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_WW_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 M_DRM, 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 u32 i;
108
109 dma_fence_get(fence);
110
111 preempt_disable();
112 write_seqcount_begin(&obj->seq);
113
114 for (i = 0; i < fobj->shared_count; ++i) {
115 struct dma_fence *old_fence;
116
117 old_fence = rcu_dereference_protected(fobj->shared[i],
118 reservation_object_held(obj));
119
120 if (old_fence->context == fence->context) {
121 /* memory barrier is added by write_seqcount_begin */
122 RCU_INIT_POINTER(fobj->shared[i], fence);
123 write_seqcount_end(&obj->seq);
124 preempt_enable();
125
126 dma_fence_put(old_fence);
127 return;
128 }
129 }
130
131 /*
132 * memory barrier is added by write_seqcount_begin,
133 * fobj->shared_count is protected by this lock too
134 */
135 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
136 fobj->shared_count++;
137
138 write_seqcount_end(&obj->seq);
139 preempt_enable();
140 }
141
142 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)143 reservation_object_add_shared_replace(struct reservation_object *obj,
144 struct reservation_object_list *old,
145 struct reservation_object_list *fobj,
146 struct dma_fence *fence)
147 {
148 unsigned i;
149 struct dma_fence *old_fence = NULL;
150
151 dma_fence_get(fence);
152
153 if (!old) {
154 RCU_INIT_POINTER(fobj->shared[0], fence);
155 fobj->shared_count = 1;
156 goto done;
157 }
158
159 /*
160 * no need to bump fence refcounts, rcu_read access
161 * requires the use of kref_get_unless_zero, and the
162 * references from the old struct are carried over to
163 * the new.
164 */
165 fobj->shared_count = old->shared_count;
166
167 for (i = 0; i < old->shared_count; ++i) {
168 struct dma_fence *check;
169
170 check = rcu_dereference_protected(old->shared[i],
171 reservation_object_held(obj));
172
173 if (!old_fence && check->context == fence->context) {
174 old_fence = check;
175 RCU_INIT_POINTER(fobj->shared[i], fence);
176 } else
177 RCU_INIT_POINTER(fobj->shared[i], check);
178 }
179 if (!old_fence) {
180 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
181 fobj->shared_count++;
182 }
183
184 done:
185 preempt_disable();
186 write_seqcount_begin(&obj->seq);
187 /*
188 * RCU_INIT_POINTER can be used here,
189 * seqcount provides the necessary barriers
190 */
191 RCU_INIT_POINTER(obj->fence, fobj);
192 write_seqcount_end(&obj->seq);
193 preempt_enable();
194
195 if (old)
196 kfree_rcu(old, NULL);
197
198 dma_fence_put(old_fence);
199 }
200
201 /**
202 * reservation_object_add_shared_fence - Add a fence to a shared slot
203 * @obj: the reservation object
204 * @fence: the shared fence to add
205 *
206 * Add a fence to a shared slot, obj->lock must be held, and
207 * reservation_object_reserve_shared() has been called.
208 */
reservation_object_add_shared_fence(struct reservation_object * obj,struct dma_fence * fence)209 void reservation_object_add_shared_fence(struct reservation_object *obj,
210 struct dma_fence *fence)
211 {
212 struct reservation_object_list *old, *fobj = obj->staged;
213
214 old = reservation_object_get_list(obj);
215 obj->staged = NULL;
216
217 if (!fobj) {
218 BUG_ON(old->shared_count >= old->shared_max);
219 reservation_object_add_shared_inplace(obj, old, fence);
220 } else
221 reservation_object_add_shared_replace(obj, old, fobj, fence);
222 }
223 EXPORT_SYMBOL(reservation_object_add_shared_fence);
224
225 /**
226 * reservation_object_add_excl_fence - Add an exclusive fence.
227 * @obj: the reservation object
228 * @fence: the shared fence to add
229 *
230 * Add a fence to the exclusive slot. The obj->lock must be held.
231 */
reservation_object_add_excl_fence(struct reservation_object * obj,struct dma_fence * fence)232 void reservation_object_add_excl_fence(struct reservation_object *obj,
233 struct dma_fence *fence)
234 {
235 struct dma_fence *old_fence = reservation_object_get_excl(obj);
236 struct reservation_object_list *old;
237 u32 i = 0;
238
239 old = reservation_object_get_list(obj);
240 if (old)
241 i = old->shared_count;
242
243 if (fence)
244 dma_fence_get(fence);
245
246 preempt_disable();
247 write_seqcount_begin(&obj->seq);
248 /* write_seqcount_begin provides the necessary memory barrier */
249 RCU_INIT_POINTER(obj->fence_excl, fence);
250 if (old)
251 old->shared_count = 0;
252 write_seqcount_end(&obj->seq);
253 preempt_enable();
254
255 /* inplace update, no shared fences */
256 while (i--)
257 dma_fence_put(rcu_dereference_protected(old->shared[i],
258 reservation_object_held(obj)));
259
260 dma_fence_put(old_fence);
261 }
262 EXPORT_SYMBOL(reservation_object_add_excl_fence);
263
264 /**
265 * reservation_object_copy_fences - Copy all fences from src to dst.
