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bbad9379 | 1 | /* |
a57eb940 | 2 | * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition |
bbad9379 | 3 | * Internal non-public definitions that provide either classic |
a57eb940 | 4 | * or preemptible semantics. |
bbad9379 PM |
5 | * |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program; if not, write to the Free Software | |
18 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
19 | * | |
a57eb940 | 20 | * Copyright (c) 2010 Linaro |
bbad9379 PM |
21 | * |
22 | * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
23 | */ | |
24 | ||
b2c0710c | 25 | #include <linux/kthread.h> |
9e571a82 PM |
26 | #include <linux/debugfs.h> |
27 | #include <linux/seq_file.h> | |
28 | ||
29 | #ifdef CONFIG_RCU_TRACE | |
30 | #define RCU_TRACE(stmt) stmt | |
31 | #else /* #ifdef CONFIG_RCU_TRACE */ | |
32 | #define RCU_TRACE(stmt) | |
33 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ | |
b2c0710c | 34 | |
24278d14 PM |
35 | /* Global control variables for rcupdate callback mechanism. */ |
36 | struct rcu_ctrlblk { | |
37 | struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ | |
38 | struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ | |
39 | struct rcu_head **curtail; /* ->next pointer of last CB. */ | |
9e571a82 | 40 | RCU_TRACE(long qlen); /* Number of pending CBs. */ |
24278d14 PM |
41 | }; |
42 | ||
43 | /* Definition for rcupdate control block. */ | |
44 | static struct rcu_ctrlblk rcu_sched_ctrlblk = { | |
45 | .donetail = &rcu_sched_ctrlblk.rcucblist, | |
46 | .curtail = &rcu_sched_ctrlblk.rcucblist, | |
47 | }; | |
48 | ||
49 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { | |
50 | .donetail = &rcu_bh_ctrlblk.rcucblist, | |
51 | .curtail = &rcu_bh_ctrlblk.rcucblist, | |
52 | }; | |
53 | ||
54 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
55 | int rcu_scheduler_active __read_mostly; | |
56 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
57 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
58 | ||
a57eb940 PM |
59 | #ifdef CONFIG_TINY_PREEMPT_RCU |
60 | ||
61 | #include <linux/delay.h> | |
62 | ||
a57eb940 PM |
63 | /* Global control variables for preemptible RCU. */ |
64 | struct rcu_preempt_ctrlblk { | |
65 | struct rcu_ctrlblk rcb; /* curtail: ->next ptr of last CB for GP. */ | |
66 | struct rcu_head **nexttail; | |
67 | /* Tasks blocked in a preemptible RCU */ | |
68 | /* read-side critical section while an */ | |
69 | /* preemptible-RCU grace period is in */ | |
70 | /* progress must wait for a later grace */ | |
71 | /* period. This pointer points to the */ | |
72 | /* ->next pointer of the last task that */ | |
73 | /* must wait for a later grace period, or */ | |
74 | /* to &->rcb.rcucblist if there is no */ | |
75 | /* such task. */ | |
76 | struct list_head blkd_tasks; | |
77 | /* Tasks blocked in RCU read-side critical */ | |
78 | /* section. Tasks are placed at the head */ | |
79 | /* of this list and age towards the tail. */ | |
80 | struct list_head *gp_tasks; | |
81 | /* Pointer to the first task blocking the */ | |
82 | /* current grace period, or NULL if there */ | |
24278d14 | 83 | /* is no such task. */ |
a57eb940 PM |
84 | struct list_head *exp_tasks; |
85 | /* Pointer to first task blocking the */ | |
86 | /* current expedited grace period, or NULL */ | |
87 | /* if there is no such task. If there */ | |
88 | /* is no current expedited grace period, */ | |
89 | /* then there cannot be any such task. */ | |
24278d14 PM |
90 | #ifdef CONFIG_RCU_BOOST |
91 | struct list_head *boost_tasks; | |
92 | /* Pointer to first task that needs to be */ | |
93 | /* priority-boosted, or NULL if no priority */ | |
94 | /* boosting is needed. If there is no */ | |
95 | /* current or expedited grace period, there */ | |
96 | /* can be no such task. */ | |
97 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
98 | u8 gpnum; /* Current grace period. */ |
99 | u8 gpcpu; /* Last grace period blocked by the CPU. */ | |
100 | u8 completed; /* Last grace period completed. */ | |
101 | /* If all three are equal, RCU is idle. */ | |
9e571a82 | 102 | #ifdef CONFIG_RCU_BOOST |
24278d14 | 103 | unsigned long boost_time; /* When to start boosting (jiffies) */ |
9e571a82 PM |
104 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
105 | #ifdef CONFIG_RCU_TRACE | |
106 | unsigned long n_grace_periods; | |
107 | #ifdef CONFIG_RCU_BOOST | |
108 | unsigned long n_tasks_boosted; | |
109 | unsigned long n_exp_boosts; | |
110 | unsigned long n_normal_boosts; | |
111 | unsigned long n_normal_balk_blkd_tasks; | |
112 | unsigned long n_normal_balk_gp_tasks; | |
113 | unsigned long n_normal_balk_boost_tasks; | |
9e571a82 PM |
114 | unsigned long n_normal_balk_notyet; |
115 | unsigned long n_normal_balk_nos; | |
116 | unsigned long n_exp_balk_blkd_tasks; | |
117 | unsigned long n_exp_balk_nos; | |
118 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
