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f41d911f PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) | |
3 | * Internal non-public definitions that provide either classic | |
4 | * or preemptable semantics. | |
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 | * | |
20 | * Copyright Red Hat, 2009 | |
21 | * Copyright IBM Corporation, 2009 | |
22 | * | |
23 | * Author: Ingo Molnar <mingo@elte.hu> | |
24 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
25 | */ | |
26 | ||
27 | ||
28 | #ifdef CONFIG_TREE_PREEMPT_RCU | |
29 | ||
30 | struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state); | |
31 | DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); | |
32 | ||
33 | /* | |
34 | * Tell them what RCU they are running. | |
35 | */ | |
dbe01350 | 36 | static void rcu_bootup_announce(void) |
f41d911f PM |
37 | { |
38 | printk(KERN_INFO | |
39 | "Experimental preemptable hierarchical RCU implementation.\n"); | |
40 | } | |
41 | ||
42 | /* | |
43 | * Return the number of RCU-preempt batches processed thus far | |
44 | * for debug and statistics. | |
45 | */ | |
46 | long rcu_batches_completed_preempt(void) | |
47 | { | |
48 | return rcu_preempt_state.completed; | |
49 | } | |
50 | EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); | |
51 | ||
52 | /* | |
53 | * Return the number of RCU batches processed thus far for debug & stats. | |
54 | */ | |
55 | long rcu_batches_completed(void) | |
56 | { | |
57 | return rcu_batches_completed_preempt(); | |
58 | } | |
59 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
60 | ||
61 | /* | |
62 | * Record a preemptable-RCU quiescent state for the specified CPU. Note | |
63 | * that this just means that the task currently running on the CPU is | |
64 | * not in a quiescent state. There might be any number of tasks blocked | |
65 | * while in an RCU read-side critical section. | |
66 | */ | |
c3422bea | 67 | static void rcu_preempt_qs(int cpu) |
f41d911f PM |
68 | { |
69 | struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); | |
f41d911f | 70 | rdp->passed_quiesc_completed = rdp->completed; |
c3422bea PM |
71 | barrier(); |
72 | rdp->passed_quiesc = 1; | |
f41d911f PM |
73 | } |
74 | ||
75 | /* | |
c3422bea PM |
76 | * We have entered the scheduler, and the current task might soon be |
77 | * context-switched away from. If this task is in an RCU read-side | |
78 | * critical section, we will no longer be able to rely on the CPU to | |
79 | * record that fact, so we enqueue the task on the appropriate entry | |
80 | * of the blocked_tasks[] array. The task will dequeue itself when | |
81 | * it exits the outermost enclosing RCU read-side critical section. | |
82 | * Therefore, the current grace period cannot be permitted to complete | |
83 | * until the blocked_tasks[] entry indexed by the low-order bit of | |
84 | * rnp->gpnum empties. | |
85 | * | |
86 | * Caller must disable preemption. | |
f41d911f | 87 | */ |
c3422bea | 88 | static void rcu_preempt_note_context_switch(int cpu) |
f41d911f PM |
89 | { |
90 | struct task_struct *t = current; | |
c3422bea | 91 | unsigned long flags; |
f41d911f PM |
92 | int phase; |
93 | struct rcu_data *rdp; | |
94 | struct rcu_node *rnp; | |
95 | ||
96 | if (t->rcu_read_lock_nesting && | |
97 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { | |
98 | ||
99 | /* Possibly blocking in an RCU read-side critical section. */ | |
100 | rdp = rcu_preempt_state.rda[cpu]; | |
101 | rnp = rdp->mynode; | |
c3422bea | 102 | spin_lock_irqsave(&rnp->lock, flags); |
f41d911f | 103 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; |
86848966 | 104 | t->rcu_blocked_node = rnp; |
f41d911f PM |
105 | |
106 | /* | |
107 | * If this CPU has already checked in, then this task | |
108 | * will hold up the next grace period rather than the | |
109 | * current grace period. Queue the task accordingly. | |
110 | * If the task is queued for the current grace period | |
111 | * (i.e., this CPU has not yet passed through a quiescent | |
112 | * state for the current grace period), then as long | |
113 | * as that task remains queued, the current grace period | |
114 | * cannot end. | |
b0e165c0 PM |
115 | * |
116 | * But first, note that the current CPU must still be | |
117 | * on line! | |
f41d911f | 118 | */ |
b0e165c0 | 119 | WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); |
e7d8842e PM |
120 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
121 | phase = (rnp->gpnum + !(rnp->qsmask & rdp->grpmask)) & 0x1; | |
f41d911f | 122 | list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]); |
c3422bea | 123 | spin_unlock_irqrestore(&rnp->lock, flags); |
f41d911f PM |
124 | } |
125 | ||
126 | /* | |
127 | * Either we were not in an RCU read-side critical section to | |
128 | * begin with, or we have now recorded that critical section | |
129 | * globally. Either way, we can now note a quiescent state | |
130 | * for this CPU. Again, if we were in an RCU read-side critical | |
131 | * section, and if that critical section was blocking the current | |
132 | * grace period, then the fact that the task has been enqueued | |
133 | * means that we continue to block the current grace period. | |
134 | */ | |
c3422bea | 135 | rcu_preempt_qs(cpu); |
e7d8842e | 136 | local_irq_save(flags); |
c3422bea | 137 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; |
e7d8842e | 138 | local_irq_restore(flags); |
f41d911f PM |
139 | } |
140 | ||
141 | /* | |
142 | * Tree-preemptable RCU implementation for rcu_read_lock(). | |
143 | * Just increment ->rcu_read_lock_nesting, shared state will be updated | |
144 | * if we block. | |
145 | */ | |
146 | void __rcu_read_lock(void) | |
147 | { | |
148 | ACCESS_ONCE(current->rcu_read_lock_nesting)++; | |
149 | barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ | |
150 | } | |
151 | EXPORT_SYMBOL_GPL(__rcu_read_lock); | |
152 | ||
fc2219d4 PM |
153 | /* |
154 | * Check for preempted RCU readers blocking the current grace period | |
155 | * for the specified rcu_node structure. If the caller needs a reliable | |
156 | * answer, it must hold the rcu_node's ->lock. | |
157 | */ | |
158 | static int rcu_preempted_readers(struct rcu_node *rnp) | |
159 | { | |
160 | return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); | |
161 | } | |
162 | ||
f41d911f PM |
163 | static void rcu_read_unlock_special(struct task_struct *t) |
164 | { | |
165 | int empty; | |
166 | unsigned long flags; | |
167 | unsigned long mask; | |
168 | struct rcu_node *rnp; | |
169 | int special; | |
170 | ||
171 | /* NMI handlers cannot block and cannot safely manipulate state. */ | |
172 | if (in_nmi()) | |
173 | return; | |
174 | ||
175 | local_irq_save(flags); | |
176 | ||
177 | /* | |
178 | * If RCU core is waiting for this CPU to exit critical section, | |
179 | * let it know that we have done so. | |
180 | */ | |
181 | special = t->rcu_read_unlock_special; | |
182 | if (special & RCU_READ_UNLOCK_NEED_QS) { | |
183 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; | |
c3422bea | 184 | rcu_preempt_qs(smp_processor_id()); |
f41d911f PM |
185 | } |
186 | ||
187 | /* Hardware IRQ handlers cannot block. */ | |
188 | if (in_irq()) { | |
189 | local_irq_restore(flags); | |
190 | return; | |
191 | } | |
192 | ||
193 | /* Clean up if blocked during RCU read-side critical section. */ | |
194 | if (special & RCU_READ_UNLOCK_BLOCKED) { | |
195 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; | |
196 | ||
dd5d19ba PM |
197 | /* |
198 | * Remove this task from the list it blocked on. The | |
199 | * task can migrate while we acquire the lock, but at | |
200 | * most one time. So at most two passes through loop. | |
201 | */ | |
202 | for (;;) { | |
86848966 | 203 | rnp = t->rcu_blocked_node; |
e7d8842e | 204 | spin_lock(&rnp->lock); /* irqs already disabled. */ |
86848966 | 205 | if (rnp == t->rcu_blocked_node) |
dd5d19ba | 206 | break; |
e7d8842e | 207 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
dd5d19ba | 208 | } |
fc2219d4 | 209 | empty = !rcu_preempted_readers(rnp); |
f41d911f | 210 | list_del_init(&t->rcu_node_entry); |
dd5d19ba | 211 | t->rcu_blocked_node = NULL; |
f41d911f PM |
212 | |
213 | /* | |
214 | * If this was the last task on the current list, and if | |
215 | * we aren't waiting on any CPUs, report the quiescent state. | |
216 | * Note that both cpu_quiet_msk_finish() and cpu_quiet_msk() | |
217 | * drop rnp->lock and restore irq. | |
218 | */ | |
219 | if (!empty && rnp->qsmask == 0 && | |
fc2219d4 | 220 | !rcu_preempted_readers(rnp)) { |
28ecd580 PM |
221 | struct rcu_node *rnp_p; |
222 | ||
f41d911f PM |
223 | if (rnp->parent == NULL) { |
224 | /* Only one rcu_node in the tree. */ | |
225 | cpu_quiet_msk_finish(&rcu_preempt_state, flags); | |
226 | return; | |
227 | } | |
228 | /* Report up the rest of the hierarchy. */ | |
229 | mask = rnp->grpmask; | |
230 | spin_unlock_irqrestore(&rnp->lock, flags); | |
28ecd580 PM |
231 | rnp_p = rnp->parent; |
232 | spin_lock_irqsave(&rnp_p->lock, flags); | |
233 | WARN_ON_ONCE(rnp->qsmask); | |
234 | cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags); | |
f41d911f PM |
235 | return; |
236 | } | |
237 | spin_unlock(&rnp->lock); | |
238 | } | |
239 | local_irq_restore(flags); | |
240 | } | |
241 | ||
242 | /* | |
243 | * Tree-preemptable RCU implementation for rcu_read_unlock(). | |
244 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost | |
245 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then | |
246 | * invoke rcu_read_unlock_special() to clean up after a context switch | |
247 | * in an RCU read-side critical section and other special cases. | |
248 | */ | |
249 | void __rcu_read_unlock(void) | |
250 | { | |
251 | struct task_struct *t = current; | |
252 | ||
253 | barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ | |
254 | if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 && | |
255 | unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) | |
256 | rcu_read_unlock_special(t); | |
257 | } | |
258 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); | |
259 | ||
260 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
261 | ||
262 | /* | |
263 | * Scan the current list of tasks blocked within RCU read-side critical | |
264 | * sections, printing out the tid of each. | |
265 | */ | |
266 | static void rcu_print_task_stall(struct rcu_node *rnp) | |
267 | { | |
268 | unsigned long flags; | |
269 | struct list_head *lp; | |
fc2219d4 | 270 | int phase; |
f41d911f PM |
271 | struct task_struct *t; |
272 | ||
fc2219d4 | 273 | if (rcu_preempted_readers(rnp)) { |
f41d911f | 274 | spin_lock_irqsave(&rnp->lock, flags); |
fc2219d4 | 275 | phase = rnp->gpnum & 0x1; |
f41d911f PM |
276 | lp = &rnp->blocked_tasks[phase]; |
277 | list_for_each_entry(t, lp, rcu_node_entry) | |
278 | printk(" P%d", t->pid); | |
279 | spin_unlock_irqrestore(&rnp->lock, flags); | |
280 | } | |
281 | } | |
282 | ||
283 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
284 | ||
b0e165c0 PM |
285 | /* |
286 | * Check that the list of blocked tasks for the newly completed grace | |
287 | * period is in fact empty. It is a serious bug to complete a grace | |
288 | * period that still has RCU readers blocked! This function must be | |
289 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock | |
290 | * must be held by the caller. | |
291 | */ | |
292 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
293 | { | |
fc2219d4 | 294 | WARN_ON_ONCE(rcu_preempted_readers(rnp)); |
28ecd580 | 295 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
296 | } |
297 | ||
33f76148 PM |
298 | #ifdef CONFIG_HOTPLUG_CPU |
299 | ||
dd5d19ba PM |
300 | /* |
301 | * Handle tasklist migration for case in which all CPUs covered by the | |
302 | * specified rcu_node have gone offline. Move them up to the root | |
303 | * rcu_node. The reason for not just moving them to the immediate | |
304 | * parent is to remove the need for rcu_read_unlock_special() to | |
305 | * make more than two attempts to acquire the target rcu_node's lock. | |
306 | * | |
237c80c5 PM |
307 | * Returns 1 if there was previously a task blocking the current grace |
308 | * period on the specified rcu_node structure. | |
309 | * | |
dd5d19ba PM |
310 | * The caller must hold rnp->lock with irqs disabled. |
311 | */ | |
237c80c5 PM |
312 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
313 | struct rcu_node *rnp, | |
314 | struct rcu_data *rdp) | |
dd5d19ba PM |
315 | { |
316 | int i; | |
317 | struct list_head *lp; | |
318 | struct list_head *lp_root; | |
237c80c5 | 319 | int retval = rcu_preempted_readers(rnp); |
dd5d19ba PM |
320 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
321 | struct task_struct *tp; | |
322 | ||
86848966 PM |
323 | if (rnp == rnp_root) { |
324 | WARN_ONCE(1, "Last CPU thought to be offlined?"); | |
237c80c5 | 325 | return 0; /* Shouldn't happen: at least one CPU online. */ |
86848966 | 326 | } |
28ecd580 PM |
327 | WARN_ON_ONCE(rnp != rdp->mynode && |
328 | (!list_empty(&rnp->blocked_tasks[0]) || | |
329 | !list_empty(&rnp->blocked_tasks[1]))); | |
dd5d19ba PM |
330 | |
331 | /* | |
332 | * Move tasks up to root rcu_node. Rely on the fact that the | |
333 | * root rcu_node can be at most one ahead of the rest of the | |
334 | * rcu_nodes in terms of gp_num value. This fact allows us to | |
335 | * move the blocked_tasks[] array directly, element by element. | |
336 | */ | |
337 | for (i = 0; i < 2; i++) { | |
338 | lp = &rnp->blocked_tasks[i]; | |
339 | lp_root = &rnp_root->blocked_tasks[i]; | |
340 | while (!list_empty(lp)) { | |
341 | tp = list_entry(lp->next, typeof(*tp), rcu_node_entry); | |
342 | spin_lock(&rnp_root->lock); /* irqs already disabled */ | |
343 | list_del(&tp->rcu_node_entry); | |
344 | tp->rcu_blocked_node = rnp_root; | |
345 | list_add(&tp->rcu_node_entry, lp_root); | |
346 | spin_unlock(&rnp_root->lock); /* irqs remain disabled */ | |
347 | } | |
348 | } | |
237c80c5 PM |
349 | |
350 | return retval; | |
dd5d19ba PM |
351 | } |
352 | ||
33f76148 PM |
353 | /* |
354 | * Do CPU-offline processing for preemptable RCU. | |
355 | */ | |
356 | static void rcu_preempt_offline_cpu(int cpu) | |
357 | { | |
358 | __rcu_offline_cpu(cpu, &rcu_preempt_state); | |
359 | } | |
360 | ||
361 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
362 | ||
f41d911f PM |
363 | /* |
364 | * Check for a quiescent state from the current CPU. When a task blocks, | |
365 | * the task is recorded in the corresponding CPU's rcu_node structure, | |
366 | * which is checked elsewhere. | |
367 | * | |
368 | * Caller must disable hard irqs. | |
369 | */ | |
370 | static void rcu_preempt_check_callbacks(int cpu) | |
371 | { | |
372 | struct task_struct *t = current; | |
373 | ||
374 | if (t->rcu_read_lock_nesting == 0) { | |
c3422bea PM |
375 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; |
376 | rcu_preempt_qs(cpu); | |
f41d911f PM |
377 | return; |
378 | } | |
a71fca58 | 379 | if (per_cpu(rcu_preempt_data, cpu).qs_pending) |
c3422bea | 380 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
f41d911f PM |
381 | } |
382 | ||
383 | /* | |
384 | * Process callbacks for preemptable RCU. | |
385 | */ | |
386 | static void rcu_preempt_process_callbacks(void) | |
387 | { | |
388 | __rcu_process_callbacks(&rcu_preempt_state, | |
389 | &__get_cpu_var(rcu_preempt_data)); | |
390 | } | |
391 | ||
392 | /* | |
393 | * Queue a preemptable-RCU callback for invocation after a grace period. | |
394 | */ | |
395 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
396 | { | |
397 | __call_rcu(head, func, &rcu_preempt_state); | |
398 | } | |
399 | EXPORT_SYMBOL_GPL(call_rcu); | |
400 | ||
019129d5 PM |
401 | /* |
402 | * Wait for an rcu-preempt grace period. We are supposed to expedite the | |
