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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 | ||
24278d14 PM |
29 | /* Global control variables for rcupdate callback mechanism. */ |
30 | struct rcu_ctrlblk { | |
31 | struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ | |
32 | struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ | |
33 | struct rcu_head **curtail; /* ->next pointer of last CB. */ | |
9e571a82 | 34 | RCU_TRACE(long qlen); /* Number of pending CBs. */ |
e99033c5 | 35 | RCU_TRACE(char *name); /* Name of RCU type. */ |
24278d14 PM |
36 | }; |
37 | ||
38 | /* Definition for rcupdate control block. */ | |
39 | static struct rcu_ctrlblk rcu_sched_ctrlblk = { | |
40 | .donetail = &rcu_sched_ctrlblk.rcucblist, | |
41 | .curtail = &rcu_sched_ctrlblk.rcucblist, | |
e99033c5 | 42 | RCU_TRACE(.name = "rcu_sched") |
24278d14 PM |
43 | }; |
44 | ||
45 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { | |
46 | .donetail = &rcu_bh_ctrlblk.rcucblist, | |
47 | .curtail = &rcu_bh_ctrlblk.rcucblist, | |
e99033c5 | 48 | RCU_TRACE(.name = "rcu_bh") |
24278d14 PM |
49 | }; |
50 | ||
51 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
52 | int rcu_scheduler_active __read_mostly; | |
53 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
54 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
55 | ||
a57eb940 PM |
56 | #ifdef CONFIG_TINY_PREEMPT_RCU |
57 | ||
58 | #include <linux/delay.h> | |
59 | ||
a57eb940 PM |
60 | /* Global control variables for preemptible RCU. */ |
61 | struct rcu_preempt_ctrlblk { | |
62 | struct rcu_ctrlblk rcb; /* curtail: ->next ptr of last CB for GP. */ | |
63 | struct rcu_head **nexttail; | |
64 | /* Tasks blocked in a preemptible RCU */ | |
65 | /* read-side critical section while an */ | |
66 | /* preemptible-RCU grace period is in */ | |
67 | /* progress must wait for a later grace */ | |
68 | /* period. This pointer points to the */ | |
69 | /* ->next pointer of the last task that */ | |
70 | /* must wait for a later grace period, or */ | |
71 | /* to &->rcb.rcucblist if there is no */ | |
72 | /* such task. */ | |
73 | struct list_head blkd_tasks; | |
74 | /* Tasks blocked in RCU read-side critical */ | |
75 | /* section. Tasks are placed at the head */ | |
76 | /* of this list and age towards the tail. */ | |
77 | struct list_head *gp_tasks; | |
78 | /* Pointer to the first task blocking the */ | |
79 | /* current grace period, or NULL if there */ | |
24278d14 | 80 | /* is no such task. */ |
a57eb940 PM |
81 | struct list_head *exp_tasks; |
82 | /* Pointer to first task blocking the */ | |
83 | /* current expedited grace period, or NULL */ | |
84 | /* if there is no such task. If there */ | |
85 | /* is no current expedited grace period, */ | |
86 | /* then there cannot be any such task. */ | |
24278d14 PM |
87 | #ifdef CONFIG_RCU_BOOST |
88 | struct list_head *boost_tasks; | |
89 | /* Pointer to first task that needs to be */ | |
90 | /* priority-boosted, or NULL if no priority */ | |
91 | /* boosting is needed. If there is no */ | |
92 | /* current or expedited grace period, there */ | |
93 | /* can be no such task. */ | |
94 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
95 | u8 gpnum; /* Current grace period. */ |
96 | u8 gpcpu; /* Last grace period blocked by the CPU. */ | |
97 | u8 completed; /* Last grace period completed. */ | |
98 | /* If all three are equal, RCU is idle. */ | |
9e571a82 | 99 | #ifdef CONFIG_RCU_BOOST |
24278d14 | 100 | unsigned long boost_time; /* When to start boosting (jiffies) */ |
9e571a82 PM |
101 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
102 | #ifdef CONFIG_RCU_TRACE | |
103 | unsigned long n_grace_periods; | |
104 | #ifdef CONFIG_RCU_BOOST | |
105 | unsigned long n_tasks_boosted; | |
7e8b4c72 | 106 | /* Total number of tasks boosted. */ |
9e571a82 | 107 | unsigned long n_exp_boosts; |
7e8b4c72 | 108 | /* Number of tasks boosted for expedited GP. */ |
9e571a82 | 109 | unsigned long n_normal_boosts; |
7e8b4c72 PM |
110 | /* Number of tasks boosted for normal GP. */ |
111 | unsigned long n_balk_blkd_tasks; | |
112 | /* Refused to boost: no blocked tasks. */ | |
113 | unsigned long n_balk_exp_gp_tasks; | |
114 | /* Refused to boost: nothing blocking GP. */ | |
115 | unsigned long n_balk_boost_tasks; | |
116 | /* Refused to boost: already boosting. */ | |
117 | unsigned long n_balk_notyet; | |
118 | /* Refused to boost: not yet time. */ | |
119 | unsigned long n_balk_nos; | |
120 | /* Refused to boost: not sure why, though. */ | |
121 | /* This can happen due to race conditions. */ | |
9e571a82 PM |
122 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