119 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
a57eb940 PM |
120 | }; |
121 | ||
122 | static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = { | |
123 | .rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
124 | .rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
125 | .nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
126 | .blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks), | |
127 | }; | |
128 | ||
129 | static int rcu_preempted_readers_exp(void); | |
130 | static void rcu_report_exp_done(void); | |
131 | ||
132 | /* | |
133 | * Return true if the CPU has not yet responded to the current grace period. | |
134 | */ | |
dd7c4d89 | 135 | static int rcu_cpu_blocking_cur_gp(void) |
a57eb940 PM |
136 | { |
137 | return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum; | |
138 | } | |
139 | ||
140 | /* | |
141 | * Check for a running RCU reader. Because there is only one CPU, | |
142 | * there can be but one running RCU reader at a time. ;-) | |
143 | */ | |
144 | static int rcu_preempt_running_reader(void) | |
145 | { | |
146 | return current->rcu_read_lock_nesting; | |
147 | } | |
148 | ||
149 | /* | |
150 | * Check for preempted RCU readers blocking any grace period. | |
151 | * If the caller needs a reliable answer, it must disable hard irqs. | |
152 | */ | |
153 | static int rcu_preempt_blocked_readers_any(void) | |
154 | { | |
155 | return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks); | |
156 | } | |
157 | ||
158 | /* | |
159 | * Check for preempted RCU readers blocking the current grace period. | |
160 | * If the caller needs a reliable answer, it must disable hard irqs. | |
161 | */ | |
162 | static int rcu_preempt_blocked_readers_cgp(void) | |
163 | { | |
164 | return rcu_preempt_ctrlblk.gp_tasks != NULL; | |
165 | } | |
166 | ||
167 | /* | |
168 | * Return true if another preemptible-RCU grace period is needed. | |
169 | */ | |
170 | static int rcu_preempt_needs_another_gp(void) | |
171 | { | |
172 | return *rcu_preempt_ctrlblk.rcb.curtail != NULL; | |
173 | } | |
174 | ||
175 | /* | |
176 | * Return true if a preemptible-RCU grace period is in progress. | |
177 | * The caller must disable hardirqs. | |
178 | */ | |
179 | static int rcu_preempt_gp_in_progress(void) | |
180 | { | |
181 | return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum; | |
182 | } | |
183 | ||
24278d14 PM |
184 | /* |
185 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
186 | * returning NULL if at the end of the list. | |
187 | */ | |
188 | static struct list_head *rcu_next_node_entry(struct task_struct *t) | |
189 | { | |
190 | struct list_head *np; | |
191 | ||
192 | np = t->rcu_node_entry.next; | |
193 | if (np == &rcu_preempt_ctrlblk.blkd_tasks) | |
194 | np = NULL; | |
195 | return np; | |
196 | } | |
197 | ||
9e571a82 PM |
198 | #ifdef CONFIG_RCU_TRACE |
199 | ||
200 | #ifdef CONFIG_RCU_BOOST | |
201 | static void rcu_initiate_boost_trace(void); | |
202 | static void rcu_initiate_exp_boost_trace(void); | |
203 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
204 | ||
205 | /* | |
206 | * Dump additional statistice for TINY_PREEMPT_RCU. | |
207 | */ | |
208 | static void show_tiny_preempt_stats(struct seq_file *m) | |
209 | { | |
210 | seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n", | |
211 | rcu_preempt_ctrlblk.rcb.qlen, | |
212 | rcu_preempt_ctrlblk.n_grace_periods, | |
213 | rcu_preempt_ctrlblk.gpnum, | |
214 | rcu_preempt_ctrlblk.gpcpu, | |
215 | rcu_preempt_ctrlblk.completed, | |
216 | "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)], | |
217 | "N."[!rcu_preempt_ctrlblk.gp_tasks], | |
218 | "E."[!rcu_preempt_ctrlblk.exp_tasks]); | |
219 | #ifdef CONFIG_RCU_BOOST | |
203373c8 PM |
220 | seq_printf(m, "%sttb=%c ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n", |
221 | " ", | |
222 | "B."[!rcu_preempt_ctrlblk.boost_tasks], | |
9e571a82 PM |
223 | rcu_preempt_ctrlblk.n_tasks_boosted, |
224 | rcu_preempt_ctrlblk.n_exp_boosts, | |
225 | rcu_preempt_ctrlblk.n_normal_boosts, | |
226 | (int)(jiffies & 0xffff), | |
227 | (int)(rcu_preempt_ctrlblk.boost_time & 0xffff)); | |
203373c8 | 228 | seq_printf(m, " %s: nt=%lu gt=%lu bt=%lu ny=%lu nos=%lu\n", |
9e571a82 PM |
229 | "normal balk", |
230 | rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks, | |
231 | rcu_preempt_ctrlblk.n_normal_balk_gp_tasks, | |
232 | rcu_preempt_ctrlblk.n_normal_balk_boost_tasks, | |
9e571a82 PM |
233 | rcu_preempt_ctrlblk.n_normal_balk_notyet, |
234 | rcu_preempt_ctrlblk.n_normal_balk_nos); | |
235 | seq_printf(m, " exp balk: bt=%lu nos=%lu\n", | |
236 | rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks, | |
237 | rcu_preempt_ctrlblk.n_exp_balk_nos); | |
238 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
239 | } | |
240 | ||
241 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
242 | ||
24278d14 PM |
