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 fence *fence)
 106 {
 107         u32 i;
 108
 109         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 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                         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 fence *fence)
 147 {
 148         unsigned i;
 149         struct fence *old_fence = NULL;
 150
 151         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 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         if (old_fence)
 199                 fence_put(old_fence);
 200 }
 201
 202 /**
 203  * reservation_object_add_shared_fence - Add a fence to a shared slot
 204  * @obj: the reservation object
 205  * @fence: the shared fence to add
 206  *
 207  * Add a fence to a shared slot, obj->lock must be held, and
 208  * reservation_object_reserve_shared() has been called.
 209  */
 210 void reservation_object_add_shared_fence(struct reservation_object *obj,
 211                                          struct fence *fence)
 212 {
 213         struct reservation_object_list *old, *fobj = obj->staged;
 214
 215         old = reservation_object_get_list(obj);
 216         obj->staged = NULL;
 217
 218         if (!fobj) {
 219                 BUG_ON(old->shared_count >= old->shared_max);
 220                 reservation_object_add_shared_inplace(obj, old, fence);
 221         } else
 222                 reservation_object_add_shared_replace(obj, old, fobj, fence);
 223 }
 224 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 225
 226 /**
 227  * reservation_object_add_excl_fence - Add an exclusive fence.
 228  * @obj: the reservation object
 229  * @fence: the shared fence to add
 230  *
 231  * Add a fence to the exclusive slot.  The obj->lock must be held.
 232  */
 233 void reservation_object_add_excl_fence(struct reservation_object *obj,
 234                                        struct fence *fence)
 235 {
 236         struct fence *old_fence = reservation_object_get_excl(obj);
 237         struct reservation_object_list *old;
 238         u32 i = 0;
 239
 240         old = reservation_object_get_list(obj);
 241         if (old)
 242                 i = old->shared_count;
 243
 244         if (fence)
 245                 fence_get(fence);
 246
 247         preempt_disable();
 248         write_seqcount_begin(&obj->seq);
 249         /* write_seqcount_begin provides the necessary memory barrier */
 250         RCU_INIT_POINTER(obj->fence_excl, fence);
 251         if (old)
 252                 old->shared_count = 0;
 253         write_seqcount_end(&obj->seq);
 254         preempt_enable();
 255
 256         /* inplace update, no shared fences */
 257         while (i--)
 258                 fence_put(rcu_dereference_protected(old->shared[i],
 259                                                 reservation_object_held(obj)));
 260
 261         if (old_fence)
 262                 fence_put(old_fence);
 263 }
 264 EXPORT_SYMBOL(reservation_object_add_excl_fence);
 265
 266 /**
 267  * reservation_object_get_fences_rcu - Get an object's shared and exclusive
 268  * fences without update side lock held
 269  * @obj: the reservation object
 270  * @pfence_excl: the returned exclusive fence (or NULL)
 271  * @pshared_count: the number of shared fences returned
 272  * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 273  * the required size, and must be freed by caller)
 274  *
 275  * RETURNS
 276  * Zero or -errno
 277  */
 278 int reservation_object_get_fences_rcu(struct reservation_object *obj,
 279                                       struct fence **pfence_excl,
 280                                       unsigned *pshared_count,
 281                                       struct fence ***pshared)
 282 {
 283         unsigned shared_count = 0;
 284         unsigned retry = 1;
 285         struct fence **shared = NULL, *fence_excl = NULL;
 286         int ret = 0;
 287
 288         while (retry) {
 289                 struct reservation_object_list *fobj;
 290                 unsigned seq;
 291
 292                 seq = read_seqcount_begin(&obj->seq);
 293
 294                 rcu_read_lock();
 295
 296                 fobj = rcu_dereference(obj->fence);
 297                 if (fobj) {
 298                         struct fence **nshared;
 299                         size_t sz = sizeof(*shared) * fobj->shared_max;
 300
 301                         nshared = krealloc(shared, sz,
 302                                            GFP_NOWAIT | __GFP_NOWARN);
 303                         if (!nshared) {
 304                                 rcu_read_unlock();
 305                                 nshared = krealloc(shared, sz, GFP_KERNEL);
 306                                 if (nshared) {
 307                                         shared = nshared;
 308                                         continue;
 309                                 }
 310
 311                                 ret = -ENOMEM;
 312                                 shared_count = 0;
 313                                 break;
 314                         }
 315                         shared = nshared;
 316                         memcpy(shared, fobj->shared, sz);
 317                         shared_count = fobj->shared_count;
 318                 } else
 319                         shared_count = 0;
 320                 fence_excl = rcu_dereference(obj->fence_excl);
 321
 322                 retry = read_seqcount_retry(&obj->seq, seq);
 323                 if (retry)
 324                         goto unlock;
 325
 326                 if (!fence_excl || fence_get_rcu(fence_excl)) {
 327                         unsigned i;
 328
 329                         for (i = 0; i < shared_count; ++i) {
 330                                 if (fence_get_rcu(shared[i]))
 331                                         continue;
 332
 333                                 /* uh oh, refcount failed, abort and retry */
 334                                 while (i--)
 335                                         fence_put(shared[i]);
 336
 337                                 if (fence_excl) {
 338                                         fence_put(fence_excl);
 339                                         fence_excl = NULL;
 340                                 }
 341
 342                                 retry = 1;
 343                                 break;
 344                         }
 345                 } else
 346                         retry = 1;
 347
 348 unlock:
 349                 rcu_read_unlock();
 350         }
 351         *pshared_count = shared_count;
 352         if (shared_count)
 353                 *pshared = shared;
 354         else {
 355                 *pshared = NULL;
 356                 kfree(shared);
 357         }
 358         *pfence_excl = fence_excl;
 359
 360         return ret;
 361 }
 362 EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
 363
 364 /**
 365  * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 366  * shared and/or exclusive fences.
 367  * @obj: the reservation object
 368  * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 369  * @intr: if true, do interruptible wait
 370  * @timeout: timeout value in jiffies or zero to return immediately
 371  *
 372  * RETURNS
 373  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 374  * greater than zer on success.
 375  */
 376 long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
 377                                          bool wait_all, bool intr,
 378                                          unsigned long timeout)
 379 {
 380         struct fence *fence;
 381         unsigned seq, shared_count, i = 0;
 382         long ret = timeout;
 383
 384         if (!timeout)
 385                 return reservation_object_test_signaled_rcu(obj, wait_all);
 386
 387 retry:
 388         fence = NULL;
 389         shared_count = 0;
 390         seq = read_seqcount_begin(&obj->seq);
 391         rcu_read_lock();
 392
 393         if (wait_all) {
 394                 struct reservation_object_list *fobj =
 395                                                 rcu_dereference(obj->fence);
 396
 397                 if (fobj)
 398                         shared_count = fobj->shared_count;
 399
 400                 if (read_seqcount_retry(&obj->seq, seq))
 401                         goto unlock_retry;
 402
 403                 for (i = 0; i < shared_count; ++i) {
 404                         struct fence *lfence = rcu_dereference(fobj->shared[i]);
 405
 406                         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
 407                                 continue;
 408
 409                         if (!fence_get_rcu(lfence))
 410                                 goto unlock_retry;
 411
 412                         if (fence_is_signaled(lfence)) {
 413                                 fence_put(lfence);
 414                                 continue;
 415                         }
 416
 417                         fence = lfence;
 418                         break;
 419                 }
 420         }
 421
 422         if (!shared_count) {
 423                 struct fence *fence_excl = rcu_dereference(obj->fence_excl);
 424
 425                 if (read_seqcount_retry(&obj->seq, seq))
 426                         goto unlock_retry;
 427
 428                 if (fence_excl &&
 429                     !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
 430                         if (!fence_get_rcu(fence_excl))
 431                                 goto unlock_retry;
 432
 433                         if (fence_is_signaled(fence_excl))
 434                                 fence_put(fence_excl);
 435                         else
 436                                 fence = fence_excl;
 437                 }
 438         }
 439
 440         rcu_read_unlock();
 441         if (fence) {
 442                 ret = fence_wait_timeout(fence, intr, ret);
 443                 fence_put(fence);
 444                 if (ret > 0 && wait_all && (i + 1 < shared_count))
 445                         goto retry;
 446         }
 447         return ret;
 448
 449 unlock_retry:
 450         rcu_read_unlock();
 451         goto retry;
 452 }
 453 EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
 454
 455
 456 static inline int
 457 reservation_object_test_signaled_single(struct fence *passed_fence)
 458 {
 459         struct fence *fence, *lfence = passed_fence;
 460         int ret = 1;
 461
 462         if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
 463                 fence = fence_get_rcu(lfence);
 464                 if (!fence)
 465                         return -1;
 466
 467                 ret = !!fence_is_signaled(fence);
 468                 fence_put(fence);
 469         }
 470         return ret;
 471 }
 472
 473 /**
 474  * reservation_object_test_signaled_rcu - Test if a reservation object's
 475  * fences have been signaled.
 476  * @obj: the reservation object
 477  * @test_all: if true, test all fences, otherwise only test the exclusive
 478  * fence
 479  *
 480  * RETURNS
 481  * true if all fences signaled, else false
 482  */
 483 bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
 484                                           bool test_all)
 485 {
 486         unsigned seq, shared_count;
 487         int ret = true;
 488
 489 retry:
 490         shared_count = 0;
 491         seq = read_seqcount_begin(&obj->seq);
 492         rcu_read_lock();
 493
 494         if (test_all) {
 495                 unsigned i;
 496
 497                 struct reservation_object_list *fobj =
 498                                                 rcu_dereference(obj->fence);
 499
 500                 if (fobj)
 501                         shared_count = fobj->shared_count;
 502
 503                 if (read_seqcount_retry(&obj->seq, seq))
 504                         goto unlock_retry;
 505
 506                 for (i = 0; i < shared_count; ++i) {
 507                         struct fence *fence = rcu_dereference(fobj->shared[i]);
 508
 509                         ret = reservation_object_test_signaled_single(fence);
 510                         if (ret < 0)
 511                                 goto unlock_retry;
 512                         else if (!ret)
 513                                 break;
 514                 }
 515
 516                 /*
 517                  * There could be a read_seqcount_retry here, but nothing cares
 518                  * about whether it's the old or newer fence pointers that are
 519                  * signaled. That race could still have happened after checking
 520                  * read_seqcount_retry. If you care, use ww_mutex_lock.
 521                  */
 522         }
 523
 524         if (!shared_count) {
 525                 struct fence *fence_excl = rcu_dereference(obj->fence_excl);
 526
 527                 if (read_seqcount_retry(&obj->seq, seq))
 528                         goto unlock_retry;
 529
 530                 if (fence_excl) {
 531                         ret = reservation_object_test_signaled_single(
 532                                                                 fence_excl);
 533                         if (ret < 0)
 534                                 goto unlock_retry;
 535                 }
 536         }
 537
 538         rcu_read_unlock();
 539         return ret;
 540
 541 unlock_retry:
 542         rcu_read_unlock();
 543         goto retry;
 544 }
 545 EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);