123 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
a57eb940 PM |
124 | }; |
125 | ||
126 | static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = { | |
127 | .rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
128 | .rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
129 | .nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
130 | .blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks), | |
e99033c5 | 131 | RCU_TRACE(.rcb.name = "rcu_preempt") |
a57eb940 PM |
132 | }; |
133 | ||
134 | static int rcu_preempted_readers_exp(void); | |
135 | static void rcu_report_exp_done(void); | |
136 | ||
137 | /* | |
138 | * Return true if the CPU has not yet responded to the current grace period. | |
139 | */ | |
dd7c4d89 | 140 | static int rcu_cpu_blocking_cur_gp(void) |
a57eb940 PM |
141 | { |
142 | return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum; | |
143 | } | |
144 | ||
145 | /* | |
146 | * Check for a running RCU reader. Because there is only one CPU, | |
147 | * there can be but one running RCU reader at a time. ;-) | |
148 | */ | |
149 | static int rcu_preempt_running_reader(void) | |
150 | { | |
151 | return current->rcu_read_lock_nesting; | |
152 | } | |
153 | ||
154 | /* | |
155 | * Check for preempted RCU readers blocking any grace period. | |
156 | * If the caller needs a reliable answer, it must disable hard irqs. | |
157 | */ | |
158 | static int rcu_preempt_blocked_readers_any(void) | |
159 | { | |
160 | return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks); | |
161 | } | |
162 | ||
163 | /* | |
164 | * Check for preempted RCU readers blocking the current grace period. | |
165 | * If the caller needs a reliable answer, it must disable hard irqs. | |
166 | */ | |
167 | static int rcu_preempt_blocked_readers_cgp(void) | |
168 | { | |
169 | return rcu_preempt_ctrlblk.gp_tasks != NULL; | |
170 | } | |
171 | ||
172 | /* | |
173 | * Return true if another preemptible-RCU grace period is needed. | |
174 | */ | |
175 | static int rcu_preempt_needs_another_gp(void) | |
176 | { | |
177 | return *rcu_preempt_ctrlblk.rcb.curtail != NULL; | |
178 | } | |
179 | ||
180 | /* | |
181 | * Return true if a preemptible-RCU grace period is in progress. | |
182 | * The caller must disable hardirqs. | |
183 | */ | |
184 | static int rcu_preempt_gp_in_progress(void) | |
185 | { | |
186 | return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum; | |
187 | } | |
188 | ||
24278d14 PM |
189 | /* |
190 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
191 | * returning NULL if at the end of the list. | |
192 | */ | |
193 | static struct list_head *rcu_next_node_entry(struct task_struct *t) | |
194 | { | |
195 | struct list_head *np; | |
196 | ||
197 | np = t->rcu_node_entry.next; | |
198 | if (np == &rcu_preempt_ctrlblk.blkd_tasks) | |
199 | np = NULL; | |
200 | return np; | |
201 | } | |
202 | ||
9e571a82 PM |
203 | #ifdef CONFIG_RCU_TRACE |
204 | ||
205 | #ifdef CONFIG_RCU_BOOST | |
206 | static void rcu_initiate_boost_trace(void); | |
9e571a82 PM |
207 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
208 | ||
209 | /* | |
210 | * Dump additional statistice for TINY_PREEMPT_RCU. | |
211 | */ | |
212 | static void show_tiny_preempt_stats(struct seq_file *m) | |
213 | { | |
214 | seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n", | |
215 | rcu_preempt_ctrlblk.rcb.qlen, | |
216 | rcu_preempt_ctrlblk.n_grace_periods, | |
217 | rcu_preempt_ctrlblk.gpnum, | |
218 | rcu_preempt_ctrlblk.gpcpu, | |
219 | rcu_preempt_ctrlblk.completed, | |
220 | "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)], | |
221 | "N."[!rcu_preempt_ctrlblk.gp_tasks], | |
222 | "E."[!rcu_preempt_ctrlblk.exp_tasks]); | |
223 | #ifdef CONFIG_RCU_BOOST | |
203373c8 PM |
224 | seq_printf(m, "%sttb=%c ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n", |
225 | " ", | |
226 | "B."[!rcu_preempt_ctrlblk.boost_tasks], | |
9e571a82 PM |
227 | rcu_preempt_ctrlblk.n_tasks_boosted, |
228 | rcu_preempt_ctrlblk.n_exp_boosts, | |
229 | rcu_preempt_ctrlblk.n_normal_boosts, | |
230 | (int)(jiffies & 0xffff), | |
231 | (int)(rcu_preempt_ctrlblk.boost_time & 0xffff)); | |
7e8b4c72 PM |
232 | seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu ny=%lu nos=%lu\n", |
233 | " balk", | |
234 | rcu_preempt_ctrlblk.n_balk_blkd_tasks, | |
235 | rcu_preempt_ctrlblk.n_balk_exp_gp_tasks, | |
236 | rcu_preempt_ctrlblk.n_balk_boost_tasks, | |
237 | rcu_preempt_ctrlblk.n_balk_notyet, | |
238 | rcu_preempt_ctrlblk.n_balk_nos); | |
9e571a82 PM |
239 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
240 | } | |
241 | ||
