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1 : : // SPDX-License-Identifier: GPL-2.0+
2 : : /*
3 : : * RCU segmented callback lists, function definitions
4 : : *
5 : : * Copyright IBM Corporation, 2017
6 : : *
7 : : * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
8 : : */
9 : :
10 : : #include <linux/types.h>
11 : : #include <linux/kernel.h>
12 : : #include <linux/interrupt.h>
13 : : #include <linux/rcupdate.h>
14 : :
15 : : #include "rcu_segcblist.h"
16 : :
17 : : /* Initialize simple callback list. */
18 : 402 : void rcu_cblist_init(struct rcu_cblist *rclp)
19 : : {
20 : 402 : rclp->head = NULL;
21 : 402 : rclp->tail = &rclp->head;
22 : 402 : rclp->len = 0;
23 : 402 : }
24 : :
25 : : /*
26 : : * Enqueue an rcu_head structure onto the specified callback list.
27 : : */
28 : 0 : void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp)
29 : : {
30 : 0 : *rclp->tail = rhp;
31 : 0 : rclp->tail = &rhp->next;
32 : 0 : WRITE_ONCE(rclp->len, rclp->len + 1);
33 : 0 : }
34 : :
35 : : /*
36 : : * Flush the second rcu_cblist structure onto the first one, obliterating
37 : : * any contents of the first. If rhp is non-NULL, enqueue it as the sole
38 : : * element of the second rcu_cblist structure, but ensuring that the second
39 : : * rcu_cblist structure, if initially non-empty, always appears non-empty
40 : : * throughout the process. If rdp is NULL, the second rcu_cblist structure
41 : : * is instead initialized to empty.
42 : : */
43 : 0 : void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
44 : : struct rcu_cblist *srclp,
45 : : struct rcu_head *rhp)
46 : : {
47 : 0 : drclp->head = srclp->head;
48 [ # # ]: 0 : if (drclp->head)
49 : 0 : drclp->tail = srclp->tail;
50 : : else
51 : 0 : drclp->tail = &drclp->head;
52 : 0 : drclp->len = srclp->len;
53 [ # # ]: 0 : if (!rhp) {
54 : 0 : rcu_cblist_init(srclp);
55 : : } else {
56 : 0 : rhp->next = NULL;
57 : 0 : srclp->head = rhp;
58 : 0 : srclp->tail = &rhp->next;
59 : 0 : WRITE_ONCE(srclp->len, 1);
60 : : }
61 : 0 : }
62 : :
63 : : /*
64 : : * Dequeue the oldest rcu_head structure from the specified callback
65 : : * list.
66 : : */
67 : 806311 : struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp)
68 : : {
69 : 806311 : struct rcu_head *rhp;
70 : :
71 : 806311 : rhp = rclp->head;
72 [ + + ]: 806311 : if (!rhp)
73 : : return NULL;
74 : 795507 : rclp->len--;
75 : 795507 : rclp->head = rhp->next;
76 [ + + ]: 795507 : if (!rclp->head)
77 : 12033 : rclp->tail = &rclp->head;
78 : : return rhp;
79 : : }
80 : :
81 : : /* Set the length of an rcu_segcblist structure. */
82 : 66 : static void rcu_segcblist_set_len(struct rcu_segcblist *rsclp, long v)
83 : : {
84 : : #ifdef CONFIG_RCU_NOCB_CPU
85 : : atomic_long_set(&rsclp->len, v);
86 : : #else
87 : 66 : WRITE_ONCE(rsclp->len, v);
88 : : #endif
89 : : }
90 : :
91 : : /*
92 : : * Increase the numeric length of an rcu_segcblist structure by the
93 : : * specified amount, which can be negative. This can cause the ->len
94 : : * field to disagree with the actual number of callbacks on the structure.
95 : : * This increase is fully ordered with respect to the callers accesses
96 : : * both before and after.
97 : : */
98 : 881390 : static void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v)
99 : : {
100 : : #ifdef CONFIG_RCU_NOCB_CPU
101 : : smp_mb__before_atomic(); /* Up to the caller! */
102 : : atomic_long_add(v, &rsclp->len);
103 : : smp_mb__after_atomic(); /* Up to the caller! */
104 : : #else
105 : 881390 : smp_mb(); /* Up to the caller! */
106 : 881390 : WRITE_ONCE(rsclp->len, rsclp->len + v);
107 : 881390 : smp_mb(); /* Up to the caller! */
108 : : #endif
109 : : }
110 : :
111 : : /*
112 : : * Increase the numeric length of an rcu_segcblist structure by one.
