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/export.h>
47 #include <linux/hardirq.h>
48
49 #define CREATE_TRACE_POINTS
50 #include <trace/events/rcu.h>
51
52 #include "rcu.h"
53
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);
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);
69 #endif
70
71 #ifdef CONFIG_DEBUG_LOCK_ALLOC
72
debug_lockdep_rcu_enabled(void)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
80 /**
81 * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
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)
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.
89 *
90 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
91 */
rcu_read_lock_bh_held(void)92 int rcu_read_lock_bh_held(void)
93 {
94 if (!debug_lockdep_rcu_enabled())
95 return 1;
96 if (rcu_is_cpu_idle())
97 return 0;
98 return in_softirq() || irqs_disabled();
99 }
100 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
101
102 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
103
104 struct rcu_synchronize {
105 struct rcu_head head;
106 struct completion completion;
107 };
108
109 /*
110 * Awaken the corresponding synchronize_rcu() instance now that a
111 * grace period has elapsed.
112 */
wakeme_after_rcu(struct rcu_head * head)113 static void wakeme_after_rcu(struct rcu_head *head)
114 {
115 struct rcu_synchronize *rcu;
116
117 rcu = container_of(head, struct rcu_synchronize, head);
118 complete(&rcu->completion);
119 }
120
wait_rcu_gp(call_rcu_func_t crf)121 void wait_rcu_gp(call_rcu_func_t crf)
122 {
123 struct rcu_synchronize rcu;
124
125 init_rcu_head_on_stack(&rcu.head);
126 init_completion(&rcu.completion);
127 /* Will wake me after RCU finished. */
128 crf(&rcu.head, wakeme_after_rcu);
129 /* Wait for it. */
130 wait_for_completion(&rcu.completion);
131 destroy_rcu_head_on_stack(&rcu.head);
132 }
133 EXPORT_SYMBOL_GPL(wait_rcu_gp);
134
135 #ifdef CONFIG_PROVE_RCU
136 /*
137 * wrapper function to avoid #include problems.
138 */
rcu_my_thread_group_empty(void)139 int rcu_my_thread_group_empty(void)
140 {
141 return thread_group_empty(current);
142 }
143 EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
144 #endif /* #ifdef CONFIG_PROVE_RCU */
145
146 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
debug_init_rcu_head(struct rcu_head * head)147 static inline void debug_init_rcu_head(struct rcu_head *head)
148 {
149 debug_object_init(head, &rcuhead_debug_descr);
150 }
151
debug_rcu_head_free(struct rcu_head * head)152 static inline void debug_rcu_head_free(struct rcu_head *head)
153 {
154 debug_object_free(head, &rcuhead_debug_descr);
155 }
156
157 /*
158 * fixup_init is called when:
159 * - an active object is initialized
160 */
rcuhead_fixup_init(void * addr,enum debug_obj_state state)161 static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
162 {
163 struct rcu_head *head = addr;
164
165 switch (state) {
166 case ODEBUG_STATE_ACTIVE:
167 /*
168 * Ensure that queued callbacks are all executed.
169 * If we detect that we are nested in a RCU read-side critical
170 * section, we should simply fail, otherwise we would deadlock.
171 * In !PREEMPT configurations, there is no way to tell if we are
172 * in a RCU read-side critical section or not, so we never
173 * attempt any fixup and just print a warning.
174 */
175 #ifndef CONFIG_PREEMPT
176 WARN_ON_ONCE(1);
177 return 0;
178 #endif
179 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
180 irqs_disabled()) {
181 WARN_ON_ONCE(1);
182 return 0;
183 }
184 rcu_barrier();
185 rcu_barrier_sched();
186 rcu_barrier_bh();
187 debug_object_init(head, &rcuhead_debug_descr);
188 return 1;
189 default:
190 return 0;
191 }
192 }
193
194 /*
195 * fixup_activate is called when:
196 * - an active object is activated
197 * - an unknown object is activated (might be a statically initialized object)
198 * Activation is performed internally by call_rcu().
