~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/rcutiny.c

Version: ~ [ linux-5.1-rc1 ] ~ [ linux-5.0.3 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.30 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.107 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.164 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.176 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.136 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.63 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
  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, 2008
 19  *
 20  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 21  *
 22  * For detailed explanation of Read-Copy Update mechanism see -
 23  *              Documentation/RCU
 24  */
 25 #include <linux/moduleparam.h>
 26 #include <linux/completion.h>
 27 #include <linux/interrupt.h>
 28 #include <linux/notifier.h>
 29 #include <linux/rcupdate.h>
 30 #include <linux/kernel.h>
 31 #include <linux/module.h>
 32 #include <linux/mutex.h>
 33 #include <linux/sched.h>
 34 #include <linux/types.h>
 35 #include <linux/init.h>
 36 #include <linux/time.h>
 37 #include <linux/cpu.h>
 38 #include <linux/prefetch.h>
 39 
 40 /* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */
 41 static struct task_struct *rcu_kthread_task;
 42 static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
 43 static unsigned long have_rcu_kthread_work;
 44 
 45 /* Forward declarations for rcutiny_plugin.h. */
 46 struct rcu_ctrlblk;
 47 static void invoke_rcu_kthread(void);
 48 static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
 49 static int rcu_kthread(void *arg);
 50 static void __call_rcu(struct rcu_head *head,
 51                        void (*func)(struct rcu_head *rcu),
 52                        struct rcu_ctrlblk *rcp);
 53 
 54 #include "rcutiny_plugin.h"
 55 
 56 #ifdef CONFIG_NO_HZ
 57 
 58 static long rcu_dynticks_nesting = 1;
 59 
 60 /*
 61  * Enter dynticks-idle mode, which is an extended quiescent state
 62  * if we have fully entered that mode (i.e., if the new value of
 63  * dynticks_nesting is zero).
 64  */
 65 void rcu_enter_nohz(void)
 66 {
 67         if (--rcu_dynticks_nesting == 0)
 68                 rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
 69 }
 70 
 71 /*
 72  * Exit dynticks-idle mode, so that we are no longer in an extended
 73  * quiescent state.
 74  */
 75 void rcu_exit_nohz(void)
 76 {
 77         rcu_dynticks_nesting++;
 78 }
 79 
 80 #endif /* #ifdef CONFIG_NO_HZ */
 81 
 82 /*
 83  * Helper function for rcu_sched_qs() and rcu_bh_qs().
 84  * Also irqs are disabled to avoid confusion due to interrupt handlers
 85  * invoking call_rcu().
 86  */
 87 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
 88 {
 89         if (rcp->rcucblist != NULL &&
 90             rcp->donetail != rcp->curtail) {
 91                 rcp->donetail = rcp->curtail;
 92                 return 1;
 93         }
 94 
 95         return 0;
 96 }
 97 
 98 /*
 99  * Wake up rcu_kthread() to process callbacks now eligible for invocation
100  * or to boost readers.
101  */
102 static void invoke_rcu_kthread(void)
103 {
104         have_rcu_kthread_work = 1;
105         wake_up(&rcu_kthread_wq);
106 }
107 
108 /*
109  * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
110  * are at it, given that any rcu quiescent state is also an rcu_bh
111  * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
112  */
113 void rcu_sched_qs(int cpu)
114 {
115         unsigned long flags;
116 
117         local_irq_save(flags);
118         if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
119             rcu_qsctr_help(&rcu_bh_ctrlblk))
120                 invoke_rcu_kthread();
121         local_irq_restore(flags);
122 }
123 
124 /*
125  * Record an rcu_bh quiescent state.
126  */
127 void rcu_bh_qs(int cpu)
128 {
129         unsigned long flags;
130 
131         local_irq_save(flags);
132         if (rcu_qsctr_help(&rcu_bh_ctrlblk))
133                 invoke_rcu_kthread();
134         local_irq_restore(flags);
135 }
136 
137 /*
138  * Check to see if the scheduling-clock interrupt came from an extended
139  * quiescent state, and, if so, tell RCU about it.
140  */
141 void rcu_check_callbacks(int cpu, int user)
142 {
143         if (user ||
144             (idle_cpu(cpu) &&
145              !in_softirq() &&
146              hardirq_count() <= (1 << HARDIRQ_SHIFT)))
147                 rcu_sched_qs(cpu);
148         else if (!in_softirq())
149                 rcu_bh_qs(cpu);
150         rcu_preempt_check_callbacks();
151 }
152 
153 /*
154  * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
155  * whose grace period has elapsed.
156  */
157 static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
158 {
159         struct rcu_head *next, *list;
160         unsigned long flags;
161         RCU_TRACE(int cb_count = 0);
162 
163         /* If no RCU callbacks ready to invoke, just return. */
164         if (&rcp->rcucblist == rcp->donetail)
165                 return;
166 
167         /* Move the ready-to-invoke callbacks to a local list. */
168         local_irq_save(flags);
169         list = rcp->rcucblist;
170         rcp->rcucblist = *rcp->donetail;
171         *rcp->donetail = NULL;
172         if (rcp->curtail == rcp->donetail)
173                 rcp->curtail = &rcp->rcucblist;
174         rcu_preempt_remove_callbacks(rcp);
175         rcp->donetail = &rcp->rcucblist;
176         local_irq_restore(flags);
177 
178         /* Invoke the callbacks on the local list. */
179         while (list) {
180                 next = list->next;
181                 prefetch(next);
182                 debug_rcu_head_unqueue(list);
183                 local_bh_disable();
184                 __rcu_reclaim(list);
185                 local_bh_enable();
186                 list = next;
187                 RCU_TRACE(cb_count++);
188         }
189         RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
190 }
191 
192 /*
193  * This kthread invokes RCU callbacks whose grace periods have
194  * elapsed.  It is awakened as needed, and takes the place of the
195  * RCU_SOFTIRQ that was used previously for this purpose.
196  * This is a kthread, but it is never stopped, at least not until
197  * the system goes down.
198  */
199 static int rcu_kthread(void *arg)
200 {
201         unsigned long work;
202         unsigned long morework;
203         unsigned long flags;
204 
205         for (;;) {
206                 wait_event_interruptible(rcu_kthread_wq,
207                                          have_rcu_kthread_work != 0);
208                 morework = rcu_boost();
209                 local_irq_save(flags);
210                 work = have_rcu_kthread_work;
211                 have_rcu_kthread_work = morework;
212                 local_irq_restore(flags);
213                 if (work) {
214                         rcu_process_callbacks(&rcu_sched_ctrlblk);
215                         rcu_process_callbacks(&rcu_bh_ctrlblk);
216                         rcu_preempt_process_callbacks();
217                 }
218                 schedule_timeout_interruptible(1); /* Leave CPU for others. */
219         }
220 
221         return 0;  /* Not reached, but needed to shut gcc up. */
222 }
223 
224 /*
225  * Wait for a grace period to elapse.  But it is illegal to invoke
226  * synchronize_sched() from within an RCU read-side critical section.
227  * Therefore, any legal call to synchronize_sched() is a quiescent
228  * state, and so on a UP system, synchronize_sched() need do nothing.
229  * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
230  * benefits of doing might_sleep() to reduce latency.)
231  *
232  * Cool, huh?  (Due to Josh Triplett.)
233  *
234  * But we want to make this a static inline later.  The cond_resched()
235  * currently makes this problematic.
236  */
237 void synchronize_sched(void)
238 {
239         cond_resched();
240 }
241 EXPORT_SYMBOL_GPL(synchronize_sched);
242 
243 /*
244  * Helper function for call_rcu() and call_rcu_bh().
245  */
246 static void __call_rcu(struct rcu_head *head,
247                        void (*func)(struct rcu_head *rcu),
248                        struct rcu_ctrlblk *rcp)
249 {
250         unsigned long flags;
251 
252         debug_rcu_head_queue(head);
253         head->func = func;
254         head->next = NULL;
255 
256         local_irq_save(flags);
257         *rcp->curtail = head;
258         rcp->curtail = &head->next;
259         RCU_TRACE(rcp->qlen++);
260         local_irq_restore(flags);
261 }
262 
263 /*
264  * Post an RCU callback to be invoked after the end of an RCU-sched grace
265  * period.  But since we have but one CPU, that would be after any
266  * quiescent state.
267  */
268 void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
269 {
270         __call_rcu(head, func, &rcu_sched_ctrlblk);
271 }
272 EXPORT_SYMBOL_GPL(call_rcu_sched);
273 
274 /*
275  * Post an RCU bottom-half callback to be invoked after any subsequent
276  * quiescent state.
277  */
278 void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
279 {
280         __call_rcu(head, func, &rcu_bh_ctrlblk);
281 }
282 EXPORT_SYMBOL_GPL(call_rcu_bh);
283 
284 void rcu_barrier_bh(void)
285 {
286         struct rcu_synchronize rcu;
287 
288         init_rcu_head_on_stack(&rcu.head);
289         init_completion(&rcu.completion);
290         /* Will wake me after RCU finished. */
291         call_rcu_bh(&rcu.head, wakeme_after_rcu);
292         /* Wait for it. */
293         wait_for_completion(&rcu.completion);
294         destroy_rcu_head_on_stack(&rcu.head);
295 }
296 EXPORT_SYMBOL_GPL(rcu_barrier_bh);
297 
298 void rcu_barrier_sched(void)
299 {
300         struct rcu_synchronize rcu;
301 
302         init_rcu_head_on_stack(&rcu.head);
303         init_completion(&rcu.completion);
304         /* Will wake me after RCU finished. */
305         call_rcu_sched(&rcu.head, wakeme_after_rcu);
306         /* Wait for it. */
307         wait_for_completion(&rcu.completion);
308         destroy_rcu_head_on_stack(&rcu.head);
309 }
310 EXPORT_SYMBOL_GPL(rcu_barrier_sched);
311 
312 /*
313  * Spawn the kthread that invokes RCU callbacks.
314  */
315 static int __init rcu_spawn_kthreads(void)
316 {
317         struct sched_param sp;
318 
319         rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
320         sp.sched_priority = RCU_BOOST_PRIO;
321         sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
322         return 0;
323 }
324 early_initcall(rcu_spawn_kthreads);
325 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp