1 /*
2 * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
3 *
4 * Based on bo.c which bears the following copyright notice,
5 * but is dual licensed:
6 *
7 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
8 * All Rights Reserved.
9 *
10 * Permission is hereby granted, free of charge, to any person obtaining a
11 * copy of this software and associated documentation files (the
12 * "Software"), to deal in the Software without restriction, including
13 * without limitation the rights to use, copy, modify, merge, publish,
14 * distribute, sub license, and/or sell copies of the Software, and to
15 * permit persons to whom the Software is furnished to do so, subject to
16 * the following conditions:
17 *
18 * The above copyright notice and this permission notice (including the
19 * next paragraph) shall be included in all copies or substantial portions
20 * of the Software.
21 *
22 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
23 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
24 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
25 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
26 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
27 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
28 * USE OR OTHER DEALINGS IN THE SOFTWARE.
29 *
30 **************************************************************************/
31 /*
32 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
33 */
34
35 #include <linux/reservation.h>
36 #include <linux/export.h>
37
38 /**
39 * DOC: Reservation Object Overview
40 *
41 * The reservation object provides a mechanism to manage shared and
42 * exclusive fences associated with a buffer. A reservation object
43 * can have attached one exclusive fence (normally associated with
44 * write operations) or N shared fences (read operations). The RCU
45 * mechanism is used to protect read access to fences from locked
46 * write-side updates.
47 */
48
49 DEFINE_WD_CLASS(reservation_ww_class);
50 EXPORT_SYMBOL(reservation_ww_class);
51
52 struct lock_class_key reservation_seqcount_class;
53 EXPORT_SYMBOL(reservation_seqcount_class);
54
55 const char reservation_seqcount_string[] = "reservation_seqcount";
56 EXPORT_SYMBOL(reservation_seqcount_string);
57
58 /**
59 * reservation_object_reserve_shared - Reserve space to add a shared
60 * fence to a reservation_object.
61 * @obj: reservation object
62 *
63 * Should be called before reservation_object_add_shared_fence(). Must
64 * be called with obj->lock held.
65 *
66 * RETURNS
67 * Zero for success, or -errno
68 */
reservation_object_reserve_shared(struct reservation_object * obj)69 int reservation_object_reserve_shared(struct reservation_object *obj)
70 {
71 struct reservation_object_list *fobj, *old;
72 u32 max;
73
74 old = reservation_object_get_list(obj);
75
76 if (old && old->shared_max) {
77 if (old->shared_count < old->shared_max) {
78 /* perform an in-place update */
79 kfree(obj->staged);
80 obj->staged = NULL;
81 return 0;
82 } else
83 max = old->shared_max * 2;
84 } else
85 max = 4;
86
87 /*
88 * resize obj->staged or allocate if it doesn't exist,
89 * noop if already correct size
90 */
91 fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
92 GFP_KERNEL);
93 if (!fobj)
94 return -ENOMEM;
95
96 obj->staged = fobj;
97 fobj->shared_max = max;
98 return 0;
99 }
100 EXPORT_SYMBOL(reservation_object_reserve_shared);
101
102 static void
reservation_object_add_shared_inplace(struct reservation_object * obj,struct reservation_object_list * fobj,struct dma_fence * fence)103 reservation_object_add_shared_inplace(struct reservation_object *obj,
104 struct reservation_object_list *fobj,
105 struct dma_fence *fence)
106 {
107 struct dma_fence *signaled = NULL;
108 u32 i, signaled_idx;
109
110 dma_fence_get(fence);
111
112 preempt_disable();
113 write_seqcount_begin(&obj->seq);
114
115 for (i = 0; i < fobj->shared_count; ++i) {
116 struct dma_fence *old_fence;
117
118 old_fence = rcu_dereference_protected(fobj->shared[i],
119 reservation_object_held(obj));
120
121 if (old_fence->context == fence->context) {
122 /* memory barrier is added by write_seqcount_begin */
123 RCU_INIT_POINTER(fobj->shared[i], fence);
124 write_seqcount_end(&obj->seq);
125 preempt_enable();
126
127 dma_fence_put(old_fence);
128 return;
129 }
130
131 if (!signaled && dma_fence_is_signaled(old_fence)) {
132 signaled = old_fence;
133 signaled_idx = i;
134 }
135 }
136
137 /*
138 * memory barrier is added by write_seqcount_begin,
139 * fobj->shared_count is protected by this lock too
140 */
141 if (signaled) {
142 RCU_INIT_POINTER(fobj->shared[signaled_idx], fence);
143 } else {
144 BUG_ON(fobj->shared_count >= fobj->shared_max);
145 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
146 fobj->shared_count++;
147 }
148
149 write_seqcount_end(&obj->seq);
150 preempt_enable();
151
152 dma_fence_put(signaled);
153 }
154
155 static void
reservation_object_add_shared_replace(struct reservation_object * obj,struct reservation_object_list * old,struct reservation_object_list * fobj,struct dma_fence * fence)156 reservation_object_add_shared_replace(struct reservation_object *obj,
157 struct reservation_object_list *old,
158 struct reservation_object_list *fobj,
159 struct dma_fence *fence)
160 {
161 unsigned i, j, k;
162
163 dma_fence_get(fence);
164
165 if (!old) {
166 RCU_INIT_POINTER(fobj->shared[0], fence);
167 fobj->shared_count = 1;
168 goto done;
169 }
170
171 /*
172 * no need to bump fence refcounts, rcu_read access
173 * requires the use of kref_get_unless_zero, and the
174 * references from the old struct are carried over to
175 * the new.
176 */
177 for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; ++i) {
178 struct dma_fence *check;
179
180 check = rcu_dereference_protected(old->shared[i],
181 reservation_object_held(obj));
182
183 if (check->context == fence->context ||
184 dma_fence_is_signaled(check))
185 RCU_INIT_POINTER(fobj->shared[--k], check);
186 else
187 RCU_INIT_POINTER(fobj->shared[j++], check);
188 }
189 fobj->shared_count = j;
190 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
191 fobj->shared_count++;
192
193 done:
194 preempt_disable();
195 write_seqcount_begin(&obj->seq);
196 /*
197 * RCU_INIT_POINTER can be used here,
198 * seqcount provides the necessary barriers
199 */
200 RCU_INIT_POINTER(obj->fence, fobj);
201 write_seqcount_end(&obj->seq);
202 preempt_enable();
203
204 if (!old)
205 return;
206
207 /* Drop the references to the signaled fences */
208 for (i = k; i < fobj->shared_max; ++i) {
209 struct dma_fence *f;
210
211 f = rcu_dereference_protected(fobj->shared[i],
212 reservation_object_held(obj));
213 dma_fence_put(f);
214 }
215 kfree_rcu(old, rcu);
216 }
217
218 /**
219 * reservation_object_add_shared_fence - Add a fence to a shared slot
220 * @obj: the reservation object
221 * @fence: the shared fence to add
222 *
223 * Add a fence to a shared slot, obj->lock must be held, and
224 * reservation_object_reserve_shared() has been called.
225 */
reservation_object_add_shared_fence(struct reservation_object * obj,struct dma_fence * fence)226 void reservation_object_add_shared_fence(struct reservation_object *obj,
227 struct dma_fence *fence)
228 {
229 struct reservation_object_list *old, *fobj = obj->staged;
230
231 old = reservation_object_get_list(obj);
232 obj->staged = NULL;
233
234 if (!fobj)
235 reservation_object_add_shared_inplace(obj, old, fence);
236 else
237 reservation_object_add_shared_replace(obj, old, fobj, fence);
238 }
239 EXPORT_SYMBOL(reservation_object_add_shared_fence);
240
241 /**
242 * reservation_object_add_excl_fence - Add an exclusive fence.
243 * @obj: the reservation object
244 * @fence: the shared fence to add
245 *
246 * Add a fence to the exclusive slot. The obj->lock must be held.
247 */
reservation_object_add_excl_fence(struct reservation_object * obj,struct dma_fence * fence)248 void reservation_object_add_excl_fence(struct reservation_object *obj,
249 struct dma_fence *fence)
250 {
251 struct dma_fence *old_fence = reservation_object_get_excl(obj);
252 struct reservation_object_list *old;
253 u32 i = 0;
254
255 old = reservation_object_get_list(obj);
256 if (old)
257 i = old->shared_count;
258
259 if (fence)
260 dma_fence_get(fence);
261
262 preempt_disable();
263 write_seqcount_begin(&obj->seq);
264 /* write_seqcount_begin provides the necessary memory barrier */
265 RCU_INIT_POINTER(obj->fence_excl, fence);
266 if (old)
267 old->shared_count = 0;
268 write_seqcount_end(&obj->seq);
269 preempt_enable();
270
271 /* inplace update, no shared fences */
272 while (i--)
273 dma_fence_put(rcu_dereference_protected(old->shared[i],
274 reservation_object_held(obj)));
275
276 dma_fence_put(old_fence);
277 }
278 EXPORT_SYMBOL(reservation_object_add_excl_fence);
279
280 /**
281 * reservation_object_copy_fences - Copy all fences from src to dst.
282 * @dst: the destination reservation object
283 * @src: the source reservation object
284 *
285 * Copy all fences from src to dst. dst-lock must be held.
286 */
reservation_object_copy_fences(struct reservation_object * dst,struct reservation_object * src)287 int reservation_object_copy_fences(struct reservation_object *dst,
288 struct reservation_object *src)
289 {
290 struct reservation_object_list *src_list, *dst_list;
291 struct dma_fence *old, *new;
292 size_t size;
293 unsigned i;
294
295 rcu_read_lock();
296 src_list = rcu_dereference(src->fence);
297
298 retry:
299 if (src_list) {
300 unsigned shared_count = src_list->shared_count;
301
302 size = offsetof(typeof(*src_list), shared[shared_count]);
303 rcu_read_unlock();
304
305 dst_list = kmalloc(size, GFP_KERNEL);
306 if (!dst_list)
307 return -ENOMEM;
308
309 rcu_read_lock();
310 src_list = rcu_dereference(src->fence);
311 if (!src_list || src_list->shared_count > shared_count) {
312 kfree(dst_list);
313 goto retry;
314 }
315
316 dst_list->shared_count = 0;
317 dst_list->shared_max = shared_count;
318 for (i = 0; i < src_list->shared_count; ++i) {
319 struct dma_fence *fence;
320
321 fence = rcu_dereference(src_list->shared[i]);
322 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
323 &fence->flags))
324 continue;
325
326 if (!dma_fence_get_rcu(fence)) {
327 kfree(dst_list);
328 src_list = rcu_dereference(src->fence);
329 goto retry;
330 }
331
332 if (dma_fence_is_signaled(fence)) {
333 dma_fence_put(fence);
334 continue;
335 }
336
337 rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
338 }
339 } else {
340 dst_list = NULL;
341 }
342
343 new = dma_fence_get_rcu_safe(&src->fence_excl);
344 rcu_read_unlock();
345
346 kfree(dst->staged);
347 dst->staged = NULL;
348
349 src_list = reservation_object_get_list(dst);
350 old = reservation_object_get_excl(dst);
351
352 preempt_disable();
353 write_seqcount_begin(&dst->seq);
354 /* write_seqcount_begin provides the necessary memory barrier */
355 RCU_INIT_POINTER(dst->fence_excl, new);
356 RCU_INIT_POINTER(dst->fence, dst_list);
357 write_seqcount_end(&dst->seq);
358 preempt_enable();
359
360 if (src_list)
361 kfree_rcu(src_list, rcu);
362 dma_fence_put(old);
363
364 return 0;
365 }
366 EXPORT_SYMBOL(reservation_object_copy_fences);
367
368 /**
369 * reservation_object_get_fences_rcu - Get an object's shared and exclusive
370 * fences without update side lock held
371 * @obj: the reservation object
372 * @pfence_excl: the returned exclusive fence (or NULL)
373 * @pshared_count: the number of shared fences returned
374 * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
375 * the required size, and must be freed by caller)
376 *
377 * Retrieve all fences from the reservation object. If the pointer for the
378 * exclusive fence is not specified the fence is put into the array of the
379 * shared fences as well. Returns either zero or -ENOMEM.
380 */
reservation_object_get_fences_rcu(struct reservation_object * obj,struct dma_fence ** pfence_excl,unsigned * pshared_count,struct dma_fence *** pshared)381 int reservation_object_get_fences_rcu(struct reservation_object *obj,
382 struct dma_fence **pfence_excl,
383 unsigned *pshared_count,
384 struct dma_fence ***pshared)
385 {
386 struct dma_fence **shared = NULL;
387 struct dma_fence *fence_excl;
388 unsigned int shared_count;
389 int ret = 1;
390
391 do {
392 struct reservation_object_list *fobj;
393 unsigned int i, seq;
394 size_t sz = 0;
395
396 shared_count = i = 0;
397
398 rcu_read_lock();
399 seq = read_seqcount_begin(&obj->seq);
400
401 fence_excl = rcu_dereference(obj->fence_excl);
402 if (fence_excl && !dma_fence_get_rcu(fence_excl))
403 goto unlock;
404
405 fobj = rcu_dereference(obj->fence);
406 if (fobj)
407 sz += sizeof(*shared) * fobj->shared_max;
408
409 if (!pfence_excl && fence_excl)
410 sz += sizeof(*shared);
411
412 if (sz) {
413 struct dma_fence **nshared;
414
415 nshared = krealloc(shared, sz,
416 GFP_NOWAIT | __GFP_NOWARN);
417 if (!nshared) {
418 rcu_read_unlock();
419
420 dma_fence_put(fence_excl);
421 fence_excl = NULL;
422
423 nshared = krealloc(shared, sz, GFP_KERNEL);
424 if (nshared) {
425 shared = nshared;
426 continue;
427 }
428
429 ret = -ENOMEM;
430 break;
431 }
432 shared = nshared;
433 shared_count = fobj ? fobj->shared_count : 0;
434 for (i = 0; i < shared_count; ++i) {
435 shared[i] = rcu_dereference(fobj->shared[i]);
436 if (!dma_fence_get_rcu(shared[i]))
437 break;
438 }
439
440 if (!pfence_excl && fence_excl) {
441 shared[i] = fence_excl;
442 fence_excl = NULL;
443 ++i;
444 ++shared_count;
445 }
446 }
447
448 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
449 while (i--)
450 dma_fence_put(shared[i]);
451 dma_fence_put(fence_excl);
452 goto unlock;
453 }
454
455 ret = 0;
456 unlock:
457 rcu_read_unlock();
458 } while (ret);
459
460 if (!shared_count) {
461 kfree(shared);
462 shared = NULL;
463 }
464
465 *pshared_count = shared_count;
466 *pshared = shared;
467 if (pfence_excl)
468 *pfence_excl = fence_excl;
469
470 return ret;
471 }
472 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
473
474 /**
475 * reservation_object_wait_timeout_rcu - Wait on reservation's objects
476 * shared and/or exclusive fences.
477 * @obj: the reservation object
478 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
479 * @intr: if true, do interruptible wait
480 * @timeout: timeout value in jiffies or zero to return immediately
481 *
482 * RETURNS
483 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
484 * greater than zer on success.
485 */
reservation_object_wait_timeout_rcu(struct reservation_object * obj,bool wait_all,bool intr,unsigned long timeout)486 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
487 bool wait_all, bool intr,
488 unsigned long timeout)
489 {
490 struct dma_fence *fence;
491 unsigned seq, shared_count;
492 long ret = timeout ? timeout : 1;
493 int i;
494
495 retry:
496 shared_count = 0;
497 seq = read_seqcount_begin(&obj->seq);
498 rcu_read_lock();
499 i = -1;
500
501 fence = rcu_dereference(obj->fence_excl);
502 if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
503 if (!dma_fence_get_rcu(fence))
504 goto unlock_retry;
505
506 if (dma_fence_is_signaled(fence)) {
507 dma_fence_put(fence);
508 fence = NULL;
509 }
510
511 } else {
512 fence = NULL;
513 }
514
515 if (wait_all) {
516 struct reservation_object_list *fobj =
517 rcu_dereference(obj->fence);
518
519 if (fobj)
520 shared_count = fobj->shared_count;
521
522 for (i = 0; !fence && i < shared_count; ++i) {
523 struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
524
525 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
526 &lfence->flags))
527 continue;
528
529 if (!dma_fence_get_rcu(lfence))
530 goto unlock_retry;
531
532 if (dma_fence_is_signaled(lfence)) {
533 dma_fence_put(lfence);
534 continue;
535 }
536
537 fence = lfence;
538 break;
539 }
540 }
541
542 rcu_read_unlock();
543 if (fence) {
544 if (read_seqcount_retry(&obj->seq, seq)) {
545 dma_fence_put(fence);
546 goto retry;
547 }
548
549 ret = dma_fence_wait_timeout(fence, intr, ret);
550 dma_fence_put(fence);
551 if (ret > 0 && wait_all && (i + 1 < shared_count))
552 goto retry;
553 }
554 return ret;
555
556 unlock_retry:
557 rcu_read_unlock();
558 goto retry;
559 }
560 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
561
562
563 static inline int
reservation_object_test_signaled_single(struct dma_fence * passed_fence)564 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
565 {
566 struct dma_fence *fence, *lfence = passed_fence;
567 int ret = 1;
568
569 if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
570 fence = dma_fence_get_rcu(lfence);
571 if (!fence)
572 return -1;
573
574 ret = !!dma_fence_is_signaled(fence);
575 dma_fence_put(fence);
576 }
577 return ret;
578 }
579
580 /**
581 * reservation_object_test_signaled_rcu - Test if a reservation object's
582 * fences have been signaled.
583 * @obj: the reservation object
584 * @test_all: if true, test all fences, otherwise only test the exclusive
585 * fence
586 *
587 * RETURNS
588 * true if all fences signaled, else false
589 */
reservation_object_test_signaled_rcu(struct reservation_object * obj,bool test_all)590 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
591 bool test_all)
592 {
593 unsigned seq, shared_count;
594 int ret;
595
596 rcu_read_lock();
597 retry:
598 ret = true;
599 shared_count = 0;
600 seq = read_seqcount_begin(&obj->seq);
601
602 if (test_all) {
603 unsigned i;
604
605 struct reservation_object_list *fobj =
606 rcu_dereference(obj->fence);
607
608 if (fobj)
609 shared_count = fobj->shared_count;
610
611 for (i = 0; i < shared_count; ++i) {
612 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
613
614 ret = reservation_object_test_signaled_single(fence);
615 if (ret < 0)
616 goto retry;
617 else if (!ret)
618 break;
619 }
620
621 if (read_seqcount_retry(&obj->seq, seq))
622 goto retry;
623 }
624
625 if (!shared_count) {
626 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
627
628 if (fence_excl) {
629 ret = reservation_object_test_signaled_single(
630 fence_excl);
631 if (ret < 0)
632 goto retry;
633
634 if (read_seqcount_retry(&obj->seq, seq))
635 goto retry;
636 }
637 }
638
639 rcu_read_unlock();
640 return ret;
641 }
642 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
643