_irq_restore(flags); | |
143 | return; | |
144 | } | |
486e2593 | 145 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1)); |
9b1d82fa PM |
146 | list = rcp->rcucblist; |
147 | rcp->rcucblist = *rcp->donetail; | |
148 | *rcp->donetail = NULL; | |
149 | if (rcp->curtail == rcp->donetail) | |
150 | rcp->curtail = &rcp->rcucblist; | |
151 | rcp->donetail = &rcp->rcucblist; | |
152 | local_irq_restore(flags); | |
153 | ||
154 | /* Invoke the callbacks on the local list. */ | |
d4c08f2a | 155 | RCU_TRACE(rn = rcp->name); |
9b1d82fa PM |
156 | while (list) { |
157 | next = list->next; | |
158 | prefetch(next); | |
551d55a9 | 159 | debug_rcu_head_unqueue(list); |
b2c0710c | 160 | local_bh_disable(); |
d4c08f2a | 161 | __rcu_reclaim(rn, list); |
b2c0710c | 162 | local_bh_enable(); |
9b1d82fa | 163 | list = next; |
9e571a82 | 164 | RCU_TRACE(cb_count++); |
9b1d82fa | 165 | } |
9e571a82 | 166 | RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
0d752924 PM |
167 | RCU_TRACE(trace_rcu_batch_end(rcp->name, |
168 | cb_count, 0, need_resched(), | |
4968c300 | 169 | is_idle_task(current), |
9dc5ad32 | 170 | false)); |
9b1d82fa PM |
171 | } |
172 | ||
965a002b | 173 | static void rcu_process_callbacks(struct softirq_action *unused) |
b2c0710c | 174 | { |
965a002b PM |
175 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
176 | __rcu_process_callbacks(&rcu_bh_ctrlblk); | |
b2c0710c PM |
177 | } |
178 | ||
9b1d82fa PM |
179 | /* |
180 | * Wait for a grace period to elapse. But it is illegal to invoke | |
181 | * synchronize_sched() from within an RCU read-side critical section. | |
182 | * Therefore, any legal call to synchronize_sched() is a quiescent | |
183 | * state, and so on a UP system, synchronize_sched() need do nothing. | |
184 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the | |
185 | * benefits of doing might_sleep() to reduce latency.) | |
186 | * | |
187 | * Cool, huh? (Due to Josh Triplett.) | |
188 | * | |
da848c47 PM |
189 | * But we want to make this a static inline later. The cond_resched() |
190 | * currently makes this problematic. | |
9b1d82fa PM |
191 | */ |
192 | void synchronize_sched(void) | |
193 | { | |
fe15d706 PM |
194 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
195 | !lock_is_held(&rcu_lock_map) && | |
196 | !lock_is_held(&rcu_sched_lock_map), | |
197 | "Illegal synchronize_sched() in RCU read-side critical section"); | |
9b1d82fa PM |
198 | cond_resched(); |
199 | } | |
200 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
201 | ||
9b1d82fa PM |
202 | /* |
203 | * Helper function for call_rcu() and call_rcu_bh(). | |
204 | */ | |
205 | static void __call_rcu(struct rcu_head *head, | |
206 | void (*func)(struct rcu_head *rcu), | |
207 | struct rcu_ctrlblk *rcp) | |
208 | { | |
209 | unsigned long flags; | |
210 | ||
551d55a9 | 211 | debug_rcu_head_queue(head); |
9b1d82fa PM |
212 | head->func = func; |
213 | head->next = NULL; | |
4ce5b903 | 214 | |
9b1d82fa PM |
215 | local_irq_save(flags); |
216 | *rcp->curtail = head; | |
217 | rcp->curtail = &head->next; | |
9e571a82 | 218 | RCU_TRACE(rcp->qlen++); |
9b1d82fa | 219 | local_irq_restore(flags); |
5f6130fa LJ |
220 | |
221 | if (unlikely(is_idle_task(current))) { | |
222 | /* force scheduling for rcu_sched_qs() */ | |
223 | resched_cpu(0); | |
224 | } | |
9b1d82fa PM |
225 | } |
226 | ||
227 | /* | |
a57eb940 | 228 | * Post an RCU callback to be invoked after the end of an RCU-sched grace |
9b1d82fa PM |
229 | * period. But since we have but one CPU, that would be after any |
230 | * quiescent state. | |
231 | */ | |
a57eb940 | 232 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa | 233 | { |
99652b54 | 234 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
9b1d82fa | 235 | } |
a57eb940 | 236 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
9b1d82fa PM |
237 | |
238 | /* | |
239 | * Post an RCU bottom-half callback to be invoked after any subsequent | |
240 | * quiescent state. | |
241 | */ | |
4ce5b903 | 242 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa PM |
243 | { |
244 | __call_rcu(head, func, &rcu_bh_ctrlblk); | |
245 | } | |
246 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
9dc5ad32 | 247 | |
aa23c6fb | 248 | void __init rcu_init(void) |
9dc5ad32 PM |
249 | { |
250 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); | |
630181c4 PM |
251 | RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk)); |
252 | RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk)); | |
aa23c6fb PK |
253 | |
254 | rcu_early_boot_tests(); | |
9dc5ad32 | 255 | } |