Commit | Line | Data |
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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> | |
a71fca58 | 22 | * |
1da177e4 LT |
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 - | |
a71fca58 | 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
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> | |
60063497 | 40 | #include <linux/atomic.h> |
1da177e4 | 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> |
9984de1a | 46 | #include <linux/export.h> |
e3818b8d | 47 | #include <linux/hardirq.h> |
1da177e4 | 48 | |
29c00b4a PM |
49 | #define CREATE_TRACE_POINTS |
50 | #include <trace/events/rcu.h> | |
51 | ||
52 | #include "rcu.h" | |
53 | ||
162cc279 PM |
54 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
55 | static struct lock_class_key rcu_lock_key; | |
56 | struct lockdep_map rcu_lock_map = | |
57 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); | |
58 | EXPORT_SYMBOL_GPL(rcu_lock_map); | |
632ee200 PM |
59 | |
60 | static struct lock_class_key rcu_bh_lock_key; | |
61 | struct lockdep_map rcu_bh_lock_map = | |
62 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); | |
63 | EXPORT_SYMBOL_GPL(rcu_bh_lock_map); | |
64 | ||
65 | static struct lock_class_key rcu_sched_lock_key; | |
66 | struct lockdep_map rcu_sched_lock_map = | |
67 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); | |
68 | EXPORT_SYMBOL_GPL(rcu_sched_lock_map); | |
162cc279 PM |
69 | #endif |
70 | ||
e3818b8d PM |
71 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
72 | ||
bc293d62 PM |
73 | int debug_lockdep_rcu_enabled(void) |
74 | { | |
75 | return rcu_scheduler_active && debug_locks && | |
76 | current->lockdep_recursion == 0; | |
77 | } | |
78 | EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); | |
79 | ||
e3818b8d | 80 | /** |
ca5ecddf | 81 | * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? |
e3818b8d PM |
82 | * |
83 | * Check for bottom half being disabled, which covers both the | |
84 | * CONFIG_PROVE_RCU and not cases. Note that if someone uses | |
85 | * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) | |
ca5ecddf PM |
86 | * will show the situation. This is useful for debug checks in functions |
87 | * that require that they be called within an RCU read-side critical | |
88 | * section. | |
e3818b8d PM |
89 | * |
90 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. | |
91 | */ | |
92 | int rcu_read_lock_bh_held(void) | |
93 | { | |
94 | if (!debug_lockdep_rcu_enabled()) | |
95 | return 1; | |
773e3f93 | 96 | return in_softirq() || irqs_disabled(); |
e3818b8d PM |
97 | } |
98 | EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); | |
99 | ||
100 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
101 | ||
2c42818e PM |
102 | struct rcu_synchronize { |
103 | struct rcu_head head; | |
104 | struct completion completion; | |
105 | }; | |
106 | ||
fbf6bfca PM |
107 | /* |
108 | * Awaken the corresponding synchronize_rcu() instance now that a | |
109 | * grace period has elapsed. | |
110 | */ | |
2c42818e | 111 | static void wakeme_after_rcu(struct rcu_head *head) |
21a1ea9e | 112 | { |
01c1c660 PM |
113 | struct rcu_synchronize *rcu; |
114 | ||
115 | rcu = container_of(head, struct rcu_synchronize, head); | |
116 | complete(&rcu->completion); | |
21a1ea9e | 117 | } |
ee84b824 | 118 | |
2c42818e PM |
119 | void wait_rcu_gp(call_rcu_func_t crf) |
120 | { | |
121 | struct rcu_synchronize rcu; | |
122 | ||
123 | init_rcu_head_on_stack(&rcu.head); | |
124 | init_completion(&rcu.completion); | |
125 | /* Will wake me after RCU finished. */ | |
126 | crf(&rcu.head, wakeme_after_rcu); | |
127 | /* Wait for it. */ | |
128 | wait_for_completion(&rcu.completion); | |
129 | destroy_rcu_head_on_stack(&rcu.head); | |
130 | } | |
131 | EXPORT_SYMBOL_GPL(wait_rcu_gp); | |
132 | ||
ee84b824 PM |
133 | #ifdef CONFIG_PROVE_RCU |
134 | /* | |
135 | * wrapper function to avoid #include problems. | |
136 | */ | |
137 | int rcu_my_thread_group_empty(void) | |
138 | { | |
139 | return thread_group_empty(current); | |
140 | } | |
141 | EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty); | |
142 | #endif /* #ifdef CONFIG_PROVE_RCU */ | |
551d55a9 MD |
143 | |
144 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD | |
145 | static inline void debug_init_rcu_head(struct rcu_head *head) | |
146 | { | |
147 | debug_object_init(head, &rcuhead_debug_descr); | |
148 | } | |
149 | ||
150 | static inline void debug_rcu_head_free(struct rcu_head *head) | |
151 | { | |
152 | debug_object_free(head, &rcuhead_debug_descr); | |
153 | } | |
154 | ||
155 | /* | |
156 | * fixup_init is called when: | |
157 | * - an active object is initialized | |
158 | */ | |
159 | static int rcuhead_fixup_init(void *addr, enum debug_obj_state state) | |
160 | { | |
161 | struct rcu_head *head = addr; | |
162 | ||
163 | switch (state) { | |
164 | case ODEBUG_STATE_ACTIVE: | |
165 | /* | |
166 | * Ensure that queued callbacks are all executed. | |
167 | * If we detect that we are nested in a RCU read-side critical | |
168 | * section, we should simply fail, otherwise we would deadlock. | |
fc2ecf7e MD |
169 | * In !PREEMPT configurations, there is no way to tell if we are |
170 | * in a RCU read-side critical section or not, so we never | |
171 | * attempt any fixup and just print a warning. | |
551d55a9 | 172 | */ |
fc2ecf7e | 173 | #ifndef CONFIG_PREEMPT |
108aae22 | 174 | WARN_ON_ONCE(1); |
fc2ecf7e MD |
175 | return 0; |
176 | #endif | |
551d55a9 MD |
177 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
178 | irqs_disabled()) { | |
108aae22 | 179 | WARN_ON_ONCE(1); |
551d55a9 MD |
180 | return 0; |
181 | } | |
182 | rcu_barrier(); | |
183 | rcu_barrier_sched(); | |
184 | rcu_barrier_bh(); | |
185 | debug_object_init(head, &rcuhead_debug_descr); | |
186 | return 1; | |
187 | default: | |
188 | return 0; | |
189 | } | |
190 | } | |
191 | ||
192 | /* | |
193 | * fixup_activate is called when: | |
194 | * - an active object is activated | |
195 | * - an unknown object is activated (might be a statically initialized object) | |
196 | * Activation is performed internally by call_rcu(). | |
197 | */ | |
198 | static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state) | |
199 | { | |
200 | struct rcu_head *head = addr; | |
201 | ||
202 | switch (state) { | |
203 | ||
204 | case ODEBUG_STATE_NOTAVAILABLE: | |
205 | /* | |
206 | * This is not really a fixup. We just make sure that it is | |
207 | * tracked in the object tracker. | |
208 | */ | |
209 | debug_object_init(head, &rcuhead_debug_descr); | |
210 | debug_object_activate(head, &rcuhead_debug_descr); | |
211 | return 0; | |
212 | ||
213 | case ODEBUG_STATE_ACTIVE: | |
214 | /* | |
215 | * Ensure that queued callbacks are all executed. | |
216 | * If we detect that we are nested in a RCU read-side critical | |
217 | * section, we should simply fail, otherwise we would deadlock. | |
fc2ecf7e MD |
218 | * In !PREEMPT configurations, there is no way to tell if we are |
219 | * in a RCU read-side critical section or not, so we never | |
220 | * attempt any fixup and just print a warning. | |
551d55a9 | 221 | */ |
fc2ecf7e | 222 | #ifndef CONFIG_PREEMPT |
108aae22 | 223 | WARN_ON_ONCE(1); |
fc2ecf7e MD |
224 | return 0; |
225 | #endif | |
551d55a9 MD |
226 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
