2 * Read-Copy Update mechanism for mutual exclusion
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.
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.
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.
18 * Copyright IBM Corporation, 2001
20 * Authors: Dipankar Sarma <dipankar@in.ibm.com>
21 * Manfred Spraul <manfred@colorfullife.com>
23 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
24 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
26 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
27 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
29 * For detailed explanation of Read-Copy Update mechanism see -
30 * http://lse.sourceforge.net/locking/rcupdate.html
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>
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);
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);
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);
66 #ifdef CONFIG_DEBUG_LOCK_ALLOC
68 int debug_lockdep_rcu_enabled(void)
70 return rcu_scheduler_active && debug_locks &&
71 current->lockdep_recursion == 0;
73 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
76 * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
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
85 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
87 int rcu_read_lock_bh_held(void)
89 if (!debug_lockdep_rcu_enabled())
91 return in_softirq() || irqs_disabled();
93 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
95 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
97 struct rcu_synchronize {
99 struct completion completion;
103 * Awaken the corresponding synchronize_rcu() instance now that a
104 * grace period has elapsed.
106 static void wakeme_after_rcu(struct rcu_head *head)
108 struct rcu_synchronize *rcu;
110 rcu = container_of(head, struct rcu_synchronize, head);
111 complete(&rcu->completion);
114 void wait_rcu_gp(call_rcu_func_t crf)
116 struct rcu_synchronize rcu;
118 init_rcu_head_on_stack(&rcu.head);
119 init_completion(&rcu.completion);
120 /* Will wake me after RCU finished. */
121 crf(&rcu.head, wakeme_after_rcu);
123 wait_for_completion(&rcu.completion);
124 destroy_rcu_head_on_stack(&rcu.head);
126 EXPORT_SYMBOL_GPL(wait_rcu_gp);
128 #ifdef CONFIG_PROVE_RCU
130 * wrapper function to avoid #include problems.
132 int rcu_my_thread_group_empty(void)
134 return thread_group_empty(current);
136 EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
137 #endif /* #ifdef CONFIG_PROVE_RCU */
139 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
140 static inline void debug_init_rcu_head(struct rcu_head *head)
142 debug_object_init(head, &rcuhead_debug_descr);
145 static inline void debug_rcu_head_free(struct rcu_head *head)
147 debug_object_free(head, &rcuhead_debug_descr);
151 * fixup_init is called when:
152 * - an active object is initialized
154 static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
156 struct rcu_head *head = addr;
159 case ODEBUG_STATE_ACTIVE:
161 * Ensure that queued callbacks are all executed.
162 * If we detect that we are nested in a RCU read-side critical
163 * section, we should simply fail, otherwise we would deadlock.
164 * In !PREEMPT configurations, there is no way to tell if we are
165 * in a RCU read-side critical section or not, so we never
166 * attempt any fixup and just print a warning.
168 #ifndef CONFIG_PREEMPT
172 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
180 debug_object_init(head, &rcuhead_debug_descr);
188 * fixup_activate is called when:
189 * - an active object is activated
190 * - an unknown object is activated (might be a statically initialized object)
191 * Activation is performed internally by call_rcu().
193 static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
195 struct rcu_head *head = addr;
199 case ODEBUG_STATE_NOTAVAILABLE:
201 * This is not really a fixup. We just make sure that it is
202 * tracked in the object tracker.
204 debug_object_init(head, &rcuhead_debug_descr);
205 debug_object_activate(head, &rcuhead_debug_descr);
208 case ODEBUG_STATE_ACTIVE:
210 * Ensure that queued callbacks are all executed.
211 * If we detect that we are nested in a RCU read-side critical
212 * section, we should simply fail, otherwise we would deadlock.
213 * In !PREEMPT configurations, there is no way to tell if we are
214 * in a RCU read-side critical section or not, so we never
215 * attempt any fixup and just print a warning.
217 #ifndef CONFIG_PREEMPT
221 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
229 debug_object_activate(head, &rcuhead_debug_descr);
237 * fixup_free is called when:
238 * - an active object is freed
240 static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
242 struct rcu_head *head = addr;
245 case ODEBUG_STATE_ACTIVE:
247 * Ensure that queued callbacks are all executed.
248 * If we detect that we are nested in a RCU read-side critical
249 * section, we should simply fail, otherwise we would deadlock.
250 * In !PREEMPT configurations, there is no way to tell if we are
251 * in a RCU read-side critical section or not, so we never
252 * attempt any fixup and just print a warning.
254 #ifndef CONFIG_PREEMPT
258 if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
266 debug_object_free(head, &rcuhead_debug_descr);
274 * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
275 * @head: pointer to rcu_head structure to be initialized
277 * This function informs debugobjects of a new rcu_head structure that
278 * has been allocated as an auto variable on the stack. This function
279 * is not required for rcu_head structures that are statically defined or
280 * that are dynamically allocated on the heap. This function has no
281 * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
283 void init_rcu_head_on_stack(struct rcu_head *head)
285 debug_object_init_on_stack(head, &rcuhead_debug_descr);
287 EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
290 * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
291 * @head: pointer to rcu_head structure to be initialized
293 * This function informs debugobjects that an on-stack rcu_head structure
294 * is about to go out of scope. As with init_rcu_head_on_stack(), this
295 * function is not required for rcu_head structures that are statically
296 * defined or that are dynamically allocated on the heap. Also as with
297 * init_rcu_head_on_stack(), this function has no effect for
298 * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
300 void destroy_rcu_head_on_stack(struct rcu_head *head)
302 debug_object_free(head, &rcuhead_debug_descr);
304 EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
306 struct debug_obj_descr rcuhead_debug_descr = {
308 .fixup_init = rcuhead_fixup_init,
309 .fixup_activate = rcuhead_fixup_activate,
310 .fixup_free = rcuhead_fixup_free,
312 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
313 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */