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_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  */
  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
 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                 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
 145                 fobj->shared_count++;
 146         }
 147
 148         write_seqcount_end(&obj->seq);
 149         preempt_enable();
 150
 151         dma_fence_put(signaled);
 152 }
 153
 154 static void
 155 reservation_object_add_shared_replace(struct reservation_object *obj,
 156                                       struct reservation_object_list *old,
 157                                       struct reservation_object_list *fobj,
 158                                       struct dma_fence *fence)
 159 {
 160         unsigned i, j, k;
 161
 162         dma_fence_get(fence);
 163
 164         if (!old) {
 165                 RCU_INIT_POINTER(fobj->shared[0], fence);
 166                 fobj->shared_count = 1;
 167                 goto done;
 168         }
 169
 170         /*
 171          * no need to bump fence refcounts, rcu_read access
 172          * requires the use of kref_get_unless_zero, and the
 173          * references from the old struct are carried over to
 174          * the new.
 175          */
 176         for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; ++i) {
 177                 struct dma_fence *check;
 178
 179                 check = rcu_dereference_protected(old->shared[i],
 180                                                 reservation_object_held(obj));
 181
 182                 if (check->context == fence->context ||
 183                     dma_fence_is_signaled(check))
 184                         RCU_INIT_POINTER(fobj->shared[--k], check);
 185                 else
 186                         RCU_INIT_POINTER(fobj->shared[j++], check);
 187         }
 188         fobj->shared_count = j;
 189         RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
 190         fobj->shared_count++;
 191
 192 done:
 193         preempt_disable();
 194         write_seqcount_begin(&obj->seq);
 195         /*
 196          * RCU_INIT_POINTER can be used here,
 197          * seqcount provides the necessary barriers
 198          */
 199         RCU_INIT_POINTER(obj->fence, fobj);
 200         write_seqcount_end(&obj->seq);
 201         preempt_enable();
 202
 203         if (!old)
 204                 return;
 205
 206         /* Drop the references to the signaled fences */
 207         for (i = k; i < fobj->shared_max; ++i) {
 208                 struct dma_fence *f;
 209
 210                 f = rcu_dereference_protected(fobj->shared[i],
 211                                               reservation_object_held(obj));
 212                 dma_fence_put(f);
 213         }
 214         kfree_rcu(old, rcu);
 215 }
 216
 217 /**
 218  * reservation_object_add_shared_fence - Add a fence to a shared slot
 219  * @obj: the reservation object
 220  * @fence: the shared fence to add
 221  *
 222  * Add a fence to a shared slot, obj->lock must be held, and
 223  * reservation_object_reserve_shared() has been called.
 224  */
 225 void reservation_object_add_shared_fence(struct reservation_object *obj,
 226                                          struct dma_fence *fence)
 227 {
 228         struct reservation_object_list *old, *fobj = obj->staged;
 229
 230         old = reservation_object_get_list(obj);
 231         obj->staged = NULL;
 232
 233         if (!fobj) {
 234                 BUG_ON(old->shared_count >= old->shared_max);
 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  */
 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 */
 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  * RETURNS
 378  * Zero or -errno
 379  */
 380 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 381                                       struct dma_fence **pfence_excl,
 382                                       unsigned *pshared_count,
 383                                       struct dma_fence ***pshared)
 384 {
 385         struct dma_fence **shared = NULL;
 386         struct dma_fence *fence_excl;
 387         unsigned int shared_count;
 388         int ret = 1;
 389
 390         do {
 391                 struct reservation_object_list *fobj;
 392                 unsigned seq;
 393                 unsigned int i;
 394
 395                 shared_count = i = 0;
 396
 397                 rcu_read_lock();
 398                 seq = read_seqcount_begin(&obj->seq);
 399
 400                 fence_excl = rcu_dereference(obj->fence_excl);
 401                 if (fence_excl && !dma_fence_get_rcu(fence_excl))
 402                         goto unlock;
 403
 404                 fobj = rcu_dereference(obj->fence);
 405                 if (fobj) {
 406                         struct dma_fence **nshared;
 407                         size_t sz = sizeof(*shared) * fobj->shared_max;
 408
 409                         nshared = krealloc(shared, sz,
 410                                            GFP_NOWAIT | __GFP_NOWARN);
 411                         if (!nshared) {
 412                                 rcu_read_unlock();
 413                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 414                                 if (nshared) {
 415                                         shared = nshared;
 416                                         continue;
 417                                 }
 418
 419                                 ret = -ENOMEM;
 420                                 break;
 421                         }
 422                         shared = nshared;
 423                         shared_count = fobj->shared_count;
 424
 425                         for (i = 0; i < shared_count; ++i) {
 426                                 shared[i] = rcu_dereference(fobj->shared[i]);
 427                                 if (!dma_fence_get_rcu(shared[i]))
 428                                         break;
 429                         }
 430                 }
 431
 432                 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
 433                         while (i--)
 434                                 dma_fence_put(shared[i]);
 435                         dma_fence_put(fence_excl);
 436                         goto unlock;
 437                 }
 438
 439                 ret = 0;
 440 unlock:
 441                 rcu_read_unlock();
 442         } while (ret);
 443
 444         if (!shared_count) {
 445                 kfree(shared);
 446                 shared = NULL;
 447         }
 448
 449         *pshared_count = shared_count;
 450         *pshared = shared;
 451         *pfence_excl = fence_excl;
 452
 453         return ret;
 454 }
 455 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 456
 457 /**
 458  * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 459  * shared and/or exclusive fences.
 460  * @obj: the reservation object
 461  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 462  * @intr: if true, do interruptible wait
 463  * @timeout: timeout value in jiffies or zero to return immediately
 464  *
 465  * RETURNS
 466  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 467  * greater than zer on success.
 468  */
 469 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 470                                          bool wait_all, bool intr,
 471                                          unsigned long timeout)
 472 {
 473         struct dma_fence *fence;
 474         unsigned seq, shared_count;
 475         long ret = timeout ? timeout : 1;
 476         int i;
 477
 478 retry:
 479         shared_count = 0;
 480         seq = read_seqcount_begin(&obj->seq);
 481         rcu_read_lock();
 482         i = -1;
 483
 484         fence = rcu_dereference(obj->fence_excl);
 485         if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 486                 if (!dma_fence_get_rcu(fence))
 487                         goto unlock_retry;
 488
 489                 if (dma_fence_is_signaled(fence)) {
 490                         dma_fence_put(fence);
 491                         fence = NULL;
 492                 }
 493
 494         } else {
 495                 fence = NULL;
 496         }
 497
 498         if (wait_all) {
 499                 struct reservation_object_list *fobj =
 500                                                 rcu_dereference(obj->fence);
 501
 502                 if (fobj)
 503                         shared_count = fobj->shared_count;
 504
 505                 for (i = 0; !fence && i < shared_count; ++i) {
 506                         struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
 507
 508                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 509                                      &lfence->flags))
 510                                 continue;
 511
 512                         if (!dma_fence_get_rcu(lfence))
 513                                 goto unlock_retry;
 514
 515                         if (dma_fence_is_signaled(lfence)) {
 516                                 dma_fence_put(lfence);
 517                                 continue;
 518                         }
 519
 520                         fence = lfence;
 521                         break;
 522                 }
 523         }
 524
 525         rcu_read_unlock();
 526         if (fence) {
 527                 if (read_seqcount_retry(&obj->seq, seq)) {
 528                         dma_fence_put(fence);
 529                         goto retry;
 530                 }
 531
 532                 ret = dma_fence_wait_timeout(fence, intr, ret);
 533                 dma_fence_put(fence);
 534                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 535                         goto retry;
 536         }
 537         return ret;
 538
 539 unlock_retry:
 540         rcu_read_unlock();
 541         goto retry;
 542 }
 543 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
 544
 545
 546 static inline int
 547 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
 548 {
 549         struct dma_fence *fence, *lfence = passed_fence;
 550         int ret = 1;
 551
 552         if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 553                 fence = dma_fence_get_rcu(lfence);
 554                 if (!fence)
 555                         return -1;
 556
 557                 ret = !!dma_fence_is_signaled(fence);
 558                 dma_fence_put(fence);
 559         }
 560         return ret;
 561 }
 562
 563 /**
 564  * reservation_object_test_signaled_rcu - Test if a reservation object's
 565  * fences have been signaled.
 566  * @obj: the reservation object
 567  * @test_all: if true, test all fences, otherwise only test the exclusive
 568  * fence
 569  *
 570  * RETURNS
 571  * true if all fences signaled, else false
 572  */
 573 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 574                                           bool test_all)
 575 {
 576         unsigned seq, shared_count;
 577         int ret;
 578
 579         rcu_read_lock();
 580 retry:
 581         ret = true;
 582         shared_count = 0;
 583         seq = read_seqcount_begin(&obj->seq);
 584
 585         if (test_all) {
 586                 unsigned i;
 587
 588                 struct reservation_object_list *fobj =
 589                                                 rcu_dereference(obj->fence);
 590
 591                 if (fobj)
 592                         shared_count = fobj->shared_count;
 593
 594                 for (i = 0; i < shared_count; ++i) {
 595                         struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
 596
 597                         ret = reservation_object_test_signaled_single(fence);
 598                         if (ret < 0)
 599                                 goto retry;
 600                         else if (!ret)
 601                                 break;
 602                 }
 603
 604                 if (read_seqcount_retry(&obj->seq, seq))
 605                         goto retry;
 606         }
 607
 608         if (!shared_count) {
 609                 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
 610
 611                 if (fence_excl) {
 612                         ret = reservation_object_test_signaled_single(
 613                                                                 fence_excl);
 614                         if (ret < 0)
 615                                 goto retry;
 616
 617                         if (read_seqcount_retry(&obj->seq, seq))
 618                                 goto retry;
 619                 }
 620         }
 621
 622         rcu_read_unlock();
 623         return ret;
 624 }
 625 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);