Commit | Line | Data |
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9b1d82fa PM |
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 - | |
4ce5b903 | 23 | * Documentation/RCU |
9b1d82fa | 24 | */ |
4ce5b903 IM |
25 | #include <linux/completion.h> |
26 | #include <linux/interrupt.h> | |
9b1d82fa | 27 | #include <linux/notifier.h> |
4ce5b903 IM |
28 | #include <linux/rcupdate.h> |
29 | #include <linux/kernel.h> | |
9984de1a | 30 | #include <linux/export.h> |
9b1d82fa | 31 | #include <linux/mutex.h> |
4ce5b903 IM |
32 | #include <linux/sched.h> |
33 | #include <linux/types.h> | |
34 | #include <linux/init.h> | |
9b1d82fa | 35 | #include <linux/time.h> |
4ce5b903 | 36 | #include <linux/cpu.h> |
268bb0ce | 37 | #include <linux/prefetch.h> |
9b1d82fa | 38 | |
29c00b4a | 39 | #ifdef CONFIG_RCU_TRACE |
29c00b4a | 40 | #include <trace/events/rcu.h> |
29c00b4a PM |
41 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
42 | ||
43 | #include "rcu.h" | |
44 | ||
a57eb940 | 45 | /* Forward declarations for rcutiny_plugin.h. */ |
24278d14 | 46 | struct rcu_ctrlblk; |
965a002b PM |
47 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); |
48 | static void rcu_process_callbacks(struct softirq_action *unused); | |
a57eb940 PM |
49 | static void __call_rcu(struct rcu_head *head, |
50 | void (*func)(struct rcu_head *rcu), | |
51 | struct rcu_ctrlblk *rcp); | |
52 | ||
29e37d81 | 53 | static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
9b1d82fa | 54 | |
6bfc09e2 PM |
55 | #include "rcutiny_plugin.h" |
56 | ||
9b2e4f18 | 57 | /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */ |
818615c4 | 58 | static void rcu_idle_enter_common(long long newval) |
9b2e4f18 | 59 | { |
818615c4 | 60 | if (newval) { |
4145fa7f | 61 | RCU_TRACE(trace_rcu_dyntick("--=", |
818615c4 PM |
62 | rcu_dynticks_nesting, newval)); |
63 | rcu_dynticks_nesting = newval; | |
9b2e4f18 PM |
64 | return; |
65 | } | |
818615c4 | 66 | RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting, newval)); |
99745b6a | 67 | if (!is_idle_task(current)) { |
0989cb46 PM |
68 | struct task_struct *idle = idle_task(smp_processor_id()); |
69 | ||
9b2e4f18 | 70 | RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task", |
818615c4 | 71 | rcu_dynticks_nesting, newval)); |
9b2e4f18 | 72 | ftrace_dump(DUMP_ALL); |
0989cb46 PM |
73 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
74 | current->pid, current->comm, | |
75 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 | 76 | } |
22a76726 | 77 | rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ |
818615c4 PM |
78 | barrier(); |
79 | rcu_dynticks_nesting = newval; | |
9b2e4f18 PM |
80 | } |
81 | ||
82 | /* | |
83 | * Enter idle, which is an extended quiescent state if we have fully | |
84 | * entered that mode (i.e., if the new value of dynticks_nesting is zero). | |
85 | */ | |
86 | void rcu_idle_enter(void) | |
87 | { | |
88 | unsigned long flags; | |
818615c4 | 89 | long long newval; |
9b2e4f18 PM |
90 | |
91 | local_irq_save(flags); | |
29e37d81 PM |
92 | WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0); |
93 | if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == | |
94 | DYNTICK_TASK_NEST_VALUE) | |
818615c4 | 95 | newval = 0; |
29e37d81 | 96 | else |
818615c4 PM |
97 | newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE; |
98 | rcu_idle_enter_common(newval); | |
9b2e4f18 PM |
99 | local_irq_restore(flags); |
100 | } | |
8a2ecf47 | 101 | EXPORT_SYMBOL_GPL(rcu_idle_enter); |
9b2e4f18 PM |
102 | |
103 | /* | |
104 | * Exit an interrupt handler towards idle. | |
105 | */ | |
106 | void rcu_irq_exit(void) | |
107 | { | |
