drivers/dma-buf/dma-resv.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/dma-resv.h>
  36 #include <linux/export.h>
  37 #include <linux/sched/mm.h>
  38
  39 /**
  40  * DOC: Reservation Object Overview
  41  *
  42  * The reservation object provides a mechanism to manage shared and
  43  * exclusive fences associated with a buffer.  A reservation object
  44  * can have attached one exclusive fence (normally associated with
  45  * write operations) or N shared fences (read operations).  The RCU
  46  * mechanism is used to protect read access to fences from locked
  47  * write-side updates.
  48  */
  49
  50 DEFINE_WD_CLASS(reservation_ww_class);
  51 EXPORT_SYMBOL(reservation_ww_class);
  52
  53 struct lock_class_key reservation_seqcount_class;
  54 EXPORT_SYMBOL(reservation_seqcount_class);
  55
  56 const char reservation_seqcount_string[] = "reservation_seqcount";
  57 EXPORT_SYMBOL(reservation_seqcount_string);
  58
  59 /**
  60  * dma_resv_list_alloc - allocate fence list
  61  * @shared_max: number of fences we need space for
  62  *
  63  * Allocate a new dma_resv_list and make sure to correctly initialize
  64  * shared_max.
  65  */
  66 static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
  67 {
  68         struct dma_resv_list *list;
  69
  70         list = kmalloc(offsetof(typeof(*list), shared[shared_max]), GFP_KERNEL);
  71         if (!list)
  72                 return NULL;
  73
  74         list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
  75                 sizeof(*list->shared);
  76
  77         return list;
  78 }
  79
  80 /**
  81  * dma_resv_list_free - free fence list
  82  * @list: list to free
  83  *
  84  * Free a dma_resv_list and make sure to drop all references.
  85  */
  86 static void dma_resv_list_free(struct dma_resv_list *list)
  87 {
  88         unsigned int i;
  89
  90         if (!list)
  91                 return;
  92
  93         for (i = 0; i < list->shared_count; ++i)
  94                 dma_fence_put(rcu_dereference_protected(list->shared[i], true));
  95
  96         kfree_rcu(list, rcu);
  97 }
  98
  99 #if IS_ENABLED(CONFIG_LOCKDEP)
 100 static int __init dma_resv_lockdep(void)
 101 {
 102         struct mm_struct *mm = mm_alloc();
 103         struct ww_acquire_ctx ctx;
 104         struct dma_resv obj;
 105         int ret;
 106
 107         if (!mm)
 108                 return -ENOMEM;
 109
 110         dma_resv_init(&obj);
 111
 112         down_read(&mm->mmap_sem);
 113         ww_acquire_init(&ctx, &reservation_ww_class);
 114         ret = dma_resv_lock(&obj, &ctx);
 115         if (ret == -EDEADLK)
 116                 dma_resv_lock_slow(&obj, &ctx);
 117         fs_reclaim_acquire(GFP_KERNEL);
 118         fs_reclaim_release(GFP_KERNEL);
 119         ww_mutex_unlock(&obj.lock);
 120         ww_acquire_fini(&ctx);
 121         up_read(&mm->mmap_sem);
 122
 123         mmput(mm);
 124
 125         return 0;
 126 }
 127 subsys_initcall(dma_resv_lockdep);
 128 #endif
 129
 130 /**
 131  * dma_resv_init - initialize a reservation object
 132  * @obj: the reservation object
 133  */
 134 void dma_resv_init(struct dma_resv *obj)
 135 {
 136         ww_mutex_init(&obj->lock, &reservation_ww_class);
 137
 138         __seqcount_init(&obj->seq, reservation_seqcount_string,
 139                         &reservation_seqcount_class);
 140         RCU_INIT_POINTER(obj->fence, NULL);
 141         RCU_INIT_POINTER(obj->fence_excl, NULL);
 142 }
 143 EXPORT_SYMBOL(dma_resv_init);
 144
 145 /**
 146  * dma_resv_fini - destroys a reservation object
 147  * @obj: the reservation object
 148  */
 149 void dma_resv_fini(struct dma_resv *obj)
 150 {
 151         struct dma_resv_list *fobj;
 152         struct dma_fence *excl;
 153
 154         /*
 155          * This object should be dead and all references must have
 156          * been released to it, so no need to be protected with rcu.
 157          */
 158         excl = rcu_dereference_protected(obj->fence_excl, 1);
 159         if (excl)
 160                 dma_fence_put(excl);
 161
 162         fobj = rcu_dereference_protected(obj->fence, 1);
 163         dma_resv_list_free(fobj);
 164         ww_mutex_destroy(&obj->lock);
 165 }
 166 EXPORT_SYMBOL(dma_resv_fini);
 167
 168 /**
 169  * dma_resv_reserve_shared - Reserve space to add shared fences to
 170  * a dma_resv.
 171  * @obj: reservation object
 172  * @num_fences: number of fences we want to add
 173  *
 174  * Should be called before dma_resv_add_shared_fence().  Must
 175  * be called with obj->lock held.
 176  *
 177  * RETURNS
 178  * Zero for success, or -errno
 179  */
 180 int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 181 {
 182         struct dma_resv_list *old, *new;
 183         unsigned int i, j, k, max;
 184
 185         dma_resv_assert_held(obj);
 186
 187         old = dma_resv_get_list(obj);
 188
 189         if (old && old->shared_max) {
 190                 if ((old->shared_count + num_fences) <= old->shared_max)
 191                         return 0;
 192                 else
 193                         max = max(old->shared_count + num_fences,
 194                                   old->shared_max * 2);
 195         } else {
 196                 max = 4;
 197         }
 198
 199         new = dma_resv_list_alloc(max);
 200         if (!new)
 201                 return -ENOMEM;
 202
 203         /*
 204          * no need to bump fence refcounts, rcu_read access
 205          * requires the use of kref_get_unless_zero, and the
 206          * references from the old struct are carried over to
 207          * the new.
 208          */
 209         for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
 210                 struct dma_fence *fence;
 211
 212                 fence = rcu_dereference_protected(old->shared[i],
 213                                                   dma_resv_held(obj));
 214                 if (dma_fence_is_signaled(fence))
 215                         RCU_INIT_POINTER(new->shared[--k], fence);
 216                 else
 217                         RCU_INIT_POINTER(new->shared[j++], fence);
 218         }
 219         new->shared_count = j;
 220
 221         /*
 222          * We are not changing the effective set of fences here so can
 223          * merely update the pointer to the new array; both existing
 224          * readers and new readers will see exactly the same set of
 225          * active (unsignaled) shared fences. Individual fences and the
 226          * old array are protected by RCU and so will not vanish under
 227          * the gaze of the rcu_read_lock() readers.
 228          */
 229         rcu_assign_pointer(obj->fence, new);
 230
 231         if (!old)
 232                 return 0;
 233
 234         /* Drop the references to the signaled fences */
 235         for (i = k; i < max; ++i) {
 236                 struct dma_fence *fence;
 237
 238                 fence = rcu_dereference_protected(new->shared[i],
 239                                                   dma_resv_held(obj));
 240                 dma_fence_put(fence);
 241         }
 242         kfree_rcu(old, rcu);
 243
 244         return 0;
 245 }
 246 EXPORT_SYMBOL(dma_resv_reserve_shared);
 247
 248 /**
 249  * dma_resv_add_shared_fence - Add a fence to a shared slot
 250  * @obj: the reservation object
 251  * @fence: the shared fence to add
 252  *
 253  * Add a fence to a shared slot, obj->lock must be held, and
 254  * dma_resv_reserve_shared() has been called.
 255  */
 256 void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
 257 {
 258         struct dma_resv_list *fobj;
 259         struct dma_fence *old;
 260         unsigned int i, count;
 261
 262         dma_fence_get(fence);
 263
 264         dma_resv_assert_held(obj);
 265
 266         fobj = dma_resv_get_list(obj);
 267         count = fobj->shared_count;
 268
 269         preempt_disable();
 270         write_seqcount_begin(&obj->seq);
 271
 272         for (i = 0; i < count; ++i) {
 273
 274                 old = rcu_dereference_protected(fobj->shared[i],
 275                                                 dma_resv_held(obj));
 276                 if (old->context == fence->context ||
 277                     dma_fence_is_signaled(old))
 278                         goto replace;
 279         }
 280
 281         BUG_ON(fobj->shared_count >= fobj->shared_max);
 282         old = NULL;
 283         count++;
 284
 285 replace:
 286         RCU_INIT_POINTER(fobj->shared[i], fence);
 287         /* pointer update must be visible before we extend the shared_count */
 288         smp_store_mb(fobj->shared_count, count);
 289
 290         write_seqcount_end(&obj->seq);
 291         preempt_enable();
 292         dma_fence_put(old);
 293 }
 294 EXPORT_SYMBOL(dma_resv_add_shared_fence);
 295
 296 /**
 297  * dma_resv_add_excl_fence - Add an exclusive fence.