243 | #ifdef CONFIG_RCU_BOOST |
244 | ||
245 | #include "rtmutex_common.h" | |
246 | ||
247 | /* | |
248 | * Carry out RCU priority boosting on the task indicated by ->boost_tasks, | |
249 | * and advance ->boost_tasks to the next task in the ->blkd_tasks list. | |
250 | */ | |
251 | static int rcu_boost(void) | |
252 | { | |
253 | unsigned long flags; | |
254 | struct rt_mutex mtx; | |
255 | struct list_head *np; | |
256 | struct task_struct *t; | |
257 | ||
258 | if (rcu_preempt_ctrlblk.boost_tasks == NULL) | |
259 | return 0; /* Nothing to boost. */ | |
260 | raw_local_irq_save(flags); | |
24278d14 PM |
261 | t = container_of(rcu_preempt_ctrlblk.boost_tasks, struct task_struct, |
262 | rcu_node_entry); | |
263 | np = rcu_next_node_entry(t); | |
264 | rt_mutex_init_proxy_locked(&mtx, t); | |
265 | t->rcu_boost_mutex = &mtx; | |
266 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED; | |
267 | raw_local_irq_restore(flags); | |
268 | rt_mutex_lock(&mtx); | |
9e571a82 | 269 | RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); |
24278d14 PM |
270 | rt_mutex_unlock(&mtx); |
271 | return rcu_preempt_ctrlblk.boost_tasks != NULL; | |
272 | } | |
273 | ||
274 | /* | |
275 | * Check to see if it is now time to start boosting RCU readers blocking | |
276 | * the current grace period, and, if so, tell the rcu_kthread_task to | |
277 | * start boosting them. If there is an expedited boost in progress, | |
278 | * we wait for it to complete. | |
9e571a82 PM |
279 | * |
280 | * If there are no blocked readers blocking the current grace period, | |
281 | * return 0 to let the caller know, otherwise return 1. Note that this | |
282 | * return value is independent of whether or not boosting was done. | |
24278d14 | 283 | */ |
9e571a82 | 284 | static int rcu_initiate_boost(void) |
24278d14 | 285 | { |
9e571a82 PM |
286 | if (!rcu_preempt_blocked_readers_cgp()) { |
287 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks++); | |
288 | return 0; | |
289 | } | |
24278d14 PM |
290 | if (rcu_preempt_ctrlblk.gp_tasks != NULL && |
291 | rcu_preempt_ctrlblk.boost_tasks == NULL && | |
24278d14 PM |
292 | ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) { |
293 | rcu_preempt_ctrlblk.boost_tasks = rcu_preempt_ctrlblk.gp_tasks; | |
294 | invoke_rcu_kthread(); | |
9e571a82 PM |
295 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++); |
296 | } else | |
297 | RCU_TRACE(rcu_initiate_boost_trace()); | |
298 | return 1; | |
24278d14 PM |
299 | } |
300 | ||
301 | /* | |
302 | * Initiate boosting for an expedited grace period. | |
303 | */ | |
304 | static void rcu_initiate_expedited_boost(void) | |
305 | { | |
306 | unsigned long flags; | |
307 | ||
308 | raw_local_irq_save(flags); | |
309 | if (!list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) { | |
310 | rcu_preempt_ctrlblk.boost_tasks = | |
311 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
24278d14 | 312 | invoke_rcu_kthread(); |
9e571a82 PM |
313 | RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++); |
314 | } else | |
315 | RCU_TRACE(rcu_initiate_exp_boost_trace()); | |
24278d14 PM |
316 | raw_local_irq_restore(flags); |
317 | } | |
318 | ||
ddeb7581 | 319 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
24278d14 PM |
320 | |
321 | /* | |
322 | * Do priority-boost accounting for the start of a new grace period. | |
323 | */ | |
324 | static void rcu_preempt_boost_start_gp(void) | |
325 | { | |
326 | rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
24278d14 PM |
327 | } |
328 | ||
329 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
330 | ||
331 | /* | |
332 | * If there is no RCU priority boosting, we don't boost. | |
333 | */ | |
334 | static int rcu_boost(void) | |
335 | { | |
336 | return 0; | |
337 | } | |
338 | ||
339 | /* | |
9e571a82 PM |
340 | * If there is no RCU priority boosting, we don't initiate boosting, |
341 | * but we do indicate whether there are blocked readers blocking the | |
342 | * current grace period. | |
24278d14 | 343 | */ |
9e571a82 | 344 | static int rcu_initiate_boost(void) |
24278d14 | 345 | { |
9e571a82 | 346 | return rcu_preempt_blocked_readers_cgp(); |
24278d14 PM |
347 | } |
348 | ||
349 | /* | |
350 | * If there is no RCU priority boosting, we don't initiate expedited boosting. | |
351 | */ | |
352 | static void rcu_initiate_expedited_boost(void) | |
353 | { | |
354 | } | |
355 | ||
356 | /* | |
357 | * If there is no RCU priority boosting, nothing to do at grace-period start. | |
358 | */ | |
359 | static void rcu_preempt_boost_start_gp(void) | |
360 | { | |
361 | } | |
362 | ||
363 | #endif /* else #ifdef CONFIG_RCU_BOOST */ | |
364 | ||
a57eb940 PM |
365 | /* |
366 | * Record a preemptible-RCU quiescent state for the specified CPU. Note | |
367 | * that this just means that the task currently running on the CPU is | |
368 | * in a quiescent state. There might be any number of tasks blocked | |
