drivers/dma-buf/reservation.c

   1 /*
   2  * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
   3  *
   4  * Based on bo.c which bears the following copyright notice,
   5  * but is dual licensed:
   6  *
   7  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
   8  * All Rights Reserved.
   9  *
  10  * Permission is hereby granted, free of charge, to any person obtaining a
  11  * copy of this software and associated documentation files (the
  12  * "Software"), to deal in the Software without restriction, including
  13  * without limitation the rights to use, copy, modify, merge, publish,
  14  * distribute, sub license, and/or sell copies of the Software, and to
  15  * permit persons to whom the Software is furnished to do so, subject to
  16  * the following conditions:
  17  *
  18  * The above copyright notice and this permission notice (including the
  19  * next paragraph) shall be included in all copies or substantial portions
  20  * of the Software.
  21  *
  22  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  23  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  25  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  26  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  27  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  28  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  29  *
  30  **************************************************************************/
  31 /*
  32  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  33  */
  34
  35 #include <linux/reservation.h>
  36 #include <linux/export.h>
  37
  38 /**
  39  * DOC: Reservation Object Overview
  40  *
  41  * The reservation object provides a mechanism to manage shared and
  42  * exclusive fences associated with a buffer.  A reservation object
  43  * can have attached one exclusive fence (normally associated with
  44  * write operations) or N shared fences (read operations).  The RCU
  45  * mechanism is used to protect read access to fences from locked
  46  * write-side updates.
  47  */
  48
  49 DEFINE_WD_CLASS(reservation_ww_class);
  50 EXPORT_SYMBOL(reservation_ww_class);
  51
  52 /**
  53  * reservation_object_list_alloc - allocate fence list
  54  * @shared_max: number of fences we need space for
  55  *
  56  * Allocate a new reservation_object_list and make sure to correctly initialize
  57  * shared_max.
  58  */
  59 static struct reservation_object_list *
  60 reservation_object_list_alloc(unsigned int shared_max)
  61 {
  62         struct reservation_object_list *list;
  63
  64         list = kmalloc(offsetof(typeof(*list), shared[shared_max]), GFP_KERNEL);
  65         if (!list)
  66                 return NULL;
  67
  68         list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
  69                 sizeof(*list->shared);
  70
  71         return list;
  72 }
  73
  74 /**
  75  * reservation_object_list_free - free fence list
  76  * @list: list to free
  77  *
  78  * Free a reservation_object_list and make sure to drop all references.
  79  */
  80 static void reservation_object_list_free(struct reservation_object_list *list)
  81 {
  82         unsigned int i;
  83
  84         if (!list)
  85                 return;
  86
  87         for (i = 0; i < list->shared_count; ++i)
  88                 dma_fence_put(rcu_dereference_protected(list->shared[i], true));
  89
  90         kfree_rcu(list, rcu);
  91 }
  92
  93 /**
  94  * reservation_object_init - initialize a reservation object
  95  * @obj: the reservation object
  96  */
  97 void reservation_object_init(struct reservation_object *obj)
  98 {
  99         ww_mutex_init(&obj->lock, &reservation_ww_class);
 100         RCU_INIT_POINTER(obj->fence, NULL);
 101         RCU_INIT_POINTER(obj->fence_excl, NULL);
 102 }
 103 EXPORT_SYMBOL(reservation_object_init);
 104
 105 /**
 106  * reservation_object_fini - destroys a reservation object
 107  * @obj: the reservation object
 108  */
 109 void reservation_object_fini(struct reservation_object *obj)
 110 {
 111         struct reservation_object_list *fobj;
 112         struct dma_fence *excl;
 113
 114         /*
 115          * This object should be dead and all references must have
 116          * been released to it, so no need to be protected with rcu.
 117          */
 118         excl = rcu_dereference_protected(obj->fence_excl, 1);
 119         if (excl)
 120                 dma_fence_put(excl);
 121
 122         fobj = rcu_dereference_protected(obj->fence, 1);
 123         reservation_object_list_free(fobj);
 124         ww_mutex_destroy(&obj->lock);
 125 }
 126 EXPORT_SYMBOL(reservation_object_fini);
 127
 128 /**
 129  * reservation_object_reserve_shared - Reserve space to add shared fences to
 130  * a reservation_object.
 131  * @obj: reservation object
 132  * @num_fences: number of fences we want to add
 133  *
 134  * Should be called before reservation_object_add_shared_fence().  Must
 135  * be called with obj->lock held.