242 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
243 | ||
24278d14 PM |
244 | #ifdef CONFIG_RCU_BOOST |
245 | ||
246 | #include "rtmutex_common.h" | |
247 | ||
965a002b PM |
248 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO |
249 | ||
250 | /* Controls for rcu_kthread() kthread. */ | |
251 | static struct task_struct *rcu_kthread_task; | |
252 | static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq); | |
253 | static unsigned long have_rcu_kthread_work; | |
254 | ||
24278d14 PM |
255 | /* |
256 | * Carry out RCU priority boosting on the task indicated by ->boost_tasks, | |
257 | * and advance ->boost_tasks to the next task in the ->blkd_tasks list. | |
258 | */ | |
259 | static int rcu_boost(void) | |
260 | { | |
261 | unsigned long flags; | |
262 | struct rt_mutex mtx; | |
24278d14 | 263 | struct task_struct *t; |
7e8b4c72 | 264 | struct list_head *tb; |
24278d14 | 265 | |
7e8b4c72 PM |
266 | if (rcu_preempt_ctrlblk.boost_tasks == NULL && |
267 | rcu_preempt_ctrlblk.exp_tasks == NULL) | |
24278d14 | 268 | return 0; /* Nothing to boost. */ |
7e8b4c72 | 269 | |
24278d14 | 270 | raw_local_irq_save(flags); |
7e8b4c72 PM |
271 | |
272 | /* | |
273 | * Recheck with irqs disabled: all tasks in need of boosting | |
274 | * might exit their RCU read-side critical sections on their own | |
275 | * if we are preempted just before disabling irqs. | |
276 | */ | |
277 | if (rcu_preempt_ctrlblk.boost_tasks == NULL && | |
278 | rcu_preempt_ctrlblk.exp_tasks == NULL) { | |
279 | raw_local_irq_restore(flags); | |
280 | return 0; | |
281 | } | |
282 | ||
283 | /* | |
284 | * Preferentially boost tasks blocking expedited grace periods. | |
285 | * This cannot starve the normal grace periods because a second | |
286 | * expedited grace period must boost all blocked tasks, including | |
287 | * those blocking the pre-existing normal grace period. | |
288 | */ | |
289 | if (rcu_preempt_ctrlblk.exp_tasks != NULL) { | |
290 | tb = rcu_preempt_ctrlblk.exp_tasks; | |
291 | RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++); | |
292 | } else { | |
293 | tb = rcu_preempt_ctrlblk.boost_tasks; | |
294 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++); | |
295 | } | |
296 | RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); | |
297 | ||
298 | /* | |
299 | * We boost task t by manufacturing an rt_mutex that appears to | |
300 | * be held by task t. We leave a pointer to that rt_mutex where | |
301 | * task t can find it, and task t will release the mutex when it | |
302 | * exits its outermost RCU read-side critical section. Then | |
303 | * simply acquiring this artificial rt_mutex will boost task | |
304 | * t's priority. (Thanks to tglx for suggesting this approach!) | |
305 | */ | |
306 | t = container_of(tb, struct task_struct, rcu_node_entry); | |
24278d14 PM |
307 | rt_mutex_init_proxy_locked(&mtx, t); |
308 | t->rcu_boost_mutex = &mtx; | |
309 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED; | |
310 | raw_local_irq_restore(flags); | |
311 | rt_mutex_lock(&mtx); | |
7e8b4c72 PM |
312 | rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ |
313 | ||
314 | return rcu_preempt_ctrlblk.boost_tasks != NULL || | |
315 | rcu_preempt_ctrlblk.exp_tasks != NULL; | |
24278d14 PM |
316 | } |
317 | ||
318 | /* | |
319 | * Check to see if it is now time to start boosting RCU readers blocking | |
320 | * the current grace period, and, if so, tell the rcu_kthread_task to | |
321 | * start boosting them. If there is an expedited boost in progress, | |
322 | * we wait for it to complete. | |
9e571a82 PM |
323 | * |
324 | * If there are no blocked readers blocking the current grace period, | |
325 | * return 0 to let the caller know, otherwise return 1. Note that this | |
326 | * return value is independent of whether or not boosting was done. | |
24278d14 | 327 | */ |
9e571a82 | 328 | static int rcu_initiate_boost(void) |
24278d14 | 329 | { |
7e8b4c72 PM |
330 | if (!rcu_preempt_blocked_readers_cgp() && |
331 | rcu_preempt_ctrlblk.exp_tasks == NULL) { | |
332 | RCU_TRACE(rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++); | |
9e571a82 PM |
333 | return 0; |
334 | } | |
7e8b4c72 PM |
335 | if (rcu_preempt_ctrlblk.exp_tasks != NULL || |
336 | (rcu_preempt_ctrlblk.gp_tasks != NULL && | |
337 | rcu_preempt_ctrlblk.boost_tasks == NULL && | |
338 | ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))) { | |
339 | if (rcu_preempt_ctrlblk.exp_tasks == NULL) | |
340 | rcu_preempt_ctrlblk.boost_tasks = | |
341 | rcu_preempt_ctrlblk.gp_tasks; | |
965a002b | 342 | invoke_rcu_callbacks(); |
9e571a82 PM |
343 | } else |
344 | RCU_TRACE(rcu_initiate_boost_trace()); | |