369 | * while in an RCU read-side critical section. | |
370 | * | |
371 | * Unlike the other rcu_*_qs() functions, callers to this function | |
372 | * must disable irqs in order to protect the assignment to | |
373 | * ->rcu_read_unlock_special. | |
374 | * | |
375 | * Because this is a single-CPU implementation, the only way a grace | |
376 | * period can end is if the CPU is in a quiescent state. The reason is | |
377 | * that a blocked preemptible-RCU reader can exit its critical section | |
378 | * only if the CPU is running it at the time. Therefore, when the | |
379 | * last task blocking the current grace period exits its RCU read-side | |
380 | * critical section, neither the CPU nor blocked tasks will be stopping | |
381 | * the current grace period. (In contrast, SMP implementations | |
382 | * might have CPUs running in RCU read-side critical sections that | |
383 | * block later grace periods -- but this is not possible given only | |
384 | * one CPU.) | |
385 | */ | |
386 | static void rcu_preempt_cpu_qs(void) | |
387 | { | |
388 | /* Record both CPU and task as having responded to current GP. */ | |
389 | rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum; | |
390 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; | |
391 | ||
24278d14 | 392 | /* If there is no GP then there is nothing more to do. */ |
9e571a82 | 393 | if (!rcu_preempt_gp_in_progress()) |
a57eb940 | 394 | return; |
9e571a82 | 395 | /* |
ddeb7581 | 396 | * Check up on boosting. If there are readers blocking the |
9e571a82 PM |
397 | * current grace period, leave. |
398 | */ | |
399 | if (rcu_initiate_boost()) | |
24278d14 | 400 | return; |
a57eb940 PM |
401 | |
402 | /* Advance callbacks. */ | |
403 | rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum; | |
404 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail; | |
405 | rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail; | |
406 | ||
407 | /* If there are no blocked readers, next GP is done instantly. */ | |
408 | if (!rcu_preempt_blocked_readers_any()) | |
409 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail; | |
410 | ||
b2c0710c | 411 | /* If there are done callbacks, cause them to be invoked. */ |
a57eb940 | 412 | if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) |
24278d14 | 413 | invoke_rcu_kthread(); |
a57eb940 PM |
414 | } |
415 | ||
416 | /* | |
417 | * Start a new RCU grace period if warranted. Hard irqs must be disabled. | |
418 | */ | |
419 | static void rcu_preempt_start_gp(void) | |
420 | { | |
421 | if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) { | |
422 | ||
423 | /* Official start of GP. */ | |
424 | rcu_preempt_ctrlblk.gpnum++; | |
9e571a82 | 425 | RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); |
a57eb940 PM |
426 | |
427 | /* Any blocked RCU readers block new GP. */ | |
428 | if (rcu_preempt_blocked_readers_any()) | |
429 | rcu_preempt_ctrlblk.gp_tasks = | |
430 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
431 | ||
24278d14 PM |
432 | /* Set up for RCU priority boosting. */ |
433 | rcu_preempt_boost_start_gp(); | |
434 | ||
a57eb940 PM |
435 | /* If there is no running reader, CPU is done with GP. */ |
436 | if (!rcu_preempt_running_reader()) | |
437 | rcu_preempt_cpu_qs(); | |
438 | } | |
439 | } | |
440 | ||
441 | /* | |
442 | * We have entered the scheduler, and the current task might soon be | |
443 | * context-switched away from. If this task is in an RCU read-side | |
444 | * critical section, we will no longer be able to rely on the CPU to | |
445 | * record that fact, so we enqueue the task on the blkd_tasks list. | |
446 | * If the task started after the current grace period began, as recorded | |
447 | * by ->gpcpu, we enqueue at the beginning of the list. Otherwise | |
448 | * before the element referenced by ->gp_tasks (or at the tail if | |
449 | * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element. | |
450 | * The task will dequeue itself when it exits the outermost enclosing | |
451 | * RCU read-side critical section. Therefore, the current grace period | |
452 | * cannot be permitted to complete until the ->gp_tasks pointer becomes | |
453 | * NULL. | |
454 | * | |
455 | * Caller must disable preemption. | |
456 | */ | |
457 | void rcu_preempt_note_context_switch(void) | |
458 | { | |
459 | struct task_struct *t = current; | |
460 | unsigned long flags; | |
461 | ||
462 | local_irq_save(flags); /* must exclude scheduler_tick(). */ | |
463 | if (rcu_preempt_running_reader() && | |
464 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { | |
465 | ||
466 | /* Possibly blocking in an RCU read-side critical section. */ | |
467 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; | |
468 | ||
469 | /* | |
470 | * If this CPU has already checked in, then this task | |
471 | * will hold up the next grace period rather than the | |
472 | * current grace period. Queue the task accordingly. | |
