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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> |
bdfa97bf | 26 | #include <linux/module.h> |
9e571a82 PM |
27 | #include <linux/debugfs.h> |
28 | #include <linux/seq_file.h> | |
29 | ||
24278d14 PM |
30 | /* Global control variables for rcupdate callback mechanism. */ |
31 | struct rcu_ctrlblk { | |
32 | struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ | |
33 | struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ | |
34 | struct rcu_head **curtail; /* ->next pointer of last CB. */ | |
9e571a82 | 35 | RCU_TRACE(long qlen); /* Number of pending CBs. */ |
e99033c5 | 36 | RCU_TRACE(char *name); /* Name of RCU type. */ |
24278d14 PM |
37 | }; |
38 | ||
39 | /* Definition for rcupdate control block. */ | |
40 | static struct rcu_ctrlblk rcu_sched_ctrlblk = { | |
41 | .donetail = &rcu_sched_ctrlblk.rcucblist, | |
42 | .curtail = &rcu_sched_ctrlblk.rcucblist, | |
e99033c5 | 43 | RCU_TRACE(.name = "rcu_sched") |
24278d14 PM |
44 | }; |
45 | ||
46 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { | |
47 | .donetail = &rcu_bh_ctrlblk.rcucblist, | |
48 | .curtail = &rcu_bh_ctrlblk.rcucblist, | |
e99033c5 | 49 | RCU_TRACE(.name = "rcu_bh") |
24278d14 PM |
50 | }; |
51 | ||
52 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
53 | int rcu_scheduler_active __read_mostly; | |
54 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
55 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
56 | ||
a57eb940 PM |
57 | #ifdef CONFIG_TINY_PREEMPT_RCU |
58 | ||
59 | #include <linux/delay.h> | |
60 | ||
a57eb940 PM |
61 | /* Global control variables for preemptible RCU. */ |
62 | struct rcu_preempt_ctrlblk { | |
63 | struct rcu_ctrlblk rcb; /* curtail: ->next ptr of last CB for GP. */ | |
64 | struct rcu_head **nexttail; | |
65 | /* Tasks blocked in a preemptible RCU */ | |
66 | /* read-side critical section while an */ | |
67 | /* preemptible-RCU grace period is in */ | |
68 | /* progress must wait for a later grace */ | |
69 | /* period. This pointer points to the */ | |
70 | /* ->next pointer of the last task that */ | |
71 | /* must wait for a later grace period, or */ | |
72 | /* to &->rcb.rcucblist if there is no */ | |
73 | /* such task. */ | |
74 | struct list_head blkd_tasks; | |
75 | /* Tasks blocked in RCU read-side critical */ | |
76 | /* section. Tasks are placed at the head */ | |
77 | /* of this list and age towards the tail. */ | |
78 | struct list_head *gp_tasks; | |
79 | /* Pointer to the first task blocking the */ | |
80 | /* current grace period, or NULL if there */ | |
24278d14 | 81 | /* is no such task. */ |
a57eb940 PM |
82 | struct list_head *exp_tasks; |
83 | /* Pointer to first task blocking the */ | |
84 | /* current expedited grace period, or NULL */ | |
85 | /* if there is no such task. If there */ | |
86 | /* is no current expedited grace period, */ | |
87 | /* then there cannot be any such task. */ | |
24278d14 PM |
88 | #ifdef CONFIG_RCU_BOOST |
89 | struct list_head *boost_tasks; | |
90 | /* Pointer to first task that needs to be */ | |
91 | /* priority-boosted, or NULL if no priority */ | |
92 | /* boosting is needed. If there is no */ | |
93 | /* current or expedited grace period, there */ | |
94 | /* can be no such task. */ | |
95 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
96 | u8 gpnum; /* Current grace period. */ |
97 | u8 gpcpu; /* Last grace period blocked by the CPU. */ | |
98 | u8 completed; /* Last grace period completed. */ | |
99 | /* If all three are equal, RCU is idle. */ | |
9e571a82 | 100 | #ifdef CONFIG_RCU_BOOST |
24278d14 | 101 | unsigned long boost_time; /* When to start boosting (jiffies) */ |
9e571a82 PM |
102 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
103 | #ifdef CONFIG_RCU_TRACE | |
104 | unsigned long n_grace_periods; | |
105 | #ifdef CONFIG_RCU_BOOST | |
106 | unsigned long n_tasks_boosted; | |
7e8b4c72 | 107 | /* Total number of tasks boosted. */ |
9e571a82 | 108 | unsigned long n_exp_boosts; |
7e8b4c72 | 109 | /* Number of tasks boosted for expedited GP. */ |
9e571a82 | 110 | unsigned long n_normal_boosts; |
7e8b4c72 PM |
111 | /* Number of tasks boosted for normal GP. */ |
112 | unsigned long n_balk_blkd_tasks; | |
113 | /* Refused to boost: no blocked tasks. */ | |
114 | unsigned long n_balk_exp_gp_tasks; | |
115 | /* Refused to boost: nothing blocking GP. */ | |
116 | unsigned long n_balk_boost_tasks; | |
117 | /* Refused to boost: already boosting. */ | |
118 | unsigned long n_balk_notyet; | |
119 | /* Refused to boost: not yet time. */ | |
120 | unsigned long n_balk_nos; | |
121 | /* Refused to boost: not sure why, though. */ | |
122 | /* This can happen due to race conditions. */ | |
9e571a82 PM |
123 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
124 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
a57eb940 PM |
125 | }; |
126 | ||
127 | static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = { | |
128 | .rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
129 | .rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
130 | .nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist, | |
131 | .blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks), | |
e99033c5 | 132 | RCU_TRACE(.rcb.name = "rcu_preempt") |
a57eb940 PM |
133 | }; |
134 | ||
135 | static int rcu_preempted_readers_exp(void); | |
136 | static void rcu_report_exp_done(void); | |
137 | ||
138 | /* | |
139 | * Return true if the CPU has not yet responded to the current grace period. | |
140 | */ | |
dd7c4d89 | 141 | static int rcu_cpu_blocking_cur_gp(void) |
a57eb940 PM |
142 | { |
143 | return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum; | |
144 | } | |
145 | ||
146 | /* | |
147 | * Check for a running RCU reader. Because there is only one CPU, | |
148 | * there can be but one running RCU reader at a time. ;-) | |
26861faf PM |
149 | * |
150 | * Returns zero if there are no running readers. Returns a positive | |
151 | * number if there is at least one reader within its RCU read-side | |
152 | * critical section. Returns a negative number if an outermost reader | |
153 | * is in the midst of exiting from its RCU read-side critical section | |
154 | * | |
155 | * Returns zero if there are no running readers. Returns a positive | |
156 | * number if there is at least one reader within its RCU read-side | |
157 | * critical section. Returns a negative number if an outermost reader | |
158 | * is in the midst of exiting from its RCU read-side critical section. | |
a57eb940 PM |
159 | */ |
160 | static int rcu_preempt_running_reader(void) | |
161 | { | |
162 | return current->rcu_read_lock_nesting; | |
163 | } | |
164 | ||
165 | /* | |
166 | * Check for preempted RCU readers blocking any grace period. | |
167 | * If the caller needs a reliable answer, it must disable hard irqs. | |
168 | */ | |
169 | static int rcu_preempt_blocked_readers_any(void) | |
170 | { | |
171 | return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks); | |
172 | } | |
173 | ||
174 | /* | |
175 | * Check for preempted RCU readers blocking the current grace period. | |
176 | * If the caller needs a reliable answer, it must disable hard irqs. | |
177 | */ | |
178 | static int rcu_preempt_blocked_readers_cgp(void) | |
179 | { | |
180 | return rcu_preempt_ctrlblk.gp_tasks != NULL; | |
181 | } | |
182 | ||
183 | /* | |
184 | * Return true if another preemptible-RCU grace period is needed. | |
185 | */ | |
186 | static int rcu_preempt_needs_another_gp(void) | |
187 | { | |
188 | return *rcu_preempt_ctrlblk.rcb.curtail != NULL; | |
189 | } | |
190 | ||
191 | /* | |
192 | * Return true if a preemptible-RCU grace period is in progress. | |
193 | * The caller must disable hardirqs. | |
194 | */ | |
195 | static int rcu_preempt_gp_in_progress(void) | |
196 | { | |
197 | return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum; | |
198 | } | |
199 | ||
24278d14 PM |
200 | /* |
201 | * Advance a ->blkd_tasks-list pointer to the next entry, instead | |
202 | * returning NULL if at the end of the list. | |
203 | */ | |
204 | static struct list_head *rcu_next_node_entry(struct task_struct *t) | |
205 | { | |
206 | struct list_head *np; | |
207 | ||
208 | np = t->rcu_node_entry.next; | |
209 | if (np == &rcu_preempt_ctrlblk.blkd_tasks) | |
210 | np = NULL; | |
211 | return np; | |
212 | } | |
213 | ||
9e571a82 PM |
214 | #ifdef CONFIG_RCU_TRACE |
215 | ||
216 | #ifdef CONFIG_RCU_BOOST | |
217 | static void rcu_initiate_boost_trace(void); | |
9e571a82 PM |
218 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
219 | ||
220 | /* | |
221 | * Dump additional statistice for TINY_PREEMPT_RCU. | |
222 | */ | |
223 | static void show_tiny_preempt_stats(struct seq_file *m) | |
224 | { | |
225 | seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n", | |
226 | rcu_preempt_ctrlblk.rcb.qlen, | |
227 | rcu_preempt_ctrlblk.n_grace_periods, | |
228 | rcu_preempt_ctrlblk.gpnum, | |
229 | rcu_preempt_ctrlblk.gpcpu, | |
230 | rcu_preempt_ctrlblk.completed, | |
231 | "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)], | |
232 | "N."[!rcu_preempt_ctrlblk.gp_tasks], | |
233 | "E."[!rcu_preempt_ctrlblk.exp_tasks]); | |
234 | #ifdef CONFIG_RCU_BOOST | |
203373c8 PM |
235 | seq_printf(m, "%sttb=%c ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n", |
236 | " ", | |
237 | "B."[!rcu_preempt_ctrlblk.boost_tasks], | |
9e571a82 PM |
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)); | |
7e8b4c72 PM |
243 | seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu ny=%lu nos=%lu\n", |
244 | " balk", | |
245 | rcu_preempt_ctrlblk.n_balk_blkd_tasks, | |
246 | rcu_preempt_ctrlblk.n_balk_exp_gp_tasks, | |
247 | rcu_preempt_ctrlblk.n_balk_boost_tasks, | |
248 | rcu_preempt_ctrlblk.n_balk_notyet, | |
249 | rcu_preempt_ctrlblk.n_balk_nos); | |
9e571a82 PM |
250 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
251 | } | |
252 | ||
253 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
254 | ||
24278d14 PM |
255 | #ifdef CONFIG_RCU_BOOST |
256 | ||
257 | #include "rtmutex_common.h" | |
258 | ||
965a002b PM |
259 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO |
260 | ||
261 | /* Controls for rcu_kthread() kthread. */ | |
262 | static struct task_struct *rcu_kthread_task; | |
263 | static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq); | |
264 | static unsigned long have_rcu_kthread_work; | |
265 | ||
24278d14 PM |
266 | /* |
267 | * Carry out RCU priority boosting on the task indicated by ->boost_tasks, | |
268 | * and advance ->boost_tasks to the next task in the ->blkd_tasks list. | |
269 | */ | |
270 | static int rcu_boost(void) | |
271 | { | |
272 | unsigned long flags; | |
273 | struct rt_mutex mtx; | |
24278d14 | 274 | struct task_struct *t; |
7e8b4c72 | 275 | struct list_head *tb; |
24278d14 | 276 | |
7e8b4c72 PM |
277 | if (rcu_preempt_ctrlblk.boost_tasks == NULL && |
278 | rcu_preempt_ctrlblk.exp_tasks == NULL) | |
24278d14 | 279 | return 0; /* Nothing to boost. */ |
7e8b4c72 | 280 | |
7a11e205 | 281 | local_irq_save(flags); |
7e8b4c72 PM |
282 | |
283 | /* | |
284 | * Recheck with irqs disabled: all tasks in need of boosting | |
285 | * might exit their RCU read-side critical sections on their own | |
286 | * if we are preempted just before disabling irqs. | |
287 | */ | |
288 | if (rcu_preempt_ctrlblk.boost_tasks == NULL && | |
289 | rcu_preempt_ctrlblk.exp_tasks == NULL) { | |
7a11e205 | 290 | local_irq_restore(flags); |
7e8b4c72 PM |
291 | return 0; |
292 | } | |
293 | ||
294 | /* | |
295 | * Preferentially boost tasks blocking expedited grace periods. | |
296 | * This cannot starve the normal grace periods because a second | |
297 | * expedited grace period must boost all blocked tasks, including | |
298 | * those blocking the pre-existing normal grace period. | |
299 | */ | |
300 | if (rcu_preempt_ctrlblk.exp_tasks != NULL) { | |
301 | tb = rcu_preempt_ctrlblk.exp_tasks; | |
302 | RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++); | |
303 | } else { | |
304 | tb = rcu_preempt_ctrlblk.boost_tasks; | |
305 | RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++); | |
306 | } | |
307 | RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); | |
308 | ||
309 | /* | |
310 | * We boost task t by manufacturing an rt_mutex that appears to | |
311 | * be held by task t. We leave a pointer to that rt_mutex where | |
312 | * task t can find it, and task t will release the mutex when it | |
313 | * exits its outermost RCU read-side critical section. Then | |
314 | * simply acquiring this artificial rt_mutex will boost task | |
315 | * t's priority. (Thanks to tglx for suggesting this approach!) | |
316 | */ | |
317 | t = container_of(tb, struct task_struct, rcu_node_entry); | |
24278d14 PM |
318 | rt_mutex_init_proxy_locked(&mtx, t); |
319 | t->rcu_boost_mutex = &mtx; | |
7a11e205 | 320 | local_irq_restore(flags); |
24278d14 | 321 | rt_mutex_lock(&mtx); |
7e8b4c72 PM |
322 | rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ |
323 | ||
4f89b336 PM |
324 | return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL || |
325 | ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL; | |
24278d14 PM |
326 | } |
327 | ||
328 | /* | |
329 | * Check to see if it is now time to start boosting RCU readers blocking | |
330 | * the current grace period, and, if so, tell the rcu_kthread_task to | |
331 | * start boosting them. If there is an expedited boost in progress, | |
332 | * we wait for it to complete. | |
9e571a82 PM |
333 | * |
334 | * If there are no blocked readers blocking the current grace period, | |
335 | * return 0 to let the caller know, otherwise return 1. Note that this | |
336 | * return value is independent of whether or not boosting was done. | |
24278d14 | 337 | */ |
9e571a82 | 338 | static int rcu_initiate_boost(void) |
24278d14 | 339 | { |
7e8b4c72 PM |
340 | if (!rcu_preempt_blocked_readers_cgp() && |
341 | rcu_preempt_ctrlblk.exp_tasks == NULL) { | |
342 | RCU_TRACE(rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++); | |
9e571a82 PM |
343 | return 0; |
344 | } | |
7e8b4c72 PM |
345 | if (rcu_preempt_ctrlblk.exp_tasks != NULL || |
346 | (rcu_preempt_ctrlblk.gp_tasks != NULL && | |
347 | rcu_preempt_ctrlblk.boost_tasks == NULL && | |
348 | ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))) { | |
349 | if (rcu_preempt_ctrlblk.exp_tasks == NULL) | |
350 | rcu_preempt_ctrlblk.boost_tasks = | |
351 | rcu_preempt_ctrlblk.gp_tasks; | |
965a002b | 352 | invoke_rcu_callbacks(); |
c701d5d9 | 353 | } else { |
9e571a82 | 354 | RCU_TRACE(rcu_initiate_boost_trace()); |
c701d5d9 | 355 | } |
9e571a82 | 356 | return 1; |
24278d14 PM |
357 | } |
358 | ||
ddeb7581 | 359 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
24278d14 PM |
360 | |
361 | /* | |
362 | * Do priority-boost accounting for the start of a new grace period. | |
363 | */ | |
364 | static void rcu_preempt_boost_start_gp(void) | |
365 | { | |
366 | rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; | |
24278d14 PM |
367 | } |
368 | ||
369 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
370 | ||
24278d14 | 371 | /* |
9e571a82 PM |
372 | * If there is no RCU priority boosting, we don't initiate boosting, |
373 | * but we do indicate whether there are blocked readers blocking the | |
374 | * current grace period. | |
24278d14 | 375 | */ |
9e571a82 | 376 | static int rcu_initiate_boost(void) |
24278d14 | 377 | { |
9e571a82 | 378 | return rcu_preempt_blocked_readers_cgp(); |
24278d14 PM |
379 | } |
380 | ||
24278d14 PM |
381 | /* |
382 | * If there is no RCU priority boosting, nothing to do at grace-period start. | |
383 | */ | |
384 | static void rcu_preempt_boost_start_gp(void) | |
385 | { | |
386 | } | |
387 | ||
388 | #endif /* else #ifdef CONFIG_RCU_BOOST */ | |
389 | ||
a57eb940 PM |
390 | /* |
391 | * Record a preemptible-RCU quiescent state for the specified CPU. Note | |
392 | * that this just means that the task currently running on the CPU is | |
393 | * in a quiescent state. There might be any number of tasks blocked | |
394 | * while in an RCU read-side critical section. | |
395 | * | |
396 | * Unlike the other rcu_*_qs() functions, callers to this function | |
397 | * must disable irqs in order to protect the assignment to | |
398 | * ->rcu_read_unlock_special. | |
399 | * | |
400 | * Because this is a single-CPU implementation, the only way a grace | |
401 | * period can end is if the CPU is in a quiescent state. The reason is | |
402 | * that a blocked preemptible-RCU reader can exit its critical section | |
403 | * only if the CPU is running it at the time. Therefore, when the | |
404 | * last task blocking the current grace period exits its RCU read-side | |
405 | * critical section, neither the CPU nor blocked tasks will be stopping | |
406 | * the current grace period. (In contrast, SMP implementations | |
407 | * might have CPUs running in RCU read-side critical sections that | |
408 | * block later grace periods -- but this is not possible given only | |
409 | * one CPU.) | |
410 | */ | |
411 | static void rcu_preempt_cpu_qs(void) | |
412 | { | |
413 | /* Record both CPU and task as having responded to current GP. */ | |
414 | rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum; | |
415 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; | |
416 | ||
24278d14 | 417 | /* If there is no GP then there is nothing more to do. */ |
9e571a82 | 418 | if (!rcu_preempt_gp_in_progress()) |
a57eb940 | 419 | return; |
9e571a82 | 420 | /* |
ddeb7581 | 421 | * Check up on boosting. If there are readers blocking the |
9e571a82 PM |
422 | * current grace period, leave. |
423 | */ | |
424 | if (rcu_initiate_boost()) | |
24278d14 | 425 | return; |
a57eb940 PM |
426 | |
427 | /* Advance callbacks. */ | |
428 | rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum; | |
429 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail; | |
430 | rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail; | |
431 | ||
432 | /* If there are no blocked readers, next GP is done instantly. */ | |
433 | if (!rcu_preempt_blocked_readers_any()) | |
434 | rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail; | |
435 | ||
b2c0710c | 436 | /* If there are done callbacks, cause them to be invoked. */ |
a57eb940 | 437 | if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) |
965a002b | 438 | invoke_rcu_callbacks(); |
a57eb940 PM |
439 | } |
440 | ||
441 | /* | |
442 | * Start a new RCU grace period if warranted. Hard irqs must be disabled. | |
443 | */ | |
444 | static void rcu_preempt_start_gp(void) | |
445 | { | |
446 | if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) { | |
447 | ||
448 | /* Official start of GP. */ | |
449 | rcu_preempt_ctrlblk.gpnum++; | |
9e571a82 | 450 | RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); |
a57eb940 PM |
451 | |
452 | /* Any blocked RCU readers block new GP. */ | |
453 | if (rcu_preempt_blocked_readers_any()) | |
454 | rcu_preempt_ctrlblk.gp_tasks = | |
455 | rcu_preempt_ctrlblk.blkd_tasks.next; | |
456 | ||
24278d14 PM |
457 | /* Set up for RCU priority boosting. */ |
458 | rcu_preempt_boost_start_gp(); | |
459 | ||
a57eb940 PM |
460 | /* If there is no running reader, CPU is done with GP. */ |
461 | if (!rcu_preempt_running_reader()) | |
462 | rcu_preempt_cpu_qs(); | |
463 | } | |
464 | } | |
465 | ||
466 | /* | |
467 | * We have entered the scheduler, and the current task might soon be | |
468 | * context-switched away from. If this task is in an RCU read-side | |
469 | * critical section, we will no longer be able to rely on the CPU to | |
470 | * record that fact, so we enqueue the task on the blkd_tasks list. | |
471 | * If the task started after the current grace period began, as recorded | |
472 | * by ->gpcpu, we enqueue at the beginning of the list. Otherwise | |
473 | * before the element referenced by ->gp_tasks (or at the tail if | |
474 | * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element. | |
475 | * The task will dequeue itself when it exits the outermost enclosing | |
476 | * RCU read-side critical section. Therefore, the current grace period | |
477 | * cannot be permitted to complete until the ->gp_tasks pointer becomes | |
478 | * NULL. | |
479 | * | |
480 | * Caller must disable preemption. | |
481 | */ | |
482 | void rcu_preempt_note_context_switch(void) | |
483 | { | |
484 | struct task_struct *t = current; | |
485 | unsigned long flags; | |
486 | ||
487 | local_irq_save(flags); /* must exclude scheduler_tick(). */ | |
26861faf | 488 | if (rcu_preempt_running_reader() > 0 && |
a57eb940 PM |
489 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { |
490 | ||
491 | /* Possibly blocking in an RCU read-side critical section. */ | |
492 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; | |
493 | ||
494 | /* | |
495 | * If this CPU has already checked in, then this task | |
496 | * will hold up the next grace period rather than the | |
497 | * current grace period. Queue the task accordingly. | |
498 | * If the task is queued for the current grace period | |
499 | * (i.e., this CPU has not yet passed through a quiescent | |
500 | * state for the current grace period), then as long | |
501 | * as that task remains queued, the current grace period | |
502 | * cannot end. | |
503 | */ | |
504 | list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks); | |
dd7c4d89 | 505 | if (rcu_cpu_blocking_cur_gp()) |
a57eb940 | 506 | rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry; |
26861faf PM |
507 | } else if (rcu_preempt_running_reader() < 0 && |
508 | t->rcu_read_unlock_special) { | |
509 | /* | |
510 | * Complete exit from RCU read-side critical section on | |
511 | * behalf of preempted instance of __rcu_read_unlock(). | |
512 | */ | |
513 | rcu_read_unlock_special(t); | |
a57eb940 PM |
514 | } |
515 | ||
516 | /* | |
517 | * Either we were not in an RCU read-side critical section to | |
518 | * begin with, or we have now recorded that critical section | |
519 | * globally. Either way, we can now note a quiescent state | |
520 | * for this CPU. Again, if we were in an RCU read-side critical | |
521 | * section, and if that critical section was blocking the current | |
522 | * grace period, then the fact that the task has been enqueued | |
523 | * means that current grace period continues to be blocked. | |
524 | */ | |
525 | rcu_preempt_cpu_qs(); | |
526 | local_irq_restore(flags); | |
527 | } | |
528 | ||
a57eb940 PM |
529 | /* |
530 | * Handle special cases during rcu_read_unlock(), such as needing to | |
531 | * notify RCU core processing or task having blocked during the RCU | |
532 | * read-side critical section. | |
533 | */ | |
2a3fa843 | 534 | void rcu_read_unlock_special(struct task_struct *t) |
a57eb940 PM |
535 | { |
536 | int empty; | |
537 | int empty_exp; | |
538 | unsigned long flags; | |
539 | struct list_head *np; | |
1aa03f11 PM |
540 | #ifdef CONFIG_RCU_BOOST |
541 | struct rt_mutex *rbmp = NULL; | |
542 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
543 | int special; |
544 | ||
545 | /* | |
546 | * NMI handlers cannot block and cannot safely manipulate state. | |
547 | * They therefore cannot possibly be special, so just leave. | |
548 | */ | |
549 | if (in_nmi()) | |
550 | return; | |
551 | ||
552 | local_irq_save(flags); | |
553 | ||
554 | /* | |
555 | * If RCU core is waiting for this CPU to exit critical section, | |
556 | * let it know that we have done so. | |
557 | */ | |
558 | special = t->rcu_read_unlock_special; | |
559 | if (special & RCU_READ_UNLOCK_NEED_QS) | |
560 | rcu_preempt_cpu_qs(); | |
561 | ||
562 | /* Hardware IRQ handlers cannot block. */ | |
8762705a | 563 | if (in_irq() || in_serving_softirq()) { |
a57eb940 PM |
564 | local_irq_restore(flags); |
565 | return; | |
566 | } | |
567 | ||
568 | /* Clean up if blocked during RCU read-side critical section. */ | |
569 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
570 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
571 | ||
572 | /* | |
573 | * Remove this task from the ->blkd_tasks list and adjust | |
574 | * any pointers that might have been referencing it. | |
575 | */ | |
576 | empty = !rcu_preempt_blocked_readers_cgp(); | |
577 | empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL; | |
24278d14 | 578 | np = rcu_next_node_entry(t); |
ddeb7581 | 579 | list_del_init(&t->rcu_node_entry); |
a57eb940 PM |
580 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks) |
581 | rcu_preempt_ctrlblk.gp_tasks = np; | |
582 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks) | |
583 | rcu_preempt_ctrlblk.exp_tasks = np; | |
24278d14 PM |
584 | #ifdef CONFIG_RCU_BOOST |
585 | if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks) | |
586 | rcu_preempt_ctrlblk.boost_tasks = np; | |
587 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
588 | |
589 | /* | |
590 | * If this was the last task on the current list, and if | |
591 | * we aren't waiting on the CPU, report the quiescent state | |
592 | * and start a new grace period if needed. | |
593 | */ | |
594 | if (!empty && !rcu_preempt_blocked_readers_cgp()) { | |
595 | rcu_preempt_cpu_qs(); | |
596 | rcu_preempt_start_gp(); | |
597 | } | |
598 | ||
599 | /* | |
600 | * If this was the last task on the expedited lists, | |
601 | * then we need wake up the waiting task. | |
602 | */ | |
603 | if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL) | |
604 | rcu_report_exp_done(); | |
605 | } | |
24278d14 PM |
606 | #ifdef CONFIG_RCU_BOOST |
607 | /* Unboost self if was boosted. */ | |
1aa03f11 PM |
608 | if (t->rcu_boost_mutex != NULL) { |
609 | rbmp = t->rcu_boost_mutex; | |
24278d14 | 610 | t->rcu_boost_mutex = NULL; |
1aa03f11 | 611 | rt_mutex_unlock(rbmp); |
24278d14 PM |
612 | } |
613 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
a57eb940 PM |
614 | local_irq_restore(flags); |
615 | } | |
616 | ||
a57eb940 PM |
617 | /* |
618 | * Check for a quiescent state from the current CPU. When a task blocks, | |
619 | * the task is recorded in the rcu_preempt_ctrlblk structure, which is | |
620 | * checked elsewhere. This is called from the scheduling-clock interrupt. | |
621 | * | |
622 | * Caller must disable hard irqs. | |
623 | */ | |
624 | static void rcu_preempt_check_callbacks(void) | |
625 | { | |
626 | struct task_struct *t = current; | |
627 | ||
dd7c4d89 PM |
628 | if (rcu_preempt_gp_in_progress() && |
629 | (!rcu_preempt_running_reader() || | |
630 | !rcu_cpu_blocking_cur_gp())) | |
a57eb940 PM |
631 | rcu_preempt_cpu_qs(); |
632 | if (&rcu_preempt_ctrlblk.rcb.rcucblist != | |
633 | rcu_preempt_ctrlblk.rcb.donetail) | |
965a002b | 634 | invoke_rcu_callbacks(); |
dd7c4d89 PM |
635 | if (rcu_preempt_gp_in_progress() && |
636 | rcu_cpu_blocking_cur_gp() && | |
26861faf | 637 | rcu_preempt_running_reader() > 0) |
a57eb940 PM |
638 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
639 | } | |
640 | ||
641 | /* | |
642 | * TINY_PREEMPT_RCU has an extra callback-list tail pointer to | |
b2c0710c | 643 | * update, so this is invoked from rcu_process_callbacks() to |
a57eb940 PM |
644 | * handle that case. Of course, it is invoked for all flavors of |
645 | * RCU, but RCU callbacks can appear only on one of the lists, and | |
646 | * neither ->nexttail nor ->donetail can possibly be NULL, so there | |
647 | * is no need for an explicit check. | |
648 | */ | |
649 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
650 | { | |
651 | if (rcu_preempt_ctrlblk.nexttail == rcp->donetail) | |
652 | rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist; | |
653 | } | |
654 | ||
655 | /* | |
656 | * Process callbacks for preemptible RCU. | |
657 | */ | |
658 | static void rcu_preempt_process_callbacks(void) | |
659 | { | |
965a002b | 660 | __rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); |
a57eb940 PM |
661 | } |
662 | ||
663 | /* | |
664 | * Queue a preemptible -RCU callback for invocation after a grace period. | |
665 | */ | |
666 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
667 | { | |
668 | unsigned long flags; | |
669 | ||
670 | debug_rcu_head_queue(head); | |
671 | head->func = func; | |
672 | head->next = NULL; | |
673 | ||
674 | local_irq_save(flags); | |
675 | *rcu_preempt_ctrlblk.nexttail = head; | |
676 | rcu_preempt_ctrlblk.nexttail = &head->next; | |
9e571a82 | 677 | RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++); |
a57eb940 PM |
678 | rcu_preempt_start_gp(); /* checks to see if GP needed. */ |
679 | local_irq_restore(flags); | |
680 | } | |
681 | EXPORT_SYMBOL_GPL(call_rcu); | |
682 | ||
a57eb940 PM |
683 | /* |
684 | * synchronize_rcu - wait until a grace period has elapsed. | |
685 | * | |
686 | * Control will return to the caller some time after a full grace | |
687 | * period has elapsed, in other words after all currently executing RCU | |
688 | * read-side critical sections have completed. RCU read-side critical | |
689 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), | |
690 | * and may be nested. | |
691 | */ | |
692 | void synchronize_rcu(void) | |
693 | { | |
fe15d706 PM |
694 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
695 | !lock_is_held(&rcu_lock_map) && | |
696 | !lock_is_held(&rcu_sched_lock_map), | |
697 | "Illegal synchronize_rcu() in RCU read-side critical section"); | |
698 | ||
a57eb940 PM |
699 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
700 | if (!rcu_scheduler_active) | |
701 | return; | |
702 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
703 | ||
704 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
705 | if (!rcu_preempt_blocked_readers_any()) | |
706 | return; | |
707 | ||
708 | /* Once we get past the fastpath checks, same code as rcu_barrier(). */ | |
709 | rcu_barrier(); | |
710 | } | |
711 | EXPORT_SYMBOL_GPL(synchronize_rcu); | |
712 | ||
713 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); | |
714 | static unsigned long sync_rcu_preempt_exp_count; | |
715 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); | |
716 | ||
717 | /* | |
718 | * Return non-zero if there are any tasks in RCU read-side critical | |
719 | * sections blocking the current preemptible-RCU expedited grace period. | |
720 | * If there is no preemptible-RCU expedited grace period currently in | |
721 | * progress, returns zero unconditionally. | |
722 | */ | |
723 | static int rcu_preempted_readers_exp(void) | |
724 | { | |
725 | return rcu_preempt_ctrlblk.exp_tasks != NULL; | |
726 | } | |
727 | ||
728 | /* | |
729 | * Report the exit from RCU read-side critical section for the last task | |
730 | * that queued itself during or before the current expedited preemptible-RCU | |
731 | * grace period. | |
732 | */ | |
733 | static void rcu_report_exp_done(void) | |
734 | { | |
735 | wake_up(&sync_rcu_preempt_exp_wq); | |
736 | } | |
737 | ||
738 | /* | |
739 | * Wait for an rcu-preempt grace period, but expedite it. The basic idea | |
740 | * is to rely in the fact that there is but one CPU, and that it is | |
741 | * illegal for a task to invoke synchronize_rcu_expedited() while in a | |
742 | * preemptible-RCU read-side critical section. Therefore, any such | |
743 | * critical sections must correspond to blocked tasks, which must therefore | |
744 | * be on the ->blkd_tasks list. So just record the current head of the | |
745 | * list in the ->exp_tasks pointer, and wait for all tasks including and | |
746 | * after the task pointed to by ->exp_tasks to drain. | |
747 | */ | |
748 | void synchronize_rcu_expedited(void) | |
749 | { | |
750 | unsigned long flags; | |
751 | struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk; | |
752 | unsigned long snap; | |
753 | ||
754 | barrier(); /* ensure prior action seen before grace period. */ | |
755 | ||
756 | WARN_ON_ONCE(rcu_preempt_running_reader()); | |
757 | ||
758 | /* | |
759 | * Acquire lock so that there is only one preemptible RCU grace | |
760 | * period in flight. Of course, if someone does the expedited | |
761 | * grace period for us while we are acquiring the lock, just leave. | |
762 | */ | |
763 | snap = sync_rcu_preempt_exp_count + 1; | |
764 | mutex_lock(&sync_rcu_preempt_exp_mutex); | |
765 | if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count)) | |
766 | goto unlock_mb_ret; /* Others did our work for us. */ | |
767 | ||
768 | local_irq_save(flags); | |
769 | ||
770 | /* | |
771 | * All RCU readers have to already be on blkd_tasks because | |
772 | * we cannot legally be executing in an RCU read-side critical | |
773 | * section. | |
774 | */ | |
775 | ||
776 | /* Snapshot current head of ->blkd_tasks list. */ | |
777 | rpcp->exp_tasks = rpcp->blkd_tasks.next; | |
778 | if (rpcp->exp_tasks == &rpcp->blkd_tasks) | |
779 | rpcp->exp_tasks = NULL; | |
a57eb940 PM |
780 | |
781 | /* Wait for tail of ->blkd_tasks list to drain. */ | |
c701d5d9 | 782 | if (!rcu_preempted_readers_exp()) { |
7e8b4c72 | 783 | local_irq_restore(flags); |
c701d5d9 | 784 | } else { |
7e8b4c72 PM |
785 | rcu_initiate_boost(); |
786 | local_irq_restore(flags); | |
a57eb940 PM |
787 | wait_event(sync_rcu_preempt_exp_wq, |
788 | !rcu_preempted_readers_exp()); | |
7e8b4c72 | 789 | } |
a57eb940 PM |
790 | |
791 | /* Clean up and exit. */ | |
792 | barrier(); /* ensure expedited GP seen before counter increment. */ | |
793 | sync_rcu_preempt_exp_count++; | |
794 | unlock_mb_ret: | |
795 | mutex_unlock(&sync_rcu_preempt_exp_mutex); | |
796 | barrier(); /* ensure subsequent action seen after grace period. */ | |
797 | } | |
798 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
799 | ||
800 | /* | |
801 | * Does preemptible RCU need the CPU to stay out of dynticks mode? | |
802 | */ | |
803 | int rcu_preempt_needs_cpu(void) | |
804 | { | |
a57eb940 PM |
805 | return rcu_preempt_ctrlblk.rcb.rcucblist != NULL; |
806 | } | |
807 | ||
a57eb940 PM |
808 | #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */ |
809 | ||
9e571a82 PM |
810 | #ifdef CONFIG_RCU_TRACE |
811 | ||
812 | /* | |
813 | * Because preemptible RCU does not exist, it is not necessary to | |
814 | * dump out its statistics. | |
815 | */ | |
816 | static void show_tiny_preempt_stats(struct seq_file *m) | |
817 | { | |
818 | } | |
819 | ||
820 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
821 | ||
a57eb940 PM |
822 | /* |
823 | * Because preemptible RCU does not exist, it never has any callbacks | |
824 | * to check. | |
825 | */ | |
826 | static void rcu_preempt_check_callbacks(void) | |
827 | { | |
828 | } | |
829 | ||
830 | /* | |
831 | * Because preemptible RCU does not exist, it never has any callbacks | |
832 | * to remove. | |
833 | */ | |
834 | static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) | |
835 | { | |
836 | } | |
837 | ||
838 | /* | |
839 | * Because preemptible RCU does not exist, it never has any callbacks | |
840 | * to process. | |
841 | */ | |
842 | static void rcu_preempt_process_callbacks(void) | |
843 | { | |
844 | } | |
845 | ||
846 | #endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */ | |
847 | ||
965a002b PM |
848 | #ifdef CONFIG_RCU_BOOST |
849 | ||
850 | /* | |
851 | * Wake up rcu_kthread() to process callbacks now eligible for invocation | |
852 | * or to boost readers. | |
853 | */ | |
854 | static void invoke_rcu_callbacks(void) | |
855 | { | |
856 | have_rcu_kthread_work = 1; | |
768dfffd PM |
857 | if (rcu_kthread_task != NULL) |
858 | wake_up(&rcu_kthread_wq); | |
965a002b PM |
859 | } |
860 | ||
4968c300 PM |
861 | #ifdef CONFIG_RCU_TRACE |
862 | ||
863 | /* | |
864 | * Is the current CPU running the RCU-callbacks kthread? | |
865 | * Caller must have preemption disabled. | |
866 | */ | |
867 | static bool rcu_is_callbacks_kthread(void) | |
868 | { | |
869 | return rcu_kthread_task == current; | |
870 | } | |
871 | ||
872 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
873 | ||
965a002b PM |
874 | /* |
875 | * This kthread invokes RCU callbacks whose grace periods have | |
876 | * elapsed. It is awakened as needed, and takes the place of the | |
877 | * RCU_SOFTIRQ that is used for this purpose when boosting is disabled. | |
878 | * This is a kthread, but it is never stopped, at least not until | |
879 | * the system goes down. | |
880 | */ | |
881 | static int rcu_kthread(void *arg) | |
882 | { | |
883 | unsigned long work; | |
884 | unsigned long morework; | |
885 | unsigned long flags; | |
886 | ||
887 | for (;;) { | |
888 | wait_event_interruptible(rcu_kthread_wq, | |
889 | have_rcu_kthread_work != 0); | |
890 | morework = rcu_boost(); | |
891 | local_irq_save(flags); | |
892 | work = have_rcu_kthread_work; | |
893 | have_rcu_kthread_work = morework; | |
894 | local_irq_restore(flags); | |
895 | if (work) | |
896 | rcu_process_callbacks(NULL); | |
897 | schedule_timeout_interruptible(1); /* Leave CPU for others. */ | |
898 | } | |
899 | ||
900 | return 0; /* Not reached, but needed to shut gcc up. */ | |
901 | } | |
902 | ||