108 | unsigned long flags; | |
818615c4 | 109 | long long newval; |
9b2e4f18 PM |
110 | |
111 | local_irq_save(flags); | |
818615c4 PM |
112 | newval = rcu_dynticks_nesting - 1; |
113 | WARN_ON_ONCE(newval < 0); | |
114 | rcu_idle_enter_common(newval); | |
9b2e4f18 PM |
115 | local_irq_restore(flags); |
116 | } | |
b4270ee3 | 117 | EXPORT_SYMBOL_GPL(rcu_irq_exit); |
9b2e4f18 PM |
118 | |
119 | /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */ | |
120 | static void rcu_idle_exit_common(long long oldval) | |
121 | { | |
122 | if (oldval) { | |
4145fa7f PM |
123 | RCU_TRACE(trace_rcu_dyntick("++=", |
124 | oldval, rcu_dynticks_nesting)); | |
9b2e4f18 PM |
125 | return; |
126 | } | |
4145fa7f | 127 | RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting)); |
99745b6a | 128 | if (!is_idle_task(current)) { |
0989cb46 PM |
129 | struct task_struct *idle = idle_task(smp_processor_id()); |
130 | ||
9b2e4f18 | 131 | RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task", |
4145fa7f | 132 | oldval, rcu_dynticks_nesting)); |
9b2e4f18 | 133 | ftrace_dump(DUMP_ALL); |
0989cb46 PM |
134 | WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
135 | current->pid, current->comm, | |
136 | idle->pid, idle->comm); /* must be idle task! */ | |
9b2e4f18 PM |
137 | } |
138 | } | |
9b1d82fa PM |
139 | |
140 | /* | |
9b2e4f18 | 141 | * Exit idle, so that we are no longer in an extended quiescent state. |
9b1d82fa | 142 | */ |
9b2e4f18 | 143 | void rcu_idle_exit(void) |
9b1d82fa | 144 | { |
9b2e4f18 PM |
145 | unsigned long flags; |
146 | long long oldval; | |
147 | ||
148 | local_irq_save(flags); | |
149 | oldval = rcu_dynticks_nesting; | |
29e37d81 PM |
150 | WARN_ON_ONCE(rcu_dynticks_nesting < 0); |
151 | if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) | |
152 | rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE; | |
153 | else | |
154 | rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; | |
9b2e4f18 PM |
155 | rcu_idle_exit_common(oldval); |
156 | local_irq_restore(flags); | |
9b1d82fa | 157 | } |
8a2ecf47 | 158 | EXPORT_SYMBOL_GPL(rcu_idle_exit); |
9b1d82fa PM |
159 | |
160 | /* | |
9b2e4f18 | 161 | * Enter an interrupt handler, moving away from idle. |
9b1d82fa | 162 | */ |
9b2e4f18 | 163 | void rcu_irq_enter(void) |
9b1d82fa | 164 | { |
9b2e4f18 PM |
165 | unsigned long flags; |
166 | long long oldval; | |
167 | ||
168 | local_irq_save(flags); | |
169 | oldval = rcu_dynticks_nesting; | |
9b1d82fa | 170 | rcu_dynticks_nesting++; |
9b2e4f18 PM |
171 | WARN_ON_ONCE(rcu_dynticks_nesting == 0); |
172 | rcu_idle_exit_common(oldval); | |
173 | local_irq_restore(flags); | |
9b1d82fa | 174 | } |
b4270ee3 | 175 | EXPORT_SYMBOL_GPL(rcu_irq_enter); |
9b1d82fa | 176 | |
d7118175 | 177 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
9b2e4f18 PM |
178 | |
179 | /* | |
180 | * Test whether RCU thinks that the current CPU is idle. | |
181 | */ | |
182 | int rcu_is_cpu_idle(void) | |
183 | { | |
184 | return !rcu_dynticks_nesting; | |
185 | } | |
e6b80a3b | 186 | EXPORT_SYMBOL(rcu_is_cpu_idle); |
9b2e4f18 | 187 | |
d7118175 | 188 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
9b2e4f18 PM |
189 | |
190 | /* | |
191 | * Test whether the current CPU was interrupted from idle. Nested | |
192 | * interrupts don't count, we must be running at the first interrupt | |
193 | * level. | |
194 | */ | |
62e3cb14 | 195 | static int rcu_is_cpu_rrupt_from_idle(void) |
9b2e4f18 | 196 | { |
351573a8 | 197 | return rcu_dynticks_nesting <= 1; |
9b2e4f18 | 198 | } |
9b1d82fa PM |
199 | |
200 | /* | |
b554d7de ED |
201 | * Helper function for rcu_sched_qs() and rcu_bh_qs(). |
202 | * Also irqs are disabled to avoid confusion due to interrupt handlers | |
4ce5b903 | 203 | * invoking call_rcu(). |
9b1d82fa PM |
204 | */ |
205 | static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) | |
206 | { | |
14961444 | 207 | RCU_TRACE(reset_cpu_stall_ticks(rcp)); |
9b1d82fa PM |
208 | if (rcp->rcucblist != NULL && |
209 | rcp->donetail != rcp->curtail) { | |
210 | rcp->donetail = rcp->curtail; | |
9b1d82fa PM |
211 | return 1; |
212 | } | |
4ce5b903 | 213 | |
9b1d82fa PM |
214 | return 0; |
215 | } | |
216 | ||
217 | /* | |
218 | * Record an rcu quiescent state. And an rcu_bh quiescent state while we | |
219 | * are at it, given that any rcu quiescent state is also an rcu_bh | |
220 | * quiescent state. Use "+" instead of "||" to defeat short circuiting. | |
221 | */ | |
222 | void rcu_sched_qs(int cpu) | |
223 | { | |
b554d7de ED |
224 | unsigned long flags; |
225 | ||
226 | local_irq_save(flags); | |
99652b54 PM |
227 | if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
228 | rcu_qsctr_help(&rcu_bh_ctrlblk)) | |
9dc5ad32 | 229 | raise_softirq(RCU_SOFTIRQ); |
b554d7de | 230 | local_irq_restore(flags); |
9b1d82fa PM |
231 | } |
232 | ||
233 | /* | |
234 | * Record an rcu_bh quiescent state. | |
235 | */ | |
236 | void rcu_bh_qs(int cpu) | |
237 | { | |
b554d7de ED |
238 | unsigned long flags; |
239 | ||
240 | local_irq_save(flags); | |
9b1d82fa | 241 | if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
9dc5ad32 | 242 | raise_softirq(RCU_SOFTIRQ); |
b554d7de | 243 | local_irq_restore(flags); |
9b1d82fa PM |
244 | } |
245 | ||
246 | /* | |
247 | * Check to see if the scheduling-clock interrupt came from an extended | |
9b2e4f18 PM |
248 | * quiescent state, and, if so, tell RCU about it. This function must |
249 | * be called from hardirq context. It is normally called from the | |
250 | * scheduling-clock interrupt. | |
9b1d82fa PM |
251 | */ |
252 | void rcu_check_callbacks(int cpu, int user) | |
253 | { | |
14961444 | 254 | RCU_TRACE(check_cpu_stalls()); |
9b2e4f18 | 255 | if (user || rcu_is_cpu_rrupt_from_idle()) |
9b1d82fa PM |
256 | rcu_sched_qs(cpu); |
257 | else if (!in_softirq()) | |
258 | rcu_bh_qs(cpu); | |
259 | } | |
260 | ||
261 | /* | |
b2c0710c PM |
262 | * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure |
263 | * whose grace period has elapsed. | |
9b1d82fa | 264 | */ |
965a002b | 265 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
9b1d82fa | 266 | { |
d4c08f2a | 267 | char *rn = NULL; |
9b1d82fa | 268 | struct rcu_head *next, *list; |
4ce5b903 | 269 | unsigned long flags; |
9e571a82 | 270 | RCU_TRACE(int cb_count = 0); |
9b1d82fa PM |
271 | |
272 | /* If no RCU callbacks ready to invoke, just return. */ | |
29c00b4a | 273 | if (&rcp->rcucblist == rcp->donetail) { |
486e2593 | 274 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1)); |
4968c300 PM |
275 | RCU_TRACE(trace_rcu_batch_end(rcp->name, 0, |
276 | ACCESS_ONCE(rcp->rcucblist), | |
277 | need_resched(), | |
278 | is_idle_task(current), | |
9dc5ad32 | 279 | false)); |
9b1d82fa | 280 | return; |
29c00b4a | 281 | } |
9b1d82fa PM |
282 | |
283 | /* Move the ready-to-invoke callbacks to a local list. */ | |
284 | local_irq_save(flags); | |
486e2593 | 285 | RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1)); |
9b1d82fa PM |
286 | list = rcp->rcucblist; |
287 | rcp->rcucblist = *rcp->donetail; | |
288 | *rcp->donetail = NULL; | |
289 | if (rcp->curtail == rcp->donetail) | |
290 | rcp->curtail = &rcp->rcucblist; | |
291 | rcp->donetail = &rcp->rcucblist; | |
292 | local_irq_restore(flags); | |
293 | ||
294 | /* Invoke the callbacks on the local list. */ | |
d4c08f2a | 295 | RCU_TRACE(rn = rcp->name); |
9b1d82fa PM |
296 | while (list) { |
297 | next = list->next; | |
298 | prefetch(next); | |
551d55a9 | 299 | debug_rcu_head_unqueue(list); |
b2c0710c | 300 | local_bh_disable(); |
d4c08f2a | 301 | __rcu_reclaim(rn, list); |
b2c0710c | 302 | local_bh_enable(); |
9b1d82fa | 303 | list = next; |
9e571a82 | 304 | RCU_TRACE(cb_count++); |
9b1d82fa | 305 | } |
9e571a82 | 306 | RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
4968c300 PM |
307 | RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(), |
308 | is_idle_task(current), | |
9dc5ad32 | 309 | false)); |
9b1d82fa PM |
310 | } |
311 | ||
965a002b | 312 | static void rcu_process_callbacks(struct softirq_action *unused) |
b2c0710c | 313 | { |
965a002b PM |
314 | __rcu_process_callbacks(&rcu_sched_ctrlblk); |
315 | __rcu_process_callbacks(&rcu_bh_ctrlblk); | |
b2c0710c PM |
316 | } |
317 | ||
9b1d82fa PM |
318 | /* |
319 | * Wait for a grace period to elapse. But it is illegal to invoke | |
320 | * synchronize_sched() from within an RCU read-side critical section. | |
321 | * Therefore, any legal call to synchronize_sched() is a quiescent | |
322 | * state, and so on a UP system, synchronize_sched() need do nothing. | |
323 | * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the | |
324 | * benefits of doing might_sleep() to reduce latency.) | |
325 | * | |
326 | * Cool, huh? (Due to Josh Triplett.) | |
327 | * | |
da848c47 PM |
328 | * But we want to make this a static inline later. The cond_resched() |
329 | * currently makes this problematic. | |
9b1d82fa PM |
330 | */ |
331 | void synchronize_sched(void) | |
332 | { | |
fe15d706 PM |
333 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
334 | !lock_is_held(&rcu_lock_map) && | |
335 | !lock_is_held(&rcu_sched_lock_map), | |
336 | "Illegal synchronize_sched() in RCU read-side critical section"); | |
9b1d82fa PM |
337 | cond_resched(); |
338 | } | |
339 | EXPORT_SYMBOL_GPL(synchronize_sched); | |
340 | ||
9b1d82fa PM |
341 | /* |
342 | * Helper function for call_rcu() and call_rcu_bh(). | |
343 | */ | |
344 | static void __call_rcu(struct rcu_head *head, | |
345 | void (*func)(struct rcu_head *rcu), | |
346 | struct rcu_ctrlblk *rcp) | |
347 | { | |
348 | unsigned long flags; | |
349 | ||
551d55a9 | 350 | debug_rcu_head_queue(head); |
9b1d82fa PM |
351 | head->func = func; |
352 | head->next = NULL; | |
4ce5b903 | 353 | |
9b1d82fa PM |
354 | local_irq_save(flags); |
355 | *rcp->curtail = head; | |
356 | rcp->curtail = &head->next; | |
9e571a82 | 357 | RCU_TRACE(rcp->qlen++); |
9b1d82fa PM |
358 | local_irq_restore(flags); |
359 | } | |
360 | ||
361 | /* | |
a57eb940 | 362 | * Post an RCU callback to be invoked after the end of an RCU-sched grace |
9b1d82fa PM |
363 | * period. But since we have but one CPU, that would be after any |
364 | * quiescent state. | |
365 | */ | |
a57eb940 | 366 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa | 367 | { |
99652b54 | 368 | __call_rcu(head, func, &rcu_sched_ctrlblk); |
9b1d82fa | 369 | } |
a57eb940 | 370 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
9b1d82fa PM |
371 | |
372 | /* | |
373 | * Post an RCU bottom-half callback to be invoked after any subsequent | |
374 | * quiescent state. | |
375 | */ | |
4ce5b903 | 376 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
9b1d82fa PM |
377 | { |
378 | __call_rcu(head, func, &rcu_bh_ctrlblk); | |
379 | } | |
380 | EXPORT_SYMBOL_GPL(call_rcu_bh); | |
9dc5ad32 PM |
381 | |
382 | void rcu_init(void) | |
383 | { | |
384 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); | |
385 | } |