345 | return 1; | |
24278d14 PM |
346 | } |
347 | ||
ddeb7581 | 348 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
24278d14 PM |
349 | |
350 | /* | |
351 | * Do priority-boost accounting for the start of a new grace period. | |
352 | */ | |
353 | static void rcu_preempt_boost_start_gp(void) | |
354 | { | |
355 | rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
24278d14 PM |
356 | } |
357 | ||
358 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
359 | ||
24278d14 | 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 | ||
24278d14 PM |
370 | /* |
371 | * If there is no RCU priority boosting, nothing to do at grace-period start. | |
372 | */ | |
373 | static void rcu_preempt_boost_start_gp(void) | |
374 | { | |
375 | } | |
376 | ||
377 | #endif /* else #ifdef CONFIG_RCU_BOOST */ | |
378 | ||
a57eb940 PM |
379 | /* |
380 | * Record a preemptible-RCU quiescent state for the specified CPU. Note | |
381 | * that this just means that the task currently running on the CPU is | |
382 | * in a quiescent state. There might be any number of tasks blocked | |
383 | * while in an RCU read-side critical section. | |
384 | * | |
385 | * Unlike the other rcu_*_qs() functions, callers to this function | |
386 | * must disable irqs in order to protect the assignment to | |
387 | * ->rcu_read_unlock_special. | |
388 | * | |
389 | * Because this is a single-CPU implementation, the only way a grace | |
390 | * period can end is if the CPU is in a quiescent state. The reason is | |
391 | * that a blocked preemptible-RCU reader can exit its critical section | |
392 | * only if the CPU is running it at the time. Therefore, when the | |
393 | * last task blocking the current grace period exits its RCU read-side | |
394 | * critical section, neither the CPU nor blocked tasks will be stopping | |
395 | * the current grace period. (In contrast, SMP implementations | |
396 | * might have CPUs running in RCU read-side critical sections that | |
397 | * block later grace periods -- but this is not possible given only | |
398 | * one CPU.) | |
399 | */ | |
400 | static void rcu_preempt_cpu_qs(void) | |
401 | { | |
402 | /* Record both CPU and task as having responded to current GP. */ | |
403 | rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum; | |
404 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; | |
405 | ||
24278d14 | 406 | /* If there is no GP then there is nothing more to do. */ |
9e571a82 | 407 | if (!rcu_preempt_gp_in_progress()) |
a57eb940 | 408 | return; |
9e571a82 | 409 | /* |
ddeb7581 | 410 | * Check up on boosting. If there are readers blocking the |
9e571a82 PM |
411 | * current grace period, leave. |
412 | */ | |
413 | if (rcu_initiate_boost()) | |
24278d14 | 414 | return; |
a57eb940 PM |
415 | |
416 | /* Advance callbacks. */ | |
417 | rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum; | |
418 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail; | |
419 | rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail; | |
420 | ||
421 | /* If there are no blocked readers, next GP is done instantly. */ | |
422 | if (!rcu_preempt_blocked_readers_any()) | |
423 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail; | |
424 | ||
b2c0710c | 425 | /* If there are done callbacks, cause them to be invoked. */ |
a57eb940 | 426 | if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) |
965a002b | 427 | invoke_rcu_callbacks(); |
a57eb940 PM |
428 | } |
429 | ||
430 | /* | |
431 | * Start a new RCU grace period if warranted. Hard irqs must be disabled. | |
432 | */ | |
433 | static void rcu_preempt_start_gp(void) | |
434 | { | |
435 | if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) { | |
436 | ||
437 | /* Official start of GP. */ | |
438 | rcu_preempt_ctrlblk.gpnum++; | |
9e571a82 | 439 | RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); |
a57eb940 PM |
440 | |
441 | /* Any blocked RCU readers block new GP. */ | |
442 | if (rcu_preempt_blocked_readers_any()) | |
443 | rcu_preempt_ctrlblk.gp_tasks = | |
444 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
445 | ||
24278d14 PM |
446 | /* Set up for RCU priority boosting. */ |
447 | rcu_preempt_boost_start_gp(); | |
448 | ||
a57eb940 PM |
449 | /* If there is no running reader, CPU is done with GP. */ |
450 | if (!rcu_preempt_running_reader()) | |
451 | rcu_preempt_cpu_qs(); | |
452 | } | |
453 | } | |
454 | ||
455 | /* | |
456 | * We have entered the scheduler, and the current task might soon be | |
457 | * context-switched away from. If this task is in an RCU read-side | |
458 | * critical section, we will no longer be able to rely on the CPU to | |