199 */
rcuhead_fixup_activate(void * addr,enum debug_obj_state state)200 static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
201 {
202 struct rcu_head *head = addr;
203
204 switch (state) {
205
206 case ODEBUG_STATE_NOTAVAILABLE:
207 /*
208 * This is not really a fixup. We just make sure that it is
209 * tracked in the object tracker.
210 */
211 debug_object_init(head, &rcuhead_debug_descr);
212 debug_object_activate(head, &rcuhead_debug_descr);
213 return 0;
214
215 case ODEBUG_STATE_ACTIVE:
216 /*
217 * Ensure that queued callbacks are all executed.
218 * If we detect that we are nested in a RCU read-side critical
219 * section, we should simply fail, otherwise we would deadlock.
220 * In !PREEMPT configurations, there is no way to tell if we are
221 * in a RCU read-side critical section or not, so we never
222 * attempt any fixup and just print a warning.
223 */
224 #ifndef CONFIG_PREEMPT
225 WARN_ON_ONCE(1);
226 return 0;
227 #endif
228 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
229 irqs_disabled()) {
230 WARN_ON_ONCE(1);
231 return 0;
232 }
233 rcu_barrier();
234 rcu_barrier_sched();
235 rcu_barrier_bh();
236 debug_object_activate(head, &rcuhead_debug_descr);
237 return 1;
238 default:
239 return 0;
240 }
241 }
242
243 /*
244 * fixup_free is called when:
245 * - an active object is freed
246 */
rcuhead_fixup_free(void * addr,enum debug_obj_state state)247 static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
248 {
249 struct rcu_head *head = addr;
250
251 switch (state) {
252 case ODEBUG_STATE_ACTIVE:
253 /*
254 * Ensure that queued callbacks are all executed.
255 * If we detect that we are nested in a RCU read-side critical
256 * section, we should simply fail, otherwise we would deadlock.
257 * In !PREEMPT configurations, there is no way to tell if we are
258 * in a RCU read-side critical section or not, so we never
259 * attempt any fixup and just print a warning.
260 */
261 #ifndef CONFIG_PREEMPT
262 WARN_ON_ONCE(1);
263 return 0;
264 #endif
265 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
266 irqs_disabled()) {
267 WARN_ON_ONCE(1);
268 return 0;
269 }
270 rcu_barrier();
271 rcu_barrier_sched();
272 rcu_barrier_bh();
273 debug_object_free(head, &rcuhead_debug_descr);
274 return 1;
275 default:
276 return 0;
277 }
278 }
279
280 /**
281 * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
282 * @head: pointer to rcu_head structure to be initialized
283 *
284 * This function informs debugobjects of a new rcu_head structure that
285 * has been allocated as an auto variable on the stack. This function
286 * is not required for rcu_head structures that are statically defined or
287 * that are dynamically allocated on the heap. This function has no
288 * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
289 */
init_rcu_head_on_stack(struct rcu_head * head)290 void init_rcu_head_on_stack(struct rcu_head *head)
291 {
292 debug_object_init_on_stack(head, &rcuhead_debug_descr);
293 }
294 EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
295
296 /**
297 * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
298 * @head: pointer to rcu_head structure to be initialized
299 *
300 * This function informs debugobjects that an on-stack rcu_head structure
301 * is about to go out of scope. As with init_rcu_head_on_stack(), this
302 * function is not required for rcu_head structures that are statically
303 * defined or that are dynamically allocated on the heap. Also as with
304 * init_rcu_head_on_stack(), this function has no effect for
305 * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
306 */
destroy_rcu_head_on_stack(struct rcu_head * head)307 void destroy_rcu_head_on_stack(struct rcu_head *head)
308 {
309 debug_object_free(head, &rcuhead_debug_descr);
310 }
311 EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
312
313 struct debug_obj_descr rcuhead_debug_descr = {
314 .name = "rcu_head",
315 .fixup_init = rcuhead_fixup_init,
316 .fixup_activate = rcuhead_fixup_activate,
317 .fixup_free = rcuhead_fixup_free,
318 };
319 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
320 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
321
322 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
do_trace_rcu_torture_read(char * rcutorturename,struct rcu_head * rhp)323 void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)
324 {
325 trace_rcu_torture_read(rcutorturename, rhp);
326 }
327 EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
328 #else
329 #define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
330 #endif
331