227 | irqs_disabled()) { | |
108aae22 | 228 | WARN_ON_ONCE(1); |
551d55a9 MD |
229 | return 0; |
230 | } | |
231 | rcu_barrier(); | |
232 | rcu_barrier_sched(); | |
233 | rcu_barrier_bh(); | |
234 | debug_object_activate(head, &rcuhead_debug_descr); | |
235 | return 1; | |
236 | default: | |
237 | return 0; | |
238 | } | |
239 | } | |
240 | ||
241 | /* | |
242 | * fixup_free is called when: | |
243 | * - an active object is freed | |
244 | */ | |
245 | static int rcuhead_fixup_free(void *addr, enum debug_obj_state state) | |
246 | { | |
247 | struct rcu_head *head = addr; | |
248 | ||
249 | switch (state) { | |
250 | case ODEBUG_STATE_ACTIVE: | |
251 | /* | |
252 | * Ensure that queued callbacks are all executed. | |
253 | * If we detect that we are nested in a RCU read-side critical | |
254 | * section, we should simply fail, otherwise we would deadlock. | |
fc2ecf7e MD |
255 | * In !PREEMPT configurations, there is no way to tell if we are |
256 | * in a RCU read-side critical section or not, so we never | |
257 | * attempt any fixup and just print a warning. | |
551d55a9 | 258 | */ |
fc2ecf7e | 259 | #ifndef CONFIG_PREEMPT |
108aae22 | 260 | WARN_ON_ONCE(1); |
fc2ecf7e MD |
261 | return 0; |
262 | #endif | |
551d55a9 MD |
263 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
264 | irqs_disabled()) { | |
108aae22 | 265 | WARN_ON_ONCE(1); |
551d55a9 MD |
266 | return 0; |
267 | } | |
268 | rcu_barrier(); | |
269 | rcu_barrier_sched(); | |
270 | rcu_barrier_bh(); | |
271 | debug_object_free(head, &rcuhead_debug_descr); | |
272 | return 1; | |
551d55a9 MD |
273 | default: |
274 | return 0; | |
275 | } | |
276 | } | |
277 | ||
278 | /** | |
279 | * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects | |
280 | * @head: pointer to rcu_head structure to be initialized | |
281 | * | |
282 | * This function informs debugobjects of a new rcu_head structure that | |
283 | * has been allocated as an auto variable on the stack. This function | |
284 | * is not required for rcu_head structures that are statically defined or | |
285 | * that are dynamically allocated on the heap. This function has no | |
286 | * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. | |
287 | */ | |
288 | void init_rcu_head_on_stack(struct rcu_head *head) | |
289 | { | |
290 | debug_object_init_on_stack(head, &rcuhead_debug_descr); | |
291 | } | |
292 | EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); | |
293 | ||
294 | /** | |
295 | * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects | |
296 | * @head: pointer to rcu_head structure to be initialized | |
297 | * | |
298 | * This function informs debugobjects that an on-stack rcu_head structure | |
299 | * is about to go out of scope. As with init_rcu_head_on_stack(), this | |
300 | * function is not required for rcu_head structures that are statically | |
301 | * defined or that are dynamically allocated on the heap. Also as with | |
302 | * init_rcu_head_on_stack(), this function has no effect for | |
303 | * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. | |
304 | */ | |
305 | void destroy_rcu_head_on_stack(struct rcu_head *head) | |
306 | { | |
307 | debug_object_free(head, &rcuhead_debug_descr); | |
308 | } | |
309 | EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); | |
310 | ||
311 | struct debug_obj_descr rcuhead_debug_descr = { | |
312 | .name = "rcu_head", | |
313 | .fixup_init = rcuhead_fixup_init, | |
314 | .fixup_activate = rcuhead_fixup_activate, | |
315 | .fixup_free = rcuhead_fixup_free, | |
316 | }; | |
317 | EXPORT_SYMBOL_GPL(rcuhead_debug_descr); | |
318 | #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |