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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
49DEFINE_WW_CLASS(reservation_ww_class);
50EXPORT_SYMBOL(reservation_ww_class);
51
52struct lock_class_key reservation_seqcount_class;
53EXPORT_SYMBOL(reservation_seqcount_class);
54
55const char reservation_seqcount_string[] = "reservation_seqcount";
56EXPORT_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 */
69int 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}
100EXPORT_SYMBOL(reservation_object_reserve_shared);
101
102static void
103reservation_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
142static void
143reservation_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
184done:
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, rcu);
197
198 if (old_fence)
199 dma_fence_put(old_fence);
200}
201
202/**
203 * reservation_object_add_shared_fence - Add a fence to a shared slot
204 * @obj: the reservation object
205 * @fence: the shared fence to add
206 *
207 * Add a fence to a shared slot, obj->lock must be held, and
208 * reservation_object_reserve_shared() has been called.
209 */
210void reservation_object_add_shared_fence(struct reservation_object *obj,
211 struct dma_fence *fence)
212{
213 struct reservation_object_list *old, *fobj = obj->staged;
214
215 old = reservation_object_get_list(obj);
216 obj->staged = NULL;
217
218 if (!fobj) {
219 BUG_ON(old->shared_count >= old->shared_max);
220 reservation_object_add_shared_inplace(obj, old, fence);
221 } else
222 reservation_object_add_shared_replace(obj, old, fobj, fence);
223}
224EXPORT_SYMBOL(reservation_object_add_shared_fence);
225
226/**
227 * reservation_object_add_excl_fence - Add an exclusive fence.
228 * @obj: the reservation object
229 * @fence: the shared fence to add
230 *
231 * Add a fence to the exclusive slot. The obj->lock must be held.
232 */
233void reservation_object_add_excl_fence(struct reservation_object *obj,
234 struct dma_fence *fence)
235{
236 struct dma_fence *old_fence = reservation_object_get_excl(obj);
237 struct reservation_object_list *old;
238 u32 i = 0;
239
240 old = reservation_object_get_list(obj);
241 if (old)
242 i = old->shared_count;
243
244 if (fence)
245 dma_fence_get(fence);
246
247 preempt_disable();
248 write_seqcount_begin(&obj->seq);
249 /* write_seqcount_begin provides the necessary memory barrier */
250 RCU_INIT_POINTER(obj->fence_excl, fence);
251 if (old)
252 old->shared_count = 0;
253 write_seqcount_end(&obj->seq);
254 preempt_enable();
255
256 /* inplace update, no shared fences */
257 while (i--)
258 dma_fence_put(rcu_dereference_protected(old->shared[i],
259 reservation_object_held(obj)));
260
261 if (old_fence)
262 dma_fence_put(old_fence);
263}
264EXPORT_SYMBOL(reservation_object_add_excl_fence);
265
266/**
267 * reservation_object_get_fences_rcu - Get an object's shared and exclusive
268 * fences without update side lock held
269 * @obj: the reservation object
270 * @pfence_excl: the returned exclusive fence (or NULL)
271 * @pshared_count: the number of shared fences returned
272 * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
273 * the required size, and must be freed by caller)
274 *
275 * RETURNS
276 * Zero or -errno
277 */
278int reservation_object_get_fences_rcu(struct reservation_object *obj,
279 struct dma_fence **pfence_excl,
280 unsigned *pshared_count,
281 struct dma_fence ***pshared)
282{
283 struct dma_fence **shared = NULL;
284 struct dma_fence *fence_excl;
285 unsigned int shared_count;
286 int ret = 1;
287
288 do {
289 struct reservation_object_list *fobj;
290 unsigned seq;
291 unsigned int i;
292
293 shared_count = i = 0;
294
295 rcu_read_lock();
296 seq = read_seqcount_begin(&obj->seq);
297
298 fence_excl = rcu_dereference(obj->fence_excl);
299 if (fence_excl && !dma_fence_get_rcu(fence_excl))
300 goto unlock;
301
302 fobj = rcu_dereference(obj->fence);
303 if (fobj) {
304 struct dma_fence **nshared;
305 size_t sz = sizeof(*shared) * fobj->shared_max;
306
307 nshared = krealloc(shared, sz,
308 GFP_NOWAIT | __GFP_NOWARN);
309 if (!nshared) {
310 rcu_read_unlock();
311 nshared = krealloc(shared, sz, GFP_KERNEL);
312 if (nshared) {
313 shared = nshared;
314 continue;
315 }
316
317 ret = -ENOMEM;
318 break;
319 }
320 shared = nshared;
321 shared_count = fobj->shared_count;
322
323 for (i = 0; i < shared_count; ++i) {
324 shared[i] = rcu_dereference(fobj->shared[i]);
325 if (!dma_fence_get_rcu(shared[i]))
326 break;
327 }
328 }
329
330 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
331 while (i--)
332 dma_fence_put(shared[i]);
333 dma_fence_put(fence_excl);
334 goto unlock;
335 }
336
337 ret = 0;
338unlock:
339 rcu_read_unlock();
340 } while (ret);
341
342 if (!shared_count) {
343 kfree(shared);
344 shared = NULL;
345 }
346
347 *pshared_count = shared_count;
348 *pshared = shared;
349 *pfence_excl = fence_excl;
350
351 return ret;
352}
353EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
354
355/**
356 * reservation_object_wait_timeout_rcu - Wait on reservation's objects
357 * shared and/or exclusive fences.
358 * @obj: the reservation object
359 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
360 * @intr: if true, do interruptible wait
361 * @timeout: timeout value in jiffies or zero to return immediately
362 *
363 * RETURNS
364 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
365 * greater than zer on success.
366 */
367long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
368 bool wait_all, bool intr,
369 unsigned long timeout)
370{
371 struct dma_fence *fence;
372 unsigned seq, shared_count, i = 0;
373 long ret = timeout ? timeout : 1;
374
375retry:
376 fence = NULL;
377 shared_count = 0;
378 seq = read_seqcount_begin(&obj->seq);
379 rcu_read_lock();
380
381 if (wait_all) {
382 struct reservation_object_list *fobj =
383 rcu_dereference(obj->fence);
384
385 if (fobj)
386 shared_count = fobj->shared_count;
387
388 for (i = 0; i < shared_count; ++i) {
389 struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
390
391 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
392 &lfence->flags))
393 continue;
394
395 if (!dma_fence_get_rcu(lfence))
396 goto unlock_retry;
397
398 if (dma_fence_is_signaled(lfence)) {
399 dma_fence_put(lfence);
400 continue;
401 }
402
403 fence = lfence;
404 break;
405 }
406 }
407
408 if (!shared_count) {
409 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
410
411 if (fence_excl &&
412 !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
413 &fence_excl->flags)) {
414 if (!dma_fence_get_rcu(fence_excl))
415 goto unlock_retry;
416
417 if (dma_fence_is_signaled(fence_excl))
418 dma_fence_put(fence_excl);
419 else
420 fence = fence_excl;
421 }
422 }
423
424 rcu_read_unlock();
425 if (fence) {
426 if (read_seqcount_retry(&obj->seq, seq)) {
427 dma_fence_put(fence);
428 goto retry;
429 }
430
431 ret = dma_fence_wait_timeout(fence, intr, ret);
432 dma_fence_put(fence);
433 if (ret > 0 && wait_all && (i + 1 < shared_count))
434 goto retry;
435 }
436 return ret;
437
438unlock_retry:
439 rcu_read_unlock();
440 goto retry;
441}
442EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
443
444
445static inline int
446reservation_object_test_signaled_single(struct dma_fence *passed_fence)
447{
448 struct dma_fence *fence, *lfence = passed_fence;
449 int ret = 1;
450
451 if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
452 fence = dma_fence_get_rcu(lfence);
453 if (!fence)
454 return -1;
455
456 ret = !!dma_fence_is_signaled(fence);
457 dma_fence_put(fence);
458 }
459 return ret;
460}
461
462/**
463 * reservation_object_test_signaled_rcu - Test if a reservation object's
464 * fences have been signaled.
465 * @obj: the reservation object
466 * @test_all: if true, test all fences, otherwise only test the exclusive
467 * fence
468 *
469 * RETURNS
470 * true if all fences signaled, else false
471 */
472bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
473 bool test_all)
474{
475 unsigned seq, shared_count;
476 int ret;
477
478 rcu_read_lock();
479retry:
480 ret = true;
481 shared_count = 0;
482 seq = read_seqcount_begin(&obj->seq);
483
484 if (test_all) {
485 unsigned i;
486
487 struct reservation_object_list *fobj =
488 rcu_dereference(obj->fence);
489
490 if (fobj)
491 shared_count = fobj->shared_count;
492
493 for (i = 0; i < shared_count; ++i) {
494 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
495
496 ret = reservation_object_test_signaled_single(fence);
497 if (ret < 0)
498 goto retry;
499 else if (!ret)
500 break;
501 }
502
503 if (read_seqcount_retry(&obj->seq, seq))
504 goto retry;
505 }
506
507 if (!shared_count) {
508 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
509
510 if (fence_excl) {
511 ret = reservation_object_test_signaled_single(
512 fence_excl);
513 if (ret < 0)
514 goto retry;
515
516 if (read_seqcount_retry(&obj->seq, seq))
517 goto retry;
518 }
519 }
520
521 rcu_read_unlock();
522 return ret;
523}
524EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);