 298  * @obj: the reservation object
 299  * @fence: the shared fence to add
 300  *
 301  * Add a fence to the exclusive slot.  The obj->lock must be held.
 302  */
 303 void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
 304 {
 305         struct dma_fence *old_fence = dma_resv_get_excl(obj);
 306         struct dma_resv_list *old;
 307         u32 i = 0;
 308
 309         dma_resv_assert_held(obj);
 310
 311         old = dma_resv_get_list(obj);
 312         if (old)
 313                 i = old->shared_count;
 314
 315         if (fence)
 316                 dma_fence_get(fence);
 317
 318         preempt_disable();
 319         write_seqcount_begin(&obj->seq);
 320         /* write_seqcount_begin provides the necessary memory barrier */
 321         RCU_INIT_POINTER(obj->fence_excl, fence);
 322         if (old)
 323                 old->shared_count = 0;
 324         write_seqcount_end(&obj->seq);
 325         preempt_enable();
 326
 327         /* inplace update, no shared fences */
 328         while (i--)
 329                 dma_fence_put(rcu_dereference_protected(old->shared[i],
 330                                                 dma_resv_held(obj)));
 331
 332         dma_fence_put(old_fence);
 333 }
 334 EXPORT_SYMBOL(dma_resv_add_excl_fence);
 335
 336 /**
 337 * dma_resv_copy_fences - Copy all fences from src to dst.
 338 * @dst: the destination reservation object
 339 * @src: the source reservation object
 340 *
 341 * Copy all fences from src to dst. dst-lock must be held.
 342 */
 343 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 344 {
 345         struct dma_resv_list *src_list, *dst_list;
 346         struct dma_fence *old, *new;
 347         unsigned i;
 348
 349         dma_resv_assert_held(dst);
 350
 351         rcu_read_lock();
 352         src_list = rcu_dereference(src->fence);
 353
 354 retry:
 355         if (src_list) {
 356                 unsigned shared_count = src_list->shared_count;
 357
 358                 rcu_read_unlock();
 359
 360                 dst_list = dma_resv_list_alloc(shared_count);
 361                 if (!dst_list)
 362                         return -ENOMEM;
 363
 364                 rcu_read_lock();
 365                 src_list = rcu_dereference(src->fence);
 366                 if (!src_list || src_list->shared_count > shared_count) {
 367                         kfree(dst_list);
 368                         goto retry;
 369                 }
 370
 371                 dst_list->shared_count = 0;
 372                 for (i = 0; i < src_list->shared_count; ++i) {
 373                         struct dma_fence *fence;
 374
 375                         fence = rcu_dereference(src_list->shared[i]);
 376                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 377                                      &fence->flags))
 378                                 continue;
 379
 380                         if (!dma_fence_get_rcu(fence)) {
 381                                 dma_resv_list_free(dst_list);
 382                                 src_list = rcu_dereference(src->fence);
 383                                 goto retry;
 384                         }
 385
 386                         if (dma_fence_is_signaled(fence)) {
 387                                 dma_fence_put(fence);
 388                                 continue;
 389                         }
 390
 391                         rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
 392                 }
 393         } else {
 394                 dst_list = NULL;
 395         }
 396
 397         new = dma_fence_get_rcu_safe(&src->fence_excl);
 398         rcu_read_unlock();
 399
 400         src_list = dma_resv_get_list(dst);
 401         old = dma_resv_get_excl(dst);
 402
 403         preempt_disable();
 404         write_seqcount_begin(&dst->seq);
 405         /* write_seqcount_begin provides the necessary memory barrier */
 406         RCU_INIT_POINTER(dst->fence_excl, new);
 407         RCU_INIT_POINTER(dst->fence, dst_list);
 408         write_seqcount_end(&dst->seq);
 409         preempt_enable();
 410
 411         dma_resv_list_free(src_list);
 412         dma_fence_put(old);
 413
 414         return 0;
 415 }
 416 EXPORT_SYMBOL(dma_resv_copy_fences);
 417
 418 /**
 419  * dma_resv_get_fences_rcu - Get an object's shared and exclusive
 420  * fences without update side lock held
 421  * @obj: the reservation object
 422  * @pfence_excl: the returned exclusive fence (or NULL)
 423  * @pshared_count: the number of shared fences returned
 424  * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 425  * the required size, and must be freed by caller)
 426  *
 427  * Retrieve all fences from the reservation object. If the pointer for the
 428  * exclusive fence is not specified the fence is put into the array of the
 429  * shared fences as well. Returns either zero or -ENOMEM.
 430  */
 431 int dma_resv_get_fences_rcu(struct dma_resv *obj,
 432                             struct dma_fence **pfence_excl,
 433                             unsigned *pshared_count,
 434                             struct dma_fence ***pshared)
 435 {
 436         struct dma_fence **shared = NULL;
 437         struct dma_fence *fence_excl;
 438         unsigned int shared_count;
 439         int ret = 1;
 440
 441         do {
 442                 struct dma_resv_list *fobj;
 443                 unsigned int i, seq;
 444                 size_t sz = 0;
 445
 446                 shared_count = i = 0;
 447
 448                 rcu_read_lock();
 449                 seq = read_seqcount_begin(&obj->seq);
 450
 451                 fence_excl = rcu_dereference(obj->fence_excl);
 452                 if (fence_excl && !dma_fence_get_rcu(fence_excl))
 453                         goto unlock;
 454
 455                 fobj = rcu_dereference(obj->fence);
 456                 if (fobj)
 457                         sz += sizeof(*shared) * fobj->shared_max;
 458
 459                 if (!pfence_excl && fence_excl)
 460                         sz += sizeof(*shared);
 461
 462                 if (sz) {
 463                         struct dma_fence **nshared;
 464
 465                         nshared = krealloc(shared, sz,
 466                                            GFP_NOWAIT | __GFP_NOWARN);
 467                         if (!nshared) {
 468                                 rcu_read_unlock();
 469
 470                                 dma_fence_put(fence_excl);
 471                                 fence_excl = NULL;
 472
 473                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 474                                 if (nshared) {
 475                                         shared = nshared;
 476                                         continue;
 477                                 }
 478
 479                                 ret = -ENOMEM;
 480                                 break;
 481                         }
 482                         shared = nshared;
 483                         shared_count = fobj ? fobj->shared_count : 0;
 484                         for (i = 0; i < shared_count; ++i) {
 485                                 shared[i] = rcu_dereference(fobj->shared[i]);
 486                                 if (!dma_fence_get_rcu(shared[i]))
 487                                         break;
 488                         }
 489                 }
 490
 491                 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
 492                         while (i--)
 493                                 dma_fence_put(shared[i]);
 494                         dma_fence_put(fence_excl);
 495                         goto unlock;
 496                 }
 497
 498                 ret = 0;
 499 unlock:
 500                 rcu_read_unlock();
 501         } while (ret);
 502
 503         if (pfence_excl)
 504                 *pfence_excl = fence_excl;
 505         else if (fence_excl)
 506                 shared[shared_count++] = fence_excl;
 507
 508         if (!shared_count) {
 509                 kfree(shared);
 510                 shared = NULL;
 511         }
 512
 513         *pshared_count = shared_count;
 514         *pshared = shared;
 515         return ret;
 516 }
 517 EXPORT_SYMBOL_GPL(dma_resv_get_fences_rcu);
 518
 519 /**
 520  * dma_resv_wait_timeout_rcu - Wait on reservation's objects
 521  * shared and/or exclusive fences.
 522  * @obj: the reservation object
 523  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 524  * @intr: if true, do interruptible wait
 525  * @timeout: timeout value in jiffies or zero to return immediately
 526  *
 527  * RETURNS
 528  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 529  * greater than zer on success.
