drivers/gpu/drm/i915/i915_active.c

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright © 2019 Intel Corporation
   5  */
   6
   7 #include <linux/debugobjects.h>
   8
   9 #include "gt/intel_context.h"
  10 #include "gt/intel_engine_heartbeat.h"
  11 #include "gt/intel_engine_pm.h"
  12 #include "gt/intel_ring.h"
  13
  14 #include "i915_drv.h"
  15 #include "i915_active.h"
  16
  17 /*
  18  * Active refs memory management
  19  *
  20  * To be more economical with memory, we reap all the i915_active trees as
  21  * they idle (when we know the active requests are inactive) and allocate the
  22  * nodes from a local slab cache to hopefully reduce the fragmentation.
  23  */
  24 static struct kmem_cache *slab_cache;
  25
  26 struct active_node {
  27         struct rb_node node;
  28         struct i915_active_fence base;
  29         struct i915_active *ref;
  30         u64 timeline;
  31 };
  32
  33 #define fetch_node(x) rb_entry(READ_ONCE(x), typeof(struct active_node), node)
  34
  35 static inline struct active_node *
  36 node_from_active(struct i915_active_fence *active)
  37 {
  38         return container_of(active, struct active_node, base);
  39 }
  40
  41 #define take_preallocated_barriers(x) llist_del_all(&(x)->preallocated_barriers)
  42
  43 static inline bool is_barrier(const struct i915_active_fence *active)
  44 {
  45         return IS_ERR(rcu_access_pointer(active->fence));
  46 }
  47
  48 static inline struct llist_node *barrier_to_ll(struct active_node *node)
  49 {
  50         GEM_BUG_ON(!is_barrier(&node->base));
  51         return (struct llist_node *)&node->base.cb.node;
  52 }
  53
  54 static inline struct intel_engine_cs *
  55 __barrier_to_engine(struct active_node *node)
  56 {
  57         return (struct intel_engine_cs *)READ_ONCE(node->base.cb.node.prev);
  58 }
  59
  60 static inline struct intel_engine_cs *
  61 barrier_to_engine(struct active_node *node)
  62 {
  63         GEM_BUG_ON(!is_barrier(&node->base));
  64         return __barrier_to_engine(node);
  65 }
  66
  67 static inline struct active_node *barrier_from_ll(struct llist_node *x)
  68 {
  69         return container_of((struct list_head *)x,
  70                             struct active_node, base.cb.node);
  71 }
  72
  73 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && IS_ENABLED(CONFIG_DEBUG_OBJECTS)
  74
  75 static void *active_debug_hint(void *addr)
  76 {
  77         struct i915_active *ref = addr;
  78
  79         return (void *)ref->active ?: (void *)ref->retire ?: (void *)ref;
  80 }
  81
  82 static const struct debug_obj_descr active_debug_desc = {
  83         .name = "i915_active",
  84         .debug_hint = active_debug_hint,
  85 };
  86
  87 static void debug_active_init(struct i915_active *ref)
  88 {
  89         debug_object_init(ref, &active_debug_desc);
  90 }
  91
  92 static void debug_active_activate(struct i915_active *ref)
  93 {
  94         lockdep_assert_held(&ref->tree_lock);
  95         if (!atomic_read(&ref->count)) /* before the first inc */
  96                 debug_object_activate(ref, &active_debug_desc);
  97 }
  98
  99 static void debug_active_deactivate(struct i915_active *ref)
 100 {
 101         lockdep_assert_held(&ref->tree_lock);
 102         if (!atomic_read(&ref->count)) /* after the last dec */
 103                 debug_object_deactivate(ref, &active_debug_desc);
 104 }
 105
 106 static void debug_active_fini(struct i915_active *ref)
 107 {
 108         debug_object_free(ref, &active_debug_desc);
 109 }
 110
 111 static void debug_active_assert(struct i915_active *ref)
 112 {
 113         debug_object_assert_init(ref, &active_debug_desc);
 114 }
 115
 116 #else
 117
 118 static inline void debug_active_init(struct i915_active *ref) { }
 119 static inline void debug_active_activate(struct i915_active *ref) { }
 120 static inline void debug_active_deactivate(struct i915_active *ref) { }
 121 static inline void debug_active_fini(struct i915_active *ref) { }
 122 static inline void debug_active_assert(struct i915_active *ref) { }
 123
 124 #endif
 125
 126 static void
 127 __active_retire(struct i915_active *ref)
 128 {
 129         struct rb_root root = RB_ROOT;
 130         struct active_node *it, *n;
 131         unsigned long flags;
 132
 133         GEM_BUG_ON(i915_active_is_idle(ref));
 134
 135         /* return the unused nodes to our slabcache -- flushing the allocator */
 136         if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags))
 137                 return;
 138
 139         GEM_BUG_ON(rcu_access_pointer(ref->excl.fence));
 140         debug_active_deactivate(ref);
 141
 142         /* Even if we have not used the cache, we may still have a barrier */
 143         if (!ref->cache)
 144                 ref->cache = fetch_node(ref->tree.rb_node);
 145
 146         /* Keep the MRU cached node for reuse */
 147         if (ref->cache) {
 148                 /* Discard all other nodes in the tree */
 149                 rb_erase(&ref->cache->node, &ref->tree);
 150                 root = ref->tree;
 151
 152                 /* Rebuild the tree with only the cached node */
 153                 rb_link_node(&ref->cache->node, NULL, &ref->tree.rb_node);
 154                 rb_insert_color(&ref->cache->node, &ref->tree);
 155                 GEM_BUG_ON(ref->tree.rb_node != &ref->cache->node);
 156
 157                 /* Make the cached node available for reuse with any timeline */
 158                 ref->cache->timeline = 0; /* needs cmpxchg(u64) */
 159         }
 160
 161         spin_unlock_irqrestore(&ref->tree_lock, flags);
 162
 163         /* After the final retire, the entire struct may be freed */
 164         if (ref->retire)
 165                 ref->retire(ref);
 166
 167         /* ... except if you wait on it, you must manage your own references! */
 168         wake_up_var(ref);
 169
 170         /* Finally free the discarded timeline tree  */
 171         rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
 172                 GEM_BUG_ON(i915_active_fence_isset(&it->base));
 173                 kmem_cache_free(slab_cache, it);
 174         }
 175 }
 176
 177 static void
 178 active_work(struct work_struct *wrk)
 179 {
 180         struct i915_active *ref = container_of(wrk, typeof(*ref), work);
 181
 182         GEM_BUG_ON(!atomic_read(&ref->count));
 183         if (atomic_add_unless(&ref->count, -1, 1))
 184                 return;
 185
 186         __active_retire(ref);
 187 }
 188
 189 static void
 190 active_retire(struct i915_active *ref)
 191 {
 192         GEM_BUG_ON(!atomic_read(&ref->count));
 193         if (atomic_add_unless(&ref->count, -1, 1))
 194                 return;
 195
 196         if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {
 197                 queue_work(system_unbound_wq, &ref->work);
 198                 return;
 199         }
 200
 201         __active_retire(ref);
 202 }
 203
 204 static inline struct dma_fence **
 205 __active_fence_slot(struct i915_active_fence *active)
 206 {
 207         return (struct dma_fence ** __force)&active->fence;
 208 }
 209
 210 static inline bool
 211 active_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
 212 {
 213         struct i915_active_fence *active =
 214                 container_of(cb, typeof(*active), cb);
 215
 216         return cmpxchg(__active_fence_slot(active), fence, NULL) == fence;
 217 }
 218
 219 static void
 220 node_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
 221 {
 222         if (active_fence_cb(fence, cb))
 223                 active_retire(container_of(cb, struct active_node, base.cb)->ref);
 224 }
 225
 226 static void
 227 excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
 228 {
 229         if (active_fence_cb(fence, cb))
 230                 active_retire(container_of(cb, struct i915_active, excl.cb));
 231 }
 232
 233 static struct active_node *__active_lookup(struct i915_active *ref, u64 idx)
 234 {
 235         struct active_node *it;
 236
 237         GEM_BUG_ON(idx == 0); /* 0 is the unordered timeline, rsvd for cache */
 238
 239         /*
 240          * We track the most recently used timeline to skip a rbtree search
 241          * for the common case, under typical loads we never need the rbtree
 242          * at all. We can reuse the last slot if it is empty, that is
 243          * after the previous activity has been retired, or if it matches the
 244          * current timeline.
 245          */
 246         it = READ_ONCE(ref->cache);
 247         if (it) {
 248                 u64 cached = READ_ONCE(it->timeline);
 249
 250                 /* Once claimed, this slot will only belong to this idx */
 251                 if (cached == idx)
 252                         return it;
 253
 254                 /*
 255                  * An unclaimed cache [.timeline=0] can only be claimed once.
 256                  *
 257                  * If the value is already non-zero, some other thread has
 258                  * claimed the cache and we know that is does not match our
 259                  * idx. If, and only if, the timeline is currently zero is it
 260                  * worth competing to claim it atomically for ourselves (for
 261                  * only the winner of that race will cmpxchg return the old
 262                  * value of 0).
 263                  */
 264                 if (!cached && !cmpxchg64(&it->timeline, 0, idx))
 265                         return it;
 266         }
 267
 268         BUILD_BUG_ON(offsetof(typeof(*it), node));
 269
 270         /* While active, the tree can only be built; not destroyed */
 271         GEM_BUG_ON(i915_active_is_idle(ref));
 272
 273         it = fetch_node(ref->tree.rb_node);
 274         while (it) {
 275                 if (it->timeline < idx) {
 276                         it = fetch_node(it->node.rb_right);
 277                 } else if (it->timeline > idx) {
 278                         it = fetch_node(it->node.rb_left);
 279                 } else {
 280                         WRITE_ONCE(ref->cache, it);
 281                         break;
 282                 }
 283         }
 284
 285         /* NB: If the tree rotated beneath us, we may miss our target. */
 286         return it;
 287 }
 288
 289 static struct i915_active_fence *
 290 active_instance(struct i915_active *ref, u64 idx)
 291 {
 292         struct active_node *node;
 293         struct rb_node **p, *parent;
 294
 295         node = __active_lookup(ref, idx);
 296         if (likely(node))
 297                 return &node->base;
 298
 299         spin_lock_irq(&ref->tree_lock);
 300         GEM_BUG_ON(i915_active_is_idle(ref));
 301
 302         parent = NULL;
 303         p = &ref->tree.rb_node;
 304         while (*p) {
 305                 parent = *p;
 306
 307                 node = rb_entry(parent, struct active_node, node);
 308                 if (node->timeline == idx)
 309                         goto out;
 310
 311                 if (node->timeline < idx)
 312                         p = &parent->rb_right;
 313                 else
 314                         p = &parent->rb_left;
 315         }
 316
 317         /*
 318          * XXX: We should preallocate this before i915_active_ref() is ever
 319          *  called, but we cannot call into fs_reclaim() anyway, so use GFP_ATOMIC.
 320          */
 321         node = kmem_cache_alloc(slab_cache, GFP_ATOMIC);
 322         if (!node)
 323                 goto out;
 324
 325         __i915_active_fence_init(&node->base, NULL, node_retire);
 326         node->ref = ref;
 327         node->timeline = idx;
 328
 329         rb_link_node(&node->node, parent, p);
 330         rb_insert_color(&node->node, &ref->tree);
 331
 332 out:
 333         WRITE_ONCE(ref->cache, node);
 334         spin_unlock_irq(&ref->tree_lock);
 335
 336         return &node->base;
 337 }
 338
 339 void __i915_active_init(struct i915_active *ref,
 340                         int (*active)(struct i915_active *ref),
 341                         void (*retire)(struct i915_active *ref),
 342                         unsigned long flags,
 343                         struct lock_class_key *mkey,
 344                         struct lock_class_key *wkey)
 345 {
 346         debug_active_init(ref);
 347
 348         ref->flags = flags;
 349         ref->active = active;
 350         ref->retire = retire;
 351
 352         spin_lock_init(&ref->tree_lock);
 353         ref->tree = RB_ROOT;
 354         ref->cache = NULL;
 355
 356         init_llist_head(&ref->preallocated_barriers);
 357         atomic_set(&ref->count, 0);
 358         __mutex_init(&ref->mutex, "i915_active", mkey);
 359         __i915_active_fence_init(&ref->excl, NULL, excl_retire);
 360         INIT_WORK(&ref->work, active_work);
 361 #if IS_ENABLED(CONFIG_LOCKDEP)
 362         lockdep_init_map(&ref->work.lockdep_map, "i915_active.work", wkey, 0);
 363 #endif
 364 }
 365
 366 static bool ____active_del_barrier(struct i915_active *ref,
 367                                    struct active_node *node,
 368                                    struct intel_engine_cs *engine)
 369
 370 {
 371         struct llist_node *head = NULL, *tail = NULL;
 372         struct llist_node *pos, *next;
 373
 374         GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context);
 375
 376         /*
 377          * Rebuild the llist excluding our node. We may perform this
 378          * outside of the kernel_context timeline mutex and so someone
 379          * else may be manipulating the engine->barrier_tasks, in
 380          * which case either we or they will be upset :)
 381          *
 382          * A second __active_del_barrier() will report failure to claim
 383          * the active_node and the caller will just shrug and know not to
 384          * claim ownership of its node.
 385          *
 386          * A concurrent i915_request_add_active_barriers() will miss adding
 387          * any of the tasks, but we will try again on the next -- and since
 388          * we are actively using the barrier, we know that there will be
 389          * at least another opportunity when we idle.
 390          */
 391         llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {
 392                 if (node == barrier_from_ll(pos)) {
 393                         node = NULL;
 394                         continue;
 395                 }
 396
 397                 pos->next = head;
 398                 head = pos;
 399                 if (!tail)
 400                         tail = pos;
 401         }
 402         if (head)
 403                 llist_add_batch(head, tail, &engine->barrier_tasks);
 404
 405         return !node;
 406 }
 407
 408 static bool
 409 __active_del_barrier(struct i915_active *ref, struct active_node *node)
 410 {
 411         return ____active_del_barrier(ref, node, barrier_to_engine(node));
 412 }
 413
 414 static bool
 415 replace_barrier(struct i915_active *ref, struct i915_active_fence *active)
 416 {
 417         if (!is_barrier(active)) /* proto-node used by our idle barrier? */
 418                 return false;
 419
 420         /*
 421          * This request is on the kernel_context timeline, and so
 422          * we can use it to substitute for the pending idle-barrer
 423          * request that we want to emit on the kernel_context.
 424          */
 425         __active_del_barrier(ref, node_from_active(active));
 426         return true;
 427 }
 428
 429 int i915_active_add_request(struct i915_active *ref, struct i915_request *rq)
 430 {
 431         struct dma_fence *fence = &rq->fence;
 432         struct i915_active_fence *active;
 433         int err;
 434
 435         /* Prevent reaping in case we malloc/wait while building the tree */
 436         err = i915_active_acquire(ref);
 437         if (err)
 438                 return err;
 439
 440         active = active_instance(ref, i915_request_timeline(rq)->fence_context);
 441         if (!active) {
 442                 err = -ENOMEM;
 443                 goto out;
 444         }
 445
 446         if (replace_barrier(ref, active)) {
 447                 RCU_INIT_POINTER(active->fence, NULL);
 448                 atomic_dec(&ref->count);
 449         }
 450         if (!__i915_active_fence_set(active, fence))
 451                 __i915_active_acquire(ref);
 452
 453 out:
 454         i915_active_release(ref);
 455         return err;
 456 }
 457
 458 static struct dma_fence *
 459 __i915_active_set_fence(struct i915_active *ref,
 460                         struct i915_active_fence *active,
 461                         struct dma_fence *fence)
 462 {
 463         struct dma_fence *prev;
 464
 465         if (replace_barrier(ref, active)) {
 466                 RCU_INIT_POINTER(active->fence, fence);
 467                 return NULL;
 468         }
 469
 470         rcu_read_lock();
 471         prev = __i915_active_fence_set(active, fence);
 472         if (prev)
 473                 prev = dma_fence_get_rcu(prev);
 474         else
 475                 __i915_active_acquire(ref);
 476         rcu_read_unlock();
 477
 478         return prev;
 479 }
 480
 481 struct dma_fence *
 482 i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
 483 {
 484         /* We expect the caller to manage the exclusive timeline ordering */
 485         return __i915_active_set_fence(ref, &ref->excl, f);
 486 }
 487
 488 bool i915_active_acquire_if_busy(struct i915_active *ref)
 489 {
 490         debug_active_assert(ref);
 491         return atomic_add_unless(&ref->count, 1, 0);
 492 }
 493
 494 static void __i915_active_activate(struct i915_active *ref)
 495 {
 496         spin_lock_irq(&ref->tree_lock); /* __active_retire() */
 497         if (!atomic_fetch_inc(&ref->count))
 498                 debug_active_activate(ref);
 499         spin_unlock_irq(&ref->tree_lock);
 500 }
 501
 502 int i915_active_acquire(struct i915_active *ref)
 503 {
 504         int err;
 505
 506         if (i915_active_acquire_if_busy(ref))
 507                 return 0;
 508
 509         if (!ref->active) {
 510                 __i915_active_activate(ref);
 511                 return 0;
 512         }
 513
 514         err = mutex_lock_interruptible(&ref->mutex);
 515         if (err)
 516                 return err;
 517
 518         if (likely(!i915_active_acquire_if_busy(ref))) {
 519                 err = ref->active(ref);
 520                 if (!err)
 521                         __i915_active_activate(ref);
 522         }
 523
 524         mutex_unlock(&ref->mutex);
 525
 526         return err;
 527 }
 528
 529 int i915_active_acquire_for_context(struct i915_active *ref, u64 idx)
 530 {
 531         struct i915_active_fence *active;
 532         int err;
 533
 534         err = i915_active_acquire(ref);
 535         if (err)
 536                 return err;
 537
 538         active = active_instance(ref, idx);
 539         if (!active) {
 540                 i915_active_release(ref);
 541                 return -ENOMEM;
 542         }
 543
 544         return 0; /* return with active ref */
 545 }
 546
 547 void i915_active_release(struct i915_active *ref)
 548 {
 549         debug_active_assert(ref);
 550         active_retire(ref);
 551 }
 552
 553 static void enable_signaling(struct i915_active_fence *active)
 554 {
 555         struct dma_fence *fence;
 556
 557         if (unlikely(is_barrier(active)))
 558                 return;
 559
 560         fence = i915_active_fence_get(active);
 561         if (!fence)
 562                 return;
 563
 564         dma_fence_enable_sw_signaling(fence);
 565         dma_fence_put(fence);
 566 }
 567
 568 static int flush_barrier(struct active_node *it)
 569 {
 570         struct intel_engine_cs *engine;
 571
 572         if (likely(!is_barrier(&it->base)))
 573                 return 0;
 574
 575         engine = __barrier_to_engine(it);
 576         smp_rmb(); /* serialise with add_active_barriers */
 577         if (!is_barrier(&it->base))
 578                 return 0;
 579
 580         return intel_engine_flush_barriers(engine);
 581 }
 582
 583 static int flush_lazy_signals(struct i915_active *ref)
 584 {
 585         struct active_node *it, *n;
 586         int err = 0;
 587
 588         enable_signaling(&ref->excl);
 589         rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 590                 err = flush_barrier(it); /* unconnected idle barrier? */
 591                 if (err)
 592                         break;
 593
 594                 enable_signaling(&it->base);
 595         }
 596
 597         return err;
 598 }
 599
 600 int __i915_active_wait(struct i915_active *ref, int state)
 601 {
 602         might_sleep();
 603
 604         /* Any fence added after the wait begins will not be auto-signaled */
 605         if (i915_active_acquire_if_busy(ref)) {
 606                 int err;
 607
 608                 err = flush_lazy_signals(ref);
 609                 i915_active_release(ref);
 610                 if (err)
 611                         return err;
 612
 613                 if (___wait_var_event(ref, i915_active_is_idle(ref),
 614                                       state, 0, 0, schedule()))
 615                         return -EINTR;
 616         }
 617
 618         /*
 619          * After the wait is complete, the caller may free the active.
