Loading...
Note: File does not exist in v6.13.7.
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 <linux/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
50static struct lock_class_key rcu_lock_key;
51struct lockdep_map rcu_lock_map =
52 STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
53EXPORT_SYMBOL_GPL(rcu_lock_map);
54
55static struct lock_class_key rcu_bh_lock_key;
56struct lockdep_map rcu_bh_lock_map =
57 STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
58EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
59
60static struct lock_class_key rcu_sched_lock_key;
61struct lockdep_map rcu_sched_lock_map =
62 STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
63EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
64#endif
65
66#ifdef CONFIG_DEBUG_LOCK_ALLOC
67
68int debug_lockdep_rcu_enabled(void)
69{
70 return rcu_scheduler_active && debug_locks &&
71 current->lockdep_recursion == 0;
72}
73EXPORT_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. This is useful for debug checks in functions
82 * that require that they be called within an RCU read-side critical
83 * section.
84 *
85 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
86 */
87int rcu_read_lock_bh_held(void)
88{
89 if (!debug_lockdep_rcu_enabled())
90 return 1;
91 return in_softirq() || irqs_disabled();
92}
93EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
94
95#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
96
97/*
98 * Awaken the corresponding synchronize_rcu() instance now that a
99 * grace period has elapsed.
100 */
101void wakeme_after_rcu(struct rcu_head *head)
102{
103 struct rcu_synchronize *rcu;
104
105 rcu = container_of(head, struct rcu_synchronize, head);
106 complete(&rcu->completion);
107}
108
109#ifdef CONFIG_PROVE_RCU
110/*
111 * wrapper function to avoid #include problems.
112 */
113int rcu_my_thread_group_empty(void)
114{
115 return thread_group_empty(current);
116}
117EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
118#endif /* #ifdef CONFIG_PROVE_RCU */
119
120#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
121static inline void debug_init_rcu_head(struct rcu_head *head)
122{
123 debug_object_init(head, &rcuhead_debug_descr);
124}
125
126static inline void debug_rcu_head_free(struct rcu_head *head)
127{
128 debug_object_free(head, &rcuhead_debug_descr);
129}
130
131/*
132 * fixup_init is called when:
133 * - an active object is initialized
134 */
135static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
136{
137 struct rcu_head *head = addr;
138
139 switch (state) {
140 case ODEBUG_STATE_ACTIVE:
141 /*
142 * Ensure that queued callbacks are all executed.
143 * If we detect that we are nested in a RCU read-side critical
144 * section, we should simply fail, otherwise we would deadlock.
145 * In !PREEMPT configurations, there is no way to tell if we are
146 * in a RCU read-side critical section or not, so we never
147 * attempt any fixup and just print a warning.
148 */
149#ifndef CONFIG_PREEMPT
150 WARN_ON_ONCE(1);
151 return 0;
152#endif
153 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
154 irqs_disabled()) {
155 WARN_ON_ONCE(1);
156 return 0;
157 }
158 rcu_barrier();
159 rcu_barrier_sched();
160 rcu_barrier_bh();
161 debug_object_init(head, &rcuhead_debug_descr);
162 return 1;
163 default:
164 return 0;
165 }
166}
167
168/*
169 * fixup_activate is called when:
170 * - an active object is activated
171 * - an unknown object is activated (might be a statically initialized object)
172 * Activation is performed internally by call_rcu().
173 */
174static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
175{
176 struct rcu_head *head = addr;
177
178 switch (state) {
179
180 case ODEBUG_STATE_NOTAVAILABLE:
181 /*
182 * This is not really a fixup. We just make sure that it is
183 * tracked in the object tracker.
184 */
185 debug_object_init(head, &rcuhead_debug_descr);
186 debug_object_activate(head, &rcuhead_debug_descr);
187 return 0;
188
189 case ODEBUG_STATE_ACTIVE:
190 /*
191 * Ensure that queued callbacks are all executed.
192 * If we detect that we are nested in a RCU read-side critical
193 * section, we should simply fail, otherwise we would deadlock.
194 * In !PREEMPT configurations, there is no way to tell if we are
195 * in a RCU read-side critical section or not, so we never
196 * attempt any fixup and just print a warning.
197 */
198#ifndef CONFIG_PREEMPT
199 WARN_ON_ONCE(1);
200 return 0;
201#endif
202 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
203 irqs_disabled()) {
204 WARN_ON_ONCE(1);
205 return 0;
206 }
207 rcu_barrier();
208 rcu_barrier_sched();
209 rcu_barrier_bh();
210 debug_object_activate(head, &rcuhead_debug_descr);
211 return 1;
212 default:
213 return 0;
214 }
215}
216
217/*
218 * fixup_free is called when:
219 * - an active object is freed
220 */
221static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
222{
223 struct rcu_head *head = addr;
224
225 switch (state) {
226 case ODEBUG_STATE_ACTIVE:
227 /*
228 * Ensure that queued callbacks are all executed.
229 * If we detect that we are nested in a RCU read-side critical
230 * section, we should simply fail, otherwise we would deadlock.
231 * In !PREEMPT configurations, there is no way to tell if we are
232 * in a RCU read-side critical section or not, so we never
233 * attempt any fixup and just print a warning.
234 */
235#ifndef CONFIG_PREEMPT
236 WARN_ON_ONCE(1);
237 return 0;
238#endif
239 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
240 irqs_disabled()) {
241 WARN_ON_ONCE(1);
242 return 0;
243 }
244 rcu_barrier();
245 rcu_barrier_sched();
246 rcu_barrier_bh();
247 debug_object_free(head, &rcuhead_debug_descr);
248 return 1;
249 default:
250 return 0;
251 }
252}
253
254/**
255 * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
256 * @head: pointer to rcu_head structure to be initialized
257 *
258 * This function informs debugobjects of a new rcu_head structure that
259 * has been allocated as an auto variable on the stack. This function
260 * is not required for rcu_head structures that are statically defined or
261 * that are dynamically allocated on the heap. This function has no
262 * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
263 */
264void init_rcu_head_on_stack(struct rcu_head *head)
265{
266 debug_object_init_on_stack(head, &rcuhead_debug_descr);
267}
268EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
269
270/**
271 * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
272 * @head: pointer to rcu_head structure to be initialized
273 *
274 * This function informs debugobjects that an on-stack rcu_head structure
275 * is about to go out of scope. As with init_rcu_head_on_stack(), this
276 * function is not required for rcu_head structures that are statically
277 * defined or that are dynamically allocated on the heap. Also as with
278 * init_rcu_head_on_stack(), this function has no effect for
279 * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
280 */
281void destroy_rcu_head_on_stack(struct rcu_head *head)
282{
283 debug_object_free(head, &rcuhead_debug_descr);
284}
285EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
286
287struct debug_obj_descr rcuhead_debug_descr = {
288 .name = "rcu_head",
289 .fixup_init = rcuhead_fixup_init,
290 .fixup_activate = rcuhead_fixup_activate,
291 .fixup_free = rcuhead_fixup_free,
292};
293EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
294#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */