2 * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
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, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
18 * Copyright IBM Corporation, 2008
20 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
22 * For detailed explanation of Read-Copy Update mechanism see -
25 #include <linux/completion.h>
26 #include <linux/interrupt.h>
27 #include <linux/notifier.h>
28 #include <linux/rcupdate.h>
29 #include <linux/kernel.h>
30 #include <linux/export.h>
31 #include <linux/mutex.h>
32 #include <linux/sched.h>
33 #include <linux/types.h>
34 #include <linux/init.h>
35 #include <linux/time.h>
36 #include <linux/cpu.h>
37 #include <linux/prefetch.h>
38 #include <linux/ftrace_event.h>
42 /* Forward declarations for tiny_plugin.h. */
44 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
45 static void rcu_process_callbacks(struct softirq_action *unused);
46 static void __call_rcu(struct rcu_head *head,
47 void (*func)(struct rcu_head *rcu),
48 struct rcu_ctrlblk *rcp);
50 #include "tiny_plugin.h"
53 * Enter idle, which is an extended quiescent state if we have fully
56 void rcu_idle_enter(void)
59 EXPORT_SYMBOL_GPL(rcu_idle_enter);
62 * Exit an interrupt handler towards idle.
64 void rcu_irq_exit(void)
67 EXPORT_SYMBOL_GPL(rcu_irq_exit);
70 * Exit idle, so that we are no longer in an extended quiescent state.
72 void rcu_idle_exit(void)
75 EXPORT_SYMBOL_GPL(rcu_idle_exit);
78 * Enter an interrupt handler, moving away from idle.
80 void rcu_irq_enter(void)
83 EXPORT_SYMBOL_GPL(rcu_irq_enter);
85 #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)
88 * Test whether RCU thinks that the current CPU is idle.
90 bool notrace __rcu_is_watching(void)
94 EXPORT_SYMBOL(__rcu_is_watching);
96 #endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
99 * Helper function for rcu_sched_qs() and rcu_bh_qs().
100 * Also irqs are disabled to avoid confusion due to interrupt handlers
101 * invoking call_rcu().
103 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
105 RCU_TRACE(reset_cpu_stall_ticks(rcp));
106 if (rcp->donetail != rcp->curtail) {
107 rcp->donetail = rcp->curtail;
115 * Record an rcu quiescent state. And an rcu_bh quiescent state while we
116 * are at it, given that any rcu quiescent state is also an rcu_bh
117 * quiescent state. Use "+" instead of "||" to defeat short circuiting.
119 void rcu_sched_qs(void)
123 local_irq_save(flags);
124 if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
125 rcu_qsctr_help(&rcu_bh_ctrlblk))
126 raise_softirq(RCU_SOFTIRQ);
127 local_irq_restore(flags);
131 * Record an rcu_bh quiescent state.
137 local_irq_save(flags);
138 if (rcu_qsctr_help(&rcu_bh_ctrlblk))
139 raise_softirq(RCU_SOFTIRQ);
140 local_irq_restore(flags);
144 * Check to see if the scheduling-clock interrupt came from an extended
145 * quiescent state, and, if so, tell RCU about it. This function must
146 * be called from hardirq context. It is normally called from the
147 * scheduling-clock interrupt.
149 void rcu_check_callbacks(int user)
151 RCU_TRACE(check_cpu_stalls());
154 else if (!in_softirq())
157 rcu_note_voluntary_context_switch(current);
161 * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
162 * whose grace period has elapsed.
164 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
166 const char *rn = NULL;
167 struct rcu_head *next, *list;
169 RCU_TRACE(int cb_count = 0);
171 /* Move the ready-to-invoke callbacks to a local list. */
172 local_irq_save(flags);
173 if (rcp->donetail == &rcp->rcucblist) {
174 /* No callbacks ready, so just leave. */
175 local_irq_restore(flags);
178 RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1));
179 list = rcp->rcucblist;
180 rcp->rcucblist = *rcp->donetail;
181 *rcp->donetail = NULL;
182 if (rcp->curtail == rcp->donetail)
183 rcp->curtail = &rcp->rcucblist;
184 rcp->donetail = &rcp->rcucblist;
185 local_irq_restore(flags);
187 /* Invoke the callbacks on the local list. */
188 RCU_TRACE(rn = rcp->name);
192 debug_rcu_head_unqueue(list);
194 __rcu_reclaim(rn, list);
197 RCU_TRACE(cb_count++);
199 RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
200 RCU_TRACE(trace_rcu_batch_end(rcp->name,
201 cb_count, 0, need_resched(),
202 is_idle_task(current),
206 static void rcu_process_callbacks(struct softirq_action *unused)
208 __rcu_process_callbacks(&rcu_sched_ctrlblk);
209 __rcu_process_callbacks(&rcu_bh_ctrlblk);
213 * Wait for a grace period to elapse. But it is illegal to invoke
214 * synchronize_sched() from within an RCU read-side critical section.
215 * Therefore, any legal call to synchronize_sched() is a quiescent
216 * state, and so on a UP system, synchronize_sched() need do nothing.
217 * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the
218 * benefits of doing might_sleep() to reduce latency.)
220 * Cool, huh? (Due to Josh Triplett.)
222 * But we want to make this a static inline later. The cond_resched()
223 * currently makes this problematic.
225 void synchronize_sched(void)
227 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
228 !lock_is_held(&rcu_lock_map) &&
229 !lock_is_held(&rcu_sched_lock_map),
230 "Illegal synchronize_sched() in RCU read-side critical section");
233 EXPORT_SYMBOL_GPL(synchronize_sched);
236 * Helper function for call_rcu() and call_rcu_bh().
238 static void __call_rcu(struct rcu_head *head,
239 void (*func)(struct rcu_head *rcu),
240 struct rcu_ctrlblk *rcp)
244 debug_rcu_head_queue(head);
248 local_irq_save(flags);
249 *rcp->curtail = head;
250 rcp->curtail = &head->next;
251 RCU_TRACE(rcp->qlen++);
252 local_irq_restore(flags);
254 if (unlikely(is_idle_task(current))) {
255 /* force scheduling for rcu_sched_qs() */
261 * Post an RCU callback to be invoked after the end of an RCU-sched grace
262 * period. But since we have but one CPU, that would be after any
265 void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
267 __call_rcu(head, func, &rcu_sched_ctrlblk);
269 EXPORT_SYMBOL_GPL(call_rcu_sched);
272 * Post an RCU bottom-half callback to be invoked after any subsequent
275 void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
277 __call_rcu(head, func, &rcu_bh_ctrlblk);
279 EXPORT_SYMBOL_GPL(call_rcu_bh);
281 void __init rcu_init(void)
283 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
284 RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk));
285 RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk));
287 rcu_early_boot_tests();