 620          * We have to flush any concurrent retirement before returning.
 621          */
 622         flush_work(&ref->work);
 623         return 0;
 624 }
 625
 626 static int __await_active(struct i915_active_fence *active,
 627                           int (*fn)(void *arg, struct dma_fence *fence),
 628                           void *arg)
 629 {
 630         struct dma_fence *fence;
 631
 632         if (is_barrier(active)) /* XXX flush the barrier? */
 633                 return 0;
 634
 635         fence = i915_active_fence_get(active);
 636         if (fence) {
 637                 int err;
 638
 639                 err = fn(arg, fence);
 640                 dma_fence_put(fence);
 641                 if (err < 0)
 642                         return err;
 643         }
 644
 645         return 0;
 646 }
 647
 648 struct wait_barrier {
 649         struct wait_queue_entry base;
 650         struct i915_active *ref;
 651 };
 652
 653 static int
 654 barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key)
 655 {
 656         struct wait_barrier *wb = container_of(wq, typeof(*wb), base);
 657
 658         if (i915_active_is_idle(wb->ref)) {
 659                 list_del(&wq->entry);
 660                 i915_sw_fence_complete(wq->private);
 661                 kfree(wq);
 662         }
 663
 664         return 0;
 665 }
 666
 667 static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence)
 668 {
 669         struct wait_barrier *wb;
 670
 671         wb = kmalloc(sizeof(*wb), GFP_KERNEL);
 672         if (unlikely(!wb))
 673                 return -ENOMEM;
 674
 675         GEM_BUG_ON(i915_active_is_idle(ref));
 676         if (!i915_sw_fence_await(fence)) {
 677                 kfree(wb);
 678                 return -EINVAL;
 679         }
 680
 681         wb->base.flags = 0;
 682         wb->base.func = barrier_wake;
 683         wb->base.private = fence;
 684         wb->ref = ref;
 685
 686         add_wait_queue(__var_waitqueue(ref), &wb->base);
 687         return 0;
 688 }
 689
 690 static int await_active(struct i915_active *ref,
 691                         unsigned int flags,
 692                         int (*fn)(void *arg, struct dma_fence *fence),
 693                         void *arg, struct i915_sw_fence *barrier)
 694 {
 695         int err = 0;
 696
 697         if (!i915_active_acquire_if_busy(ref))
 698                 return 0;
 699
 700         if (flags & I915_ACTIVE_AWAIT_EXCL &&
 701             rcu_access_pointer(ref->excl.fence)) {
 702                 err = __await_active(&ref->excl, fn, arg);
 703                 if (err)
 704                         goto out;
 705         }
 706
 707         if (flags & I915_ACTIVE_AWAIT_ACTIVE) {
 708                 struct active_node *it, *n;
 709
 710                 rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 711                         err = __await_active(&it->base, fn, arg);
 712                         if (err)
 713                                 goto out;
 714                 }
 715         }
 716
 717         if (flags & I915_ACTIVE_AWAIT_BARRIER) {
 718                 err = flush_lazy_signals(ref);
 719                 if (err)
 720                         goto out;
 721
 722                 err = __await_barrier(ref, barrier);
 723                 if (err)
 724                         goto out;
 725         }
 726
 727 out:
 728         i915_active_release(ref);
 729         return err;
 730 }
 731
 732 static int rq_await_fence(void *arg, struct dma_fence *fence)
 733 {
 734         return i915_request_await_dma_fence(arg, fence);
 735 }
 736
 737 int i915_request_await_active(struct i915_request *rq,
 738                               struct i915_active *ref,
 739                               unsigned int flags)
 740 {
 741         return await_active(ref, flags, rq_await_fence, rq, &rq->submit);
 742 }
 743
 744 static int sw_await_fence(void *arg, struct dma_fence *fence)
 745 {
 746         return i915_sw_fence_await_dma_fence(arg, fence, 0,
 747                                              GFP_NOWAIT | __GFP_NOWARN);
 748 }
 749
 750 int i915_sw_fence_await_active(struct i915_sw_fence *fence,
 751                                struct i915_active *ref,
 752                                unsigned int flags)
 753 {
 754         return await_active(ref, flags, sw_await_fence, fence, fence);
 755 }
 756
 757 void i915_active_fini(struct i915_active *ref)
 758 {
 759         debug_active_fini(ref);
 760         GEM_BUG_ON(atomic_read(&ref->count));
 761         GEM_BUG_ON(work_pending(&ref->work));
 762         mutex_destroy(&ref->mutex);
 763
 764         if (ref->cache)
 765                 kmem_cache_free(slab_cache, ref->cache);
 766 }
 767
 768 static inline bool is_idle_barrier(struct active_node *node, u64 idx)
 769 {
 770         return node->timeline == idx && !i915_active_fence_isset(&node->base);
 771 }
 772
 773 static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
 774 {
 775         struct rb_node *prev, *p;
 776
 777         if (RB_EMPTY_ROOT(&ref->tree))
 778                 return NULL;
 779
 780         GEM_BUG_ON(i915_active_is_idle(ref));
 781
 782         /*
 783          * Try to reuse any existing barrier nodes already allocated for this
 784          * i915_active, due to overlapping active phases there is likely a
 785          * node kept alive (as we reuse before parking). We prefer to reuse
 786          * completely idle barriers (less hassle in manipulating the llists),
 787          * but otherwise any will do.
 788          */
 789         if (ref->cache && is_idle_barrier(ref->cache, idx)) {
 790                 p = &ref->cache->node;
 791                 goto match;
 792         }
 793
 794         prev = NULL;
 795         p = ref->tree.rb_node;
 796         while (p) {
 797                 struct active_node *node =
 798                         rb_entry(p, struct active_node, node);
 799
 800                 if (is_idle_barrier(node, idx))
 801                         goto match;
 802
 803                 prev = p;
 804                 if (node->timeline < idx)
 805                         p = READ_ONCE(p->rb_right);
 806                 else
 807                         p = READ_ONCE(p->rb_left);
 808         }
 809
 810         /*
 811          * No quick match, but we did find the leftmost rb_node for the
 812          * kernel_context. Walk the rb_tree in-order to see if there were
 813          * any idle-barriers on this timeline that we missed, or just use
 814          * the first pending barrier.
 815          */
 816         for (p = prev; p; p = rb_next(p)) {
 817                 struct active_node *node =
 818                         rb_entry(p, struct active_node, node);
 819                 struct intel_engine_cs *engine;
 820
 821                 if (node->timeline > idx)
 822                         break;
 823
 824                 if (node->timeline < idx)
 825                         continue;
 826
 827                 if (is_idle_barrier(node, idx))
 828                         goto match;
 829
 830                 /*
 831                  * The list of pending barriers is protected by the
 832                  * kernel_context timeline, which notably we do not hold
 833                  * here. i915_request_add_active_barriers() may consume
 834                  * the barrier before we claim it, so we have to check
 835                  * for success.
 836                  */
 837                 engine = __barrier_to_engine(node);
 838                 smp_rmb(); /* serialise with add_active_barriers */
 839                 if (is_barrier(&node->base) &&
 840                     ____active_del_barrier(ref, node, engine))
 841                         goto match;
 842         }
 843
 844         return NULL;
 845
 846 match:
 847         spin_lock_irq(&ref->tree_lock);
 848         rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
 849         if (p == &ref->cache->node)
 850                 WRITE_ONCE(ref->cache, NULL);
 851         spin_unlock_irq(&ref->tree_lock);
 852
 853         return rb_entry(p, struct active_node, node);
 854 }
 855
 856 int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
 857                                             struct intel_engine_cs *engine)
 858 {
 859         intel_engine_mask_t tmp, mask = engine->mask;
 860         struct llist_node *first = NULL, *last = NULL;
 861         struct intel_gt *gt = engine->gt;
 862
 863         GEM_BUG_ON(i915_active_is_idle(ref));
 864
 865         /* Wait until the previous preallocation is completed */
 866         while (!llist_empty(&ref->preallocated_barriers))
 867                 cond_resched();
 868
 869         /*
 870          * Preallocate a node for each physical engine supporting the target
 871          * engine (remember virtual engines have more than one sibling).
 872          * We can then use the preallocated nodes in
 873          * i915_active_acquire_barrier()
 874          */
 875         GEM_BUG_ON(!mask);
 876         for_each_engine_masked(engine, gt, mask, tmp) {
 877                 u64 idx = engine->kernel_context->timeline->fence_context;
 878                 struct llist_node *prev = first;
 879                 struct active_node *node;
 880
 881                 rcu_read_lock();
 882                 node = reuse_idle_barrier(ref, idx);
 883                 rcu_read_unlock();
 884                 if (!node) {
 885                         node = kmem_cache_alloc(slab_cache, GFP_KERNEL);
 886                         if (!node)
 887                                 goto unwind;
 888
 889                         RCU_INIT_POINTER(node->base.fence, NULL);
 890                         node->base.cb.func = node_retire;
 891                         node->timeline = idx;
 892                         node->ref = ref;
 893                 }
 894
 895                 if (!i915_active_fence_isset(&node->base)) {
 896                         /*
 897                          * Mark this as being *our* unconnected proto-node.
 898                          *
 899                          * Since this node is not in any list, and we have
 900                          * decoupled it from the rbtree, we can reuse the
 901                          * request to indicate this is an idle-barrier node
 902                          * and then we can use the rb_node and list pointers
 903                          * for our tracking of the pending barrier.
 904                          */
 905                         RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN));
 906                         node->base.cb.node.prev = (void *)engine;
 907                         __i915_active_acquire(ref);
 908                 }
 909                 GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));
 910
 911                 GEM_BUG_ON(barrier_to_engine(node) != engine);
 912                 first = barrier_to_ll(node);
 913                 first->next = prev;
 914                 if (!last)
 915                         last = first;
 916                 intel_engine_pm_get(engine);
 917         }
 918
 919         GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
 920         llist_add_batch(first, last, &ref->preallocated_barriers);
 921
 922         return 0;
 923
 924 unwind:
 925         while (first) {
 926                 struct active_node *node = barrier_from_ll(first);
 927
 928                 first = first->next;
 929
 930                 atomic_dec(&ref->count);
 931                 intel_engine_pm_put(barrier_to_engine(node));
 932
 933                 kmem_cache_free(slab_cache, node);
 934         }
 935         return -ENOMEM;
 936 }
 937
 938 void i915_active_acquire_barrier(struct i915_active *ref)
 939 {
 940         struct llist_node *pos, *next;
 941         unsigned long flags;
 942
 943         GEM_BUG_ON(i915_active_is_idle(ref));
 944
 945         /*
 946          * Transfer the list of preallocated barriers into the
 947          * i915_active rbtree, but only as proto-nodes. They will be
 948          * populated by i915_request_add_active_barriers() to point to the
 949          * request that will eventually release them.
 950          */
 951         llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
 952                 struct active_node *node = barrier_from_ll(pos);
 953                 struct intel_engine_cs *engine = barrier_to_engine(node);
 954                 struct rb_node **p, *parent;
 955
 956                 spin_lock_irqsave_nested(&ref->tree_lock, flags,
 957                                          SINGLE_DEPTH_NESTING);
 958                 parent = NULL;
 959                 p = &ref->tree.rb_node;
 960                 while (*p) {
 961                         struct active_node *it;
 962
 963                         parent = *p;
 964
 965                         it = rb_entry(parent, struct active_node, node);
 966                         if (it->timeline < node->timeline)
 967                                 p = &parent->rb_right;
 968                         else
 969                                 p = &parent->rb_left;
 970                 }
 971                 rb_link_node(&node->node, parent, p);
 972                 rb_insert_color(&node->node, &ref->tree);
 973                 spin_unlock_irqrestore(&ref->tree_lock, flags);
 974
 975                 GEM_BUG_ON(!intel_engine_pm_is_awake(engine));
 976                 llist_add(barrier_to_ll(node), &engine->barrier_tasks);
 977                 intel_engine_pm_put_delay(engine, 2);
 978         }
 979 }
 980
 981 static struct dma_fence **ll_to_fence_slot(struct llist_node *node)
 982 {
 983         return __active_fence_slot(&barrier_from_ll(node)->base);
 984 }
 985
 986 void i915_request_add_active_barriers(struct i915_request *rq)
 987 {
 988         struct intel_engine_cs *engine = rq->engine;
 989         struct llist_node *node, *next;
 990         unsigned long flags;
 991
 992         GEM_BUG_ON(!intel_context_is_barrier(rq->context));
 993         GEM_BUG_ON(intel_engine_is_virtual(engine));
 994         GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline);
 995
 996         node = llist_del_all(&engine->barrier_tasks);
 997         if (!node)
 998                 return;
 999         /*
1000          * Attach the list of proto-fences to the in-flight request such
1001          * that the parent i915_active will be released when this request
1002          * is retired.
1003          */
1004         spin_lock_irqsave(&rq->lock, flags);
1005         llist_for_each_safe(node, next, node) {
1006                 /* serialise with reuse_idle_barrier */
1007                 smp_store_mb(*ll_to_fence_slot(node), &rq->fence);
1008                 list_add_tail((struct list_head *)node, &rq->fence.cb_list);
1009         }
1010         spin_unlock_irqrestore(&rq->lock, flags);
1011 }
1012
1013 /*
1014  * __i915_active_fence_set: Update the last active fence along its timeline
1015  * @active: the active tracker
1016  * @fence: the new fence (under construction)
1017  *
1018  * Records the new @fence as the last active fence along its timeline in
1019  * this active tracker, moving the tracking callbacks from the previous
1020  * fence onto this one. Returns the previous fence (if not already completed),
1021  * which the caller must ensure is executed before the new fence. To ensure
1022  * that the order of fences within the timeline of the i915_active_fence is
1023  * understood, it should be locked by the caller.
1024  */
1025 struct dma_fence *
1026 __i915_active_fence_set(struct i915_active_fence *active,
1027                         struct dma_fence *fence)
1028 {
1029         struct dma_fence *prev;
1030         unsigned long flags;
1031
1032         if (fence == rcu_access_pointer(active->fence))
1033                 return fence;
1034
1035         GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
1036
1037         /*
1038          * Consider that we have two threads arriving (A and B), with
1039          * C already resident as the active->fence.
1040          *
1041          * A does the xchg first, and so it sees C or NULL depending
1042          * on the timing of the interrupt handler. If it is NULL, the
1043          * previous fence must have been signaled and we know that
1044          * we are first on the timeline. If it is still present,
1045          * we acquire the lock on that fence and serialise with the interrupt
1046          * handler, in the process removing it from any future interrupt
1047          * callback. A will then wait on C before executing (if present).
1048          *
1049          * As B is second, it sees A as the previous fence and so waits for
1050          * it to complete its transition and takes over the occupancy for
1051          * itself -- remembering that it needs to wait on A before executing.
1052          *
1053          * Note the strong ordering of the timeline also provides consistent
1054          * nesting rules for the fence->lock; the inner lock is always the
1055          * older lock.
1056          */
1057         spin_lock_irqsave(fence->lock, flags);
1058         prev = xchg(__active_fence_slot(active), fence);
1059         if (prev) {
1060                 GEM_BUG_ON(prev == fence);
1061                 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
1062                 __list_del_entry(&active->cb.node);
1063                 spin_unlock(prev->lock); /* serialise with prev->cb_list */
1064         }
1065         list_add_tail(&active->cb.node, &fence->cb_list);
1066         spin_unlock_irqrestore(fence->lock, flags);
1067
1068         return prev;
1069 }
1070
1071 int i915_active_fence_set(struct i915_active_fence *active,
1072                           struct i915_request *rq)
1073 {
1074         struct dma_fence *fence;
1075         int err = 0;
1076
1077         /* Must maintain timeline ordering wrt previous active requests */
1078         rcu_read_lock();
1079         fence = __i915_active_fence_set(active, &rq->fence);
1080         if (fence) /* but the previous fence may not belong to that timeline! */
1081                 fence = dma_fence_get_rcu(fence);
1082         rcu_read_unlock();
1083         if (fence) {
1084                 err = i915_request_await_dma_fence(rq, fence);
1085                 dma_fence_put(fence);
1086         }
1087
1088         return err;
1089 }
1090
1091 void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
1092 {
1093         active_fence_cb(fence, cb);
1094 }
1095
1096 struct auto_active {
1097         struct i915_active base;
1098         struct kref ref;
1099 };
1100
1101 struct i915_active *i915_active_get(struct i915_active *ref)
1102 {
1103         struct auto_active *aa = container_of(ref, typeof(*aa), base);
1104
1105         kref_get(&aa->ref);
1106         return &aa->base;
1107 }
1108
1109 static void auto_release(struct kref *ref)
1110 {
1111         struct auto_active *aa = container_of(ref, typeof(*aa), ref);
1112
1113         i915_active_fini(&aa->base);
1114         kfree(aa);
1115 }
1116
1117 void i915_active_put(struct i915_active *ref)
1118 {
1119         struct auto_active *aa = container_of(ref, typeof(*aa), base);
1120
1121         kref_put(&aa->ref, auto_release);
1122 }
1123
1124 static int auto_active(struct i915_active *ref)
1125 {
1126         i915_active_get(ref);
1127         return 0;
1128 }
1129
1130 static void auto_retire(struct i915_active *ref)
1131 {
1132         i915_active_put(ref);
1133 }
1134
1135 struct i915_active *i915_active_create(void)
1136 {
1137         struct auto_active *aa;
1138
1139         aa = kmalloc(sizeof(*aa), GFP_KERNEL);
1140         if (!aa)
1141                 return NULL;
1142
1143         kref_init(&aa->ref);
1144         i915_active_init(&aa->base, auto_active, auto_retire, 0);
1145
1146         return &aa->base;
1147 }
1148
1149 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
1150 #include "selftests/i915_active.c"
1151 #endif
1152
1153 void i915_active_module_exit(void)
1154 {
1155         kmem_cache_destroy(slab_cache);
1156 }
1157
1158 int __init i915_active_module_init(void)
1159 {
1160         slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
1161         if (!slab_cache)
1162                 return -ENOMEM;
1163
1164         return 0;
1165 }