459 | * record that fact, so we enqueue the task on the blkd_tasks list. | |
460 | * If the task started after the current grace period began, as recorded | |
461 | * by ->gpcpu, we enqueue at the beginning of the list. Otherwise | |
462 | * before the element referenced by ->gp_tasks (or at the tail if | |
463 | * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element. | |
464 | * The task will dequeue itself when it exits the outermost enclosing | |
465 | * RCU read-side critical section. Therefore, the current grace period | |
466 | * cannot be permitted to complete until the ->gp_tasks pointer becomes | |
467 | * NULL. | |
468 | * | |
469 | * Caller must disable preemption. | |
470 | */ | |
471 | void rcu_preempt_note_context_switch(void) | |
472 | { | |
473 | struct task_struct *t = current; | |
474 | unsigned long flags; | |
475 | ||
476 | local_irq_save(flags); /* must exclude scheduler_tick(). */ | |
477 | if (rcu_preempt_running_reader() && | |
478 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { | |
479 | ||
480 | /* Possibly blocking in an RCU read-side critical section. */ | |
481 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; | |
482 | ||
483 | /* | |
484 | * If this CPU has already checked in, then this task | |
485 | * will hold up the next grace period rather than the | |
486 | * current grace period. Queue the task accordingly. | |
487 | * If the task is queued for the current grace period | |
488 | * (i.e., this CPU has not yet passed through a quiescent | |
489 | * state for the current grace period), then as long | |
490 | * as that task remains queued, the current grace period | |
491 | * cannot end. | |
492 | */ | |
493 | list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks); | |
dd7c4d89 | 494 | if (rcu_cpu_blocking_cur_gp()) |
a57eb940 PM |
495 | rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry; |
496 | } | |
497 | ||
498 | /* | |
499 | * Either we were not in an RCU read-side critical section to | |
500 | * begin with, or we have now recorded that critical section | |
501 | * globally. Either way, we can now note a quiescent state | |
502 | * for this CPU. Again, if we were in an RCU read-side critical | |
503 | * section, and if that critical section was blocking the current | |
504 | * grace period, then the fact that the task has been enqueued | |
505 | * means that current grace period continues to be blocked. | |
506 | */ | |
507 | rcu_preempt_cpu_qs(); | |
508 | local_irq_restore(flags); | |
509 | } | |
510 | ||
511 | /* | |
512 | * Tiny-preemptible RCU implementation for rcu_read_lock(). | |
513 | * Just increment ->rcu_read_lock_nesting, shared state will be updated | |
514 | * if we block. | |
515 | */ | |
516 | void __rcu_read_lock(void) | |
517 | { | |
518 | current->rcu_read_lock_nesting++; | |
519 | barrier(); /* needed if we ever invoke rcu_read_lock in rcutiny.c */ | |
520 | } | |
521 | EXPORT_SYMBOL_GPL(__rcu_read_lock); | |
522 | ||
523 | /* | |
524 | * Handle special cases during rcu_read_unlock(), such as needing to | |
525 | * notify RCU core processing or task having blocked during the RCU | |
526 | * read-side critical section. | |
527 | */ | |
528 | static void rcu_read_unlock_special(struct task_struct *t) | |
529 | { | |
530 | int empty; | |
531 | int empty_exp; | |
532 | unsigned long flags; | |
533 | struct list_head *np; | |
534 | int special; | |
535 | ||
536 | /* | |
537 | * NMI handlers cannot block and cannot safely manipulate state. | |
538 | * They therefore cannot possibly be special, so just leave. | |
539 | */ | |
540 | if (in_nmi()) | |
541 | return; | |
542 | ||
543 | local_irq_save(flags); | |
544 | ||
545 | /* | |
546 | * If RCU core is waiting for this CPU to exit critical section, | |
547 | * let it know that we have done so. | |
548 | */ | |
549 | special = t->rcu_read_unlock_special; | |
550 | if (special & RCU_READ_UNLOCK_NEED_QS) | |
551 | rcu_preempt_cpu_qs(); | |
552 | ||
553 | /* Hardware IRQ handlers cannot block. */ | |
554 | if (in_irq()) { | |
555 | local_irq_restore(flags); | |
556 | return; | |
557 | } | |
558 | ||
559 | /* Clean up if blocked during RCU read-side critical section. */ | |
560 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
561 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
562 | ||
563 | /* | |
564 | * Remove this task from the ->blkd_tasks list and adjust | |
565 | * any pointers that might have been referencing it. | |
566 | */ | |
567 | empty = !rcu_preempt_blocked_readers_cgp(); | |
568 | empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL; | |
24278d14 | 569 | np = rcu_next_node_entry(t); |
ddeb7581 | 570 | list_del_init(&t->rcu_node_entry); |
