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         u32 i;
 108
 109         dma_fence_get(fence);
 110
 111         preempt_disable();
 112         write_seqcount_begin(&obj->seq);
 113
 114         for (i = 0; i < fobj->shared_count; ++i) {
 115                 struct dma_fence *old_fence;
 116
 117                 old_fence = rcu_dereference_protected(fobj->shared[i],
 118                                                 reservation_object_held(obj));
 119
 120                 if (old_fence->context == fence->context) {
 121                         /* memory barrier is added by write_seqcount_begin */
 122                         RCU_INIT_POINTER(fobj->shared[i], fence);
 123                         write_seqcount_end(&obj->seq);
 124                         preempt_enable();
 125
 126                         dma_fence_put(old_fence);
 127                         return;
 128                 }
 129         }
 130
 131         /*
 132          * memory barrier is added by write_seqcount_begin,
 133          * fobj->shared_count is protected by this lock too
 134          */
 135         RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
 136         fobj->shared_count++;
 137
 138         write_seqcount_end(&obj->seq);
 139         preempt_enable();
 140 }
 141
 142 static void
 143 reservation_object_add_shared_replace(struct reservation_object *obj,
 144                                       struct reservation_object_list *old,
 145                                       struct reservation_object_list *fobj,
 146                                       struct dma_fence *fence)
 147 {
 148         unsigned i;
 149         struct dma_fence *old_fence = NULL;
 150
 151         dma_fence_get(fence);
 152
 153         if (!old) {
 154                 RCU_INIT_POINTER(fobj->shared[0], fence);
 155                 fobj->shared_count = 1;
 156                 goto done;
 157         }
 158
 159         /*
 160          * no need to bump fence refcounts, rcu_read access
 161          * requires the use of kref_get_unless_zero, and the
 162          * references from the old struct are carried over to
 163          * the new.
 164          */
 165         fobj->shared_count = old->shared_count;
 166
 167         for (i = 0; i < old->shared_count; ++i) {
 168                 struct dma_fence *check;
 169
 170                 check = rcu_dereference_protected(old->shared[i],
 171                                                 reservation_object_held(obj));
 172
 173                 if (!old_fence && check->context == fence->context) {
 174                         old_fence = check;
 175                         RCU_INIT_POINTER(fobj->shared[i], fence);
 176                 } else
 177                         RCU_INIT_POINTER(fobj->shared[i], check);
 178         }
 179         if (!old_fence) {
 180                 RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
 181                 fobj->shared_count++;
 182         }
 183
 184 done:
 185         preempt_disable();
 186         write_seqcount_begin(&obj->seq);
 187         /*
 188          * RCU_INIT_POINTER can be used here,
 189          * seqcount provides the necessary barriers
 190          */
 191         RCU_INIT_POINTER(obj->fence, fobj);
 192         write_seqcount_end(&obj->seq);
 193         preempt_enable();
 194
 195         if (old)
 196                 kfree_rcu(old, rcu);
 197
 198         dma_fence_put(old_fence);
 199 }
 200
 201 /**
 202  * reservation_object_add_shared_fence - Add a fence to a shared slot
 203  * @obj: the reservation object
 204  * @fence: the shared fence to add
 205  *
 206  * Add a fence to a shared slot, obj->lock must be held, and
 207  * reservation_object_reserve_shared() has been called.
 208  */
 209 void reservation_object_add_shared_fence(struct reservation_object *obj,
 210                                          struct dma_fence *fence)
 211 {
 212         struct reservation_object_list *old, *fobj = obj->staged;
 213
 214         old = reservation_object_get_list(obj);
 215         obj->staged = NULL;
 216
 217         if (!fobj) {
 218                 BUG_ON(old->shared_count >= old->shared_max);
 219                 reservation_object_add_shared_inplace(obj, old, fence);
 220         } else
 221                 reservation_object_add_shared_replace(obj, old, fobj, fence);
 222 }
 223 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 224
 225 /**
 226  * reservation_object_add_excl_fence - Add an exclusive fence.
