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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 PM |
103 | s8 boosted_this_gp; /* Has boosting already happened? */ |
104 | unsigned long boost_time; /* When to start boosting (jiffies) */ | |
9e571a82 PM |
105 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
106 | #ifdef CONFIG_RCU_TRACE | |
107 | unsigned long n_grace_periods; | |
108 | #ifdef CONFIG_RCU_BOOST | |
109 | unsigned long n_tasks_boosted; | |
110 | unsigned long n_exp_boosts; | |
111 | unsigned long n_normal_boosts; | |
112 | unsigned long n_normal_balk_blkd_tasks; | |
113 | unsigned long n_normal_balk_gp_tasks; | |
114 | unsigned long n_normal_balk_boost_tasks; | |
115 | unsigned long n_normal_balk_boosted; | |
116 | unsigned long n_normal_balk_notyet; | |
117 | unsigned long n_normal_balk_nos; | |
118 | unsigned long n_exp_balk_blkd_tasks; | |
119 | unsigned long n_exp_balk_nos; | |
120 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
121 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
a57eb940 PM |
122 | }; |
123 | ||
124 | static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = { | |
125 | .rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
126 | .rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
127 | .nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
128 | .blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks), | |
129 | }; | |
130 | ||
131 | static int rcu_preempted_readers_exp(void); | |
132 | static void rcu_report_exp_done(void); | |
133 | ||
134 | /* | |
135 | * Return true if the CPU has not yet responded to the current grace period. | |
136 | */ | |
dd7c4d89 | 137 | static int rcu_cpu_blocking_cur_gp(void) |
a57eb940 PM |
138 | { |
139 | return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum; | |
140 | } | |
141 | ||
142 | /* | |
143 | * Check for a running RCU reader. Because there is only one CPU, | |
144 | * there can be but one running RCU reader at a time. ;-) | |
145 | */ | |
146 | static int rcu_preempt_running_reader(void) | |
147 | { | |
148 | return current->rcu_read_lock_nesting; | |
149 | } | |
150 | ||
151 | /* | |
152 | * Check for preempted RCU readers blocking any grace period. | |
153 | * If the caller needs a reliable answer, it must disable hard irqs. | |
154 | */ | |
155 | static int rcu_preempt_blocked_readers_any(void) | |
156 | { | |
157 | return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks); | |
158 | } | |
159 | ||
160 | /* | |
161 | * Check for preempted RCU readers blocking the current grace period. | |
162 | * If the caller needs a reliable answer, it must disable hard irqs. | |
163 | */ | |
164 | static int rcu_preempt_blocked_readers_cgp(void) | |
165 | { | |
166 | return rcu_preempt_ctrlblk.gp_tasks != NULL; | |
167 | } | |
168 | ||
169 | /* | |
170 | * Return true if another preemptible-RCU grace period is needed. | |
171 | */ | |
172 | static int rcu_preempt_needs_another_gp(void) | |
173 | { | |
174 | return *rcu_preempt_ctrlblk.rcb.curtail != NULL; | |
175 | } | |
176 | ||
177 | /* | |
178 | * Return true if a preemptible-RCU grace period is in progress. | |
179 | * The caller must disable hardirqs. | |
180 | */ | |
181 | static int rcu_preempt_gp_in_progress(void) | |
182 | { | |
183 | return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum; | |
184 | } | |
185 | ||
24278d14 PM |
186 | /* |
187 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
188 | * returning NULL if at the end of the list. | |
189 | */ | |
190 | static struct list_head *rcu_next_node_entry(struct task_struct *t) | |
191 | { | |
192 | struct list_head *np; | |
193 | ||
194 | np = t->rcu_node_entry.next; | |
195 | if (np == &rcu_preempt_ctrlblk.blkd_tasks) | |
196 | np = NULL; | |
197 | return np; | |
198 | } | |
199 | ||
9e571a82 PM |
200 | #ifdef CONFIG_RCU_TRACE |
201 | ||
202 | #ifdef CONFIG_RCU_BOOST | |
203 | static void rcu_initiate_boost_trace(void); | |
204 | static void rcu_initiate_exp_boost_trace(void); | |
205 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
206 | ||
207 | /* | |
208 | * Dump additional statistice for TINY_PREEMPT_RCU. | |
209 | */ | |
210 | static void show_tiny_preempt_stats(struct seq_file *m) | |
211 | { | |
212 | seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n", | |
213 | rcu_preempt_ctrlblk.rcb.qlen, | |
214 | rcu_preempt_ctrlblk.n_grace_periods, | |
215 | rcu_preempt_ctrlblk.gpnum, | |
216 | rcu_preempt_ctrlblk.gpcpu, | |
217 | rcu_preempt_ctrlblk.completed, | |
218 | "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)], | |
219 | "N."[!rcu_preempt_ctrlblk.gp_tasks], | |
220 | "E."[!rcu_preempt_ctrlblk.exp_tasks]); | |
221 | #ifdef CONFIG_RCU_BOOST | |
222 | seq_printf(m, " ttb=%c btg=", | |
223 | "B."[!rcu_preempt_ctrlblk.boost_tasks]); | |
224 | switch (rcu_preempt_ctrlblk.boosted_this_gp) { | |
225 | case -1: | |
226 | seq_puts(m, "exp"); | |
227 | break; | |
228 | case 0: | |
229 | seq_puts(m, "no"); | |
230 | break; | |
231 | case 1: | |
232 | seq_puts(m, "done"); | |
233 | break; | |
234 | default: | |
235 | seq_printf(m, "?%d?", rcu_preempt_ctrlblk.boosted_this_gp); | |
236 | } | |
237 | seq_printf(m, " ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n", | |
238 | rcu_preempt_ctrlblk.n_tasks_boosted, | |
239 | rcu_preempt_ctrlblk.n_exp_boosts, | |
240 | rcu_preempt_ctrlblk.n_normal_boosts, | |
241 | (int)(jiffies & 0xffff), | |
242 | (int)(rcu_preempt_ctrlblk.boost_time & 0xffff)); | |
243 | seq_printf(m, " %s: nt=%lu gt=%lu bt=%lu b=%lu ny=%lu nos=%lu\n", | |
244 | "normal balk", | |
245 | rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks, | |
246 | rcu_preempt_ctrlblk.n_normal_balk_gp_tasks, | |
247 | rcu_preempt_ctrlblk.n_normal_balk_boost_tasks, | |
248 | rcu_preempt_ctrlblk.n_normal_balk_boosted, | |
249 | rcu_preempt_ctrlblk.n_normal_balk_notyet, | |
250 | rcu_preempt_ctrlblk.n_normal_balk_nos); | |
251 | seq_printf(m, " exp balk: bt=%lu nos=%lu\n", | |
252 | rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks, | |
253 | rcu_preempt_ctrlblk.n_exp_balk_nos); | |
254 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
255 | } | |
256 | ||
257 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
258 | ||
24278d14 PM |
259 | #ifdef CONFIG_RCU_BOOST |
260 | ||
261 | #include "rtmutex_common.h" | |
262 | ||
263 | /* | |
264 | * Carry out RCU priority boosting on the task indicated by ->boost_tasks, | |
265 | * and advance ->boost_tasks to the next task in the ->blkd_tasks list. | |
266 | */ | |
267 | static int rcu_boost(void) | |
268 | { | |
269 | unsigned long flags; | |
270 | struct rt_mutex mtx; | |
271 | struct list_head *np; | |
272 | struct task_struct *t; | |
273 | ||
274 | if (rcu_preempt_ctrlblk.boost_tasks == NULL) | |
275 | return 0; /* Nothing to boost. */ | |
276 | raw_local_irq_save(flags); | |
277 | rcu_preempt_ctrlblk.boosted_this_gp++; | |
278 | t = container_of(rcu_preempt_ctrlblk.boost_tasks, struct task_struct, | |
279 | rcu_node_entry); | |
280 | np = rcu_next_node_entry(t); | |
281 | rt_mutex_init_proxy_locked(&mtx, t); | |
282 | t->rcu_boost_mutex = &mtx; | |
283 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED; | |
284 | raw_local_irq_restore(flags); | |
285 | rt_mutex_lock(&mtx); | |
9e571a82 | 286 | RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); |
24278d14 PM |
287 | rt_mutex_unlock(&mtx); |
288 | return rcu_preempt_ctrlblk.boost_tasks != NULL; | |
289 | } | |
290 | ||
291 | /* | |
292 | * Check to see if it is now time to start boosting RCU readers blocking | |
293 | * the current grace period, and, if so, tell the rcu_kthread_task to | |
294 | * start boosting them. If there is an expedited boost in progress, | |
295 | * we wait for it to complete. | |
9e571a82 PM |
296 | * |
297 | * If there are no blocked readers blocking the current grace period, | |
298 | * return 0 to let the caller know, otherwise return 1. Note that this | |
299 | * return value is independent of whether or not boosting was done. | |
24278d14 | 300 | */ |
9e571a82 | 301 | static int rcu_initiate_boost(void) |
24278d14 | 302 | { |
9e571a82 PM |
303 | if (!rcu_preempt_blocked_readers_cgp()) { |
304 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks++); | |
305 | return 0; | |
306 | } | |
24278d14 PM |
307 | if (rcu_preempt_ctrlblk.gp_tasks != NULL && |
308 | rcu_preempt_ctrlblk.boost_tasks == NULL && | |
309 | rcu_preempt_ctrlblk.boosted_this_gp == 0 && | |
310 | ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) { | |
311 | rcu_preempt_ctrlblk.boost_tasks = rcu_preempt_ctrlblk.gp_tasks; | |
312 | invoke_rcu_kthread(); | |
9e571a82 PM |
313 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++); |
314 | } else | |
315 | RCU_TRACE(rcu_initiate_boost_trace()); | |
316 | return 1; | |
24278d14 PM |
317 | } |
318 | ||
319 | /* | |
320 | * Initiate boosting for an expedited grace period. | |
321 | */ | |
322 | static void rcu_initiate_expedited_boost(void) | |
323 | { | |
324 | unsigned long flags; | |
325 | ||
326 | raw_local_irq_save(flags); | |
327 | if (!list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) { | |
328 | rcu_preempt_ctrlblk.boost_tasks = | |
329 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
330 | rcu_preempt_ctrlblk.boosted_this_gp = -1; | |
331 | invoke_rcu_kthread(); | |
9e571a82 PM |
332 | RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++); |
333 | } else | |
334 | RCU_TRACE(rcu_initiate_exp_boost_trace()); | |
24278d14 PM |
335 | raw_local_irq_restore(flags); |
336 | } | |
337 | ||
338 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000); | |
339 | ||
340 | /* | |
341 | * Do priority-boost accounting for the start of a new grace period. | |
342 | */ | |
343 | static void rcu_preempt_boost_start_gp(void) | |
344 | { | |
345 | rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
346 | if (rcu_preempt_ctrlblk.boosted_this_gp > 0) | |
347 | rcu_preempt_ctrlblk.boosted_this_gp = 0; | |
348 | } | |
349 | ||
350 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
351 | ||
352 | /* | |
353 | * If there is no RCU priority boosting, we don't boost. | |
354 | */ | |
355 | static int rcu_boost(void) | |
356 | { | |
357 | return 0; | |
358 | } | |
359 | ||
360 | /* | |
9e571a82 PM |
361 | * If there is no RCU priority boosting, we don't initiate boosting, |
362 | * but we do indicate whether there are blocked readers blocking the | |
363 | * current grace period. | |
24278d14 | 364 | */ |
9e571a82 | 365 | static int rcu_initiate_boost(void) |
24278d14 | 366 | { |
9e571a82 | 367 | return rcu_preempt_blocked_readers_cgp(); |
24278d14 PM |
368 | } |
369 | ||
370 | /* | |
371 | * If there is no RCU priority boosting, we don't initiate expedited boosting. | |
372 | */ | |
373 | static void rcu_initiate_expedited_boost(void) | |
374 | { | |
375 | } | |
376 | ||
377 | /* | |
378 | * If there is no RCU priority boosting, nothing to do at grace-period start. | |
379 | */ | |
380 | static void rcu_preempt_boost_start_gp(void) | |
381 | { | |
382 | } | |
383 | ||
384 | #endif /* else #ifdef CONFIG_RCU_BOOST */ | |
385 | ||
a57eb940 PM |
386 | /* |
387 | * Record a preemptible-RCU quiescent state for the specified CPU. Note | |
388 | * that this just means that the task currently running on the CPU is | |
389 | * in a quiescent state. There might be any number of tasks blocked | |
390 | * while in an RCU read-side critical section. | |
391 | * | |
392 | * Unlike the other rcu_*_qs() functions, callers to this function | |
393 | * must disable irqs in order to protect the assignment to | |
394 | * ->rcu_read_unlock_special. | |
395 | * | |
396 | * Because this is a single-CPU implementation, the only way a grace | |
397 | * period can end is if the CPU is in a quiescent state. The reason is | |
398 | * that a blocked preemptible-RCU reader can exit its critical section | |
399 | * only if the CPU is running it at the time. Therefore, when the | |
400 | * last task blocking the current grace period exits its RCU read-side | |
401 | * critical section, neither the CPU nor blocked tasks will be stopping | |
402 | * the current grace period. (In contrast, SMP implementations | |
403 | * might have CPUs running in RCU read-side critical sections that | |
404 | * block later grace periods -- but this is not possible given only | |
405 | * one CPU.) | |
406 | */ | |
407 | static void rcu_preempt_cpu_qs(void) | |
408 | { | |
409 | /* Record both CPU and task as having responded to current GP. */ | |
410 | rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum; | |
411 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; | |
412 | ||
24278d14 | 413 | /* If there is no GP then there is nothing more to do. */ |
9e571a82 | 414 | if (!rcu_preempt_gp_in_progress()) |
a57eb940 | 415 | return; |
9e571a82 PM |
416 | /* |
417 | * Check up on boosting. If there are no readers blocking the | |
418 | * current grace period, leave. | |
419 | */ | |
420 | if (rcu_initiate_boost()) | |
24278d14 | 421 | return; |
a57eb940 PM |
422 | |
423 | /* Advance callbacks. */ | |
424 | rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum; | |
425 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail; | |
426 | rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail; | |
427 | ||
428 | /* If there are no blocked readers, next GP is done instantly. */ | |
429 | if (!rcu_preempt_blocked_readers_any()) | |
430 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail; | |
431 | ||
b2c0710c | 432 | /* If there are done callbacks, cause them to be invoked. */ |
a57eb940 | 433 | if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) |
24278d14 | 434 | invoke_rcu_kthread(); |
a57eb940 PM |
435 | } |
436 | ||
437 | /* | |
438 | * Start a new RCU grace period if warranted. Hard irqs must be disabled. | |
439 | */ | |
440 | static void rcu_preempt_start_gp(void) | |
441 | { | |
442 | if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) { | |
443 | ||
444 | /* Official start of GP. */ | |
445 | rcu_preempt_ctrlblk.gpnum++; | |
9e571a82 | 446 | RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); |
a57eb940 PM |
447 | |
448 | /* Any blocked RCU readers block new GP. */ | |
449 | if (rcu_preempt_blocked_readers_any()) | |
450 | rcu_preempt_ctrlblk.gp_tasks = | |
451 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
452 | ||
24278d14 PM |
453 | /* Set up for RCU priority boosting. */ |
454 | rcu_preempt_boost_start_gp(); | |
455 | ||
a57eb940 PM |
456 | /* If there is no running reader, CPU is done with GP. */ |
457 | if (!rcu_preempt_running_reader()) | |
458 | rcu_preempt_cpu_qs(); | |
459 | } | |
460 | } | |
461 | ||
462 | /* | |
463 | * We have entered the scheduler, and the current task might soon be | |
464 | * context-switched away from. If this task is in an RCU read-side | |
465 | * critical section, we will no longer be able to rely on the CPU to | |
466 | * record that fact, so we enqueue the task on the blkd_tasks list. | |
467 | * If the task started after the current grace period began, as recorded | |
468 | * by ->gpcpu, we enqueue at the beginning of the list. Otherwise | |
469 | * before the element referenced by ->gp_tasks (or at the tail if | |
470 | * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element. | |
471 | * The task will dequeue itself when it exits the outermost enclosing | |
472 | * RCU read-side critical section. Therefore, the current grace period | |
473 | * cannot be permitted to complete until the ->gp_tasks pointer becomes | |
474 | * NULL. | |
475 | * | |
476 | * Caller must disable preemption. | |
477 | */ | |
478 | void rcu_preempt_note_context_switch(void) | |
479 | { | |
480 | struct task_struct *t = current; | |
481 | unsigned long flags; | |
482 | ||
483 | local_irq_save(flags); /* must exclude scheduler_tick(). */ | |
484 | if (rcu_preempt_running_reader() && | |
485 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { | |
486 | ||
487 | /* Possibly blocking in an RCU read-side critical section. */ | |
488 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; | |
489 | ||
490 | /* | |
491 | * If this CPU has already checked in, then this task | |
492 | * will hold up the next grace period rather than the | |
493 | * current grace period. Queue the task accordingly. | |
494 | * If the task is queued for the current grace period | |
495 | * (i.e., this CPU has not yet passed through a quiescent | |
496 | * state for the current grace period), then as long | |
497 | * as that task remains queued, the current grace period | |
498 | * cannot end. | |
499 | */ | |
500 | list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks); | |
dd7c4d89 | 501 | if (rcu_cpu_blocking_cur_gp()) |
a57eb940 PM |
502 | rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry; |
503 | } | |
504 | ||
505 | /* | |
506 | * Either we were not in an RCU read-side critical section to | |
507 | * begin with, or we have now recorded that critical section | |
508 | * globally. Either way, we can now note a quiescent state | |
509 | * for this CPU. Again, if we were in an RCU read-side critical | |
510 | * section, and if that critical section was blocking the current | |
511 | * grace period, then the fact that the task has been enqueued | |
512 | * means that current grace period continues to be blocked. | |
513 | */ | |
514 | rcu_preempt_cpu_qs(); | |
515 | local_irq_restore(flags); | |
516 | } | |
517 | ||
518 | /* | |
519 | * Tiny-preemptible RCU implementation for rcu_read_lock(). | |
520 | * Just increment ->rcu_read_lock_nesting, shared state will be updated | |
521 | * if we block. | |
522 | */ | |
523 | void __rcu_read_lock(void) | |
524 | { | |
525 | current->rcu_read_lock_nesting++; | |
526 | barrier(); /* needed if we ever invoke rcu_read_lock in rcutiny.c */ | |
527 | } | |
528 | EXPORT_SYMBOL_GPL(__rcu_read_lock); | |
529 | ||
530 | /* | |
531 | * Handle special cases during rcu_read_unlock(), such as needing to | |
532 | * notify RCU core processing or task having blocked during the RCU | |
533 | * read-side critical section. | |
534 | */ | |
535 | static void rcu_read_unlock_special(struct task_struct *t) | |
536 | { | |
537 | int empty; | |
538 | int empty_exp; | |
539 | unsigned long flags; | |
540 | struct list_head *np; | |
541 | int special; | |
542 | ||
543 | /* | |
544 | * NMI handlers cannot block and cannot safely manipulate state. | |
545 | * They therefore cannot possibly be special, so just leave. | |
546 | */ | |
547 | if (in_nmi()) | |
548 | return; | |
549 | ||
550 | local_irq_save(flags); | |
551 | ||
552 | /* | |
553 | * If RCU core is waiting for this CPU to exit critical section, | |
554 | * let it know that we have done so. | |
555 | */ | |
556 | special = t->rcu_read_unlock_special; | |
557 | if (special & RCU_READ_UNLOCK_NEED_QS) | |
558 | rcu_preempt_cpu_qs(); | |
559 | ||
560 | /* Hardware IRQ handlers cannot block. */ | |
561 | if (in_irq()) { | |
562 | local_irq_restore(flags); | |
563 | return; | |
564 | } | |
565 | ||
566 | /* Clean up if blocked during RCU read-side critical section. */ | |
567 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
568 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
569 | ||
570 | /* | |
571 | * Remove this task from the ->blkd_tasks list and adjust | |
572 | * any pointers that might have been referencing it. | |
573 | */ | |
574 | empty = !rcu_preempt_blocked_readers_cgp(); | |
575 | empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL; | |
24278d14 | 576 | np = rcu_next_node_entry(t); |
a57eb940 PM |
577 | list_del(&t->rcu_node_entry); |
578 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks) | |
579 | rcu_preempt_ctrlblk.gp_tasks = np; | |
580 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks) | |
581 | rcu_preempt_ctrlblk.exp_tasks = np; | |
24278d14 PM |
582 | #ifdef CONFIG_RCU_BOOST |
583 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks) | |
584 | rcu_preempt_ctrlblk.boost_tasks = np; | |
585 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
586 | INIT_LIST_HEAD(&t->rcu_node_entry); |
587 | ||
588 | /* | |
589 | * If this was the last task on the current list, and if | |
590 | * we aren't waiting on the CPU, report the quiescent state | |
591 | * and start a new grace period if needed. | |
592 | */ | |
593 | if (!empty && !rcu_preempt_blocked_readers_cgp()) { | |
594 | rcu_preempt_cpu_qs(); | |
595 | rcu_preempt_start_gp(); | |
596 | } | |
597 | ||
598 | /* | |
599 | * If this was the last task on the expedited lists, | |
600 | * then we need wake up the waiting task. | |
601 | */ | |
602 | if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL) | |
603 | rcu_report_exp_done(); | |
604 | } | |
24278d14 PM |
605 | #ifdef CONFIG_RCU_BOOST |
606 | /* Unboost self if was boosted. */ | |
607 | if (special & RCU_READ_UNLOCK_BOOSTED) { | |
608 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED; | |
609 | rt_mutex_unlock(t->rcu_boost_mutex); | |
610 | t->rcu_boost_mutex = NULL; | |
611 | } | |
612 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
613 | local_irq_restore(flags); |
614 | } | |
615 | ||
616 | /* | |
617 | * Tiny-preemptible RCU implementation for rcu_read_unlock(). | |
618 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost | |
619 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then | |
620 | * invoke rcu_read_unlock_special() to clean up after a context switch | |
621 | * in an RCU read-side critical section and other special cases. | |
622 | */ | |
623 | void __rcu_read_unlock(void) | |
624 | { | |
625 | struct task_struct *t = current; | |
626 | ||
627 | barrier(); /* needed if we ever invoke rcu_read_unlock in rcutiny.c */ | |
628 | --t->rcu_read_lock_nesting; | |
629 | barrier(); /* decrement before load of ->rcu_read_unlock_special */ | |
630 | if (t->rcu_read_lock_nesting == 0 && | |
631 | unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) | |
632 | rcu_read_unlock_special(t); | |
633 | #ifdef CONFIG_PROVE_LOCKING | |
634 | WARN_ON_ONCE(t->rcu_read_lock_nesting < 0); | |
635 | #endif /* #ifdef CONFIG_PROVE_LOCKING */ | |
636 | } | |
637 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); | |
638 | ||
639 | /* | |
640 | * Check for a quiescent state from the current CPU. When a task blocks, | |
641 | * the task is recorded in the rcu_preempt_ctrlblk structure, which is | |
642 | * checked elsewhere. This is called from the scheduling-clock interrupt. | |
643 | * | |
644 | * Caller must disable hard irqs. | |
645 | */ | |
646 | static void rcu_preempt_check_callbacks(void) | |
647 | { | |
648 | struct task_struct *t = current; | |
649 | ||
dd7c4d89 PM |
650 | if (rcu_preempt_gp_in_progress() && |
651 | (!rcu_preempt_running_reader() || | |
652 | !rcu_cpu_blocking_cur_gp())) | |
a57eb940 PM |
653 | rcu_preempt_cpu_qs(); |
654 | if (&rcu_preempt_ctrlblk.rcb.rcucblist != | |
655 | rcu_preempt_ctrlblk.rcb.donetail) | |
24278d14 | 656 | invoke_rcu_kthread(); |
dd7c4d89 PM |
657 | if (rcu_preempt_gp_in_progress() && |
658 | rcu_cpu_blocking_cur_gp() && | |
659 | rcu_preempt_running_reader()) | |
a57eb940 PM |
660 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
661 | } | |
662 | ||
663 | /* | |
664 | * TINY_PREEMPT_RCU has an extra callback-list tail pointer to | |
b2c0710c | 665 | * update, so this is invoked from rcu_process_callbacks() to |
a57eb940 PM |
666 | * handle that case. Of course, it is invoked for all flavors of |
667 | * RCU, but RCU callbacks can appear only on one of the lists, and | |
668 | * neither ->nexttail nor ->donetail can possibly be NULL, so there | |
669 | * is no need for an explicit check. | |
670 | */ | |
671 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
672 | { | |
673 | if (rcu_preempt_ctrlblk.nexttail == rcp->donetail) | |
674 | rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist; | |
675 | } | |
676 | ||
677 | /* | |
678 | * Process callbacks for preemptible RCU. | |
679 | */ | |
680 | static void rcu_preempt_process_callbacks(void) | |
681 | { | |
b2c0710c | 682 | rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); |
a57eb940 PM |
683 | } |
684 | ||
685 | /* | |
686 | * Queue a preemptible -RCU callback for invocation after a grace period. | |
687 | */ | |
688 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
689 | { | |
690 | unsigned long flags; | |
691 | ||
692 | debug_rcu_head_queue(head); | |
693 | head->func = func; | |
694 | head->next = NULL; | |
695 | ||
696 | local_irq_save(flags); | |
697 | *rcu_preempt_ctrlblk.nexttail = head; | |
698 | rcu_preempt_ctrlblk.nexttail = &head->next; | |
9e571a82 | 699 | RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++); |
a57eb940 PM |
700 | rcu_preempt_start_gp(); /* checks to see if GP needed. */ |
701 | local_irq_restore(flags); | |
702 | } | |
703 | EXPORT_SYMBOL_GPL(call_rcu); | |
704 | ||
705 | void rcu_barrier(void) | |
706 | { | |
707 | struct rcu_synchronize rcu; | |
708 | ||
709 | init_rcu_head_on_stack(&rcu.head); | |
710 | init_completion(&rcu.completion); | |
711 | /* Will wake me after RCU finished. */ | |
712 | call_rcu(&rcu.head, wakeme_after_rcu); | |
713 | /* Wait for it. */ | |
714 | wait_for_completion(&rcu.completion); | |
715 | destroy_rcu_head_on_stack(&rcu.head); | |
716 | } | |
717 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
718 | ||
719 | /* | |
720 | * synchronize_rcu - wait until a grace period has elapsed. | |
721 | * | |
722 | * Control will return to the caller some time after a full grace | |
723 | * period has elapsed, in other words after all currently executing RCU | |
724 | * read-side critical sections have completed. RCU read-side critical | |
725 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
726 | * and may be nested. | |
727 | */ | |
728 | void synchronize_rcu(void) | |
729 | { | |
730 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
731 | if (!rcu_scheduler_active) | |
732 | return; | |
733 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
734 | ||
735 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
736 | if (!rcu_preempt_blocked_readers_any()) | |
737 | return; | |
738 | ||
739 | /* Once we get past the fastpath checks, same code as rcu_barrier(). */ | |
740 | rcu_barrier(); | |
741 | } | |
742 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
743 | ||
744 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); | |
745 | static unsigned long sync_rcu_preempt_exp_count; | |
746 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); | |
747 | ||
748 | /* | |
749 | * Return non-zero if there are any tasks in RCU read-side critical | |
750 | * sections blocking the current preemptible-RCU expedited grace period. | |
751 | * If there is no preemptible-RCU expedited grace period currently in | |
752 | * progress, returns zero unconditionally. | |
753 | */ | |
754 | static int rcu_preempted_readers_exp(void) | |
755 | { | |
756 | return rcu_preempt_ctrlblk.exp_tasks != NULL; | |
757 | } | |
758 | ||
759 | /* | |
760 | * Report the exit from RCU read-side critical section for the last task | |
761 | * that queued itself during or before the current expedited preemptible-RCU | |
762 | * grace period. | |
763 | */ | |
764 | static void rcu_report_exp_done(void) | |
765 | { | |
766 | wake_up(&sync_rcu_preempt_exp_wq); | |
767 | } | |
768 | ||
769 | /* | |
770 | * Wait for an rcu-preempt grace period, but expedite it. The basic idea | |
771 | * is to rely in the fact that there is but one CPU, and that it is | |
772 | * illegal for a task to invoke synchronize_rcu_expedited() while in a | |
773 | * preemptible-RCU read-side critical section. Therefore, any such | |
774 | * critical sections must correspond to blocked tasks, which must therefore | |
775 | * be on the ->blkd_tasks list. So just record the current head of the | |
776 | * list in the ->exp_tasks pointer, and wait for all tasks including and | |
777 | * after the task pointed to by ->exp_tasks to drain. | |
778 | */ | |
779 | void synchronize_rcu_expedited(void) | |
780 | { | |
781 | unsigned long flags; | |
782 | struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk; | |
783 | unsigned long snap; | |
784 | ||
785 | barrier(); /* ensure prior action seen before grace period. */ | |
786 | ||
787 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
788 | ||
789 | /* | |
790 | * Acquire lock so that there is only one preemptible RCU grace | |
791 | * period in flight. Of course, if someone does the expedited | |
792 | * grace period for us while we are acquiring the lock, just leave. | |
793 | */ | |
794 | snap = sync_rcu_preempt_exp_count + 1; | |
795 | mutex_lock(&sync_rcu_preempt_exp_mutex); | |
796 | if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count)) | |
797 | goto unlock_mb_ret; /* Others did our work for us. */ | |
798 | ||
799 | local_irq_save(flags); | |
800 | ||
801 | /* | |
802 | * All RCU readers have to already be on blkd_tasks because | |
803 | * we cannot legally be executing in an RCU read-side critical | |
804 | * section. | |
805 | */ | |
806 | ||
807 | /* Snapshot current head of ->blkd_tasks list. */ | |
808 | rpcp->exp_tasks = rpcp->blkd_tasks.next; | |
809 | if (rpcp->exp_tasks == &rpcp->blkd_tasks) | |
810 | rpcp->exp_tasks = NULL; | |
811 | local_irq_restore(flags); | |
812 | ||
813 | /* Wait for tail of ->blkd_tasks list to drain. */ | |
814 | if (rcu_preempted_readers_exp()) | |
24278d14 | 815 | rcu_initiate_expedited_boost(); |
a57eb940 PM |
816 | wait_event(sync_rcu_preempt_exp_wq, |
817 | !rcu_preempted_readers_exp()); | |
818 | ||
819 | /* Clean up and exit. */ | |
820 | barrier(); /* ensure expedited GP seen before counter increment. */ | |
821 | sync_rcu_preempt_exp_count++; | |
822 | unlock_mb_ret: | |
823 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
824 | barrier(); /* ensure subsequent action seen after grace period. */ | |
825 | } | |
826 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
827 | ||
828 | /* | |
829 | * Does preemptible RCU need the CPU to stay out of dynticks mode? | |
830 | */ | |
831 | int rcu_preempt_needs_cpu(void) | |
832 | { | |
833 | if (!rcu_preempt_running_reader()) | |
834 | rcu_preempt_cpu_qs(); | |
835 | return rcu_preempt_ctrlblk.rcb.rcucblist != NULL; | |
836 | } | |
837 | ||
838 | /* | |
839 | * Check for a task exiting while in a preemptible -RCU read-side | |
840 | * critical section, clean up if so. No need to issue warnings, | |
841 | * as debug_check_no_locks_held() already does this if lockdep | |
842 | * is enabled. | |
843 | */ | |
844 | void exit_rcu(void) | |
845 | { | |
846 | struct task_struct *t = current; | |
847 | ||
848 | if (t->rcu_read_lock_nesting == 0) | |
849 | return; | |
850 | t->rcu_read_lock_nesting = 1; | |
851 | rcu_read_unlock(); | |
852 | } | |
853 | ||
854 | #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
855 | ||
9e571a82 PM |
856 | #ifdef CONFIG_RCU_TRACE |
857 | ||
858 | /* | |
859 | * Because preemptible RCU does not exist, it is not necessary to | |
860 | * dump out its statistics. | |
861 | */ | |
862 | static void show_tiny_preempt_stats(struct seq_file *m) | |
863 | { | |
864 | } | |
865 | ||
866 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
867 | ||
24278d14 PM |
868 | /* |
869 | * Because preemptible RCU does not exist, it is never necessary to | |
870 | * boost preempted RCU readers. | |
871 | */ | |
872 | static int rcu_boost(void) | |
873 | { | |
874 | return 0; | |
875 | } | |
876 | ||
a57eb940 PM |
877 | /* |
878 | * Because preemptible RCU does not exist, it never has any callbacks | |