a57eb940 PM |
571 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks) |
572 | rcu_preempt_ctrlblk.gp_tasks = np; | |
573 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks) | |
574 | rcu_preempt_ctrlblk.exp_tasks = np; | |
24278d14 PM |
575 | #ifdef CONFIG_RCU_BOOST |
576 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks) | |
577 | rcu_preempt_ctrlblk.boost_tasks = np; | |
578 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
579 | |
580 | /* | |
581 | * If this was the last task on the current list, and if | |
582 | * we aren't waiting on the CPU, report the quiescent state | |
583 | * and start a new grace period if needed. | |
584 | */ | |
585 | if (!empty && !rcu_preempt_blocked_readers_cgp()) { | |
586 | rcu_preempt_cpu_qs(); | |
587 | rcu_preempt_start_gp(); | |
588 | } | |
589 | ||
590 | /* | |
591 | * If this was the last task on the expedited lists, | |
592 | * then we need wake up the waiting task. | |
593 | */ | |
594 | if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL) | |
595 | rcu_report_exp_done(); | |
596 | } | |
24278d14 PM |
597 | #ifdef CONFIG_RCU_BOOST |
598 | /* Unboost self if was boosted. */ | |
599 | if (special & RCU_READ_UNLOCK_BOOSTED) { | |
600 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED; | |
601 | rt_mutex_unlock(t->rcu_boost_mutex); | |
602 | t->rcu_boost_mutex = NULL; | |
603 | } | |
604 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
605 | local_irq_restore(flags); |
606 | } | |
607 | ||
608 | /* | |
609 | * Tiny-preemptible RCU implementation for rcu_read_unlock(). | |
610 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost | |
611 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then | |
612 | * invoke rcu_read_unlock_special() to clean up after a context switch | |
613 | * in an RCU read-side critical section and other special cases. | |
614 | */ | |
615 | void __rcu_read_unlock(void) | |
616 | { | |
617 | struct task_struct *t = current; | |
618 | ||
619 | barrier(); /* needed if we ever invoke rcu_read_unlock in rcutiny.c */ | |
620 | --t->rcu_read_lock_nesting; | |
621 | barrier(); /* decrement before load of ->rcu_read_unlock_special */ | |
622 | if (t->rcu_read_lock_nesting == 0 && | |
623 | unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) | |
624 | rcu_read_unlock_special(t); | |
625 | #ifdef CONFIG_PROVE_LOCKING | |
626 | WARN_ON_ONCE(t->rcu_read_lock_nesting < 0); | |
627 | #endif /* #ifdef CONFIG_PROVE_LOCKING */ | |
628 | } | |
629 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); | |
630 | ||
631 | /* | |
632 | * Check for a quiescent state from the current CPU. When a task blocks, | |
633 | * the task is recorded in the rcu_preempt_ctrlblk structure, which is | |
634 | * checked elsewhere. This is called from the scheduling-clock interrupt. | |
635 | * | |
636 | * Caller must disable hard irqs. | |
637 | */ | |
638 | static void rcu_preempt_check_callbacks(void) | |
639 | { | |
640 | struct task_struct *t = current; | |
641 | ||
dd7c4d89 PM |
642 | if (rcu_preempt_gp_in_progress() && |
643 | (!rcu_preempt_running_reader() || | |
644 | !rcu_cpu_blocking_cur_gp())) | |
a57eb940 PM |
645 | rcu_preempt_cpu_qs(); |
646 | if (&rcu_preempt_ctrlblk.rcb.rcucblist != | |
647 | rcu_preempt_ctrlblk.rcb.donetail) | |
965a002b | 648 | invoke_rcu_callbacks(); |
dd7c4d89 PM |
649 | if (rcu_preempt_gp_in_progress() && |
650 | rcu_cpu_blocking_cur_gp() && | |
651 | rcu_preempt_running_reader()) | |
a57eb940 PM |
652 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
653 | } | |
654 | ||
655 | /* | |
656 | * TINY_PREEMPT_RCU has an extra callback-list tail pointer to | |
b2c0710c | 657 | * update, so this is invoked from rcu_process_callbacks() to |
a57eb940 PM |
658 | * handle that case. Of course, it is invoked for all flavors of |
659 | * RCU, but RCU callbacks can appear only on one of the lists, and | |
660 | * neither ->nexttail nor ->donetail can possibly be NULL, so there | |
661 | * is no need for an explicit check. | |
662 | */ | |
663 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
664 | { | |
665 | if (rcu_preempt_ctrlblk.nexttail == rcp->donetail) | |
666 | rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist; | |
667 | } | |
668 | ||
669 | /* | |
670 | * Process callbacks for preemptible RCU. | |
671 | */ | |
672 | static void rcu_preempt_process_callbacks(void) | |
673 | { | |
965a002b | 674 | __rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); |
a57eb940 PM |
675 | } |
676 | ||
677 | /* | |
678 | * Queue a preemptible -RCU callback for invocation after a grace period. | |
679 | */ | |