403 | * grace period, but this is the crude slow compatability hack, so just | |
404 | * invoke synchronize_rcu(). | |
405 | */ | |
406 | void synchronize_rcu_expedited(void) | |
407 | { | |
408 | synchronize_rcu(); | |
409 | } | |
410 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
411 | ||
f41d911f PM |
412 | /* |
413 | * Check to see if there is any immediate preemptable-RCU-related work | |
414 | * to be done. | |
415 | */ | |
416 | static int rcu_preempt_pending(int cpu) | |
417 | { | |
418 | return __rcu_pending(&rcu_preempt_state, | |
419 | &per_cpu(rcu_preempt_data, cpu)); | |
420 | } | |
421 | ||
422 | /* | |
423 | * Does preemptable RCU need the CPU to stay out of dynticks mode? | |
424 | */ | |
425 | static int rcu_preempt_needs_cpu(int cpu) | |
426 | { | |
427 | return !!per_cpu(rcu_preempt_data, cpu).nxtlist; | |
428 | } | |
429 | ||
e74f4c45 PM |
430 | /** |
431 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. | |
432 | */ | |
433 | void rcu_barrier(void) | |
434 | { | |
435 | _rcu_barrier(&rcu_preempt_state, call_rcu); | |
436 | } | |
437 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
438 | ||
f41d911f PM |
439 | /* |
440 | * Initialize preemptable RCU's per-CPU data. | |
441 | */ | |
442 | static void __cpuinit rcu_preempt_init_percpu_data(int cpu) | |
443 | { | |
444 | rcu_init_percpu_data(cpu, &rcu_preempt_state, 1); | |
445 | } | |
446 | ||
e74f4c45 PM |
447 | /* |
448 | * Move preemptable RCU's callbacks to ->orphan_cbs_list. | |
449 | */ | |
450 | static void rcu_preempt_send_cbs_to_orphanage(void) | |
451 | { | |
452 | rcu_send_cbs_to_orphanage(&rcu_preempt_state); | |
453 | } | |
454 | ||
1eba8f84 PM |
455 | /* |
456 | * Initialize preemptable RCU's state structures. | |
457 | */ | |
458 | static void __init __rcu_init_preempt(void) | |
459 | { | |
1eba8f84 PM |
460 | RCU_INIT_FLAVOR(&rcu_preempt_state, rcu_preempt_data); |
461 | } | |
462 | ||
f41d911f PM |
463 | /* |
464 | * Check for a task exiting while in a preemptable-RCU read-side | |
465 | * critical section, clean up if so. No need to issue warnings, | |
466 | * as debug_check_no_locks_held() already does this if lockdep | |
467 | * is enabled. | |
468 | */ | |
469 | void exit_rcu(void) | |
470 | { | |
471 | struct task_struct *t = current; | |
472 | ||
473 | if (t->rcu_read_lock_nesting == 0) | |
474 | return; | |
475 | t->rcu_read_lock_nesting = 1; | |
476 | rcu_read_unlock(); | |
477 | } | |
478 | ||
479 | #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ | |
480 | ||
481 | /* | |
482 | * Tell them what RCU they are running. | |
483 | */ | |
dbe01350 | 484 | static void rcu_bootup_announce(void) |
f41d911f PM |
485 | { |
486 | printk(KERN_INFO "Hierarchical RCU implementation.\n"); | |
487 | } | |
488 | ||
489 | /* | |
490 | * Return the number of RCU batches processed thus far for debug & stats. | |
491 | */ | |
492 | long rcu_batches_completed(void) | |
493 | { | |
494 | return rcu_batches_completed_sched(); | |
495 | } | |
496 | EXPORT_SYMBOL_GPL(rcu_batches_completed); | |
497 | ||
498 | /* | |
499 | * Because preemptable RCU does not exist, we never have to check for | |
500 | * CPUs being in quiescent states. | |
501 | */ | |
c3422bea | 502 | static void rcu_preempt_note_context_switch(int cpu) |
f41d911f PM |
503 | { |
504 | } | |
505 | ||
fc2219d4 PM |
506 | /* |
507 | * Because preemptable RCU does not exist, there are never any preempted | |
508 | * RCU readers. | |
509 | */ | |
510 | static int rcu_preempted_readers(struct rcu_node *rnp) | |
511 | { | |
512 | return 0; | |
513 | } | |
514 | ||
f41d911f PM |
515 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
516 | ||
517 | /* | |
518 | * Because preemptable RCU does not exist, we never have to check for | |
519 | * tasks blocked within RCU read-side critical sections. | |
520 | */ | |
521 | static void rcu_print_task_stall(struct rcu_node *rnp) | |
522 | { | |
523 | } | |
524 | ||
525 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
526 | ||
b0e165c0 PM |
527 | /* |
528 | * Because there is no preemptable RCU, there can be no readers blocked, | |
49e29126 PM |
529 | * so there is no need to check for blocked tasks. So check only for |
530 | * bogus qsmask values. | |
b0e165c0 PM |
531 | */ |
532 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) | |
533 | { | |
49e29126 | 534 | WARN_ON_ONCE(rnp->qsmask); |
b0e165c0 PM |
535 | } |
536 | ||
33f76148 PM |
537 | #ifdef CONFIG_HOTPLUG_CPU |
538 | ||
dd5d19ba PM |
539 | /* |
540 | * Because preemptable RCU does not exist, it never needs to migrate | |
237c80c5 PM |
541 | * tasks that were blocked within RCU read-side critical sections, and |
542 | * such non-existent tasks cannot possibly have been blocking the current | |
543 | * grace period. | |
dd5d19ba | 544 | */ |
237c80c5 PM |
545 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
546 | struct rcu_node *rnp, | |
547 | struct rcu_data *rdp) | |
dd5d19ba | 548 | { |
237c80c5 | 549 | return 0; |
dd5d19ba PM |
550 | } |
551 | ||
33f76148 PM |
552 | /* |
553 | * Because preemptable RCU does not exist, it never needs CPU-offline | |
554 | * processing. | |
555 | */ | |
556 | static void rcu_preempt_offline_cpu(int cpu) | |
557 | { | |
558 | } | |
559 | ||
560 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
561 | ||
f41d911f PM |
562 | /* |
563 | * Because preemptable RCU does not exist, it never has any callbacks | |
564 | * to check. | |
565 | */ | |
1eba8f84 | 566 | static void rcu_preempt_check_callbacks(int cpu) |
f41d911f PM |
567 | { |
568 | } | |
569 | ||
570 | /* | |
571 | * Because preemptable RCU does not exist, it never has any callbacks | |
572 | * to process. | |
573 | */ | |
1eba8f84 | 574 | static void rcu_preempt_process_callbacks(void) |
f41d911f PM |
575 | { |
576 | } | |
577 | ||
578 | /* | |
579 | * In classic RCU, call_rcu() is just call_rcu_sched(). | |
580 | */ | |
581 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) | |
582 | { | |
583 | call_rcu_sched(head, func); | |
584 | } | |
585 | EXPORT_SYMBOL_GPL(call_rcu); | |
586 | ||
019129d5 PM |
587 | /* |
588 | * Wait for an rcu-preempt grace period, but make it happen quickly. | |
589 | * But because preemptable RCU does not exist, map to rcu-sched. | |
590 | */ | |
591 | void synchronize_rcu_expedited(void) | |
592 | { | |
593 | synchronize_sched_expedited(); | |
594 | } | |
595 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); | |
596 | ||
f41d911f PM |
597 | /* |
598 | * Because preemptable RCU does not exist, it never has any work to do. | |
599 | */ | |
600 | static int rcu_preempt_pending(int cpu) | |
601 | { | |
602 | return 0; | |
603 | } | |
604 | ||
605 | /* | |
606 | * Because preemptable RCU does not exist, it never needs any CPU. | |
607 | */ | |
608 | static int rcu_preempt_needs_cpu(int cpu) | |
609 | { | |
610 | return 0; | |
611 | } | |
612 | ||
e74f4c45 PM |
613 | /* |
614 | * Because preemptable RCU does not exist, rcu_barrier() is just | |
615 | * another name for rcu_barrier_sched(). | |
616 | */ | |
617 | void rcu_barrier(void) | |
618 | { | |
619 | rcu_barrier_sched(); | |
620 | } | |
621 | EXPORT_SYMBOL_GPL(rcu_barrier); | |
622 | ||
f41d911f PM |
623 | /* |
624 | * Because preemptable RCU does not exist, there is no per-CPU | |
625 | * data to initialize. | |
626 | */ | |
627 | static void __cpuinit rcu_preempt_init_percpu_data(int cpu) | |
628 | { | |
629 | } | |
630 | ||
e74f4c45 PM |
631 | /* |
632 | * Because there is no preemptable RCU, there are no callbacks to move. | |
633 | */ | |
634 | static void rcu_preempt_send_cbs_to_orphanage(void) | |
635 | { | |
636 | } | |
637 | ||
1eba8f84 PM |
638 | /* |
639 | * Because preemptable RCU does not exist, it need not be initialized. | |
640 | */ | |
641 | static void __init __rcu_init_preempt(void) | |
642 | { | |
643 | } | |
644 | ||
f41d911f | 645 | #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |