drivers/dma-buf/reservation.c

   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 shared fences to
  60  * a reservation_object.
  61  * @obj: reservation object
  62  * @num_fences: number of fences we want to add
  63  *
  64  * Should be called before reservation_object_add_shared_fence().  Must
  65  * be called with obj->lock held.
  66  *
  67  * RETURNS
  68  * Zero for success, or -errno
  69  */
  70 int reservation_object_reserve_shared(struct reservation_object *obj,
  71                                       unsigned int num_fences)
  72 {
  73         struct reservation_object_list *old, *new;
  74         unsigned int i, j, k, max;
  75
  76         reservation_object_assert_held(obj);
  77
  78         old = reservation_object_get_list(obj);
  79
  80         if (old && old->shared_max) {
  81                 if ((old->shared_count + num_fences) <= old->shared_max)
  82                         return 0;
  83                 else
  84                         max = max(old->shared_count + num_fences,
  85                                   old->shared_max * 2);
  86         } else {
  87                 max = 4;
  88         }
  89
  90         new = kmalloc(offsetof(typeof(*new), shared[max]), GFP_KERNEL);
  91         if (!new)
  92                 return -ENOMEM;
  93
  94         /*
  95          * no need to bump fence refcounts, rcu_read access
  96          * requires the use of kref_get_unless_zero, and the
  97          * references from the old struct are carried over to
  98          * the new.
  99          */
 100         for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
 101                 struct dma_fence *fence;
 102
 103                 fence = rcu_dereference_protected(old->shared[i],
 104                                                   reservation_object_held(obj));
 105                 if (dma_fence_is_signaled(fence))
 106                         RCU_INIT_POINTER(new->shared[--k], fence);
 107                 else
 108                         RCU_INIT_POINTER(new->shared[j++], fence);
 109         }
 110         new->shared_count = j;
 111         new->shared_max = max;
 112
 113         preempt_disable();
 114         write_seqcount_begin(&obj->seq);
 115         /*
 116          * RCU_INIT_POINTER can be used here,
 117          * seqcount provides the necessary barriers
 118          */
 119         RCU_INIT_POINTER(obj->fence, new);
 120         write_seqcount_end(&obj->seq);
 121         preempt_enable();
 122
 123         if (!old)
 124                 return 0;
 125
 126         /* Drop the references to the signaled fences */
 127         for (i = k; i < new->shared_max; ++i) {
 128                 struct dma_fence *fence;
 129
 130                 fence = rcu_dereference_protected(new->shared[i],
 131                                                   reservation_object_held(obj));
 132                 dma_fence_put(fence);
 133         }
 134         kfree_rcu(old, rcu);
 135
 136         return 0;
 137 }
 138 EXPORT_SYMBOL(reservation_object_reserve_shared);
 139
 140 /**
 141  * reservation_object_add_shared_fence - Add a fence to a shared slot
 142  * @obj: the reservation object
 143  * @fence: the shared fence to add
 144  *
 145  * Add a fence to a shared slot, obj->lock must be held, and
 146  * reservation_object_reserve_shared() has been called.
 147  */
 148 void reservation_object_add_shared_fence(struct reservation_object *obj,
 149                                          struct dma_fence *fence)
 150 {
 151         struct reservation_object_list *fobj;
 152         unsigned int i, count;
 153
 154         dma_fence_get(fence);
 155
 156         reservation_object_assert_held(obj);
 157
 158         fobj = reservation_object_get_list(obj);
 159         count = fobj->shared_count;
 160
 161         preempt_disable();
 162         write_seqcount_begin(&obj->seq);
 163
 164         for (i = 0; i < count; ++i) {
 165                 struct dma_fence *old_fence;
 166
 167                 old_fence = rcu_dereference_protected(fobj->shared[i],
 168                                                       reservation_object_held(obj));
 169                 if (old_fence->context == fence->context ||
 170                     dma_fence_is_signaled(old_fence)) {
 171                         dma_fence_put(old_fence);
 172                         goto replace;
 173                 }
 174         }
 175
 176         BUG_ON(fobj->shared_count >= fobj->shared_max);
 177         count++;
 178
 179 replace:
 180         RCU_INIT_POINTER(fobj->shared[i], fence);
 181         /* pointer update must be visible before we extend the shared_count */
 182         smp_store_mb(fobj->shared_count, count);
 183
 184         write_seqcount_end(&obj->seq);
 185         preempt_enable();
 186 }
 187 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 188
 189 /**
 190  * reservation_object_add_excl_fence - Add an exclusive fence.
 191  * @obj: the reservation object
 192  * @fence: the shared fence to add
 193  *
 194  * Add a fence to the exclusive slot.  The obj->lock must be held.
 195  */
 196 void reservation_object_add_excl_fence(struct reservation_object *obj,
 197                                        struct dma_fence *fence)
 198 {
 199         struct dma_fence *old_fence = reservation_object_get_excl(obj);
 200         struct reservation_object_list *old;
 201         u32 i = 0;
 202
 203         reservation_object_assert_held(obj);
 204
 205         old = reservation_object_get_list(obj);
 206         if (old)
 207                 i = old->shared_count;
 208
 209         if (fence)
 210                 dma_fence_get(fence);
 211
 212         preempt_disable();
 213         write_seqcount_begin(&obj->seq);
 214         /* write_seqcount_begin provides the necessary memory barrier */
 215         RCU_INIT_POINTER(obj->fence_excl, fence);
 216         if (old)
 217                 old->shared_count = 0;
 218         write_seqcount_end(&obj->seq);
 219         preempt_enable();
 220
 221         /* inplace update, no shared fences */
 222         while (i--)
 223                 dma_fence_put(rcu_dereference_protected(old->shared[i],
 224                                                 reservation_object_held(obj)));
 225
 226         dma_fence_put(old_fence);
 227 }
 228 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 229
 230 /**
 231 * reservation_object_copy_fences - Copy all fences from src to dst.
 232 * @dst: the destination reservation object
 233 * @src: the source reservation object
 234 *
 235 * Copy all fences from src to dst. dst-lock must be held.
 236 */
 237 int reservation_object_copy_fences(struct reservation_object *dst,
 238                                    struct reservation_object *src)
 239 {
 240         struct reservation_object_list *src_list, *dst_list;
 241         struct dma_fence *old, *new;
 242         size_t size;
 243         unsigned i;
 244
 245         reservation_object_assert_held(dst);
 246
 247         rcu_read_lock();
 248         src_list = rcu_dereference(src->fence);
 249
 250 retry:
 251         if (src_list) {
 252                 unsigned shared_count = src_list->shared_count;
 253
 254                 size = offsetof(typeof(*src_list), shared[shared_count]);
 255                 rcu_read_unlock();
 256
 257                 dst_list = kmalloc(size, GFP_KERNEL);
 258                 if (!dst_list)
 259                         return -ENOMEM;
 260
 261                 rcu_read_lock();
 262                 src_list = rcu_dereference(src->fence);
 263                 if (!src_list || src_list->shared_count > shared_count) {
 264                         kfree(dst_list);
 265                         goto retry;
 266                 }
 267
 268                 dst_list->shared_count = 0;
 269                 dst_list->shared_max = shared_count;
 270                 for (i = 0; i < src_list->shared_count; ++i) {
 271                         struct dma_fence *fence;
 272
 273                         fence = rcu_dereference(src_list->shared[i]);
 274                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 275                                      &fence->flags))
 276                                 continue;
 277
 278                         if (!dma_fence_get_rcu(fence)) {
 279                                 kfree(dst_list);
 280                                 src_list = rcu_dereference(src->fence);
 281                                 goto retry;
 282                         }
 283
 284                         if (dma_fence_is_signaled(fence)) {
 285                                 dma_fence_put(fence);
 286                                 continue;
 287                         }
 288
 289                         rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
 290                 }
 291         } else {
 292                 dst_list = NULL;
 293         }
 294
 295         new = dma_fence_get_rcu_safe(&src->fence_excl);
 296         rcu_read_unlock();
 297
 298         src_list = reservation_object_get_list(dst);
 299         old = reservation_object_get_excl(dst);
 300
 301         preempt_disable();
 302         write_seqcount_begin(&dst->seq);
 303         /* write_seqcount_begin provides the necessary memory barrier */
 304         RCU_INIT_POINTER(dst->fence_excl, new);
 305         RCU_INIT_POINTER(dst->fence, dst_list);
 306         write_seqcount_end(&dst->seq);
 307         preempt_enable();
 308
 309         if (src_list)
 310                 kfree_rcu(src_list, rcu);
 311         dma_fence_put(old);
 312
 313         return 0;
 314 }
 315 EXPORT_SYMBOL(reservation_object_copy_fences);
 316
 317 /**
 318  * reservation_object_get_fences_rcu - Get an object's shared and exclusive
 319  * fences without update side lock held
 320  * @obj: the reservation object
 321  * @pfence_excl: the returned exclusive fence (or NULL)
 322  * @pshared_count: the number of shared fences returned
 323  * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 324  * the required size, and must be freed by caller)
 325  *
 326  * Retrieve all fences from the reservation object. If the pointer for the
 327  * exclusive fence is not specified the fence is put into the array of the
 328  * shared fences as well. Returns either zero or -ENOMEM.
 329  */
 330 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 331                                       struct dma_fence **pfence_excl,
 332                                       unsigned *pshared_count,
 333                                       struct dma_fence ***pshared)
 334 {
 335         struct dma_fence **shared = NULL;
 336         struct dma_fence *fence_excl;
 337         unsigned int shared_count;
 338         int ret = 1;
 339
 340         do {
 341                 struct reservation_object_list *fobj;
 342                 unsigned int i, seq;
 343                 size_t sz = 0;
 344
 345                 shared_count = i = 0;
 346
 347                 rcu_read_lock();
 348                 seq = read_seqcount_begin(&obj->seq);
 349
 350                 fence_excl = rcu_dereference(obj->fence_excl);
 351                 if (fence_excl && !dma_fence_get_rcu(fence_excl))
 352                         goto unlock;
 353
 354                 fobj = rcu_dereference(obj->fence);
 355                 if (fobj)
 356                         sz += sizeof(*shared) * fobj->shared_max;
 357
 358                 if (!pfence_excl && fence_excl)
 359                         sz += sizeof(*shared);
 360
 361                 if (sz) {
 362                         struct dma_fence **nshared;
 363
 364                         nshared = krealloc(shared, sz,
 365                                            GFP_NOWAIT | __GFP_NOWARN);
 366                         if (!nshared) {
 367                                 rcu_read_unlock();
 368
 369                                 dma_fence_put(fence_excl);
 370                                 fence_excl = NULL;
 371
 372                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 373                                 if (nshared) {
 374                                         shared = nshared;
 375                                         continue;
 376                                 }
 377
 378                                 ret = -ENOMEM;
 379                                 break;
 380                         }
 381                         shared = nshared;
 382                         shared_count = fobj ? fobj->shared_count : 0;
 383                         for (i = 0; i < shared_count; ++i) {
 384                                 shared[i] = rcu_dereference(fobj->shared[i]);
 385                                 if (!dma_fence_get_rcu(shared[i]))
 386                                         break;
 387                         }
 388
 389                         if (!pfence_excl && fence_excl) {
 390                                 shared[i] = fence_excl;
 391                                 fence_excl = NULL;
 392                                 ++i;
 393                                 ++shared_count;
 394                         }
 395                 }
 396
 397                 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
 398                         while (i--)
 399                                 dma_fence_put(shared[i]);
 400                         dma_fence_put(fence_excl);
 401                         goto unlock;
 402                 }
 403
 404                 ret = 0;
 405 unlock:
 406                 rcu_read_unlock();
 407         } while (ret);
 408
 409         if (!shared_count) {
 410                 kfree(shared);
 411                 shared = NULL;
 412         }
 413
 414         *pshared_count = shared_count;
 415         *pshared = shared;
 416         if (pfence_excl)
 417                 *pfence_excl = fence_excl;
 418
 419         return ret;
 420 }
 421 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 422
 423 /**
 424  * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 425  * shared and/or exclusive fences.
 426  * @obj: the reservation object
 427  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 428  * @intr: if true, do interruptible wait
 429  * @timeout: timeout value in jiffies or zero to return immediately
 430  *
 431  * RETURNS
 432  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 433  * greater than zer on success.
 434  */
 435 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 436                                          bool wait_all, bool intr,
 437                                          unsigned long timeout)
 438 {
 439         struct dma_fence *fence;
 440         unsigned seq, shared_count;
 441         long ret = timeout ? timeout : 1;
 442         int i;
 443
 444 retry:
 445         shared_count = 0;
 446         seq = read_seqcount_begin(&obj->seq);
 447         rcu_read_lock();
 448         i = -1;
 449
 450         fence = rcu_dereference(obj->fence_excl);
 451         if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 452                 if (!dma_fence_get_rcu(fence))
 453                         goto unlock_retry;
 454
 455                 if (dma_fence_is_signaled(fence)) {
 456                         dma_fence_put(fence);
 457                         fence = NULL;
 458                 }
 459
 460         } else {
 461                 fence = NULL;
 462         }
 463
 464         if (wait_all) {
 465                 struct reservation_object_list *fobj =
 466                                                 rcu_dereference(obj->fence);
 467
 468                 if (fobj)
 469                         shared_count = fobj->shared_count;
 470
 471                 for (i = 0; !fence && i < shared_count; ++i) {
 472                         struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
 473
 474                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 475                                      &lfence->flags))
 476                                 continue;
 477
 478                         if (!dma_fence_get_rcu(lfence))
 479                                 goto unlock_retry;
 480
 481                         if (dma_fence_is_signaled(lfence)) {
 482                                 dma_fence_put(lfence);
 483                                 continue;
 484                         }
 485
 486                         fence = lfence;
 487                         break;
 488                 }
 489         }
 490
 491         rcu_read_unlock();
 492         if (fence) {
 493                 if (read_seqcount_retry(&obj->seq, seq)) {
 494                         dma_fence_put(fence);
 495                         goto retry;
 496                 }
 497
 498                 ret = dma_fence_wait_timeout(fence, intr, ret);
 499                 dma_fence_put(fence);
 500                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 501                         goto retry;
 502         }
 503         return ret;
 504
 505 unlock_retry:
 506         rcu_read_unlock();
 507         goto retry;
 508 }
 509 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
 510
 511
 512 static inline int
 513 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
 514 {
 515         struct dma_fence *fence, *lfence = passed_fence;
 516         int ret = 1;
 517
 518         if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 519                 fence = dma_fence_get_rcu(lfence);
 520                 if (!fence)
 521                         return -1;
 522
 523                 ret = !!dma_fence_is_signaled(fence);
 524                 dma_fence_put(fence);
 525         }
 526         return ret;
 527 }
 528
 529 /**
 530  * reservation_object_test_signaled_rcu - Test if a reservation object's
 531  * fences have been signaled.
 532  * @obj: the reservation object
 533  * @test_all: if true, test all fences, otherwise only test the exclusive
 534  * fence
 535  *
 536  * RETURNS
 537  * true if all fences signaled, else false
 538  */
 539 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 540                                           bool test_all)
 541 {
 542         unsigned seq, shared_count;
 543         int ret;
 544
 545         rcu_read_lock();
 546 retry:
 547         ret = true;
 548         shared_count = 0;
 549         seq = read_seqcount_begin(&obj->seq);
 550
 551         if (test_all) {
 552                 unsigned i;
 553
 554                 struct reservation_object_list *fobj =
 555                                                 rcu_dereference(obj->fence);
 556
 557                 if (fobj)
 558                         shared_count = fobj->shared_count;
 559
 560                 for (i = 0; i < shared_count; ++i) {
 561                         struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
 562
 563                         ret = reservation_object_test_signaled_single(fence);
 564                         if (ret < 0)
 565                                 goto retry;
 566                         else if (!ret)
 567                                 break;
 568                 }
 569
 570                 if (read_seqcount_retry(&obj->seq, seq))
 571                         goto retry;
 572         }
 573
 574         if (!shared_count) {
 575                 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
 576
 577                 if (fence_excl) {
 578                         ret = reservation_object_test_signaled_single(
 579                                                                 fence_excl);
 580                         if (ret < 0)
 581                                 goto retry;
 582
 583                         if (read_seqcount_retry(&obj->seq, seq))
 584                                 goto retry;
 585                 }
 586         }
 587
 588         rcu_read_unlock();
 589         return ret;
 590 }
 591 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);