680 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
681 | { | |
682 | unsigned long flags; | |
683 | ||
684 | debug_rcu_head_queue(head); | |
685 | head->func = func; | |
686 | head->next = NULL; | |
687 | ||
688 | local_irq_save(flags); | |
689 | *rcu_preempt_ctrlblk.nexttail = head; | |
690 | rcu_preempt_ctrlblk.nexttail = &head->next; | |
9e571a82 | 691 | RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++); |
a57eb940 PM |
692 | rcu_preempt_start_gp(); /* checks to see if GP needed. */ |
693 | local_irq_restore(flags); | |
694 | } | |
695 | EXPORT_SYMBOL_GPL(call_rcu); | |
696 | ||
a57eb940 PM |
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; | |
a57eb940 PM |
789 | |
790 | /* Wait for tail of ->blkd_tasks list to drain. */ | |
7e8b4c72 PM |
791 | if (!rcu_preempted_readers_exp()) |
792 | local_irq_restore(flags); | |
793 | else { | |
794 | rcu_initiate_boost(); | |
795 | local_irq_restore(flags); | |
a57eb940 PM |
796 | wait_event(sync_rcu_preempt_exp_wq, |
797 | !rcu_preempted_readers_exp()); | |
7e8b4c72 | 798 | } |
a57eb940 PM |
799 | |
800 | /* Clean up and exit. */ | |
801 | barrier(); /* ensure expedited GP seen before counter increment. */ | |
802 | sync_rcu_preempt_exp_count++; | |
803 | unlock_mb_ret: | |
804 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
805 | barrier(); /* ensure subsequent action seen after grace period. */ | |
806 | } | |
807 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
808 | ||
809 | /* | |
810 | * Does preemptible RCU need the CPU to stay out of dynticks mode? | |
811 | */ | |
812 | int rcu_preempt_needs_cpu(void) | |
813 | { | |
814 | if (!rcu_preempt_running_reader()) | |
815 | rcu_preempt_cpu_qs(); | |
816 | return rcu_preempt_ctrlblk.rcb.rcucblist != NULL; | |
817 | } | |
818 | ||
819 | /* | |
820 | * Check for a task exiting while in a preemptible -RCU read-side | |
821 | * critical section, clean up if so. No need to issue warnings, | |
822 | * as debug_check_no_locks_held() already does this if lockdep | |
823 | * is enabled. | |
824 | */ | |
825 | void exit_rcu(void) | |
826 | { | |
827 | struct task_struct *t = current; | |
828 | ||
829 | if (t->rcu_read_lock_nesting == 0) | |
830 | return; | |
831 | t->rcu_read_lock_nesting = 1; | |
ba74f4d7 | 832 | __rcu_read_unlock(); |
a57eb940 PM |
833 | } |
834 | ||
835 | #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
836 | ||
9e571a82 PM |
837 | #ifdef CONFIG_RCU_TRACE |
838 | ||
839 | /* | |
840 | * Because preemptible RCU does not exist, it is not necessary to | |
841 | * dump out its statistics. | |
842 | */ | |
843 | static void show_tiny_preempt_stats(struct seq_file *m) | |
844 | { | |
845 | } | |
846 | ||
847 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
848 | ||
a57eb940 PM |
849 | /* |
850 | * Because preemptible RCU does not exist, it never has any callbacks | |
851 | * to check. | |
852 | */ | |
853 | static void rcu_preempt_check_callbacks(void) | |
854 | { | |
855 | } | |
856 | ||
857 | /* | |
858 | * Because preemptible RCU does not exist, it never has any callbacks | |
859 | * to remove. | |
860 | */ | |
861 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
862 | { | |
863 | } | |
864 | ||
865 | /* | |
866 | * Because preemptible RCU does not exist, it never has any callbacks | |
867 | * to process. | |
868 | */ | |
869 | static void rcu_preempt_process_callbacks(void) | |
870 | { | |
871 | } | |
872 | ||
873 | #endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
874 | ||
965a002b PM |
875 | #ifdef CONFIG_RCU_BOOST |
876 | ||
877 | /* | |
878 | * Wake up rcu_kthread() to process callbacks now eligible for invocation | |
879 | * or to boost readers. | |
880 | */ | |
881 | static void invoke_rcu_callbacks(void) | |
882 | { | |
883 | have_rcu_kthread_work = 1; | |
884 | wake_up(&rcu_kthread_wq); | |
885 | } | |
886 | ||
887 | /* | |
888 | * This kthread invokes RCU callbacks whose grace periods have | |
889 | * elapsed. It is awakened as needed, and takes the place of the | |
890 | * RCU_SOFTIRQ that is used for this purpose when boosting is disabled. | |
891 | * This is a kthread, but it is never stopped, at least not until | |
892 | * the system goes down. | |
893 | */ | |
894 | static int rcu_kthread(void *arg) | |
895 | { | |
896 | unsigned long work; | |
897 | unsigned long morework; | |
898 | unsigned long flags; | |
899 | ||
900 | for (;;) { | |
901 | wait_event_interruptible(rcu_kthread_wq, | |
902 | have_rcu_kthread_work != 0); | |
903 | morework = rcu_boost(); | |
904 | local_irq_save(flags); | |
905 | work = have_rcu_kthread_work; | |
906 | have_rcu_kthread_work = morework; | |
907 | local_irq_restore(flags); | |