266 * @dst: the destination reservation object
267 * @src: the source reservation object
268 *
269 * Copy all fences from src to dst. Both src->lock as well as dst-lock must be
270 * held.
271 */
reservation_object_copy_fences(struct reservation_object * dst,struct reservation_object * src)272 int reservation_object_copy_fences(struct reservation_object *dst,
273 struct reservation_object *src)
274 {
275 struct reservation_object_list *src_list, *dst_list;
276 struct dma_fence *old, *new;
277 size_t size;
278 unsigned i;
279
280 src_list = reservation_object_get_list(src);
281
282 if (src_list) {
283 size = offsetof(typeof(*src_list),
284 shared[src_list->shared_count]);
285 dst_list = kmalloc(size, M_DRM, GFP_KERNEL);
286 if (!dst_list)
287 return -ENOMEM;
288
289 dst_list->shared_count = src_list->shared_count;
290 dst_list->shared_max = src_list->shared_count;
291 for (i = 0; i < src_list->shared_count; ++i)
292 dst_list->shared[i] =
293 dma_fence_get(src_list->shared[i]);
294 } else {
295 dst_list = NULL;
296 }
297
298 kfree(dst->staged);
299 dst->staged = NULL;
300
301 src_list = reservation_object_get_list(dst);
302
303 old = reservation_object_get_excl(dst);
304 new = reservation_object_get_excl(src);
305
306 dma_fence_get(new);
307
308 preempt_disable();
309 write_seqcount_begin(&dst->seq);
310 /* write_seqcount_begin provides the necessary memory barrier */
311 RCU_INIT_POINTER(dst->fence_excl, new);
312 RCU_INIT_POINTER(dst->fence, dst_list);
313 write_seqcount_end(&dst->seq);
314 preempt_enable();
315
316 if (src_list)
317 kfree_rcu(src_list, rcu);
318 dma_fence_put(old);
319
320 return 0;
321 }
322 EXPORT_SYMBOL(reservation_object_copy_fences);
323
324 /**
325 * reservation_object_get_fences_rcu - Get an object's shared and exclusive
326 * fences without update side lock held
327 * @obj: the reservation object
328 * @pfence_excl: the returned exclusive fence (or NULL)
329 * @pshared_count: the number of shared fences returned
330 * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
331 * the required size, and must be freed by caller)
332 *
333 * RETURNS
334 * Zero or -errno
335 */
reservation_object_get_fences_rcu(struct reservation_object * obj,struct dma_fence ** pfence_excl,unsigned * pshared_count,struct dma_fence *** pshared)336 int reservation_object_get_fences_rcu(struct reservation_object *obj,
337 struct dma_fence **pfence_excl,
338 unsigned *pshared_count,
339 struct dma_fence ***pshared)
340 {
341 struct dma_fence **shared = NULL;
342 struct dma_fence *fence_excl;
343 unsigned int shared_count;
344 int ret = 1;
345
346 do {
347 struct reservation_object_list *fobj;
348 unsigned seq;
349 unsigned int i;
350
351 shared_count = i = 0;
352
353 rcu_read_lock();
354 seq = read_seqcount_begin(&obj->seq);
355
356 fence_excl = rcu_dereference(obj->fence_excl);
357 if (fence_excl && !dma_fence_get_rcu(fence_excl))
358 goto unlock;
359
360 fobj = rcu_dereference(obj->fence);
361 if (fobj) {
362 struct dma_fence **nshared;
363 size_t sz = sizeof(*shared) * fobj->shared_max;
364
365 nshared = krealloc(shared, sz, M_DRM,
366 GFP_NOWAIT | __GFP_NOWARN);
367 if (!nshared) {
368 rcu_read_unlock();
369 nshared = krealloc(shared, sz, M_DRM,
370 GFP_KERNEL);
371 if (nshared) {
372 shared = nshared;
373 continue;
374 }
375
376 ret = -ENOMEM;
377 break;
378 }
379 shared = nshared;
380 shared_count = fobj->shared_count;
381
382 for (i = 0; i < shared_count; ++i) {
383 shared[i] = rcu_dereference(fobj->shared[i]);
384 if (!dma_fence_get_rcu(shared[i]))
385 break;
386 }
387 }
388
389 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
390 while (i--)
391 dma_fence_put(shared[i]);
392 dma_fence_put(fence_excl);
393 goto unlock;
394 }
395
396 ret = 0;
397 unlock:
398 rcu_read_unlock();
399 } while (ret);
400
401 if (!shared_count) {
402 kfree(shared);
403 shared = NULL;
404 }
405
406 if (pshared_count)
407 *pshared_count = shared_count;
408 if (pshared)
409 *pshared = shared;
410 if (pfence_excl)
411 *pfence_excl = fence_excl;
412
413 return ret;
414 }
415 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
416
417 /**
418 * reservation_object_wait_timeout_rcu - Wait on reservation's objects
419 * shared and/or exclusive fences.
420 * @obj: the reservation object
421 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
422 * @intr: if true, do interruptible wait
423 * @timeout: timeout value in jiffies or zero to return immediately
424 *
425 * RETURNS
426 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
427 * greater than zer on success.
428 */
reservation_object_wait_timeout_rcu(struct reservation_object * obj,bool wait_all,bool intr,unsigned long timeout)429 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
430 bool wait_all, bool intr,
431 unsigned long timeout)
432 {
433 struct dma_fence *fence;
434 unsigned seq, shared_count, i = 0;
435 long ret = timeout ? timeout : 1;
436
437 retry:
438 shared_count = 0;
439 seq = read_seqcount_begin(&obj->seq);
440 rcu_read_lock();
441
442 fence = rcu_dereference(obj->fence_excl);
443 if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
444 if (!dma_fence_get_rcu(fence))
445 goto unlock_retry;
446
447 if (dma_fence_is_signaled(fence)) {
448 dma_fence_put(fence);
449 fence = NULL;
450 }
451
452 } else {
453 fence = NULL;
454 }
455
456 if (!fence && wait_all) {
457 struct reservation_object_list *fobj =
458 rcu_dereference(obj->fence);
459
460 if (fobj)
461 shared_count = fobj->shared_count;
462
463 for (i = 0; i < shared_count; ++i) {
464 struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
465
466 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
467 &lfence->flags))
468 continue;
469
470 if (!dma_fence_get_rcu(lfence))
471 goto unlock_retry;
472
473 if (dma_fence_is_signaled(lfence)) {
474 dma_fence_put(lfence);
475 continue;
476 }
477
478 fence = lfence;
479 break;
480 }
481 }
482
483 rcu_read_unlock();
484 if (fence) {
485 if (read_seqcount_retry(&obj->seq, seq)) {
486 dma_fence_put(fence);
487 goto retry;
488 }
489
490 ret = dma_fence_wait_timeout(fence, intr, ret);
491 dma_fence_put(fence);
492 if (ret > 0 && wait_all && (i + 1 < shared_count))
493 goto retry;
494 }
495 return ret;
496
497 unlock_retry:
498 rcu_read_unlock();
499 goto retry;
500 }
501 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
502
503
504 static inline int
reservation_object_test_signaled_single(struct dma_fence * passed_fence)505 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
506 {
507 struct dma_fence *fence, *lfence = passed_fence;
508 int ret = 1;
509
510 if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
511 fence = dma_fence_get_rcu(lfence);
512 if (!fence)
513 return -1;
514
515 ret = !!dma_fence_is_signaled(fence);
516 dma_fence_put(fence);
517 }
518 return ret;
519 }
520
521 /**
522 * reservation_object_test_signaled_rcu - Test if a reservation object's
523 * fences have been signaled.
524 * @obj: the reservation object
525 * @test_all: if true, test all fences, otherwise only test the exclusive
526 * fence
527 *
528 * RETURNS
529 * true if all fences signaled, else false
530 */
reservation_object_test_signaled_rcu(struct reservation_object * obj,bool test_all)531 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
532 bool test_all)
533 {
534 unsigned seq, shared_count;
535 int ret;
536
537 rcu_read_lock();
538 retry:
539 ret = true;
540 shared_count = 0;
541 seq = read_seqcount_begin(&obj->seq);
542
543 if (test_all) {
544 unsigned i;
545
546 struct reservation_object_list *fobj =
547 rcu_dereference(obj->fence);
548
549 if (fobj)
550 shared_count = fobj->shared_count;
551
552 for (i = 0; i < shared_count; ++i) {
553 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
554
555 ret = reservation_object_test_signaled_single(fence);
556 if (ret < 0)
557 goto retry;
558 else if (!ret)
559 break;
560 }
561
562 if (read_seqcount_retry(&obj->seq, seq))
563 goto retry;
564 }
565
566 if (!shared_count) {
567 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
568
569 if (fence_excl) {
570 ret = reservation_object_test_signaled_single(
571 fence_excl);
572 if (ret < 0)
573 goto retry;
574
575 if (read_seqcount_retry(&obj->seq, seq))
576 goto retry;
577 }
578 }
579
580 rcu_read_unlock();
581 return ret;
582 }
583 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
584