 227  * @obj: the reservation object
 228  * @fence: the shared fence to add
 229  *
 230  * Add a fence to the exclusive slot.  The obj->lock must be held.
 231  */
 232 void reservation_object_add_excl_fence(struct reservation_object *obj,
 233                                        struct dma_fence *fence)
 234 {
 235         struct dma_fence *old_fence = reservation_object_get_excl(obj);
 236         struct reservation_object_list *old;
 237         u32 i = 0;
 238
 239         old = reservation_object_get_list(obj);
 240         if (old)
 241                 i = old->shared_count;
 242
 243         if (fence)
 244                 dma_fence_get(fence);
 245
 246         preempt_disable();
 247         write_seqcount_begin(&obj->seq);
 248         /* write_seqcount_begin provides the necessary memory barrier */
 249         RCU_INIT_POINTER(obj->fence_excl, fence);
 250         if (old)
 251                 old->shared_count = 0;
 252         write_seqcount_end(&obj->seq);
 253         preempt_enable();
 254
 255         /* inplace update, no shared fences */
 256         while (i--)
 257                 dma_fence_put(rcu_dereference_protected(old->shared[i],
 258                                                 reservation_object_held(obj)));
 259
 260         dma_fence_put(old_fence);
 261 }
 262 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 263
 264 /**
 265 * reservation_object_copy_fences - Copy all fences from src to dst.
 266 * @dst: the destination reservation object
 267 * @src: the source reservation object
 268 *
 269 * Copy all fences from src to dst. dst-lock must be held.
 270 */
 271 int reservation_object_copy_fences(struct reservation_object *dst,
 272                                    struct reservation_object *src)
 273 {
 274         struct reservation_object_list *src_list, *dst_list;
 275         struct dma_fence *old, *new;
 276         size_t size;
 277         unsigned i;
 278
 279         rcu_read_lock();
 280         src_list = rcu_dereference(src->fence);
 281
 282 retry:
 283         if (src_list) {
 284                 unsigned shared_count = src_list->shared_count;
 285
 286                 size = offsetof(typeof(*src_list), shared[shared_count]);
 287                 rcu_read_unlock();
 288
 289                 dst_list = kmalloc(size, GFP_KERNEL);
 290                 if (!dst_list)
 291                         return -ENOMEM;
 292
 293                 rcu_read_lock();
 294                 src_list = rcu_dereference(src->fence);
 295                 if (!src_list || src_list->shared_count > shared_count) {
 296                         kfree(dst_list);
 297                         goto retry;
 298                 }
 299
 300                 dst_list->shared_count = 0;
 301                 dst_list->shared_max = shared_count;
 302                 for (i = 0; i < src_list->shared_count; ++i) {
 303                         struct dma_fence *fence;
 304
 305                         fence = rcu_dereference(src_list->shared[i]);
 306                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 307                                      &fence->flags))
 308                                 continue;
 309
 310                         if (!dma_fence_get_rcu(fence)) {
 311                                 kfree(dst_list);
 312                                 src_list = rcu_dereference(src->fence);
 313                                 goto retry;
 314                         }
 315
 316                         if (dma_fence_is_signaled(fence)) {
 317                                 dma_fence_put(fence);
 318                                 continue;
 319                         }
 320
 321                         dst_list->shared[dst_list->shared_count++] = fence;
 322                 }
 323         } else {
 324                 dst_list = NULL;
 325         }
 326
 327         new = dma_fence_get_rcu_safe(&src->fence_excl);
 328         rcu_read_unlock();
 329
 330         kfree(dst->staged);
 331         dst->staged = NULL;
 332
 333         src_list = reservation_object_get_list(dst);
 334         old = reservation_object_get_excl(dst);
 335
 336         preempt_disable();
 337         write_seqcount_begin(&dst->seq);
 338         /* write_seqcount_begin provides the necessary memory barrier */
 339         RCU_INIT_POINTER(dst->fence_excl, new);
 340         RCU_INIT_POINTER(dst->fence, dst_list);
 341         write_seqcount_end(&dst->seq);
 342         preempt_enable();
 343
 344         if (src_list)
 345                 kfree_rcu(src_list, rcu);
 346         dma_fence_put(old);
 347
 348         return 0;
 349 }
 350 EXPORT_SYMBOL(reservation_object_copy_fences);
 351
 352 /**
 353  * reservation_object_get_fences_rcu - Get an object's shared and exclusive
 354  * fences without update side lock held
 355  * @obj: the reservation object
 356  * @pfence_excl: the returned exclusive fence (or NULL)
 357  * @pshared_count: the number of shared fences returned
 358  * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 359  * the required size, and must be freed by caller)
 360  *
 361  * RETURNS
 362  * Zero or -errno
 363  */
 364 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 365                                       struct dma_fence **pfence_excl,
 366                                       unsigned *pshared_count,
 367                                       struct dma_fence ***pshared)
 368 {
 369         struct dma_fence **shared = NULL;
 370         struct dma_fence *fence_excl;
 371         unsigned int shared_count;
 372         int ret = 1;
 373
 374         do {
 375                 struct reservation_object_list *fobj;
 376                 unsigned seq;
 377                 unsigned int i;
 378
 379                 shared_count = i = 0;
 380
 381                 rcu_read_lock();
 382                 seq = read_seqcount_begin(&obj->seq);
 383
 384                 fence_excl = rcu_dereference(obj->fence_excl);
 385                 if (fence_excl && !dma_fence_get_rcu(fence_excl))
 386                         goto unlock;
 387
 388                 fobj = rcu_dereference(obj->fence);
 389                 if (fobj) {
 390                         struct dma_fence **nshared;
 391                         size_t sz = sizeof(*shared) * fobj->shared_max;
 392
 393                         nshared = krealloc(shared, sz,
 394                                            GFP_NOWAIT | __GFP_NOWARN);
 395                         if (!nshared) {
 396                                 rcu_read_unlock();
 397                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 398                                 if (nshared) {
 399                                         shared = nshared;
 400                                         continue;
 401                                 }
 402
 403                                 ret = -ENOMEM;
 404                                 break;
 405                         }
 406                         shared = nshared;
 407                         shared_count = fobj->shared_count;
 408
 409                         for (i = 0; i < shared_count; ++i) {
 410                                 shared[i] = rcu_dereference(fobj->shared[i]);
 411                                 if (!dma_fence_get_rcu(shared[i]))
 412                                         break;
 413                         }
 414                 }
 415
 416                 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
 417                         while (i--)
 418                                 dma_fence_put(shared[i]);
 419                         dma_fence_put(fence_excl);
 420                         goto unlock;
 421                 }
 422
 423                 ret = 0;
 424 unlock:
 425                 rcu_read_unlock();
 426         } while (ret);
 427
 428         if (!shared_count) {
 429                 kfree(shared);
 430                 shared = NULL;
 431         }
 432
 433         *pshared_count = shared_count;
 434         *pshared = shared;
 435         *pfence_excl = fence_excl;
 436
 437         return ret;
 438 }
 439 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 440
 441 /**
 442  * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 443  * shared and/or exclusive fences.
 444  * @obj: the reservation object
 445  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 446  * @intr: if true, do interruptible wait
 447  * @timeout: timeout value in jiffies or zero to return immediately
 448  *
 449  * RETURNS
 450  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 451  * greater than zer on success.
 452  */
 453 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 454                                          bool wait_all, bool intr,
 455                                          unsigned long timeout)
 456 {
 457         struct dma_fence *fence;
 458         unsigned seq, shared_count;
 459         long ret = timeout ? timeout : 1;
 460         int i;
 461
 462 retry:
 463         shared_count = 0;
 464         seq = read_seqcount_begin(&obj->seq);
 465         rcu_read_lock();
 466         i = -1;
 467
 468         fence = rcu_dereference(obj->fence_excl);
 469         if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 470                 if (!dma_fence_get_rcu(fence))
 471                         goto unlock_retry;
 472
 473                 if (dma_fence_is_signaled(fence)) {
 474                         dma_fence_put(fence);
 475                         fence = NULL;
 476                 }
 477
 478         } else {
 479                 fence = NULL;
 480         }
 481
 482         if (wait_all) {
 483                 struct reservation_object_list *fobj =
 484                                                 rcu_dereference(obj->fence);
 485
 486                 if (fobj)
 487                         shared_count = fobj->shared_count;
 488
 489                 for (i = 0; !fence && i < shared_count; ++i) {
 490                         struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
 491
 492                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 493                                      &lfence->flags))
 494                                 continue;
 495
 496                         if (!dma_fence_get_rcu(lfence))
 497                                 goto unlock_retry;
 498
 499                         if (dma_fence_is_signaled(lfence)) {
 500                                 dma_fence_put(lfence);
 501                                 continue;
 502                         }
 503
 504                         fence = lfence;
 505                         break;
 506                 }
 507         }
 508
 509         rcu_read_unlock();
 510         if (fence) {
 511                 if (read_seqcount_retry(&obj->seq, seq)) {
 512                         dma_fence_put(fence);
 513                         goto retry;
 514                 }
 515
 516                 ret = dma_fence_wait_timeout(fence, intr, ret);
 517                 dma_fence_put(fence);
 518                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 519                         goto retry;
 520         }
 521         return ret;
 522
 523 unlock_retry:
 524         rcu_read_unlock();
 525         goto retry;
 526 }
 527 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
 528
 529
 530 static inline int
 531 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
 532 {
 533         struct dma_fence *fence, *lfence = passed_fence;
 534         int ret = 1;
 535
 536         if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 537                 fence = dma_fence_get_rcu(lfence);
 538                 if (!fence)
 539                         return -1;
 540
 541                 ret = !!dma_fence_is_signaled(fence);
 542                 dma_fence_put(fence);
 543         }
 544         return ret;
 545 }
 546
 547 /**
 548  * reservation_object_test_signaled_rcu - Test if a reservation object's
 549  * fences have been signaled.
 550  * @obj: the reservation object
 551  * @test_all: if true, test all fences, otherwise only test the exclusive
 552  * fence
 553  *
 554  * RETURNS
 555  * true if all fences signaled, else false
 556  */
 557 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 558                                           bool test_all)
 559 {
 560         unsigned seq, shared_count;
 561         int ret;
 562
 563         rcu_read_lock();
 564 retry:
 565         ret = true;
 566         shared_count = 0;
 567         seq = read_seqcount_begin(&obj->seq);
 568
 569         if (test_all) {
 570                 unsigned i;
 571
 572                 struct reservation_object_list *fobj =
 573                                                 rcu_dereference(obj->fence);
 574
 575                 if (fobj)
 576                         shared_count = fobj->shared_count;
 577
 578                 for (i = 0; i < shared_count; ++i) {
 579                         struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
 580
 581                         ret = reservation_object_test_signaled_single(fence);
 582                         if (ret < 0)
 583                                 goto retry;
 584                         else if (!ret)
 585                                 break;
 586                 }
 587
 588                 if (read_seqcount_retry(&obj->seq, seq))
 589                         goto retry;
 590         }
 591
 592         if (!shared_count) {
 593                 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
 594
 595                 if (fence_excl) {
 596                         ret = reservation_object_test_signaled_single(
 597                                                                 fence_excl);
 598                         if (ret < 0)
 599                                 goto retry;
 600
 601                         if (read_seqcount_retry(&obj->seq, seq))
 602                                 goto retry;
 603                 }
 604         }
 605
 606         rcu_read_unlock();
 607         return ret;
 608 }
 609 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);