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