879 | * to check. | |
880 | */ | |
881 | static void rcu_preempt_check_callbacks(void) | |
882 | { | |
883 | } | |
884 | ||
885 | /* | |
886 | * Because preemptible RCU does not exist, it never has any callbacks | |
887 | * to remove. | |
888 | */ | |
889 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
890 | { | |
891 | } | |
892 | ||
893 | /* | |
894 | * Because preemptible RCU does not exist, it never has any callbacks | |
895 | * to process. | |
896 | */ | |
897 | static void rcu_preempt_process_callbacks(void) | |
898 | { | |
899 | } | |
900 | ||
901 | #endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
902 | ||
bbad9379 | 903 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
bbad9379 PM |
904 | #include <linux/kernel_stat.h> |
905 | ||
906 | /* | |
907 | * During boot, we forgive RCU lockdep issues. After this function is | |
908 | * invoked, we start taking RCU lockdep issues seriously. | |
909 | */ | |
b2c0710c | 910 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
911 | { |
912 | WARN_ON(nr_context_switches() > 0); | |
913 | rcu_scheduler_active = 1; | |
914 | } | |
915 | ||
916 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 PM |
917 | |
918 | #ifdef CONFIG_RCU_BOOST | |
919 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO | |
920 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
921 | #define RCU_BOOST_PRIO 1 | |
922 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ | |
9e571a82 PM |
923 | |
924 | #ifdef CONFIG_RCU_TRACE | |
925 | ||
926 | #ifdef CONFIG_RCU_BOOST | |
927 | ||
928 | static void rcu_initiate_boost_trace(void) | |
929 | { | |
930 | if (rcu_preempt_ctrlblk.gp_tasks == NULL) | |
931 | rcu_preempt_ctrlblk.n_normal_balk_gp_tasks++; | |
932 | else if (rcu_preempt_ctrlblk.boost_tasks != NULL) | |
933 | rcu_preempt_ctrlblk.n_normal_balk_boost_tasks++; | |
934 | else if (rcu_preempt_ctrlblk.boosted_this_gp != 0) | |
935 | rcu_preempt_ctrlblk.n_normal_balk_boosted++; | |
936 | else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) | |
937 | rcu_preempt_ctrlblk.n_normal_balk_notyet++; | |
938 | else | |
939 | rcu_preempt_ctrlblk.n_normal_balk_nos++; | |
940 | } | |
941 | ||
942 | static void rcu_initiate_exp_boost_trace(void) | |
943 | { | |
944 | if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) | |
945 | rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks++; | |
946 | else | |
947 | rcu_preempt_ctrlblk.n_exp_balk_nos++; | |
948 | } | |
949 | ||
950 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
951 | ||
952 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) | |
953 | { | |
954 | unsigned long flags; | |
955 | ||
956 | raw_local_irq_save(flags); | |
957 | rcp->qlen -= n; | |
958 | raw_local_irq_restore(flags); | |
959 | } | |
960 | ||
961 | /* | |
962 | * Dump statistics for TINY_RCU, such as they are. | |
963 | */ | |
964 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
965 | { | |
966 | show_tiny_preempt_stats(m); | |
967 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); | |
968 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
969 | return 0; | |
970 | } | |
971 | ||
972 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
973 | { | |
974 | return single_open(file, show_tiny_stats, NULL); | |
975 | } | |
976 | ||
977 | static const struct file_operations show_tiny_stats_fops = { | |
978 | .owner = THIS_MODULE, | |
979 | .open = show_tiny_stats_open, | |
980 | .read = seq_read, | |
981 | .llseek = seq_lseek, | |
982 | .release = single_release, | |
983 | }; | |
984 | ||
985 | static struct dentry *rcudir; | |
986 | ||
987 | static int __init rcutiny_trace_init(void) | |
988 | { | |
989 | struct dentry *retval; | |
990 | ||
991 | rcudir = debugfs_create_dir("rcu", NULL); | |
992 | if (!rcudir) | |
993 | goto free_out; | |
994 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
995 | NULL, &show_tiny_stats_fops); | |
996 | if (!retval) | |
997 | goto free_out; | |
998 | return 0; | |
999 | free_out: | |
1000 | debugfs_remove_recursive(rcudir); | |
1001 | return 1; | |
1002 | } | |
1003 | ||
1004 | static void __exit rcutiny_trace_cleanup(void) | |
1005 | { | |
1006 | debugfs_remove_recursive(rcudir); | |
1007 | } | |
1008 | ||
1009 | module_init(rcutiny_trace_init); | |
1010 | module_exit(rcutiny_trace_cleanup); | |
1011 | ||
1012 | MODULE_AUTHOR("Paul E. McKenney"); | |
1013 | MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); | |
1014 | MODULE_LICENSE("GPL"); | |
1015 | ||
1016 | #endif /* #ifdef CONFIG_RCU_TRACE */ |