Commit | Line | Data |
---|---|---|
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; | |
7e8b4c72 | 109 | /* Total number of tasks boosted. */ |
9e571a82 | 110 | unsigned long n_exp_boosts; |
7e8b4c72 | 111 | /* Number of tasks boosted for expedited GP. */ |
9e571a82 | 112 | unsigned long n_normal_boosts; |
7e8b4c72 PM |
113 | /* Number of tasks boosted for normal GP. */ |
114 | unsigned long n_balk_blkd_tasks; | |
115 | /* Refused to boost: no blocked tasks. */ | |
116 | unsigned long n_balk_exp_gp_tasks; | |
117 | /* Refused to boost: nothing blocking GP. */ | |
118 | unsigned long n_balk_boost_tasks; | |
119 | /* Refused to boost: already boosting. */ | |
120 | unsigned long n_balk_notyet; | |
121 | /* Refused to boost: not yet time. */ | |
122 | unsigned long n_balk_nos; | |
123 | /* Refused to boost: not sure why, though. */ | |
124 | /* This can happen due to race conditions. */ | |
9e571a82 PM |
125 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
126 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
a57eb940 PM |
127 | }; |
128 | ||
129 | static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = { | |
130 | .rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
131 | .rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
132 | .nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
133 | .blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks), | |
134 | }; | |
135 | ||
136 | static int rcu_preempted_readers_exp(void); | |
137 | static void rcu_report_exp_done(void); | |
138 | ||
139 | /* | |
140 | * Return true if the CPU has not yet responded to the current grace period. | |
141 | */ | |
dd7c4d89 | 142 | static int rcu_cpu_blocking_cur_gp(void) |
a57eb940 PM |
143 | { |
144 | return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum; | |
145 | } | |
146 | ||
147 | /* | |
148 | * Check for a running RCU reader. Because there is only one CPU, | |
149 | * there can be but one running RCU reader at a time. ;-) | |
150 | */ | |
151 | static int rcu_preempt_running_reader(void) | |
152 | { | |
153 | return current->rcu_read_lock_nesting; | |
154 | } | |
155 | ||
156 | /* | |
157 | * Check for preempted RCU readers blocking any grace period. | |
158 | * If the caller needs a reliable answer, it must disable hard irqs. | |
159 | */ | |
160 | static int rcu_preempt_blocked_readers_any(void) | |
161 | { | |
162 | return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks); | |
163 | } | |
164 | ||
165 | /* | |
166 | * Check for preempted RCU readers blocking the current grace period. | |
167 | * If the caller needs a reliable answer, it must disable hard irqs. | |
168 | */ | |
169 | static int rcu_preempt_blocked_readers_cgp(void) | |
170 | { | |
171 | return rcu_preempt_ctrlblk.gp_tasks != NULL; | |
172 | } | |
173 | ||
174 | /* | |
175 | * Return true if another preemptible-RCU grace period is needed. | |
176 | */ | |
177 | static int rcu_preempt_needs_another_gp(void) | |
178 | { | |
179 | return *rcu_preempt_ctrlblk.rcb.curtail != NULL; | |
180 | } | |
181 | ||
182 | /* | |
183 | * Return true if a preemptible-RCU grace period is in progress. | |
184 | * The caller must disable hardirqs. | |
185 | */ | |
186 | static int rcu_preempt_gp_in_progress(void) | |
187 | { | |
188 | return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum; | |
189 | } | |
190 | ||
24278d14 PM |
191 | /* |
192 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
193 | * returning NULL if at the end of the list. | |
194 | */ | |
195 | static struct list_head *rcu_next_node_entry(struct task_struct *t) | |
196 | { | |
197 | struct list_head *np; | |
198 | ||
199 | np = t->rcu_node_entry.next; | |
200 | if (np == &rcu_preempt_ctrlblk.blkd_tasks) | |
201 | np = NULL; | |
202 | return np; | |
203 | } | |
204 | ||
9e571a82 PM |
205 | #ifdef CONFIG_RCU_TRACE |
206 | ||
207 | #ifdef CONFIG_RCU_BOOST | |
208 | static void rcu_initiate_boost_trace(void); | |
9e571a82 PM |
209 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
210 | ||
211 | /* | |
212 | * Dump additional statistice for TINY_PREEMPT_RCU. | |
213 | */ | |
214 | static void show_tiny_preempt_stats(struct seq_file *m) | |
215 | { | |
216 | seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n", | |
217 | rcu_preempt_ctrlblk.rcb.qlen, | |
218 | rcu_preempt_ctrlblk.n_grace_periods, | |
219 | rcu_preempt_ctrlblk.gpnum, | |
220 | rcu_preempt_ctrlblk.gpcpu, | |
221 | rcu_preempt_ctrlblk.completed, | |
222 | "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)], | |