908 | if (work) | |
909 | rcu_process_callbacks(NULL); | |
910 | schedule_timeout_interruptible(1); /* Leave CPU for others. */ | |
911 | } | |
912 | ||
913 | return 0; /* Not reached, but needed to shut gcc up. */ | |
914 | } | |
915 | ||
916 | /* | |
917 | * Spawn the kthread that invokes RCU callbacks. | |
918 | */ | |
919 | static int __init rcu_spawn_kthreads(void) | |
920 | { | |
921 | struct sched_param sp; | |
922 | ||
923 | rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread"); | |
924 | sp.sched_priority = RCU_BOOST_PRIO; | |
925 | sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp); | |
926 | return 0; | |
927 | } | |
928 | early_initcall(rcu_spawn_kthreads); | |
929 | ||
930 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
931 | ||
932 | /* | |
933 | * Start up softirq processing of callbacks. | |
934 | */ | |
935 | void invoke_rcu_callbacks(void) | |
936 | { | |
937 | raise_softirq(RCU_SOFTIRQ); | |
938 | } | |
939 | ||
940 | void rcu_init(void) | |
941 | { | |
942 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); | |
943 | } | |
944 | ||
945 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ | |
946 | ||
bbad9379 | 947 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
bbad9379 PM |
948 | #include <linux/kernel_stat.h> |
949 | ||
950 | /* | |
951 | * During boot, we forgive RCU lockdep issues. After this function is | |
952 | * invoked, we start taking RCU lockdep issues seriously. | |
953 | */ | |
b2c0710c | 954 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
955 | { |
956 | WARN_ON(nr_context_switches() > 0); | |
957 | rcu_scheduler_active = 1; | |
958 | } | |
959 | ||
960 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 | 961 | |
9e571a82 PM |
962 | #ifdef CONFIG_RCU_TRACE |
963 | ||
964 | #ifdef CONFIG_RCU_BOOST | |
965 | ||
966 | static void rcu_initiate_boost_trace(void) | |
967 | { | |
7e8b4c72 PM |
968 | if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) |
969 | rcu_preempt_ctrlblk.n_balk_blkd_tasks++; | |
970 | else if (rcu_preempt_ctrlblk.gp_tasks == NULL && | |
971 | rcu_preempt_ctrlblk.exp_tasks == NULL) | |
972 | rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++; | |
9e571a82 | 973 | else if (rcu_preempt_ctrlblk.boost_tasks != NULL) |
7e8b4c72 | 974 | rcu_preempt_ctrlblk.n_balk_boost_tasks++; |
9e571a82 | 975 | else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) |
7e8b4c72 | 976 | rcu_preempt_ctrlblk.n_balk_notyet++; |
9e571a82 | 977 | else |
7e8b4c72 | 978 | rcu_preempt_ctrlblk.n_balk_nos++; |
9e571a82 PM |
979 | } |
980 | ||
981 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
982 | ||
983 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) | |
984 | { | |
985 | unsigned long flags; | |
986 | ||
987 | raw_local_irq_save(flags); | |
988 | rcp->qlen -= n; | |
989 | raw_local_irq_restore(flags); | |
990 | } | |
991 | ||
992 | /* | |
993 | * Dump statistics for TINY_RCU, such as they are. | |
994 | */ | |
995 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
996 | { | |
997 | show_tiny_preempt_stats(m); | |
998 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); | |
999 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
1000 | return 0; | |
1001 | } | |
1002 | ||
1003 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
1004 | { | |
1005 | return single_open(file, show_tiny_stats, NULL); | |
1006 | } | |
1007 | ||
1008 | static const struct file_operations show_tiny_stats_fops = { | |
1009 | .owner = THIS_MODULE, | |
1010 | .open = show_tiny_stats_open, | |
1011 | .read = seq_read, | |
1012 | .llseek = seq_lseek, | |
1013 | .release = single_release, | |
1014 | }; | |
1015 | ||
1016 | static struct dentry *rcudir; | |
1017 | ||
1018 | static int __init rcutiny_trace_init(void) | |
1019 | { | |
1020 | struct dentry *retval; | |
1021 | ||
1022 | rcudir = debugfs_create_dir("rcu", NULL); | |
1023 | if (!rcudir) | |
1024 | goto free_out; | |
1025 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
1026 | NULL, &show_tiny_stats_fops); | |
1027 | if (!retval) | |
1028 | goto free_out; | |
1029 | return 0; | |
1030 | free_out: | |
1031 | debugfs_remove_recursive(rcudir); | |
1032 | return 1; | |
1033 | } | |
1034 | ||
1035 | static void __exit rcutiny_trace_cleanup(void) | |
1036 | { | |
1037 | debugfs_remove_recursive(rcudir); | |
1038 | } | |
1039 | ||
1040 | module_init(rcutiny_trace_init); | |
1041 | module_exit(rcutiny_trace_cleanup); | |
1042 | ||
1043 | MODULE_AUTHOR("Paul E. McKenney"); | |
1044 | MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); | |
1045 | MODULE_LICENSE("GPL"); | |
1046 | ||
1047 | #endif /* #ifdef CONFIG_RCU_TRACE */ |