473 | * If the task is queued for the current grace period | |
474 | * (i.e., this CPU has not yet passed through a quiescent | |
475 | * state for the current grace period), then as long | |
476 | * as that task remains queued, the current grace period | |
477 | * cannot end. | |
478 | */ | |
479 | list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks); | |
dd7c4d89 | 480 | if (rcu_cpu_blocking_cur_gp()) |
a57eb940 PM |
481 | rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry; |
482 | } | |
483 | ||
484 | /* | |
485 | * Either we were not in an RCU read-side critical section to | |
486 | * begin with, or we have now recorded that critical section | |
487 | * globally. Either way, we can now note a quiescent state | |
488 | * for this CPU. Again, if we were in an RCU read-side critical | |
489 | * section, and if that critical section was blocking the current | |
490 | * grace period, then the fact that the task has been enqueued | |
491 | * means that current grace period continues to be blocked. | |
492 | */ | |
493 | rcu_preempt_cpu_qs(); | |
494 | local_irq_restore(flags); | |
495 | } | |
496 | ||
497 | /* | |
498 | * Tiny-preemptible RCU implementation for rcu_read_lock(). | |
499 | * Just increment ->rcu_read_lock_nesting, shared state will be updated | |
500 | * if we block. | |
501 | */ | |
502 | void __rcu_read_lock(void) | |
503 | { | |
504 | current->rcu_read_lock_nesting++; | |
505 | barrier(); /* needed if we ever invoke rcu_read_lock in rcutiny.c */ | |
506 | } | |
507 | EXPORT_SYMBOL_GPL(__rcu_read_lock); | |
508 | ||
509 | /* | |
510 | * Handle special cases during rcu_read_unlock(), such as needing to | |
511 | * notify RCU core processing or task having blocked during the RCU | |
512 | * read-side critical section. | |
513 | */ | |
514 | static void rcu_read_unlock_special(struct task_struct *t) | |
515 | { | |
516 | int empty; | |
517 | int empty_exp; | |
518 | unsigned long flags; | |
519 | struct list_head *np; | |
520 | int special; | |
521 | ||
522 | /* | |
523 | * NMI handlers cannot block and cannot safely manipulate state. | |
524 | * They therefore cannot possibly be special, so just leave. | |
525 | */ | |
526 | if (in_nmi()) | |
527 | return; | |
528 | ||
529 | local_irq_save(flags); | |
530 | ||
531 | /* | |
532 | * If RCU core is waiting for this CPU to exit critical section, | |
533 | * let it know that we have done so. | |
534 | */ | |
535 | special = t->rcu_read_unlock_special; | |
536 | if (special & RCU_READ_UNLOCK_NEED_QS) | |
537 | rcu_preempt_cpu_qs(); | |
538 | ||
539 | /* Hardware IRQ handlers cannot block. */ | |
540 | if (in_irq()) { | |
541 | local_irq_restore(flags); | |
542 | return; | |
543 | } | |
544 | ||
545 | /* Clean up if blocked during RCU read-side critical section. */ | |
546 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
547 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
548 | ||
549 | /* | |
550 | * Remove this task from the ->blkd_tasks list and adjust | |
551 | * any pointers that might have been referencing it. | |
552 | */ | |
553 | empty = !rcu_preempt_blocked_readers_cgp(); | |
554 | empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL; | |
24278d14 | 555 | np = rcu_next_node_entry(t); |
ddeb7581 | 556 | list_del_init(&t->rcu_node_entry); |
a57eb940 PM |
557 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks) |
558 | rcu_preempt_ctrlblk.gp_tasks = np; | |
559 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks) | |
560 | rcu_preempt_ctrlblk.exp_tasks = np; | |
24278d14 PM |
561 | #ifdef CONFIG_RCU_BOOST |
562 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks) | |
563 | rcu_preempt_ctrlblk.boost_tasks = np; | |
564 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
565 | |
566 | /* | |
567 | * If this was the last task on the current list, and if | |
568 | * we aren't waiting on the CPU, report the quiescent state | |
569 | * and start a new grace period if needed. | |
570 | */ | |
571 | if (!empty && !rcu_preempt_blocked_readers_cgp()) { | |
572 | rcu_preempt_cpu_qs(); | |
573 | rcu_preempt_start_gp(); | |
574 | } | |
575 | ||
576 | /* | |
577 | * If this was the last task on the expedited lists, | |
578 | * then we need wake up the waiting task. | |
579 | */ | |
580 | if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL) | |
581 | rcu_report_exp_done(); | |
582 | } | |
24278d14 PM |
583 | #ifdef CONFIG_RCU_BOOST |
584 | /* Unboost self if was boosted. */ | |
585 | if (special & RCU_READ_UNLOCK_BOOSTED) { | |
586 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED; | |
587 | rt_mutex_unlock(t->rcu_boost_mutex); | |
588 | t->rcu_boost_mutex = NULL; | |
589 | } | |
590 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
591 | local_irq_restore(flags); |
592 | } | |
593 | ||
594 | /* | |
595 | * Tiny-preemptible RCU implementation for rcu_read_unlock(). | |