 136  *
 137  * RETURNS
 138  * Zero for success, or -errno
 139  */
 140 int reservation_object_reserve_shared(struct reservation_object *obj,
 141                                       unsigned int num_fences)
 142 {
 143         struct reservation_object_list *old, *new;
 144         unsigned int i, j, k, max;
 145
 146         reservation_object_assert_held(obj);
 147
 148         old = reservation_object_get_list(obj);
 149
 150         if (old && old->shared_max) {
 151                 if ((old->shared_count + num_fences) <= old->shared_max)
 152                         return 0;
 153                 else
 154                         max = max(old->shared_count + num_fences,
 155                                   old->shared_max * 2);
 156         } else {
 157                 max = 4;
 158         }
 159
 160         new = reservation_object_list_alloc(max);
 161         if (!new)
 162                 return -ENOMEM;
 163
 164         /*
 165          * no need to bump fence refcounts, rcu_read access
 166          * requires the use of kref_get_unless_zero, and the
 167          * references from the old struct are carried over to
 168          * the new.
 169          */
 170         for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
 171                 struct dma_fence *fence;
 172
 173                 fence = rcu_dereference_protected(old->shared[i],
 174                                                   reservation_object_held(obj));
 175                 if (dma_fence_is_signaled(fence))
 176                         RCU_INIT_POINTER(new->shared[--k], fence);
 177                 else
 178                         RCU_INIT_POINTER(new->shared[j++], fence);
 179         }
 180         new->shared_count = j;
 181
 182         /*
 183          * We are not changing the effective set of fences here so can
 184          * merely update the pointer to the new array; both existing
 185          * readers and new readers will see exactly the same set of
 186          * active (unsignaled) shared fences. Individual fences and the
 187          * old array are protected by RCU and so will not vanish under
 188          * the gaze of the rcu_read_lock() readers.
 189          */
 190         rcu_assign_pointer(obj->fence, new);
 191
 192         if (!old)
 193                 return 0;
 194
 195         /* Drop the references to the signaled fences */
 196         for (i = k; i < max; ++i) {
 197                 struct dma_fence *fence;
 198
 199                 fence = rcu_dereference_protected(new->shared[i],
 200                                                   reservation_object_held(obj));
 201                 dma_fence_put(fence);
 202         }
 203         kfree_rcu(old, rcu);
 204
 205         return 0;
 206 }
 207 EXPORT_SYMBOL(reservation_object_reserve_shared);
 208
 209 /**
 210  * reservation_object_add_shared_fence - Add a fence to a shared slot
 211  * @obj: the reservation object
 212  * @fence: the shared fence to add
 213  *
 214  * Add a fence to a shared slot, obj->lock must be held, and
 215  * reservation_object_reserve_shared() has been called.
 216  */
 217 void reservation_object_add_shared_fence(struct reservation_object *obj,
 218                                          struct dma_fence *fence)
 219 {
 220         struct reservation_object_list *fobj;
 221         struct dma_fence *old;
 222         unsigned int i, count;
 223
 224         dma_fence_get(fence);
 225
 226         reservation_object_assert_held(obj);
 227
 228         fobj = reservation_object_get_list(obj);
 229         count = fobj->shared_count;
 230
 231         for (i = 0; i < count; ++i) {
 232
 233                 old = rcu_dereference_protected(fobj->shared[i],
 234                                                 reservation_object_held(obj));
 235                 if (old->context == fence->context ||
 236                     dma_fence_is_signaled(old))
 237                         goto replace;
 238         }
 239
 240         BUG_ON(fobj->shared_count >= fobj->shared_max);
 241         old = NULL;
 242         count++;
 243
 244 replace:
 245         RCU_INIT_POINTER(fobj->shared[i], fence);
 246         /* pointer update must be visible before we extend the shared_count */
 247         smp_store_mb(fobj->shared_count, count);
 248         dma_fence_put(old);
 249 }
 250 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 251
 252 /**
 253  * reservation_object_add_excl_fence - Add an exclusive fence.
 254  * @obj: the reservation object
 255  * @fence: the shared fence to add
 256  *
 257  * Add a fence to the exclusive slot.  The obj->lock must be held.
 258  */
 259 void reservation_object_add_excl_fence(struct reservation_object *obj,
 260                                        struct dma_fence *fence)
 261 {
 262         struct dma_fence *old_fence = reservation_object_get_excl(obj);
 263         struct reservation_object_list *old;
 264         u32 i = 0;
 265
 266         reservation_object_assert_held(obj);
 267
 268         old = reservation_object_get_list(obj);
 269         if (old)
 270                 i = old->shared_count;
 271
 272         if (fence)
 273                 dma_fence_get(fence);
 274
 275         preempt_disable();
 276         rcu_assign_pointer(obj->fence_excl, fence);
 277         /* pointer update must be visible before we modify the shared_count */
 278         if (old)
 279                 smp_store_mb(old->shared_count, 0);
 280         preempt_enable();
 281
 282         /* inplace update, no shared fences */
 283         while (i--)
 284                 dma_fence_put(rcu_dereference_protected(old->shared[i],
 285                                                 reservation_object_held(obj)));
 286
 287         dma_fence_put(old_fence);
 288 }
 289 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 290
 291 /**
 292 * reservation_object_copy_fences - Copy all fences from src to dst.
 293 * @dst: the destination reservation object
 294 * @src: the source reservation object
 295 *
 296 * Copy all fences from src to dst. dst-lock must be held.
 297 */
 298 int reservation_object_copy_fences(struct reservation_object *dst,
 299                                    struct reservation_object *src)
 300 {
 301         struct reservation_object_list *src_list, *dst_list;
 302         struct dma_fence *old, *new;
 303         unsigned int i, shared_count;
 304
 305         reservation_object_assert_held(dst);
 306
 307         rcu_read_lock();
 308
 309 retry:
 310         reservation_object_fences(src, &new, &src_list, &shared_count);
 311         if (shared_count) {
 312                 rcu_read_unlock();
 313
 314                 dst_list = reservation_object_list_alloc(shared_count);
 315                 if (!dst_list)
 316                         return -ENOMEM;
 317
 318                 rcu_read_lock();
 319                 reservation_object_fences(src, &new, &src_list, &shared_count);
 320                 if (!src_list || shared_count > dst_list->shared_max) {
 321                         kfree(dst_list);
 322                         goto retry;
 323                 }
 324
 325                 dst_list->shared_count = 0;
 326                 for (i = 0; i < shared_count; ++i) {
 327                         struct dma_fence *fence;
 328
 329                         fence = rcu_dereference(src_list->shared[i]);
 330                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 331                                      &fence->flags))
 332                                 continue;
 333
 334                         if (!dma_fence_get_rcu(fence)) {
 335                                 reservation_object_list_free(dst_list);
 336                                 goto retry;
 337                         }
 338
 339                         if (dma_fence_is_signaled(fence)) {
 340                                 dma_fence_put(fence);
 341                                 continue;
 342                         }
 343
 344                         rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
 345                 }
 346         } else {
 347                 dst_list = NULL;
 348         }
 349
 350         if (new && !dma_fence_get_rcu(new)) {
 351                 reservation_object_list_free(dst_list);
 352                 goto retry;
 353         }
 354         rcu_read_unlock();
 355
 356         src_list = reservation_object_get_list(dst);
 357         old = reservation_object_get_excl(dst);
 358
 359         preempt_disable();
 360         rcu_assign_pointer(dst->fence_excl, new);
 361         rcu_assign_pointer(dst->fence, dst_list);
 362         preempt_enable();
 363
 364         reservation_object_list_free(src_list);
 365         dma_fence_put(old);
 366
 367         return 0;
 368 }
 369 EXPORT_SYMBOL(reservation_object_copy_fences);
 370
 371 /**
 372  * reservation_object_get_fences_rcu - Get an object's shared and exclusive
 373  * fences without update side lock held
 374  * @obj: the reservation object
 375  * @pfence_excl: the returned exclusive fence (or NULL)
 376  * @pshared_count: the number of shared fences returned
 377  * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 378  * the required size, and must be freed by caller)
 379  *
 380  * Retrieve all fences from the reservation object. If the pointer for the
 381  * exclusive fence is not specified the fence is put into the array of the
 382  * shared fences as well. Returns either zero or -ENOMEM.
 383  */
 384 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 385                                       struct dma_fence **pfence_excl,
 386                                       unsigned *pshared_count,
 387                                       struct dma_fence ***pshared)
 388 {
 389         struct dma_fence **shared = NULL;
 390         struct dma_fence *fence_excl;
 391         unsigned int shared_count;
 392         int ret = 1;
 393
 394         do {
 395                 struct reservation_object_list *fobj;
 396                 unsigned int i;
 397                 size_t sz = 0;
 398
 399                 i = 0;
 400
 401                 rcu_read_lock();
 402                 reservation_object_fences(obj, &fence_excl, &fobj,
 403                                           &shared_count);
 404
 405                 if (fence_excl && !dma_fence_get_rcu(fence_excl))
 406                         goto unlock;
 407
 408                 if (fobj)
 409                         sz += sizeof(*shared) * fobj->shared_max;
 410
 411                 if (!pfence_excl && fence_excl)
 412                         sz += sizeof(*shared);
 413
 414                 if (sz) {
 415                         struct dma_fence **nshared;
 416
 417                         nshared = krealloc(shared, sz,
 418                                            GFP_NOWAIT | __GFP_NOWARN);
 419                         if (!nshared) {
 420                                 rcu_read_unlock();
 421
 422                                 dma_fence_put(fence_excl);
 423                                 fence_excl = NULL;
 424
 425                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 426                                 if (nshared) {
 427                                         shared = nshared;
 428                                         continue;
 429                                 }
 430
 431                                 ret = -ENOMEM;
 432                                 break;
 433                         }
 434                         shared = nshared;
 435                         for (i = 0; i < shared_count; ++i) {
 436                                 shared[i] = rcu_dereference(fobj->shared[i]);
 437                                 if (!dma_fence_get_rcu(shared[i]))
 438                                         break;
 439                         }
 440                 }
 441
 442                 if (i != shared_count) {
 443                         while (i--)
 444                                 dma_fence_put(shared[i]);
 445                         dma_fence_put(fence_excl);
 446                         goto unlock;
 447                 }
 448
 449                 ret = 0;
 450 unlock:
 451                 rcu_read_unlock();
 452         } while (ret);
 453
 454         if (pfence_excl)
 455                 *pfence_excl = fence_excl;
 456         else if (fence_excl)
 457                 shared[++shared_count] = fence_excl;
 458
 459         if (!shared_count) {
 460                 kfree(shared);
 461                 shared = NULL;
 462         }
 463
 464         *pshared_count = shared_count;
 465         *pshared = shared;
 466         return ret;
 467 }
 468 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 469
 470 /**
 471  * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 472  * shared and/or exclusive fences.
