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 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 shared fences to
  60  * a reservation_object.
  61  * @obj: reservation object
  62  * @num_fences: number of fences we want to add
  63  *
  64  * Should be called before reservation_object_add_shared_fence().  Must
  65  * be called with obj->lock held.
  66  *
  67  * RETURNS
  68  * Zero for success, or -errno
  69  */
  70 int reservation_object_reserve_shared(struct reservation_object *obj,
  71                                       unsigned int num_fences)
  72 {
  73         struct reservation_object_list *old, *new;
  74         unsigned int i, j, k, max;
  75
  76         old = reservation_object_get_list(obj);
  77
  78         if (old && old->shared_max) {
  79                 if ((old->shared_count + num_fences) <= old->shared_max)
  80                         return 0;
  81                 else
  82                         max = max(old->shared_count + num_fences,
  83                                   old->shared_max * 2);
  84         } else {
  85                 max = 4;
  86         }
  87
  88         new = kmalloc(offsetof(typeof(*new), shared[max]), GFP_KERNEL);
  89         if (!new)
  90                 return -ENOMEM;
  91
  92         /*
  93          * no need to bump fence refcounts, rcu_read access
  94          * requires the use of kref_get_unless_zero, and the
  95          * references from the old struct are carried over to
  96          * the new.
  97          */
  98         for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
  99                 struct dma_fence *fence;
 100
 101                 fence = rcu_dereference_protected(old->shared[i],
 102                                                   reservation_object_held(obj));
 103                 if (dma_fence_is_signaled(fence))
 104                         RCU_INIT_POINTER(new->shared[--k], fence);
 105                 else
 106                         RCU_INIT_POINTER(new->shared[j++], fence);
 107         }
 108         new->shared_count = j;
 109         new->shared_max = max;
 110
 111         preempt_disable();
 112         write_seqcount_begin(&obj->seq);
 113         /*
 114          * RCU_INIT_POINTER can be used here,
 115          * seqcount provides the necessary barriers
 116          */
 117         RCU_INIT_POINTER(obj->fence, new);
 118         write_seqcount_end(&obj->seq);
 119         preempt_enable();
 120
 121         if (!old)
 122                 return 0;
 123
 124         /* Drop the references to the signaled fences */
 125         for (i = k; i < new->shared_max; ++i) {
 126                 struct dma_fence *fence;
 127
 128                 fence = rcu_dereference_protected(new->shared[i],
 129                                                   reservation_object_held(obj));
 130                 dma_fence_put(fence);
 131         }
 132         kfree_rcu(old, rcu);
 133
 134         return 0;
 135 }
 136 EXPORT_SYMBOL(reservation_object_reserve_shared);
 137
 138 /**
 139  * reservation_object_add_shared_fence - Add a fence to a shared slot
 140  * @obj: the reservation object
 141  * @fence: the shared fence to add
 142  *
 143  * Add a fence to a shared slot, obj->lock must be held, and
 144  * reservation_object_reserve_shared() has been called.
 145  */
 146 void reservation_object_add_shared_fence(struct reservation_object *obj,
 147                                          struct dma_fence *fence)
 148 {
 149         struct reservation_object_list *fobj;
 150         unsigned int i, count;
 151
 152         dma_fence_get(fence);
 153
 154         fobj = reservation_object_get_list(obj);
 155         count = fobj->shared_count;
 156
 157         preempt_disable();
 158         write_seqcount_begin(&obj->seq);
 159
 160         for (i = 0; i < count; ++i) {
 161                 struct dma_fence *old_fence;
 162
 163                 old_fence = rcu_dereference_protected(fobj->shared[i],
 164                                                       reservation_object_held(obj));
 165                 if (old_fence->context == fence->context ||
 166                     dma_fence_is_signaled(old_fence)) {
 167                         dma_fence_put(old_fence);
 168                         goto replace;
 169                 }
 170         }
 171
 172         BUG_ON(fobj->shared_count >= fobj->shared_max);
 173         count++;
 174
 175 replace:
 176         RCU_INIT_POINTER(fobj->shared[i], fence);
 177         /* pointer update must be visible before we extend the shared_count */
 178         smp_store_mb(fobj->shared_count, count);
 179
 180         write_seqcount_end(&obj->seq);
 181         preempt_enable();
 182 }
 183 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 184
 185 /**
 186  * reservation_object_add_excl_fence - Add an exclusive fence.
 187  * @obj: the reservation object
 188  * @fence: the shared fence to add
 189  *
 190  * Add a fence to the exclusive slot.  The obj->lock must be held.
 191  */
 192 void reservation_object_add_excl_fence(struct reservation_object *obj,
 193                                        struct dma_fence *fence)
 194 {
 195         struct dma_fence *old_fence = reservation_object_get_excl(obj);
 196         struct reservation_object_list *old;
 197         u32 i = 0;
 198
 199         old = reservation_object_get_list(obj);
 200         if (old)
 201                 i = old->shared_count;
 202
 203         if (fence)
 204                 dma_fence_get(fence);
 205
 206         preempt_disable();
 207         write_seqcount_begin(&obj->seq);
 208         /* write_seqcount_begin provides the necessary memory barrier */
 209         RCU_INIT_POINTER(obj->fence_excl, fence);
 210         if (old)
 211                 old->shared_count = 0;
 212         write_seqcount_end(&obj->seq);
 213         preempt_enable();
 214
 215         /* inplace update, no shared fences */
 216         while (i--)
 217                 dma_fence_put(rcu_dereference_protected(old->shared[i],
 218                                                 reservation_object_held(obj)));
 219
 220         dma_fence_put(old_fence);
 221 }
 222 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 223
 224 /**
 225 * reservation_object_copy_fences - Copy all fences from src to dst.
 226 * @dst: the destination reservation object
 227 * @src: the source reservation object
 228 *
 229 * Copy all fences from src to dst. dst-lock must be held.
 230 */
 231 int reservation_object_copy_fences(struct reservation_object *dst,
 232                                    struct reservation_object *src)
 233 {
 234         struct reservation_object_list *src_list, *dst_list;
 235         struct dma_fence *old, *new;
 236         size_t size;
 237         unsigned i;
 238
 239         rcu_read_lock();
 240         src_list = rcu_dereference(src->fence);
 241
 242 retry:
 243         if (src_list) {
 244                 unsigned shared_count = src_list->shared_count;
 245
 246                 size = offsetof(typeof(*src_list), shared[shared_count]);
 247                 rcu_read_unlock();
 248
 249                 dst_list = kmalloc(size, GFP_KERNEL);
 250                 if (!dst_list)
 251                         return -ENOMEM;
 252
 253                 rcu_read_lock();
 254                 src_list = rcu_dereference(src->fence);
 255                 if (!src_list || src_list->shared_count > shared_count) {
 256                         kfree(dst_list);
 257                         goto retry;
 258                 }
 259
 260                 dst_list->shared_count = 0;
 261                 dst_list->shared_max = shared_count;
 262                 for (i = 0; i < src_list->shared_count; ++i) {
 263                         struct dma_fence *fence;
 264
 265                         fence = rcu_dereference(src_list->shared[i]);
 266                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 267                                      &fence->flags))
 268                                 continue;
 269
 270                         if (!dma_fence_get_rcu(fence)) {
 271                                 kfree(dst_list);
 272                                 src_list = rcu_dereference(src->fence);
 273                                 goto retry;
 274                         }
 275
 276                         if (dma_fence_is_signaled(fence)) {
 277                                 dma_fence_put(fence);
 278                                 continue;
 279                         }
 280
 281                         rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
 282                 }
 283         } else {
 284                 dst_list = NULL;
 285         }
 286
 287         new = dma_fence_get_rcu_safe(&src->fence_excl);
 288         rcu_read_unlock();
 289
 290         src_list = reservation_object_get_list(dst);
 291         old = reservation_object_get_excl(dst);
 292
 293         preempt_disable();
 294         write_seqcount_begin(&dst->seq);
 295         /* write_seqcount_begin provides the necessary memory barrier */
 296         RCU_INIT_POINTER(dst->fence_excl, new);
 297         RCU_INIT_POINTER(dst->fence, dst_list);
 298         write_seqcount_end(&dst->seq);
 299         preempt_enable();
 300
 301         if (src_list)
 302                 kfree_rcu(src_list, rcu);
 303         dma_fence_put(old);
 304
 305         return 0;
 306 }
 307 EXPORT_SYMBOL(reservation_object_copy_fences);
 308
 309 /**
 310  * reservation_object_get_fences_rcu - Get an object's shared and exclusive
 311  * fences without update side lock held
 312  * @obj: the reservation object
 313  * @pfence_excl: the returned exclusive fence (or NULL)
 314  * @pshared_count: the number of shared fences returned
 315  * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 316  * the required size, and must be freed by caller)
 317  *
 318  * Retrieve all fences from the reservation object. If the pointer for the
 319  * exclusive fence is not specified the fence is put into the array of the
 320  * shared fences as well. Returns either zero or -ENOMEM.