596 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost | |
597 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then | |
598 | * invoke rcu_read_unlock_special() to clean up after a context switch | |
599 | * in an RCU read-side critical section and other special cases. | |
600 | */ | |
601 | void __rcu_read_unlock(void) | |
602 | { | |
603 | struct task_struct *t = current; | |
604 | ||
605 | barrier(); /* needed if we ever invoke rcu_read_unlock in rcutiny.c */ | |
606 | --t->rcu_read_lock_nesting; | |
607 | barrier(); /* decrement before load of ->rcu_read_unlock_special */ | |
608 | if (t->rcu_read_lock_nesting == 0 && | |
609 | unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) | |
610 | rcu_read_unlock_special(t); | |
611 | #ifdef CONFIG_PROVE_LOCKING | |
612 | WARN_ON_ONCE(t->rcu_read_lock_nesting < 0); | |
613 | #endif /* #ifdef CONFIG_PROVE_LOCKING */ | |
614 | } | |
615 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); | |
616 | ||
617 | /* | |
618 | * Check for a quiescent state from the current CPU. When a task blocks, | |
619 | * the task is recorded in the rcu_preempt_ctrlblk structure, which is | |
620 | * checked elsewhere. This is called from the scheduling-clock interrupt. | |
621 | * | |
622 | * Caller must disable hard irqs. | |
623 | */ | |
624 | static void rcu_preempt_check_callbacks(void) | |
625 | { | |
626 | struct task_struct *t = current; | |
627 | ||
dd7c4d89 PM |
628 | if (rcu_preempt_gp_in_progress() && |
629 | (!rcu_preempt_running_reader() || | |
630 | !rcu_cpu_blocking_cur_gp())) | |
a57eb940 PM |
631 | rcu_preempt_cpu_qs(); |
632 | if (&rcu_preempt_ctrlblk.rcb.rcucblist != | |
633 | rcu_preempt_ctrlblk.rcb.donetail) | |
24278d14 | 634 | invoke_rcu_kthread(); |
dd7c4d89 PM |
635 | if (rcu_preempt_gp_in_progress() && |
636 | rcu_cpu_blocking_cur_gp() && | |
637 | rcu_preempt_running_reader()) | |
a57eb940 PM |
638 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
639 | } | |
640 | ||
641 | /* | |
642 | * TINY_PREEMPT_RCU has an extra callback-list tail pointer to | |
b2c0710c | 643 | * update, so this is invoked from rcu_process_callbacks() to |
a57eb940 PM |
644 | * handle that case. Of course, it is invoked for all flavors of |
645 | * RCU, but RCU callbacks can appear only on one of the lists, and | |
646 | * neither ->nexttail nor ->donetail can possibly be NULL, so there | |
647 | * is no need for an explicit check. | |
648 | */ | |
649 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
650 | { | |
651 | if (rcu_preempt_ctrlblk.nexttail == rcp->donetail) | |
652 | rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist; | |
653 | } | |
654 | ||
655 | /* | |
656 | * Process callbacks for preemptible RCU. | |
657 | */ | |
658 | static void rcu_preempt_process_callbacks(void) | |
659 | { | |
b2c0710c | 660 | rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); |
a57eb940 PM |
661 | } |
662 | ||
663 | /* | |
664 | * Queue a preemptible -RCU callback for invocation after a grace period. | |
665 | */ | |
666 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
667 | { | |
668 | unsigned long flags; | |
669 | ||
670 | debug_rcu_head_queue(head); | |
671 | head->func = func; | |
672 | head->next = NULL; | |
673 | ||
674 | local_irq_save(flags); | |
675 | *rcu_preempt_ctrlblk.nexttail = head; | |
676 | rcu_preempt_ctrlblk.nexttail = &head->next; | |
9e571a82 | 677 | RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++); |
a57eb940 PM |
678 | rcu_preempt_start_gp(); /* checks to see if GP needed. */ |
679 | local_irq_restore(flags); | |
680 | } | |
681 | EXPORT_SYMBOL_GPL(call_rcu); | |
682 | ||
683 | void rcu_barrier(void) | |
684 | { | |
685 | struct rcu_synchronize rcu; | |
686 | ||
687 | init_rcu_head_on_stack(&rcu.head); | |
688 | init_completion(&rcu.completion); | |
689 | /* Will wake me after RCU finished. */ | |
690 | call_rcu(&rcu.head, wakeme_after_rcu); | |
691 | /* Wait for it. */ | |
692 | wait_for_completion(&rcu.completion); | |
693 | destroy_rcu_head_on_stack(&rcu.head); | |
694 | } | |
695 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
696 | ||
697 | /* | |
698 | * synchronize_rcu - wait until a grace period has elapsed. | |
699 | * | |
700 | * Control will return to the caller some time after a full grace | |
701 | * period has elapsed, in other words after all currently executing RCU | |
702 | * read-side critical sections have completed. RCU read-side critical | |
703 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
704 | * and may be nested. | |
705 | */ | |
706 | void synchronize_rcu(void) | |
707 | { | |
708 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
709 | if (!rcu_scheduler_active) | |
710 | return; | |
711 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
712 | ||
713 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
714 | if (!rcu_preempt_blocked_readers_any()) | |
715 | return; | |
716 | ||
717 | /* Once we get past the fastpath checks, same code as rcu_barrier(). */ | |
718 | rcu_barrier(); | |
719 | } | |
720 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
721 | ||
722 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); | |
723 | static unsigned long sync_rcu_preempt_exp_count; | |
724 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); | |
725 | ||
726 | /* | |
727 | * Return non-zero if there are any tasks in RCU read-side critical | |
728 | * sections blocking the current preemptible-RCU expedited grace period. | |
729 | * If there is no preemptible-RCU expedited grace period currently in | |
730 | * progress, returns zero unconditionally. | |
731 | */ | |
732 | static int rcu_preempted_readers_exp(void) | |
733 | { | |
734 | return rcu_preempt_ctrlblk.exp_tasks != NULL; | |
735 | } | |
736 | ||
737 | /* | |
738 | * Report the exit from RCU read-side critical section for the last task | |
739 | * that queued itself during or before the current expedited preemptible-RCU | |
740 | * grace period. | |
741 | */ | |
742 | static void rcu_report_exp_done(void) | |
743 | { | |
744 | wake_up(&sync_rcu_preempt_exp_wq); | |
745 | } | |
746 | ||
747 | /* | |
748 | * Wait for an rcu-preempt grace period, but expedite it. The basic idea | |
749 | * is to rely in the fact that there is but one CPU, and that it is | |
750 | * illegal for a task to invoke synchronize_rcu_expedited() while in a | |
751 | * preemptible-RCU read-side critical section. Therefore, any such | |
752 | * critical sections must correspond to blocked tasks, which must therefore | |
753 | * be on the ->blkd_tasks list. So just record the current head of the | |
754 | * list in the ->exp_tasks pointer, and wait for all tasks including and | |
755 | * after the task pointed to by ->exp_tasks to drain. | |
756 | */ | |
757 | void synchronize_rcu_expedited(void) | |
758 | { | |
759 | unsigned long flags; | |
760 | struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk; | |
761 | unsigned long snap; | |
762 | ||
763 | barrier(); /* ensure prior action seen before grace period. */ | |
764 | ||
765 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
766 | ||
767 | /* | |
768 | * Acquire lock so that there is only one preemptible RCU grace | |
769 | * period in flight. Of course, if someone does the expedited | |
770 | * grace period for us while we are acquiring the lock, just leave. | |
771 | */ | |
772 | snap = sync_rcu_preempt_exp_count + 1; | |
773 | mutex_lock(&sync_rcu_preempt_exp_mutex); | |
774 | if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count)) | |
775 | goto unlock_mb_ret; /* Others did our work for us. */ | |
776 | ||
777 | local_irq_save(flags); | |
778 | ||
779 | /* | |
780 | * All RCU readers have to already be on blkd_tasks because | |
781 | * we cannot legally be executing in an RCU read-side critical | |
782 | * section. | |
783 | */ | |
784 | ||
785 | /* Snapshot current head of ->blkd_tasks list. */ | |
786 | rpcp->exp_tasks = rpcp->blkd_tasks.next; | |
787 | if (rpcp->exp_tasks == &rpcp->blkd_tasks) | |
788 | rpcp->exp_tasks = NULL; | |
789 | local_irq_restore(flags); | |
790 | ||
791 | /* Wait for tail of ->blkd_tasks list to drain. */ | |
792 | if (rcu_preempted_readers_exp()) | |
24278d14 | 793 | rcu_initiate_expedited_boost(); |
a57eb940 PM |
794 | wait_event(sync_rcu_preempt_exp_wq, |
795 | !rcu_preempted_readers_exp()); | |
796 | ||
797 | /* Clean up and exit. */ | |
798 | barrier(); /* ensure expedited GP seen before counter increment. */ | |
799 | sync_rcu_preempt_exp_count++; | |
800 | unlock_mb_ret: | |
801 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
802 | barrier(); /* ensure subsequent action seen after grace period. */ | |
803 | } | |
804 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
805 | ||
806 | /* | |
807 | * Does preemptible RCU need the CPU to stay out of dynticks mode? | |
808 | */ | |
809 | int rcu_preempt_needs_cpu(void) | |
810 | { | |
811 | if (!rcu_preempt_running_reader()) | |
812 | rcu_preempt_cpu_qs(); | |
813 | return rcu_preempt_ctrlblk.rcb.rcucblist != NULL; | |
814 | } | |
815 | ||
816 | /* | |
817 | * Check for a task exiting while in a preemptible -RCU read-side | |
818 | * critical section, clean up if so. No need to issue warnings, | |
819 | * as debug_check_no_locks_held() already does this if lockdep | |
820 | * is enabled. | |
821 | */ | |
822 | void exit_rcu(void) | |
823 | { | |
824 | struct task_struct *t = current; | |
825 | ||
826 | if (t->rcu_read_lock_nesting == 0) | |
827 | return; | |
828 | t->rcu_read_lock_nesting = 1; | |
ba74f4d7 | 829 | __rcu_read_unlock(); |
a57eb940 PM |
830 | } |
831 | ||
832 | #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
833 | ||
9e571a82 PM |
834 | #ifdef CONFIG_RCU_TRACE |
835 | ||
836 | /* | |
837 | * Because preemptible RCU does not exist, it is not necessary to | |
838 | * dump out its statistics. | |
839 | */ | |
840 | static void show_tiny_preempt_stats(struct seq_file *m) | |
841 | { | |
842 | } | |
843 | ||
844 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
845 | ||
24278d14 PM |
846 | /* |
847 | * Because preemptible RCU does not exist, it is never necessary to | |
848 | * boost preempted RCU readers. | |
849 | */ | |
850 | static int rcu_boost(void) | |
851 | { | |
852 | return 0; | |
853 | } | |
854 | ||
a57eb940 PM |
855 | /* |
856 | * Because preemptible RCU does not exist, it never has any callbacks | |
857 | * to check. | |
858 | */ | |
859 | static void rcu_preempt_check_callbacks(void) | |
860 | { | |
861 | } | |
862 | ||
863 | /* | |
864 | * Because preemptible RCU does not exist, it never has any callbacks | |
865 | * to remove. | |
866 | */ | |
867 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
868 | { | |
869 | } | |
870 | ||
871 | /* | |
872 | * Because preemptible RCU does not exist, it never has any callbacks | |
873 | * to process. | |
874 | */ | |
875 | static void rcu_preempt_process_callbacks(void) | |
876 | { | |
877 | } | |
878 | ||
879 | #endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
880 | ||
bbad9379 | 881 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
bbad9379 PM |
882 | #include <linux/kernel_stat.h> |
883 | ||
884 | /* | |
885 | * During boot, we forgive RCU lockdep issues. After this function is | |
886 | * invoked, we start taking RCU lockdep issues seriously. | |
887 | */ | |
b2c0710c | 888 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
889 | { |
890 | WARN_ON(nr_context_switches() > 0); | |
891 | rcu_scheduler_active = 1; | |
892 | } | |
893 | ||
894 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 PM |
895 | |
896 | #ifdef CONFIG_RCU_BOOST | |
897 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO | |
898 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
899 | #define RCU_BOOST_PRIO 1 | |
900 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ | |
9e571a82 PM |
901 | |
902 | #ifdef CONFIG_RCU_TRACE | |
903 | ||
904 | #ifdef CONFIG_RCU_BOOST | |
905 | ||
906 | static void rcu_initiate_boost_trace(void) | |
907 | { | |
908 | if (rcu_preempt_ctrlblk.gp_tasks == NULL) | |
909 | rcu_preempt_ctrlblk.n_normal_balk_gp_tasks++; | |
910 | else if (rcu_preempt_ctrlblk.boost_tasks != NULL) | |
911 | rcu_preempt_ctrlblk.n_normal_balk_boost_tasks++; | |
9e571a82 PM |
912 | else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) |
913 | rcu_preempt_ctrlblk.n_normal_balk_notyet++; | |
914 | else | |
915 | rcu_preempt_ctrlblk.n_normal_balk_nos++; | |
916 | } | |
917 | ||
918 | static void rcu_initiate_exp_boost_trace(void) | |
919 | { | |
920 | if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) | |
921 | rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks++; | |
922 | else | |
923 | rcu_preempt_ctrlblk.n_exp_balk_nos++; | |
924 | } | |
925 | ||
926 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
927 | ||
928 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) | |
929 | { | |
930 | unsigned long flags; | |
931 | ||
932 | raw_local_irq_save(flags); | |
933 | rcp->qlen -= n; | |
934 | raw_local_irq_restore(flags); | |
935 | } | |
936 | ||
937 | /* | |
938 | * Dump statistics for TINY_RCU, such as they are. | |
939 | */ | |
940 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
941 | { | |
942 | show_tiny_preempt_stats(m); | |
943 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); | |
944 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
945 | return 0; | |
946 | } | |
947 | ||
948 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
949 | { | |
950 | return single_open(file, show_tiny_stats, NULL); | |
951 | } | |
952 | ||
953 | static const struct file_operations show_tiny_stats_fops = { | |
954 | .owner = THIS_MODULE, | |
955 | .open = show_tiny_stats_open, | |
956 | .read = seq_read, | |
957 | .llseek = seq_lseek, | |
958 | .release = single_release, | |
959 | }; | |
960 | ||
961 | static struct dentry *rcudir; | |
962 | ||
963 | static int __init rcutiny_trace_init(void) | |
964 | { | |
965 | struct dentry *retval; | |
966 | ||
967 | rcudir = debugfs_create_dir("rcu", NULL); | |
968 | if (!rcudir) | |
969 | goto free_out; | |
970 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
971 | NULL, &show_tiny_stats_fops); | |
972 | if (!retval) | |
973 | goto free_out; | |
974 | return 0; | |
975 | free_out: | |
976 | debugfs_remove_recursive(rcudir); | |
977 | return 1; | |
978 | } | |
979 | ||
980 | static void __exit rcutiny_trace_cleanup(void) | |
981 | { | |
982 | debugfs_remove_recursive(rcudir); | |
983 | } | |
984 | ||
985 | module_init(rcutiny_trace_init); | |
986 | module_exit(rcutiny_trace_cleanup); | |
987 | ||
988 | MODULE_AUTHOR("Paul E. McKenney"); | |
989 | MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); | |
990 | MODULE_LICENSE("GPL"); | |
991 | ||
992 | #endif /* #ifdef CONFIG_RCU_TRACE */ |