 530  */
 531 long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
 532                                bool wait_all, bool intr,
 533                                unsigned long timeout)
 534 {
 535         struct dma_fence *fence;
 536         unsigned seq, shared_count;
 537         long ret = timeout ? timeout : 1;
 538         int i;
 539
 540 retry:
 541         shared_count = 0;
 542         seq = read_seqcount_begin(&obj->seq);
 543         rcu_read_lock();
 544         i = -1;
 545
 546         fence = rcu_dereference(obj->fence_excl);
 547         if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 548                 if (!dma_fence_get_rcu(fence))
 549                         goto unlock_retry;
 550
 551                 if (dma_fence_is_signaled(fence)) {
 552                         dma_fence_put(fence);
 553                         fence = NULL;
 554                 }
 555
 556         } else {
 557                 fence = NULL;
 558         }
 559
 560         if (wait_all) {
 561                 struct dma_resv_list *fobj = rcu_dereference(obj->fence);
 562
 563                 if (fobj)
 564                         shared_count = fobj->shared_count;
 565
 566                 for (i = 0; !fence && i < shared_count; ++i) {
 567                         struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
 568
 569                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 570                                      &lfence->flags))
 571                                 continue;
 572
 573                         if (!dma_fence_get_rcu(lfence))
 574                                 goto unlock_retry;
 575
 576                         if (dma_fence_is_signaled(lfence)) {
 577                                 dma_fence_put(lfence);
 578                                 continue;
 579                         }
 580
 581                         fence = lfence;
 582                         break;
 583                 }
 584         }
 585
 586         rcu_read_unlock();
 587         if (fence) {
 588                 if (read_seqcount_retry(&obj->seq, seq)) {
 589                         dma_fence_put(fence);
 590                         goto retry;
 591                 }
 592
 593                 ret = dma_fence_wait_timeout(fence, intr, ret);
 594                 dma_fence_put(fence);
 595                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 596                         goto retry;
 597         }
 598         return ret;
 599
 600 unlock_retry:
 601         rcu_read_unlock();
 602         goto retry;
 603 }
 604 EXPORT_SYMBOL_GPL(dma_resv_wait_timeout_rcu);
 605
 606
 607 static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
 608 {
 609         struct dma_fence *fence, *lfence = passed_fence;
 610         int ret = 1;
 611
 612         if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 613                 fence = dma_fence_get_rcu(lfence);
 614                 if (!fence)
 615                         return -1;
 616
 617                 ret = !!dma_fence_is_signaled(fence);
 618                 dma_fence_put(fence);
 619         }
 620         return ret;
 621 }
 622
 623 /**
 624  * dma_resv_test_signaled_rcu - Test if a reservation object's
 625  * fences have been signaled.
 626  * @obj: the reservation object
 627  * @test_all: if true, test all fences, otherwise only test the exclusive
 628  * fence
 629  *
 630  * RETURNS
 631  * true if all fences signaled, else false
 632  */
 633 bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
 634 {
 635         unsigned seq, shared_count;
 636         int ret;
 637
 638         rcu_read_lock();
 639 retry:
 640         ret = true;
 641         shared_count = 0;
 642         seq = read_seqcount_begin(&obj->seq);
 643
 644         if (test_all) {
 645                 unsigned i;
 646
 647                 struct dma_resv_list *fobj = rcu_dereference(obj->fence);
 648
 649                 if (fobj)
 650                         shared_count = fobj->shared_count;
 651
 652                 for (i = 0; i < shared_count; ++i) {
 653                         struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
 654
 655                         ret = dma_resv_test_signaled_single(fence);
 656                         if (ret < 0)
 657                                 goto retry;
 658                         else if (!ret)
 659                                 break;
 660                 }
 661
 662                 if (read_seqcount_retry(&obj->seq, seq))
 663                         goto retry;
 664         }
 665
 666         if (!shared_count) {
 667                 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
 668
 669                 if (fence_excl) {
 670                         ret = dma_resv_test_signaled_single(fence_excl);
 671                         if (ret < 0)
 672                                 goto retry;
 673
 674                         if (read_seqcount_retry(&obj->seq, seq))
 675                                 goto retry;
 676                 }
 677         }
 678
 679         rcu_read_unlock();
 680         return ret;
 681 }
 682 EXPORT_SYMBOL_GPL(dma_resv_test_signaled_rcu);