 473  * @obj: the reservation object
 474  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 475  * @intr: if true, do interruptible wait
 476  * @timeout: timeout value in jiffies or zero to return immediately
 477  *
 478  * RETURNS
 479  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 480  * greater than zer on success.
 481  */
 482 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 483                                          bool wait_all, bool intr,
 484                                          unsigned long timeout)
 485 {
 486         struct reservation_object_list *fobj;
 487         struct dma_fence *fence;
 488         unsigned shared_count;
 489         long ret = timeout ? timeout : 1;
 490         int i;
 491
 492 retry:
 493         rcu_read_lock();
 494         i = -1;
 495
 496         reservation_object_fences(obj, &fence, &fobj, &shared_count);
 497         if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 498                 if (!dma_fence_get_rcu(fence))
 499                         goto unlock_retry;
 500
 501                 if (dma_fence_is_signaled(fence)) {
 502                         dma_fence_put(fence);
 503                         fence = NULL;
 504                 }
 505
 506         } else {
 507                 fence = NULL;
 508         }
 509
 510         if (wait_all) {
 511                 for (i = 0; !fence && i < shared_count; ++i) {
 512                         struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
 513
 514                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 515                                      &lfence->flags))
 516                                 continue;
 517
 518                         if (!dma_fence_get_rcu(lfence))
 519                                 goto unlock_retry;
 520
 521                         if (dma_fence_is_signaled(lfence)) {
 522                                 dma_fence_put(lfence);
 523                                 continue;
 524                         }
 525
 526                         fence = lfence;
 527                         break;
 528                 }
 529         }
 530
 531         rcu_read_unlock();
 532         if (fence) {
 533                 ret = dma_fence_wait_timeout(fence, intr, ret);
 534                 dma_fence_put(fence);
 535                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 536                         goto retry;
 537         }
 538         return ret;
 539
 540 unlock_retry:
 541         rcu_read_unlock();
 542         goto retry;
 543 }
 544 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
 545
 546
 547 static inline int
 548 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
 549 {
 550         struct dma_fence *fence, *lfence = passed_fence;
 551         int ret = 1;
 552
 553         if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 554                 fence = dma_fence_get_rcu(lfence);
 555                 if (!fence)
 556                         return -1;
 557
 558                 ret = !!dma_fence_is_signaled(fence);
 559                 dma_fence_put(fence);
 560         }
 561         return ret;
 562 }
 563
 564 /**
 565  * reservation_object_test_signaled_rcu - Test if a reservation object's
 566  * fences have been signaled.
 567  * @obj: the reservation object
 568  * @test_all: if true, test all fences, otherwise only test the exclusive
 569  * fence
 570  *
 571  * RETURNS
 572  * true if all fences signaled, else false
 573  */
 574 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 575                                           bool test_all)
 576 {
 577         struct reservation_object_list *fobj;
 578         struct dma_fence *fence_excl;
 579         unsigned shared_count;
 580         int ret;
 581
 582         rcu_read_lock();
 583 retry:
 584         ret = true;
 585
 586         reservation_object_fences(obj, &fence_excl, &fobj, &shared_count);
 587         if (test_all) {
 588                 unsigned i;
 589
 590                 for (i = 0; i < shared_count; ++i) {
 591                         struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
 592
 593                         ret = reservation_object_test_signaled_single(fence);
 594                         if (ret < 0)
 595                                 goto retry;
 596                         else if (!ret)
 597                                 break;
 598                 }
 599         }
 600
 601         if (!shared_count && fence_excl) {
 602                 ret = reservation_object_test_signaled_single(fence_excl);
 603                 if (ret < 0)
 604                         goto retry;
 605         }
 606
 607         rcu_read_unlock();
 608         return ret;
 609 }
 610 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);