223 | "N."[!rcu_preempt_ctrlblk.gp_tasks], | |
224 | "E."[!rcu_preempt_ctrlblk.exp_tasks]); | |
225 | #ifdef CONFIG_RCU_BOOST | |
203373c8 PM |
226 | seq_printf(m, "%sttb=%c ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n", |
227 | " ", | |
228 | "B."[!rcu_preempt_ctrlblk.boost_tasks], | |
9e571a82 PM |
229 | rcu_preempt_ctrlblk.n_tasks_boosted, |
230 | rcu_preempt_ctrlblk.n_exp_boosts, | |
231 | rcu_preempt_ctrlblk.n_normal_boosts, | |
232 | (int)(jiffies & 0xffff), | |
233 | (int)(rcu_preempt_ctrlblk.boost_time & 0xffff)); | |
7e8b4c72 PM |
234 | seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu ny=%lu nos=%lu\n", |
235 | " balk", | |
236 | rcu_preempt_ctrlblk.n_balk_blkd_tasks, | |
237 | rcu_preempt_ctrlblk.n_balk_exp_gp_tasks, | |
238 | rcu_preempt_ctrlblk.n_balk_boost_tasks, | |
239 | rcu_preempt_ctrlblk.n_balk_notyet, | |
240 | rcu_preempt_ctrlblk.n_balk_nos); | |
9e571a82 PM |
241 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
242 | } | |
243 | ||
244 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
245 | ||
24278d14 PM |
246 | #ifdef CONFIG_RCU_BOOST |
247 | ||
248 | #include "rtmutex_common.h" | |
249 | ||
250 | /* | |
251 | * Carry out RCU priority boosting on the task indicated by ->boost_tasks, | |
252 | * and advance ->boost_tasks to the next task in the ->blkd_tasks list. | |
253 | */ | |
254 | static int rcu_boost(void) | |
255 | { | |
256 | unsigned long flags; | |
257 | struct rt_mutex mtx; | |
24278d14 | 258 | struct task_struct *t; |
7e8b4c72 | 259 | struct list_head *tb; |
24278d14 | 260 | |
7e8b4c72 PM |
261 | if (rcu_preempt_ctrlblk.boost_tasks == NULL && |
262 | rcu_preempt_ctrlblk.exp_tasks == NULL) | |
24278d14 | 263 | return 0; /* Nothing to boost. */ |
7e8b4c72 | 264 | |
24278d14 | 265 | raw_local_irq_save(flags); |
7e8b4c72 PM |
266 | |
267 | /* | |
268 | * Recheck with irqs disabled: all tasks in need of boosting | |
269 | * might exit their RCU read-side critical sections on their own | |
270 | * if we are preempted just before disabling irqs. | |
271 | */ | |
272 | if (rcu_preempt_ctrlblk.boost_tasks == NULL && | |
273 | rcu_preempt_ctrlblk.exp_tasks == NULL) { | |
274 | raw_local_irq_restore(flags); | |
275 | return 0; | |
276 | } | |
277 | ||
278 | /* | |
279 | * Preferentially boost tasks blocking expedited grace periods. | |
280 | * This cannot starve the normal grace periods because a second | |
281 | * expedited grace period must boost all blocked tasks, including | |
282 | * those blocking the pre-existing normal grace period. | |
283 | */ | |
284 | if (rcu_preempt_ctrlblk.exp_tasks != NULL) { | |
285 | tb = rcu_preempt_ctrlblk.exp_tasks; | |
286 | RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++); | |
287 | } else { | |
288 | tb = rcu_preempt_ctrlblk.boost_tasks; | |
289 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++); | |
290 | } | |
291 | RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); | |
292 | ||
293 | /* | |
294 | * We boost task t by manufacturing an rt_mutex that appears to | |
295 | * be held by task t. We leave a pointer to that rt_mutex where | |
296 | * task t can find it, and task t will release the mutex when it | |
297 | * exits its outermost RCU read-side critical section. Then | |
298 | * simply acquiring this artificial rt_mutex will boost task | |
299 | * t's priority. (Thanks to tglx for suggesting this approach!) | |
300 | */ | |
301 | t = container_of(tb, struct task_struct, rcu_node_entry); | |
24278d14 PM |
302 | rt_mutex_init_proxy_locked(&mtx, t); |
303 | t->rcu_boost_mutex = &mtx; | |
304 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED; | |
305 | raw_local_irq_restore(flags); | |
306 | rt_mutex_lock(&mtx); | |
7e8b4c72 PM |
307 | rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ |
308 | ||
309 | return rcu_preempt_ctrlblk.boost_tasks != NULL || | |
310 | rcu_preempt_ctrlblk.exp_tasks != NULL; | |
24278d14 PM |
311 | } |
312 | ||
313 | /* | |
314 | * Check to see if it is now time to start boosting RCU readers blocking | |
315 | * the current grace period, and, if so, tell the rcu_kthread_task to | |
316 | * start boosting them. If there is an expedited boost in progress, | |
317 | * we wait for it to complete. | |
9e571a82 PM |
318 | * |
319 | * If there are no blocked readers blocking the current grace period, | |
320 | * return 0 to let the caller know, otherwise return 1. Note that this | |
321 | * return value is independent of whether or not boosting was done. | |