903 | /* | |
904 | * Spawn the kthread that invokes RCU callbacks. | |
905 | */ | |
906 | static int __init rcu_spawn_kthreads(void) | |
907 | { | |
908 | struct sched_param sp; | |
909 | ||
910 | rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread"); | |
911 | sp.sched_priority = RCU_BOOST_PRIO; | |
912 | sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp); | |
913 | return 0; | |
914 | } | |
915 | early_initcall(rcu_spawn_kthreads); | |
916 | ||
917 | #else /* #ifdef CONFIG_RCU_BOOST */ | |
918 | ||
768dfffd PM |
919 | /* Hold off callback invocation until early_initcall() time. */ |
920 | static int rcu_scheduler_fully_active __read_mostly; | |
921 | ||
965a002b PM |
922 | /* |
923 | * Start up softirq processing of callbacks. | |
924 | */ | |
925 | void invoke_rcu_callbacks(void) | |
926 | { | |
768dfffd PM |
927 | if (rcu_scheduler_fully_active) |
928 | raise_softirq(RCU_SOFTIRQ); | |
965a002b PM |
929 | } |
930 | ||
4968c300 PM |
931 | #ifdef CONFIG_RCU_TRACE |
932 | ||
933 | /* | |
934 | * There is no callback kthread, so this thread is never it. | |
935 | */ | |
936 | static bool rcu_is_callbacks_kthread(void) | |
937 | { | |
938 | return false; | |
939 | } | |
940 | ||
941 | #endif /* #ifdef CONFIG_RCU_TRACE */ | |
942 | ||
768dfffd | 943 | static int __init rcu_scheduler_really_started(void) |
965a002b | 944 | { |
768dfffd | 945 | rcu_scheduler_fully_active = 1; |
965a002b | 946 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
768dfffd PM |
947 | raise_softirq(RCU_SOFTIRQ); /* Invoke any callbacks from early boot. */ |
948 | return 0; | |
965a002b | 949 | } |
768dfffd | 950 | early_initcall(rcu_scheduler_really_started); |
965a002b PM |
951 | |
952 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ | |
953 | ||
bbad9379 | 954 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
bbad9379 PM |
955 | #include <linux/kernel_stat.h> |
956 | ||
957 | /* | |
958 | * During boot, we forgive RCU lockdep issues. After this function is | |
959 | * invoked, we start taking RCU lockdep issues seriously. | |
960 | */ | |
b2c0710c | 961 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
962 | { |
963 | WARN_ON(nr_context_switches() > 0); | |
964 | rcu_scheduler_active = 1; | |
965 | } | |
966 | ||
967 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 | 968 | |
9e571a82 PM |
969 | #ifdef CONFIG_RCU_TRACE |
970 | ||
971 | #ifdef CONFIG_RCU_BOOST | |
972 | ||
973 | static void rcu_initiate_boost_trace(void) | |
974 | { | |
7e8b4c72 PM |
975 | if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) |
976 | rcu_preempt_ctrlblk.n_balk_blkd_tasks++; | |
977 | else if (rcu_preempt_ctrlblk.gp_tasks == NULL && | |
978 | rcu_preempt_ctrlblk.exp_tasks == NULL) | |
979 | rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++; | |
9e571a82 | 980 | else if (rcu_preempt_ctrlblk.boost_tasks != NULL) |
7e8b4c72 | 981 | rcu_preempt_ctrlblk.n_balk_boost_tasks++; |
9e571a82 | 982 | else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) |
7e8b4c72 | 983 | rcu_preempt_ctrlblk.n_balk_notyet++; |
9e571a82 | 984 | else |
7e8b4c72 | 985 | rcu_preempt_ctrlblk.n_balk_nos++; |
9e571a82 PM |
986 | } |
987 | ||
988 | #endif /* #ifdef CONFIG_RCU_BOOST */ | |
989 | ||
990 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) | |
991 | { | |
992 | unsigned long flags; | |
993 | ||
7a11e205 | 994 | local_irq_save(flags); |
9e571a82 | 995 | rcp->qlen -= n; |
7a11e205 | 996 | local_irq_restore(flags); |
9e571a82 PM |
997 | } |
998 | ||
999 | /* | |
1000 | * Dump statistics for TINY_RCU, such as they are. | |
1001 | */ | |
1002 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
1003 | { | |
1004 | show_tiny_preempt_stats(m); | |
1005 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); | |
1006 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
1007 | return 0; | |
1008 | } | |
1009 | ||
1010 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
1011 | { | |
1012 | return single_open(file, show_tiny_stats, NULL); | |
1013 | } | |
1014 | ||
1015 | static const struct file_operations show_tiny_stats_fops = { | |
1016 | .owner = THIS_MODULE, | |
1017 | .open = show_tiny_stats_open, | |
1018 | .read = seq_read, | |
1019 | .llseek = seq_lseek, | |
1020 | .release = single_release, | |
1021 | }; | |
1022 | ||
1023 | static struct dentry *rcudir; | |
1024 | ||
1025 | static int __init rcutiny_trace_init(void) | |
1026 | { | |
1027 | struct dentry *retval; | |
1028 | ||
1029 | rcudir = debugfs_create_dir("rcu", NULL); | |
1030 | if (!rcudir) | |
1031 | goto free_out; | |
1032 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
1033 | NULL, &show_tiny_stats_fops); | |
1034 | if (!retval) | |
1035 | goto free_out; | |
1036 | return 0; | |
1037 | free_out: | |
1038 | debugfs_remove_recursive(rcudir); | |
1039 | return 1; | |
1040 | } | |
1041 | ||
1042 | static void __exit rcutiny_trace_cleanup(void) | |
1043 | { | |
1044 | debugfs_remove_recursive(rcudir); | |
1045 | } | |
1046 | ||
1047 | module_init(rcutiny_trace_init); | |
1048 | module_exit(rcutiny_trace_cleanup); | |
1049 | ||
1050 | MODULE_AUTHOR("Paul E. McKenney"); | |
1051 | MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); | |
1052 | MODULE_LICENSE("GPL"); | |
1053 | ||
1054 | #endif /* #ifdef CONFIG_RCU_TRACE */ |