 321  */
 322 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 323                                       struct dma_fence **pfence_excl,
 324                                       unsigned *pshared_count,
 325                                       struct dma_fence ***pshared)
 326 {
 327         struct dma_fence **shared = NULL;
 328         struct dma_fence *fence_excl;
 329         unsigned int shared_count;
 330         int ret = 1;
 331
 332         do {
 333                 struct reservation_object_list *fobj;
 334                 unsigned int i, seq;
 335                 size_t sz = 0;
 336
 337                 shared_count = i = 0;
 338
 339                 rcu_read_lock();
 340                 seq = read_seqcount_begin(&obj->seq);
 341
 342                 fence_excl = rcu_dereference(obj->fence_excl);
 343                 if (fence_excl && !dma_fence_get_rcu(fence_excl))
 344                         goto unlock;
 345
 346                 fobj = rcu_dereference(obj->fence);
 347                 if (fobj)
 348                         sz += sizeof(*shared) * fobj->shared_max;
 349
 350                 if (!pfence_excl && fence_excl)
 351                         sz += sizeof(*shared);
 352
 353                 if (sz) {
 354                         struct dma_fence **nshared;
 355
 356                         nshared = krealloc(shared, sz,
 357                                            GFP_NOWAIT | __GFP_NOWARN);
 358                         if (!nshared) {
 359                                 rcu_read_unlock();
 360                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 361                                 if (nshared) {
 362                                         shared = nshared;
 363                                         continue;
 364                                 }
 365
 366                                 ret = -ENOMEM;
 367                                 break;
 368                         }
 369                         shared = nshared;
 370                         shared_count = fobj ? fobj->shared_count : 0;
 371                         for (i = 0; i < shared_count; ++i) {
 372                                 shared[i] = rcu_dereference(fobj->shared[i]);
 373                                 if (!dma_fence_get_rcu(shared[i]))
 374                                         break;
 375                         }
 376
 377                         if (!pfence_excl && fence_excl) {
 378                                 shared[i] = fence_excl;
 379                                 fence_excl = NULL;
 380                                 ++i;
 381                                 ++shared_count;
 382                         }
 383                 }
 384
 385                 if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
 386                         while (i--)
 387                                 dma_fence_put(shared[i]);
 388                         dma_fence_put(fence_excl);
 389                         goto unlock;
 390                 }
 391
 392                 ret = 0;
 393 unlock:
 394                 rcu_read_unlock();
 395         } while (ret);
 396
 397         if (!shared_count) {
 398                 kfree(shared);
 399                 shared = NULL;
 400         }
 401
 402         *pshared_count = shared_count;
 403         *pshared = shared;
 404         if (pfence_excl)
 405                 *pfence_excl = fence_excl;
 406
 407         return ret;
 408 }
 409 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 410
 411 /**
 412  * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 413  * shared and/or exclusive fences.
 414  * @obj: the reservation object
 415  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 416  * @intr: if true, do interruptible wait
 417  * @timeout: timeout value in jiffies or zero to return immediately
 418  *
 419  * RETURNS
 420  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 421  * greater than zer on success.
 422  */
 423 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 424                                          bool wait_all, bool intr,
 425                                          unsigned long timeout)
 426 {
 427         struct dma_fence *fence;
 428         unsigned seq, shared_count;
 429         long ret = timeout ? timeout : 1;
 430         int i;
 431
 432 retry:
 433         shared_count = 0;
 434         seq = read_seqcount_begin(&obj->seq);
 435         rcu_read_lock();
 436         i = -1;
 437
 438         fence = rcu_dereference(obj->fence_excl);
 439         if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 440                 if (!dma_fence_get_rcu(fence))
 441                         goto unlock_retry;
 442
 443                 if (dma_fence_is_signaled(fence)) {
 444                         dma_fence_put(fence);
 445                         fence = NULL;
 446                 }
 447
 448         } else {
 449                 fence = NULL;
 450         }
 451
 452         if (wait_all) {
 453                 struct reservation_object_list *fobj =
 454                                                 rcu_dereference(obj->fence);
 455
 456                 if (fobj)
 457                         shared_count = fobj->shared_count;
 458
 459                 for (i = 0; !fence && i < shared_count; ++i) {
 460                         struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
 461
 462                         if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 463                                      &lfence->flags))
 464                                 continue;
 465
 466                         if (!dma_fence_get_rcu(lfence))
 467                                 goto unlock_retry;
 468
 469                         if (dma_fence_is_signaled(lfence)) {
 470                                 dma_fence_put(lfence);
 471                                 continue;
 472                         }
 473
 474                         fence = lfence;
 475                         break;
 476                 }
 477         }
 478
 479         rcu_read_unlock();
 480         if (fence) {
 481                 if (read_seqcount_retry(&obj->seq, seq)) {
 482                         dma_fence_put(fence);
 483                         goto retry;
 484                 }
 485
 486                 ret = dma_fence_wait_timeout(fence, intr, ret);
 487                 dma_fence_put(fence);
 488                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 489                         goto retry;
 490         }
 491         return ret;
 492
 493 unlock_retry:
 494         rcu_read_unlock();
 495         goto retry;
 496 }
 497 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
 498
 499
 500 static inline int
 501 reservation_object_test_signaled_single(struct dma_fence *passed_fence)
 502 {
 503         struct dma_fence *fence, *lfence = passed_fence;
 504         int ret = 1;
 505
 506         if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 507                 fence = dma_fence_get_rcu(lfence);
 508                 if (!fence)
 509                         return -1;
 510
 511                 ret = !!dma_fence_is_signaled(fence);
 512                 dma_fence_put(fence);
 513         }
 514         return ret;
 515 }
 516
 517 /**
 518  * reservation_object_test_signaled_rcu - Test if a reservation object's
 519  * fences have been signaled.
 520  * @obj: the reservation object
 521  * @test_all: if true, test all fences, otherwise only test the exclusive
 522  * fence
 523  *
 524  * RETURNS
 525  * true if all fences signaled, else false
 526  */
 527 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 528                                           bool test_all)
 529 {
 530         unsigned seq, shared_count;
 531         int ret;
 532
 533         rcu_read_lock();
 534 retry:
 535         ret = true;
 536         shared_count = 0;
 537         seq = read_seqcount_begin(&obj->seq);
 538
 539         if (test_all) {
 540                 unsigned i;
 541
 542                 struct reservation_object_list *fobj =
 543                                                 rcu_dereference(obj->fence);
 544
 545                 if (fobj)
 546                         shared_count = fobj->shared_count;
 547
 548                 for (i = 0; i < shared_count; ++i) {
 549                         struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
 550
 551                         ret = reservation_object_test_signaled_single(fence);
 552                         if (ret < 0)
 553                                 goto retry;
 554                         else if (!ret)
 555                                 break;
 556                 }
 557
 558                 if (read_seqcount_retry(&obj->seq, seq))
 559                         goto retry;
 560         }
 561
 562         if (!shared_count) {
 563                 struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
 564
 565                 if (fence_excl) {
 566                         ret = reservation_object_test_signaled_single(
 567                                                                 fence_excl);
 568                         if (ret < 0)
 569                                 goto retry;
 570
 571                         if (read_seqcount_retry(&obj->seq, seq))
 572                                 goto retry;
 573                 }
 574         }
 575
 576         rcu_read_unlock();
 577         return ret;
 578 }
 579 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);