24278d14 | 322 | */ |
9e571a82 | 323 | static int rcu_initiate_boost(void) |
24278d14 | 324 | { |
7e8b4c72 PM |
325 | if (!rcu_preempt_blocked_readers_cgp() && |
326 | rcu_preempt_ctrlblk.exp_tasks == NULL) { | |
327 | RCU_TRACE(rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++); | |
9e571a82 PM |
328 | return 0; |
329 | } | |
7e8b4c72 PM |
330 | if (rcu_preempt_ctrlblk.exp_tasks != NULL || |
331 | (rcu_preempt_ctrlblk.gp_tasks != NULL && | |
332 | rcu_preempt_ctrlblk.boost_tasks == NULL && | |
333 | ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))) { | |
334 | if (rcu_preempt_ctrlblk.exp_tasks == NULL) | |
335 | rcu_preempt_ctrlblk.boost_tasks = | |
336 | rcu_preempt_ctrlblk.gp_tasks; | |
24278d14 | 337 | invoke_rcu_kthread(); |
9e571a82 PM |
338 | } else |
339 | RCU_TRACE(rcu_initiate_boost_trace()); | |
340 | return 1; | |
24278d14 PM |
341 | } |
342 | ||
ddeb7581 | 343 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
24278d14 PM |
344 | |
345 | /* | |
346 | * Do priority-boost accounting for the start of a new grace period. | |
347 | */ | |
348 | static void rcu_preempt_boost_start_gp(void) | |
349 | { | |
350 | rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
24278d14 PM |
351 | } |
352 | ||
353 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
354 | ||
355 | /* | |
356 | * If there is no RCU priority boosting, we don't boost. | |
357 | */ | |
358 | static int rcu_boost(void) | |
359 | { | |
360 | return 0; | |
361 | } | |
362 | ||
363 | /* | |
9e571a82 PM |
364 | * If there is no RCU priority boosting, we don't initiate boosting, |
365 | * but we do indicate whether there are blocked readers blocking the | |
366 | * current grace period. | |
24278d14 | 367 | */ |
9e571a82 | 368 | static int rcu_initiate_boost(void) |
24278d14 | 369 | { |
9e571a82 | 370 | return rcu_preempt_blocked_readers_cgp(); |
24278d14 PM |
371 | } |
372 | ||
24278d14 PM |
373 | /* |
374 | * If there is no RCU priority boosting, nothing to do at grace-period start. | |
375 | */ | |
376 | static void rcu_preempt_boost_start_gp(void) | |
377 | { | |
378 | } | |
379 | ||
380 | #endif /* else #ifdef CONFIG_RCU_BOOST */ | |
381 | ||
a57eb940 PM |
382 | /* |
383 | * Record a preemptible-RCU quiescent state for the specified CPU. Note | |
384 | * that this just means that the task currently running on the CPU is | |
385 | * in a quiescent state. There might be any number of tasks blocked | |
386 | * while in an RCU read-side critical section. | |
387 | * | |
388 | * Unlike the other rcu_*_qs() functions, callers to this function | |
389 | * must disable irqs in order to protect the assignment to | |
390 | * ->rcu_read_unlock_special. | |
391 | * | |
392 | * Because this is a single-CPU implementation, the only way a grace | |
393 | * period can end is if the CPU is in a quiescent state. The reason is | |
394 | * that a blocked preemptible-RCU reader can exit its critical section | |
395 | * only if the CPU is running it at the time. Therefore, when the | |
396 | * last task blocking the current grace period exits its RCU read-side | |
397 | * critical section, neither the CPU nor blocked tasks will be stopping | |
398 | * the current grace period. (In contrast, SMP implementations | |
399 | * might have CPUs running in RCU read-side critical sections that | |
400 | * block later grace periods -- but this is not possible given only | |
401 | * one CPU.) | |
402 | */ | |
403 | static void rcu_preempt_cpu_qs(void) | |
404 | { | |
405 | /* Record both CPU and task as having responded to current GP. */ | |
406 | rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum; | |
407 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; | |
408 | ||
24278d14 | 409 | /* If there is no GP then there is nothing more to do. */ |
9e571a82 | 410 | if (!rcu_preempt_gp_in_progress()) |
a57eb940 | 411 | return; |
9e571a82 | 412 | /* |
ddeb7581 | 413 | * Check up on boosting. If there are readers blocking the |
9e571a82 PM |
414 | * current grace period, leave. |
415 | */ | |
416 | if (rcu_initiate_boost()) | |
24278d14 | 417 | return; |
a57eb940 PM |
418 | |
419 | /* Advance callbacks. */ | |
420 | rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum; | |
421 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail; | |
422 | rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail; | |
423 | ||
424 | /* If there are no blocked readers, next GP is done instantly. */ | |
425 | if (!rcu_preempt_blocked_readers_any()) | |
426 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail; | |
427 | ||
b2c0710c | 428 | /* If there are done callbacks, cause them to be invoked. */ |
a57eb940 | 429 | if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) |
24278d14 | 430 | invoke_rcu_kthread(); |
a57eb940 PM |
431 | } |
432 | ||
433 | /* | |
434 | * Start a new RCU grace period if warranted. Hard irqs must be disabled. | |
435 | */ | |
436 | static void rcu_preempt_start_gp(void) | |
437 | { | |
438 | if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) { | |
439 | ||
440 | /* Official start of GP. */ | |
441 | rcu_preempt_ctrlblk.gpnum++; | |
9e571a82 | 442 | RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); |
a57eb940 PM |
443 | |
444 | /* Any blocked RCU readers block new GP. */ | |
445 | if (rcu_preempt_blocked_readers_any()) | |
446 | rcu_preempt_ctrlblk.gp_tasks = | |
447 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
448 | ||
24278d14 PM |
449 | /* Set up for RCU priority boosting. */ |
450 | rcu_preempt_boost_start_gp(); | |
451 | ||
a57eb940 PM |
452 | /* If there is no running reader, CPU is done with GP. */ |
453 | if (!rcu_preempt_running_reader()) | |
454 | rcu_preempt_cpu_qs(); | |
455 | } | |
456 | } | |
457 | ||
458 | /* | |
459 | * We have entered the scheduler, and the current task might soon be | |
460 | * context-switched away from. If this task is in an RCU read-side | |
461 | * critical section, we will no longer be able to rely on the CPU to | |
462 | * record that fact, so we enqueue the task on the blkd_tasks list. | |
463 | * If the task started after the current grace period began, as recorded | |
464 | * by ->gpcpu, we enqueue at the beginning of the list. Otherwise | |
465 | * before the element referenced by ->gp_tasks (or at the tail if | |
466 | * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element. | |
467 | * The task will dequeue itself when it exits the outermost enclosing | |
468 | * RCU read-side critical section. Therefore, the current grace period | |
469 | * cannot be permitted to complete until the ->gp_tasks pointer becomes | |
470 | * NULL. | |
471 | * | |
472 | * Caller must disable preemption. | |
473 | */ | |
474 | void rcu_preempt_note_context_switch(void) | |
475 | { | |
476 | struct task_struct *t = current; | |
477 | unsigned long flags; | |
478 | ||
479 | local_irq_save(flags); /* must exclude scheduler_tick(). */ | |
480 | if (rcu_preempt_running_reader() && | |
481 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { | |
482 | ||
483 | /* Possibly blocking in an RCU read-side critical section. */ | |
484 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; | |
485 | ||
486 | /* | |
487 | * If this CPU has already checked in, then this task | |
488 | * will hold up the next grace period rather than the | |
489 | * current grace period. Queue the task accordingly. | |
490 | * If the task is queued for the current grace period | |
491 | * (i.e., this CPU has not yet passed through a quiescent | |
492 | * state for the current grace period), then as long | |
493 | * as that task remains queued, the current grace period | |
494 | * cannot end. | |
495 | */ | |
496 | list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks); | |
dd7c4d89 | 497 | if (rcu_cpu_blocking_cur_gp()) |
a57eb940 PM |
498 | rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry; |
499 | } | |
500 | ||
501 | /* | |
502 | * Either we were not in an RCU read-side critical section to | |
503 | * begin with, or we have now recorded that critical section | |
504 | * globally. Either way, we can now note a quiescent state | |
505 | * for this CPU. Again, if we were in an RCU read-side critical | |
506 | * section, and if that critical section was blocking the current | |
507 | * grace period, then the fact that the task has been enqueued | |
508 | * means that current grace period continues to be blocked. | |
509 | */ | |
510 | rcu_preempt_cpu_qs(); | |
511 | local_irq_restore(flags); | |
512 | } | |
513 | ||
514 | /* | |
515 | * Tiny-preemptible RCU implementation for rcu_read_lock(). | |
516 | * Just increment ->rcu_read_lock_nesting, shared state will be updated | |
517 | * if we block. | |
518 | */ | |
519 | void __rcu_read_lock(void) | |
520 | { | |
521 | current->rcu_read_lock_nesting++; | |
522 | barrier(); /* needed if we ever invoke rcu_read_lock in rcutiny.c */ | |
523 | } | |
524 | EXPORT_SYMBOL_GPL(__rcu_read_lock); | |
525 | ||
526 | /* | |
527 | * Handle special cases during rcu_read_unlock(), such as needing to | |
528 | * notify RCU core processing or task having blocked during the RCU | |
529 | * read-side critical section. | |
530 | */ | |
531 | static void rcu_read_unlock_special(struct task_struct *t) | |
532 | { | |
533 | int empty; | |
534 | int empty_exp; | |
535 | unsigned long flags; | |
536 | struct list_head *np; | |
537 | int special; | |
538 | ||
539 | /* | |
540 | * NMI handlers cannot block and cannot safely manipulate state. | |
541 | * They therefore cannot possibly be special, so just leave. | |
542 | */ | |
543 | if (in_nmi()) | |
544 | return; | |
545 | ||
546 | local_irq_save(flags); | |
547 | ||
548 | /* | |
549 | * If RCU core is waiting for this CPU to exit critical section, | |
550 | * let it know that we have done so. | |
551 | */ | |
552 | special = t->rcu_read_unlock_special; | |
553 | if (special & RCU_READ_UNLOCK_NEED_QS) | |
554 | rcu_preempt_cpu_qs(); | |
555 | ||
556 | /* Hardware IRQ handlers cannot block. */ | |
557 | if (in_irq()) { | |
558 | local_irq_restore(flags); | |
559 | return; | |
560 | } | |
561 | ||
562 | /* Clean up if blocked during RCU read-side critical section. */ | |
563 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
564 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
565 | ||
566 | /* | |
567 | * Remove this task from the ->blkd_tasks list and adjust | |
568 | * any pointers that might have been referencing it. | |
569 | */ | |
570 | empty = !rcu_preempt_blocked_readers_cgp(); | |
571 | empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL; | |
24278d14 | 572 | np = rcu_next_node_entry(t); |
ddeb7581 | 573 | list_del_init(&t->rcu_node_entry); |
a57eb940 PM |
574 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks) |
575 | rcu_preempt_ctrlblk.gp_tasks = np; | |
576 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks) | |
577 | rcu_preempt_ctrlblk.exp_tasks = np; | |
24278d14 PM |
578 | #ifdef CONFIG_RCU_BOOST |
579 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks) | |
580 | rcu_preempt_ctrlblk.boost_tasks = np; | |
581 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
582 | |
583 | /* | |
584 | * If this was the last task on the current list, and if | |
585 | * we aren't waiting on the CPU, report the quiescent state | |
586 | * and start a new grace period if needed. | |
587 | */ | |
588 | if (!empty && !rcu_preempt_blocked_readers_cgp()) { | |
589 | rcu_preempt_cpu_qs(); | |
590 | rcu_preempt_start_gp(); | |
591 | } | |
592 | ||
593 | /* | |
594 | * If this was the last task on the expedited lists, | |
595 | * then we need wake up the waiting task. | |
596 | */ | |
597 | if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL) | |
598 | rcu_report_exp_done(); | |
599 | } | |
24278d14 PM |
600 | #ifdef CONFIG_RCU_BOOST |
601 | /* Unboost self if was boosted. */ | |
602 | if (special & RCU_READ_UNLOCK_BOOSTED) { | |
603 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED; | |
604 | rt_mutex_unlock(t->rcu_boost_mutex); | |
605 | t->rcu_boost_mutex = NULL; | |
606 | } | |
607 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
608 | local_irq_restore(flags); |
609 | } | |
610 | ||
611 | /* | |
612 | * Tiny-preemptible RCU implementation for rcu_read_unlock(). | |
613 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost | |
614 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then | |
615 | * invoke rcu_read_unlock_special() to clean up after a context switch | |
616 | * in an RCU read-side critical section and other special cases. | |
617 | */ | |
618 | void __rcu_read_unlock(void) | |
619 | { | |
620 | struct task_struct *t = current; | |
621 | ||
622 | barrier(); /* needed if we ever invoke rcu_read_unlock in rcutiny.c */ | |
623 | --t->rcu_read_lock_nesting; | |
624 | barrier(); /* decrement before load of ->rcu_read_unlock_special */ | |
625 | if (t->rcu_read_lock_nesting == 0 && | |
626 | unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) | |
627 | rcu_read_unlock_special(t); | |
628 | #ifdef CONFIG_PROVE_LOCKING | |
629 | WARN_ON_ONCE(t->rcu_read_lock_nesting < 0); | |
630 | #endif /* #ifdef CONFIG_PROVE_LOCKING */ | |
631 | } | |
632 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); | |
633 | ||
634 | /* | |
635 | * Check for a quiescent state from the current CPU. When a task blocks, | |
636 | * the task is recorded in the rcu_preempt_ctrlblk structure, which is | |
637 | * checked elsewhere. This is called from the scheduling-clock interrupt. | |
638 | * | |
639 | * Caller must disable hard irqs. | |
640 | */ | |
641 | static void rcu_preempt_check_callbacks(void) | |
642 | { | |
643 | struct task_struct *t = current; | |
644 | ||
dd7c4d89 PM |
645 | if (rcu_preempt_gp_in_progress() && |
646 | (!rcu_preempt_running_reader() || | |
647 | !rcu_cpu_blocking_cur_gp())) | |
a57eb940 PM |
648 | rcu_preempt_cpu_qs(); |
649 | if (&rcu_preempt_ctrlblk.rcb.rcucblist != | |
650 | rcu_preempt_ctrlblk.rcb.donetail) | |
24278d14 | 651 | invoke_rcu_kthread(); |
dd7c4d89 PM |
652 | if (rcu_preempt_gp_in_progress() && |
653 | rcu_cpu_blocking_cur_gp() && | |
654 | rcu_preempt_running_reader()) | |
a57eb940 PM |
655 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
656 | } | |
657 | ||
658 | /* | |
659 | * TINY_PREEMPT_RCU has an extra callback-list tail pointer to | |
b2c0710c | 660 | * update, so this is invoked from rcu_process_callbacks() to |
a57eb940 PM |
661 | * handle that case. Of course, it is invoked for all flavors of |
662 | * RCU, but RCU callbacks can appear only on one of the lists, and | |
663 | * neither ->nexttail nor ->donetail can possibly be NULL, so there | |
664 | * is no need for an explicit check. | |
665 | */ | |
666 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
667 | { | |
668 | if (rcu_preempt_ctrlblk.nexttail == rcp->donetail) | |
669 | rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist; | |
670 | } | |
671 | ||
672 | /* | |
673 | * Process callbacks for preemptible RCU. | |
674 | */ | |
675 | static void rcu_preempt_process_callbacks(void) | |
676 | { | |
b2c0710c | 677 | rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); |
a57eb940 PM |
678 | } |
679 | ||
680 | /* | |
681 | * Queue a preemptible -RCU callback for invocation after a grace period. | |
682 | */ | |
683 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
684 | { | |
685 | unsigned long flags; | |
686 | ||
687 | debug_rcu_head_queue(head); | |
688 | head->func = func; | |
689 | head->next = NULL; | |
690 | ||
691 | local_irq_save(flags); | |
692 | *rcu_preempt_ctrlblk.nexttail = head; | |
693 | rcu_preempt_ctrlblk.nexttail = &head->next; | |
9e571a82 | 694 | RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++); |
a57eb940 PM |
695 | rcu_preempt_start_gp(); /* checks to see if GP needed. */ |
696 | local_irq_restore(flags); | |
697 | } | |
698 | EXPORT_SYMBOL_GPL(call_rcu); | |
699 | ||
700 | void rcu_barrier(void) | |
701 | { | |
702 | struct rcu_synchronize rcu; | |
703 | ||
704 | init_rcu_head_on_stack(&rcu.head); | |
705 | init_completion(&rcu.completion); | |
706 | /* Will wake me after RCU finished. */ | |
707 | call_rcu(&rcu.head, wakeme_after_rcu); | |
708 | /* Wait for it. */ | |
709 | wait_for_completion(&rcu.completion); | |
710 | destroy_rcu_head_on_stack(&rcu.head); | |
711 | } | |
712 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
713 | ||
714 | /* | |
715 | * synchronize_rcu - wait until a grace period has elapsed. | |
716 | * | |
717 | * Control will return to the caller some time after a full grace | |
718 | * period has elapsed, in other words after all currently executing RCU | |
719 | * read-side critical sections have completed. RCU read-side critical | |
720 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
721 | * and may be nested. | |
722 | */ | |
723 | void synchronize_rcu(void) | |
724 | { | |
725 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
726 | if (!rcu_scheduler_active) | |
727 | return; | |
728 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
729 | ||
730 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
731 | if (!rcu_preempt_blocked_readers_any()) | |
732 | return; | |
733 | ||
734 | /* Once we get past the fastpath checks, same code as rcu_barrier(). */ | |
735 | rcu_barrier(); | |
736 | } | |
737 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
738 | ||
739 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); | |
740 | static unsigned long sync_rcu_preempt_exp_count; | |
741 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); | |
742 | ||
743 | /* | |
744 | * Return non-zero if there are any tasks in RCU read-side critical | |
745 | * sections blocking the current preemptible-RCU expedited grace period. | |
746 | * If there is no preemptible-RCU expedited grace period currently in | |
747 | * progress, returns zero unconditionally. | |
748 | */ | |
749 | static int rcu_preempted_readers_exp(void) | |
750 | { | |
751 | return rcu_preempt_ctrlblk.exp_tasks != NULL; | |
752 | } | |
753 | ||
754 | /* | |
755 | * Report the exit from RCU read-side critical section for the last task | |
756 | * that queued itself during or before the current expedited preemptible-RCU | |
757 | * grace period. | |
758 | */ | |
759 | static void rcu_report_exp_done(void) | |
760 | { | |
761 | wake_up(&sync_rcu_preempt_exp_wq); | |
762 | } | |
763 | ||
764 | /* | |
765 | * Wait for an rcu-preempt grace period, but expedite it. The basic idea | |
766 | * is to rely in the fact that there is but one CPU, and that it is | |
767 | * illegal for a task to invoke synchronize_rcu_expedited() while in a | |
768 | * preemptible-RCU read-side critical section. Therefore, any such | |
769 | * critical sections must correspond to blocked tasks, which must therefore | |
770 | * be on the ->blkd_tasks list. So just record the current head of the | |
771 | * list in the ->exp_tasks pointer, and wait for all tasks including and | |
772 | * after the task pointed to by ->exp_tasks to drain. | |
773 | */ | |
774 | void synchronize_rcu_expedited(void) | |
775 | { | |
776 | unsigned long flags; | |
777 | struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk; | |
778 | unsigned long snap; | |
779 | ||
780 | barrier(); /* ensure prior action seen before grace period. */ | |
781 | ||
782 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
783 | ||
784 | /* | |
785 | * Acquire lock so that there is only one preemptible RCU grace | |
786 | * period in flight. Of course, if someone does the expedited | |
787 | * grace period for us while we are acquiring the lock, just leave. | |
788 | */ | |
789 | snap = sync_rcu_preempt_exp_count + 1; | |
790 | mutex_lock(&sync_rcu_preempt_exp_mutex); | |
791 | if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count)) | |
792 | goto unlock_mb_ret; /* Others did our work for us. */ | |
793 | ||
794 | local_irq_save(flags); | |
795 | ||
796 | /* | |
797 | * All RCU readers have to already be on blkd_tasks because | |
798 | * we cannot legally be executing in an RCU read-side critical | |
799 | * section. | |
800 | */ | |
801 | ||
802 | /* Snapshot current head of ->blkd_tasks list. */ | |
803 | rpcp->exp_tasks = rpcp->blkd_tasks.next; | |
804 | if (rpcp->exp_tasks == &rpcp->blkd_tasks) | |
805 | rpcp->exp_tasks = NULL; | |
a57eb940 PM |
806 | |
807 | /* Wait for tail of ->blkd_tasks list to drain. */ | |
7e8b4c72 PM |
808 | if (!rcu_preempted_readers_exp()) |
809 | local_irq_restore(flags); | |
810 | else { | |
811 | rcu_initiate_boost(); | |
812 | local_irq_restore(flags); | |
a57eb940 PM |
813 | wait_event(sync_rcu_preempt_exp_wq, |
814 | !rcu_preempted_readers_exp()); | |
7e8b4c72 | 815 | } |
a57eb940 PM |
816 | |
817 | /* Clean up and exit. */ | |
818 | barrier(); /* ensure expedited GP seen before counter increment. */ | |
819 | sync_rcu_preempt_exp_count++; | |
820 | unlock_mb_ret: | |
821 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
822 | barrier(); /* ensure subsequent action seen after grace period. */ | |
823 | } | |
824 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
825 | ||
826 | /* | |
827 | * Does preemptible RCU need the CPU to stay out of dynticks mode? | |
828 | */ | |
829 | int rcu_preempt_needs_cpu(void) | |
830 | { | |
831 | if (!rcu_preempt_running_reader()) | |
832 | rcu_preempt_cpu_qs(); | |
833 | return rcu_preempt_ctrlblk.rcb.rcucblist != NULL; | |
834 | } | |
835 | ||
836 | /* | |
837 | * Check for a task exiting while in a preemptible -RCU read-side | |
838 | * critical section, clean up if so. No need to issue warnings, | |
839 | * as debug_check_no_locks_held() already does this if lockdep | |
840 | * is enabled. | |
841 | */ | |
842 | void exit_rcu(void) | |
843 | { | |
844 | struct task_struct *t = current; | |
845 | ||
846 | if (t->rcu_read_lock_nesting == 0) | |
847 | return; | |
848 | t->rcu_read_lock_nesting = 1; | |
ba74f4d7 | 849 | __rcu_read_unlock(); |
a57eb940 PM |
850 | } |
851 | ||
852 | #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
853 | ||
9e571a82 PM |
854 | #ifdef CONFIG_RCU_TRACE |
855 | ||
856 | /* | |
857 | * Because preemptible RCU does not exist, it is not necessary to | |
858 | * dump out its statistics. | |
859 | */ | |
860 | static void show_tiny_preempt_stats(struct seq_file *m) | |
861 | { | |
862 | } | |
863 | ||
864 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
865 | ||
24278d14 PM |
866 | /* |
867 | * Because preemptible RCU does not exist, it is never necessary to | |
868 | * boost preempted RCU readers. | |
869 | */ | |
870 | static int rcu_boost(void) | |
871 | { | |
872 | return 0; | |
873 | } | |
874 | ||
a57eb940 PM |
875 | /* |
876 | * Because preemptible RCU does not exist, it never has any callbacks | |
877 | * to check. | |
878 | */ | |
879 | static void rcu_preempt_check_callbacks(void) | |
880 | { | |
881 | } | |
882 | ||
883 | /* | |
884 | * Because preemptible RCU does not exist, it never has any callbacks | |
885 | * to remove. | |
886 | */ | |
887 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
888 | { | |
889 | } | |
890 | ||
891 | /* | |
892 | * Because preemptible RCU does not exist, it never has any callbacks | |
893 | * to process. | |
894 | */ | |
895 | static void rcu_preempt_process_callbacks(void) | |
896 | { | |
897 | } | |
898 | ||
899 | #endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
900 | ||
bbad9379 | 901 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
bbad9379 PM |
902 | #include <linux/kernel_stat.h> |
903 | ||
904 | /* | |
905 | * During boot, we forgive RCU lockdep issues. After this function is | |
906 | * invoked, we start taking RCU lockdep issues seriously. | |
907 | */ | |
b2c0710c | 908 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
909 | { |
910 | WARN_ON(nr_context_switches() > 0); | |
911 | rcu_scheduler_active = 1; | |
912 | } | |
913 | ||
914 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 PM |
915 | |
916 | #ifdef CONFIG_RCU_BOOST | |
917 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO | |
918 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
919 | #define RCU_BOOST_PRIO 1 | |
920 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ | |
9e571a82 PM |
921 | |
922 | #ifdef CONFIG_RCU_TRACE | |
923 | ||
924 | #ifdef CONFIG_RCU_BOOST | |
925 | ||
926 | static void rcu_initiate_boost_trace(void) | |
927 | { | |
7e8b4c72 PM |
928 | if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) |
929 | rcu_preempt_ctrlblk.n_balk_blkd_tasks++; | |
930 | else if (rcu_preempt_ctrlblk.gp_tasks == NULL && | |
931 | rcu_preempt_ctrlblk.exp_tasks == NULL) | |
932 | rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++; | |
9e571a82 | 933 | else if (rcu_preempt_ctrlblk.boost_tasks != NULL) |
7e8b4c72 | 934 | rcu_preempt_ctrlblk.n_balk_boost_tasks++; |
9e571a82 | 935 | else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) |
7e8b4c72 | 936 | rcu_preempt_ctrlblk.n_balk_notyet++; |
9e571a82 | 937 | else |
7e8b4c72 | 938 | rcu_preempt_ctrlblk.n_balk_nos++; |
9e571a82 PM |
939 | } |
940 | ||
941 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
942 | ||
943 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) | |
944 | { | |
945 | unsigned long flags; | |
946 | ||
947 | raw_local_irq_save(flags); | |
948 | rcp->qlen -= n; | |
949 | raw_local_irq_restore(flags); | |
950 | } | |
951 | ||
952 | /* | |
953 | * Dump statistics for TINY_RCU, such as they are. | |
954 | */ | |
955 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
956 | { | |
957 | show_tiny_preempt_stats(m); | |
958 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); | |
959 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
960 | return 0; | |
961 | } | |
962 | ||
963 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
964 | { | |
965 | return single_open(file, show_tiny_stats, NULL); | |
966 | } | |
967 | ||
968 | static const struct file_operations show_tiny_stats_fops = { | |
969 | .owner = THIS_MODULE, | |
970 | .open = show_tiny_stats_open, | |
971 | .read = seq_read, | |
972 | .llseek = seq_lseek, | |
973 | .release = single_release, | |
974 | }; | |
975 | ||
976 | static struct dentry *rcudir; | |
977 | ||
978 | static int __init rcutiny_trace_init(void) | |
979 | { | |
980 | struct dentry *retval; | |
981 | ||
982 | rcudir = debugfs_create_dir("rcu", NULL); | |
983 | if (!rcudir) | |
984 | goto free_out; | |
985 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
986 | NULL, &show_tiny_stats_fops); | |
987 | if (!retval) | |
988 | goto free_out; | |
989 | return 0; | |
990 | free_out: | |
991 | debugfs_remove_recursive(rcudir); | |
992 | return 1; | |
993 | } | |
994 | ||
995 | static void __exit rcutiny_trace_cleanup(void) | |
996 | { | |
997 | debugfs_remove_recursive(rcudir); | |
998 | } | |
999 | ||
1000 | module_init(rcutiny_trace_init); | |
1001 | module_exit(rcutiny_trace_cleanup); | |
1002 | ||
1003 | MODULE_AUTHOR("Paul E. McKenney"); | |
1004 | MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); | |
1005 | MODULE_LICENSE("GPL"); | |
1006 | ||
1007 | #endif /* #ifdef CONFIG_RCU_TRACE */ |