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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 | * |
18 | * Copyright IBM Corporation, 2001 |
19 | * |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
21 | * Manfred Spraul <manfred@colorfullife.com> |
22 | * |
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 - |
30 | * http://lse.sourceforge.net/locking/rcupdate.html |
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> |
40 | #include <asm/atomic.h> |
41 | #include <linux/bitops.h> |
42 | #include <linux/percpu.h> |
43 | #include <linux/notifier.h> |
44 | #include <linux/cpu.h> |
45 | #include <linux/mutex.h> |
46 | #include <linux/module.h> |
47 | #include <linux/hardirq.h> |
48 | |
49 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
50 | static struct lock_class_key rcu_lock_key; |
51 | struct lockdep_map rcu_lock_map = |
52 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); |
53 | EXPORT_SYMBOL_GPL(rcu_lock_map); |
54 | |
55 | static struct lock_class_key rcu_bh_lock_key; |
56 | struct lockdep_map rcu_bh_lock_map = |
57 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); |
58 | EXPORT_SYMBOL_GPL(rcu_bh_lock_map); |
59 | |
60 | static struct lock_class_key rcu_sched_lock_key; |
61 | struct lockdep_map rcu_sched_lock_map = |
62 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); |
63 | EXPORT_SYMBOL_GPL(rcu_sched_lock_map); |
64 | #endif |
65 | |
66 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
67 | |
68 | int debug_lockdep_rcu_enabled(void) |
69 | { |
70 | return rcu_scheduler_active && debug_locks && |
71 | current->lockdep_recursion == 0; |
72 | } |
73 | EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); |
74 | |
75 | /** |
76 | * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section? |
77 | * |
78 | * Check for bottom half being disabled, which covers both the |
79 | * CONFIG_PROVE_RCU and not cases. Note that if someone uses |
80 | * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) |
81 | * will show the situation. |
82 | * |
83 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. |
84 | */ |
85 | int rcu_read_lock_bh_held(void) |
86 | { |
87 | if (!debug_lockdep_rcu_enabled()) |
88 | return 1; |
89 | return in_softirq(); |
90 | } |
91 | EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); |
92 | |
93 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
94 | |
95 | /* |
96 | * Awaken the corresponding synchronize_rcu() instance now that a |
97 | * grace period has elapsed. |
98 | */ |
99 | void wakeme_after_rcu(struct rcu_head *head) |
100 | { |
101 | struct rcu_synchronize *rcu; |
102 | |
103 | rcu = container_of(head, struct rcu_synchronize, head); |
104 | complete(&rcu->completion); |
105 | } |
106 | |
107 | #ifdef CONFIG_PROVE_RCU |
108 | /* |
109 | * wrapper function to avoid #include problems. |
110 | */ |
111 | int rcu_my_thread_group_empty(void) |
112 | { |
113 | return thread_group_empty(current); |
114 | } |
115 | EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty); |
116 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
117 | |
118 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
119 | static inline void debug_init_rcu_head(struct rcu_head *head) |
120 | { |
121 | debug_object_init(head, &rcuhead_debug_descr); |
122 | } |
123 | |
124 | static inline void debug_rcu_head_free(struct rcu_head *head) |
125 | { |
126 | debug_object_free(head, &rcuhead_debug_descr); |
127 | } |
128 | |
129 | /* |
130 | * fixup_init is called when: |
131 | * - an active object is initialized |
132 | */ |
133 | static int rcuhead_fixup_init(void *addr, enum debug_obj_state state) |
134 | { |
135 | struct rcu_head *head = addr; |
136 | |
137 | switch (state) { |
138 | case ODEBUG_STATE_ACTIVE: |
139 | /* |
140 | * Ensure that queued callbacks are all executed. |
141 | * If we detect that we are nested in a RCU read-side critical |
142 | * section, we should simply fail, otherwise we would deadlock. |
143 | */ |
144 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
145 | irqs_disabled()) { |
146 | WARN_ON(1); |
147 | return 0; |
148 | } |
149 | rcu_barrier(); |
150 | rcu_barrier_sched(); |
151 | rcu_barrier_bh(); |
152 | debug_object_init(head, &rcuhead_debug_descr); |
153 | return 1; |
154 | default: |
155 | return 0; |
156 | } |
157 | } |
158 | |
159 | /* |
160 | * fixup_activate is called when: |
161 | * - an active object is activated |
162 | * - an unknown object is activated (might be a statically initialized object) |
163 | * Activation is performed internally by call_rcu(). |
164 | */ |
165 | static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state) |
166 | { |
167 | struct rcu_head *head = addr; |
168 | |
169 | switch (state) { |
170 | |
171 | case ODEBUG_STATE_NOTAVAILABLE: |
172 | /* |
173 | * This is not really a fixup. We just make sure that it is |
174 | * tracked in the object tracker. |
175 | */ |
176 | debug_object_init(head, &rcuhead_debug_descr); |
177 | debug_object_activate(head, &rcuhead_debug_descr); |
178 | return 0; |
179 | |
180 | case ODEBUG_STATE_ACTIVE: |
181 | /* |
182 | * Ensure that queued callbacks are all executed. |
183 | * If we detect that we are nested in a RCU read-side critical |
184 | * section, we should simply fail, otherwise we would deadlock. |
185 | */ |
186 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
187 | irqs_disabled()) { |
188 | WARN_ON(1); |
189 | return 0; |
190 | } |
191 | rcu_barrier(); |
192 | rcu_barrier_sched(); |
193 | rcu_barrier_bh(); |
194 | debug_object_activate(head, &rcuhead_debug_descr); |
195 | return 1; |
196 | default: |
197 | return 0; |
198 | } |
199 | } |
200 | |
201 | /* |
202 | * fixup_free is called when: |
203 | * - an active object is freed |
204 | */ |
205 | static int rcuhead_fixup_free(void *addr, enum debug_obj_state state) |
206 | { |
207 | struct rcu_head *head = addr; |
208 | |
209 | switch (state) { |
210 | case ODEBUG_STATE_ACTIVE: |
211 | /* |
212 | * Ensure that queued callbacks are all executed. |
213 | * If we detect that we are nested in a RCU read-side critical |
214 | * section, we should simply fail, otherwise we would deadlock. |
215 | */ |
216 | #ifndef CONFIG_PREEMPT |
217 | WARN_ON(1); |
218 | return 0; |
219 | #else |
220 | if (rcu_preempt_depth() != 0 || preempt_count() != 0 || |
221 | irqs_disabled()) { |
222 | WARN_ON(1); |
223 | return 0; |
224 | } |
225 | rcu_barrier(); |
226 | rcu_barrier_sched(); |
227 | rcu_barrier_bh(); |
228 | debug_object_free(head, &rcuhead_debug_descr); |
229 | return 1; |
230 | #endif |
231 | default: |
232 | return 0; |
233 | } |
234 | } |
235 | |
236 | /** |
237 | * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects |
238 | * @head: pointer to rcu_head structure to be initialized |
239 | * |
240 | * This function informs debugobjects of a new rcu_head structure that |
241 | * has been allocated as an auto variable on the stack. This function |
242 | * is not required for rcu_head structures that are statically defined or |
243 | * that are dynamically allocated on the heap. This function has no |
244 | * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
245 | */ |
246 | void init_rcu_head_on_stack(struct rcu_head *head) |
247 | { |
248 | debug_object_init_on_stack(head, &rcuhead_debug_descr); |
249 | } |
250 | EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); |
251 | |
252 | /** |
253 | * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects |
254 | * @head: pointer to rcu_head structure to be initialized |
255 | * |
256 | * This function informs debugobjects that an on-stack rcu_head structure |
257 | * is about to go out of scope. As with init_rcu_head_on_stack(), this |
258 | * function is not required for rcu_head structures that are statically |
259 | * defined or that are dynamically allocated on the heap. Also as with |
260 | * init_rcu_head_on_stack(), this function has no effect for |
261 | * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
262 | */ |
263 | void destroy_rcu_head_on_stack(struct rcu_head *head) |
264 | { |
265 | debug_object_free(head, &rcuhead_debug_descr); |
266 | } |
267 | EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); |
268 | |
269 | struct debug_obj_descr rcuhead_debug_descr = { |
270 | .name = "rcu_head", |
271 | .fixup_init = rcuhead_fixup_init, |
272 | .fixup_activate = rcuhead_fixup_activate, |
273 | .fixup_free = rcuhead_fixup_free, |
274 | }; |
275 | EXPORT_SYMBOL_GPL(rcuhead_debug_descr); |
276 | #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
277 |
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