113 : : * This can cause the ->len field to disagree with the actual number of
114 : : * callbacks on the structure. This increase is fully ordered with respect
115 : : * to the callers accesses both before and after.
116 : : */
117 : 796032 : void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp)
118 : : {
119 : 0 : rcu_segcblist_add_len(rsclp, 1);
120 : 0 : }
121 : :
122 : : /*
123 : : * Exchange the numeric length of the specified rcu_segcblist structure
124 : : * with the specified value. This can cause the ->len field to disagree
125 : : * with the actual number of callbacks on the structure. This exchange is
126 : : * fully ordered with respect to the callers accesses both before and after.
127 : : */
128 : 0 : static long rcu_segcblist_xchg_len(struct rcu_segcblist *rsclp, long v)
129 : : {
130 : : #ifdef CONFIG_RCU_NOCB_CPU
131 : : return atomic_long_xchg(&rsclp->len, v);
132 : : #else
133 : 0 : long ret = rsclp->len;
134 : :
135 : 0 : smp_mb(); /* Up to the caller! */
136 : 0 : WRITE_ONCE(rsclp->len, v);
137 : 0 : smp_mb(); /* Up to the caller! */
138 : 0 : return ret;
139 : : #endif
140 : : }
141 : :
142 : : /*
143 : : * Initialize an rcu_segcblist structure.
144 : : */
145 : 66 : void rcu_segcblist_init(struct rcu_segcblist *rsclp)
146 : : {
147 : 66 : int i;
148 : :
149 : 66 : BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq));
150 : 66 : BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq));
151 : 66 : rsclp->head = NULL;
152 [ - - + + ]: 330 : for (i = 0; i < RCU_CBLIST_NSEGS; i++)
153 : 264 : rsclp->tails[i] = &rsclp->head;
154 : 66 : rcu_segcblist_set_len(rsclp, 0);
155 : 66 : rsclp->enabled = 1;
156 : 66 : }
157 : :
158 : : /*
159 : : * Disable the specified rcu_segcblist structure, so that callbacks can
160 : : * no longer be posted to it. This structure must be empty.
161 : : */
162 : 0 : void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
163 : : {
164 [ # # ]: 0 : WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));
165 [ # # ]: 0 : WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));
166 : 0 : rsclp->enabled = 0;
167 : 0 : }
168 : :
169 : : /*
170 : : * Mark the specified rcu_segcblist structure as offloaded. This
171 : : * structure must be empty.
172 : : */
173 : 0 : void rcu_segcblist_offload(struct rcu_segcblist *rsclp)
174 : : {
175 : 0 : rsclp->offloaded = 1;
176 : 0 : }
177 : :
178 : : /*
179 : : * Does the specified rcu_segcblist structure contain callbacks that
180 : : * are ready to be invoked?
181 : : */
182 : 352870 : bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp)
183 : : {
184 [ + - ]: 267512 : return rcu_segcblist_is_enabled(rsclp) &&
185 [ - + + + ]: 352870 : &rsclp->head != rsclp->tails[RCU_DONE_TAIL];
186 : : }
187 : :
188 : : /*
189 : : * Does the specified rcu_segcblist structure contain callbacks that
190 : : * are still pending, that is, not yet ready to be invoked?
191 : : */
192 : 107993 : bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp)
193 : : {
194 [ - - - - : 107993 : return rcu_segcblist_is_enabled(rsclp) &&
+ + + + ]
195 : : !rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL);
196 : : }
197 : :
198 : : /*
199 : : * Return a pointer to the first callback in the specified rcu_segcblist
200 : : * structure. This is useful for diagnostics.
201 : : */
202 : 0 : struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp)
203 : : {
204 [ # # ]: 0 : if (rcu_segcblist_is_enabled(rsclp))
205 : 0 : return rsclp->head;
206 : : return NULL;
207 : : }
208 : :
209 : : /*
210 : : * Return a pointer to the first pending callback in the specified
211 : : * rcu_segcblist structure. This is useful just after posting a given
212 : : * callback -- if that callback is the first pending callback, then
213 : : * you cannot rely on someone else having already started up the required
214 : : * grace period.
215 : : */
216 : 0 : struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp)
217 : : {
218 [ # # ]: 0 : if (rcu_segcblist_is_enabled(rsclp))
219 : 0 : return *rsclp->tails[RCU_DONE_TAIL];
220 : : return NULL;
221 : : }
222 : :
223 : : /*
224 : : * Return false if there are no CBs awaiting grace periods, otherwise,
225 : : * return true and store the nearest waited-upon grace period into *lp.
226 : : */
227 : 0 : bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp)
228 : : {
229 [ # # # # ]: 0 : if (!rcu_segcblist_pend_cbs(rsclp))
230 : : return false;
231 : 0 : *lp = rsclp->gp_seq[RCU_WAIT_TAIL];
232 : 0 : return true;
233 : : }
234 : :
235 : : /*
236 : : * Enqueue the specified callback onto the specified rcu_segcblist
237 : : * structure, updating accounting as needed. Note that the ->len
238 : : * field may be accessed locklessly, hence the WRITE_ONCE().
239 : : * The ->len field is used by rcu_barrier() and friends to determine
240 : : * if it must post a callback on this structure, and it is OK
241 : : * for rcu_barrier() to sometimes post callbacks needlessly, but
242 : : * absolutely not OK for it to ever miss posting a callback.
243 : : */
244 : 796022 : void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
245 : : struct rcu_head *rhp)
246 : : {
247 : 796022 : rcu_segcblist_inc_len(rsclp);
248 : 796022 : smp_mb(); /* Ensure counts are updated before callback is enqueued. */
249 : 796022 : rhp->next = NULL;
250 : 796022 : WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rhp);
251 : 796022 : WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], &rhp->next);
252 : 796022 : }
253 : :
254 : : /*
255 : : * Entrain the specified callback onto the specified rcu_segcblist at
256 : : * the end of the last non-empty segment. If the entire rcu_segcblist
257 : : * is empty, make no change, but return false.
258 : : *
259 : : * This is intended for use by rcu_barrier()-like primitives, -not-
260 : : * for normal grace-period use. IMPORTANT: The callback you enqueue
261 : : * will wait for all prior callbacks, NOT necessarily for a grace
262 : : * period. You have been warned.
263 : : */
264 : 10 : bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
265 : : struct rcu_head *rhp)
266 : : {
267 : 10 : int i;
268 : :
269 [ + - ]: 10 : if (rcu_segcblist_n_cbs(rsclp) == 0)
270 : : return false;
271 : 10 : rcu_segcblist_inc_len(rsclp);
272 : 10 : smp_mb(); /* Ensure counts are updated before callback is entrained. */
273 : 10 : rhp->next = NULL;
274 [ + + ]: 34 : for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--)
275 [ + + ]: 30 : if (rsclp->tails[i] != rsclp->tails[i - 1])
276 : : break;
277 : 10 : WRITE_ONCE(*rsclp->tails[i], rhp);
278 [ + + ]: 44 : for (; i <= RCU_NEXT_TAIL; i++)
279 : 34 : WRITE_ONCE(rsclp->tails[i], &rhp->next);
280 : : return true;
281 : : }
282 : :
283 : : /*
284 : : * Extract only the counts from the specified rcu_segcblist structure,
285 : : * and place them in the specified rcu_cblist structure. This function
286 : : * supports both callback orphaning and invocation, hence the separation
287 : : * of counts and callbacks. (Callbacks ready for invocation must be
288 : : * orphaned and adopted separately from pending callbacks, but counts
289 : : * apply to all callbacks. Locking must be used to make sure that
290 : : * both orphaned-callbacks lists are consistent.)
291 : : */
292 : 0 : void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
293 : : struct rcu_cblist *rclp)
294 : : {
295 : 0 : rclp->len = rcu_segcblist_xchg_len(rsclp, 0);
296 : 0 : }
297 : :
298 : : /*
299 : : * Extract only those callbacks ready to be invoked from the specified
300 : : * rcu_segcblist structure and place them in the specified rcu_cblist
301 : : * structure.
302 : : */
303 : 85358 : void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
304 : : struct rcu_cblist *rclp)
305 : : {
306 : 85358 : int i;
307 : :
308 [ + - + - ]: 170716 : if (!rcu_segcblist_ready_cbs(rsclp))
309 : : return; /* Nothing to do. */
310 : 85358 : *rclp->tail = rsclp->head;
311 : 85358 : WRITE_ONCE(rsclp->head, *rsclp->tails[RCU_DONE_TAIL]);
312 : 85358 : WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
313 : 85358 : rclp->tail = rsclp->tails[RCU_DONE_TAIL];
314 [ + + ]: 426790 : for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--)
315 [ + + ]: 341432 : if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL])
316 : 94524 : WRITE_ONCE(rsclp->tails[i], &rsclp->head);
317 : : }
318 : :
319 : : /*
320 : : * Extract only those callbacks still pending (not yet ready to be
321 : : * invoked) from the specified rcu_segcblist structure and place them in
322 : : * the specified rcu_cblist structure. Note that this loses information
323 : : * about any callbacks that might have been partway done waiting for
324 : : * their grace period. Too bad! They will have to start over.
325 : : */
326 : 0 : void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
327 : : struct rcu_cblist *rclp)
328 : : {
329 : 0 : int i;
330 : :
331 [ # # # # ]: 0 : if (!rcu_segcblist_pend_cbs(rsclp))
332 : : return; /* Nothing to do. */
333 : 0 : *rclp->tail = *rsclp->tails[RCU_DONE_TAIL];
334 : 0 : rclp->tail = rsclp->tails[RCU_NEXT_TAIL];
335 : 0 : WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
336 [ # # ]: 0 : for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++)
337 : 0 : WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_DONE_TAIL]);
338 : : }
339 : :
340 : : /*
341 : : * Insert counts from the specified rcu_cblist structure in the
342 : : * specified rcu_segcblist structure.
343 : : */
344 : 85358 : void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
345 : : struct rcu_cblist *rclp)
346 : : {
347 : 85358 : rcu_segcblist_add_len(rsclp, rclp->len);
348 : 85358 : rclp->len = 0;
349 : 85358 : }
350 : :
351 : : /*
352 : : * Move callbacks from the specified rcu_cblist to the beginning of the
353 : : * done-callbacks segment of the specified rcu_segcblist.
354 : : */
355 : 84956 : void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
356 : : struct rcu_cblist *rclp)
357 : : {
358 : 84956 : int i;
359 : :
360 [ + + ]: 84956 : if (!rclp->head)
361 : : return; /* No callbacks to move. */
362 : 73325 : *rclp->tail = rsclp->head;
363 : 73325 : WRITE_ONCE(rsclp->head, rclp->head);
364 [ - - + + ]: 153054 : for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
365 [ - - + + ]: 151050 : if (&rsclp->head == rsclp->tails[i])
366 : 79729 : WRITE_ONCE(rsclp->tails[i], rclp->tail);
367 : : else
368 : : break;
369 : 73325 : rclp->head = NULL;
370 : 73325 : rclp->tail = &rclp->head;
371 : : }
372 : :
373 : : /*
374 : : * Move callbacks from the specified rcu_cblist to the end of the
375 : : * new-callbacks segment of the specified rcu_segcblist.
376 : : */
377 : 0 : void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
378 : : struct rcu_cblist *rclp)
379 : : {
380 [ # # ]: 0 : if (!rclp->head)
381 : : return; /* Nothing to do. */
382 : 0 : WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rclp->head);
383 : 0 : WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], rclp->tail);
384 : 0 : rclp->head = NULL;
385 : 0 : rclp->tail = &rclp->head;
386 : : }
387 : :
388 : : /*
389 : : * Advance the callbacks in the specified rcu_segcblist structure based
390 : : * on the current value passed in for the grace-period counter.
391 : : */
392 : 22194 : void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
393 : : {
394 : 22194 : int i, j;
395 : :
396 [ - + ]: 22194 : WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
397 [ + - ]: 22194 : if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
398 : : return;
399 : :
400 : : /*
401 : : * Find all callbacks whose ->gp_seq numbers indicate that they
402 : : * are ready to invoke, and put them into the RCU_DONE_TAIL segment.
403 : : */
404 [ + + ]: 39948 : for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
405 [ + + ]: 39215 : if (ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
406 : : break;
407 : 17754 : WRITE_ONCE(rsclp->tails[RCU_DONE_TAIL], rsclp->tails[i]);
408 : : }
409 : :
410 : : /* If no callbacks moved, nothing more need be done. */
411 [ + + ]: 22194 : if (i == RCU_WAIT_TAIL)
412 : : return;
413 : :
414 : : /* Clean up tail pointers that might have been misordered above. */
415 [ + + ]: 34775 : for (j = RCU_WAIT_TAIL; j < i; j++)
416 : 17754 : WRITE_ONCE(rsclp->tails[j], rsclp->tails[RCU_DONE_TAIL]);
417 : :
418 : : /*
419 : : * Callbacks moved, so clean up the misordered ->tails[] pointers
420 : : * that now point into the middle of the list of ready-to-invoke
421 : : * callbacks. The overall effect is to copy down the later pointers
422 : : * into the gap that was created by the now-ready segments.
423 : : */
424 [ + + ]: 27972 : for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
425 [ + + ]: 16288 : if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL])
426 : : break; /* No more callbacks. */
427 : 10951 : WRITE_ONCE(rsclp->tails[j], rsclp->tails[i]);
428 : 10951 : rsclp->gp_seq[j] = rsclp->gp_seq[i];
429 : : }
430 : : }
431 : :
432 : : /*
433 : : * "Accelerate" callbacks based on more-accurate grace-period information.
434 : : * The reason for this is that RCU does not synchronize the beginnings and
435 : : * ends of grace periods, and that callbacks are posted locally. This in
436 : : * turn means that the callbacks must be labelled conservatively early
437 : : * on, as getting exact information would degrade both performance and
438 : : * scalability. When more accurate grace-period information becomes
439 : : * available, previously posted callbacks can be "accelerated", marking
440 : : * them to complete at the end of the earlier grace period.
441 : : *
442 : : * This function operates on an rcu_segcblist structure, and also the
443 : : * grace-period sequence number seq at which new callbacks would become
444 : : * ready to invoke. Returns true if there are callbacks that won't be
445 : : * ready to invoke until seq, false otherwise.
446 : : */
447 : 70276 : bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
448 : : {
449 : 70276 : int i;
450 : :
451 [ - + ]: 70276 : WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
452 [ + + ]: 70276 : if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
453 : : return false;
454 : :
455 : : /*
456 : : * Find the segment preceding the oldest segment of callbacks
457 : : * whose ->gp_seq[] completion is at or after that passed in via
458 : : * "seq", skipping any empty segments. This oldest segment, along
459 : : * with any later segments, can be merged in with any newly arrived
460 : : * callbacks in the RCU_NEXT_TAIL segment, and assigned "seq"
461 : : * as their ->gp_seq[] grace-period completion sequence number.
462 : : */
463 [ + + ]: 177231 : for (i = RCU_NEXT_READY_TAIL; i > RCU_DONE_TAIL; i--)
464 [ + + ]: 139804 : if (rsclp->tails[i] != rsclp->tails[i - 1] &&
465 [ + + ]: 60751 : ULONG_CMP_LT(rsclp->gp_seq[i], seq))
466 : : break;
467 : :
468 : : /*
469 : : * If all the segments contain callbacks that correspond to
470 : : * earlier grace-period sequence numbers than "seq", leave.
471 : : * Assuming that the rcu_segcblist structure has enough
472 : : * segments in its arrays, this can only happen if some of
473 : : * the non-done segments contain callbacks that really are
474 : : * ready to invoke. This situation will get straightened
475 : : * out by the next call to rcu_segcblist_advance().
476 : : *
477 : : * Also advance to the oldest segment of callbacks whose
478 : : * ->gp_seq[] completion is at or after that passed in via "seq",
479 : : * skipping any empty segments.
480 : : */
481 [ + - ]: 69902 : if (++i >= RCU_NEXT_TAIL)
482 : : return false;
483 : :
484 : : /*
485 : : * Merge all later callbacks, including newly arrived callbacks,
486 : : * into the segment located by the for-loop above. Assign "seq"
487 : : * as the ->gp_seq[] value in order to correctly handle the case
488 : : * where there were no pending callbacks in the rcu_segcblist
489 : : * structure other than in the RCU_NEXT_TAIL segment.
490 : : */
491 [ + + ]: 177231 : for (; i < RCU_NEXT_TAIL; i++) {
492 : 107329 : WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_NEXT_TAIL]);
493 : 107329 : rsclp->gp_seq[i] = seq;
494 : : }
495 : : return true;
496 : : }
497 : :
498 : : /*
499 : : * Merge the source rcu_segcblist structure into the destination
500 : : * rcu_segcblist structure, then initialize the source. Any pending
501 : : * callbacks from the source get to start over. It is best to
502 : : * advance and accelerate both the destination and the source
503 : : * before merging.
504 : : */
505 : 0 : void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
506 : : struct rcu_segcblist *src_rsclp)
507 : : {
508 : 0 : struct rcu_cblist donecbs;
509 : 0 : struct rcu_cblist pendcbs;
510 : :
511 : 0 : rcu_cblist_init(&donecbs);
512 : 0 : rcu_cblist_init(&pendcbs);
513 : 0 : rcu_segcblist_extract_count(src_rsclp, &donecbs);
514 : 0 : rcu_segcblist_extract_done_cbs(src_rsclp, &donecbs);
515 : 0 : rcu_segcblist_extract_pend_cbs(src_rsclp, &pendcbs);
516 : 0 : rcu_segcblist_insert_count(dst_rsclp, &donecbs);
517 [ # # ]: 0 : rcu_segcblist_insert_done_cbs(dst_rsclp, &donecbs);
518 [ # # ]: 0 : rcu_segcblist_insert_pend_cbs(dst_rsclp, &pendcbs);
519 : 0 : rcu_segcblist_init(src_rsclp);
520 : 0 : }
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