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 #include "i915_globals.h"
  17
  18 /*
  19  * Active refs memory management
  20  *
  21  * To be more economical with memory, we reap all the i915_active trees as
  22  * they idle (when we know the active requests are inactive) and allocate the
  23  * nodes from a local slab cache to hopefully reduce the fragmentation.
  24  */
  25 static struct i915_global_active {
  26         struct i915_global base;
  27         struct kmem_cache *slab_cache;
  28 } global;
  29
  30 struct active_node {
  31         struct rb_node node;
  32         struct i915_active_fence base;
  33         struct i915_active *ref;
  34         u64 timeline;
  35 };
  36
  37 #define fetch_node(x) rb_entry(READ_ONCE(x), typeof(struct active_node), node)
  38
  39 static inline struct active_node *
  40 node_from_active(struct i915_active_fence *active)
  41 {
  42         return container_of(active, struct active_node, base);
  43 }
  44
  45 #define take_preallocated_barriers(x) llist_del_all(&(x)->preallocated_barriers)
  46
  47 static inline bool is_barrier(const struct i915_active_fence *active)
  48 {
  49         return IS_ERR(rcu_access_pointer(active->fence));
  50 }
  51
  52 static inline struct llist_node *barrier_to_ll(struct active_node *node)
  53 {
  54         GEM_BUG_ON(!is_barrier(&node->base));
  55         return (struct llist_node *)&node->base.cb.node;
  56 }
  57
  58 static inline struct intel_engine_cs *
  59 __barrier_to_engine(struct active_node *node)
  60 {
  61         return (struct intel_engine_cs *)READ_ONCE(node->base.cb.node.prev);
  62 }
  63
  64 static inline struct intel_engine_cs *
  65 barrier_to_engine(struct active_node *node)
  66 {
  67         GEM_BUG_ON(!is_barrier(&node->base));
  68         return __barrier_to_engine(node);
  69 }
  70
  71 static inline struct active_node *barrier_from_ll(struct llist_node *x)
  72 {
  73         return container_of((struct list_head *)x,
  74                             struct active_node, base.cb.node);
  75 }
  76
  77 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && IS_ENABLED(CONFIG_DEBUG_OBJECTS)
  78
  79 static void *active_debug_hint(void *addr)
  80 {
  81         struct i915_active *ref = addr;
  82
  83         return (void *)ref->active ?: (void *)ref->retire ?: (void *)ref;
  84 }
  85
  86 static const struct debug_obj_descr active_debug_desc = {
  87         .name = "i915_active",
  88         .debug_hint = active_debug_hint,
  89 };
  90
  91 static void debug_active_init(struct i915_active *ref)
  92 {
  93         debug_object_init(ref, &active_debug_desc);
  94 }
  95
  96 static void debug_active_activate(struct i915_active *ref)
  97 {
  98         lockdep_assert_held(&ref->tree_lock);
  99         if (!atomic_read(&ref->count)) /* before the first inc */
 100                 debug_object_activate(ref, &active_debug_desc);
 101 }
 102
 103 static void debug_active_deactivate(struct i915_active *ref)
 104 {
 105         lockdep_assert_held(&ref->tree_lock);
 106         if (!atomic_read(&ref->count)) /* after the last dec */
 107                 debug_object_deactivate(ref, &active_debug_desc);
 108 }
 109
 110 static void debug_active_fini(struct i915_active *ref)
 111 {
 112         debug_object_free(ref, &active_debug_desc);
 113 }
 114
 115 static void debug_active_assert(struct i915_active *ref)
 116 {
 117         debug_object_assert_init(ref, &active_debug_desc);
 118 }
 119
 120 #else
 121
 122 static inline void debug_active_init(struct i915_active *ref) { }
 123 static inline void debug_active_activate(struct i915_active *ref) { }
 124 static inline void debug_active_deactivate(struct i915_active *ref) { }
 125 static inline void debug_active_fini(struct i915_active *ref) { }
 126 static inline void debug_active_assert(struct i915_active *ref) { }
 127
 128 #endif
 129
 130 static void
 131 __active_retire(struct i915_active *ref)
 132 {
 133         struct rb_root root = RB_ROOT;
 134         struct active_node *it, *n;
 135         unsigned long flags;
 136
 137         GEM_BUG_ON(i915_active_is_idle(ref));
 138
 139         /* return the unused nodes to our slabcache -- flushing the allocator */
 140         if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags))
 141                 return;
 142
 143         GEM_BUG_ON(rcu_access_pointer(ref->excl.fence));
 144         debug_active_deactivate(ref);
 145
 146         /* Even if we have not used the cache, we may still have a barrier */
 147         if (!ref->cache)
 148                 ref->cache = fetch_node(ref->tree.rb_node);
 149
 150         /* Keep the MRU cached node for reuse */
 151         if (ref->cache) {
 152                 /* Discard all other nodes in the tree */
 153                 rb_erase(&ref->cache->node, &ref->tree);
 154                 root = ref->tree;
 155
 156                 /* Rebuild the tree with only the cached node */
 157                 rb_link_node(&ref->cache->node, NULL, &ref->tree.rb_node);
 158                 rb_insert_color(&ref->cache->node, &ref->tree);
 159                 GEM_BUG_ON(ref->tree.rb_node != &ref->cache->node);
 160
 161                 /* Make the cached node available for reuse with any timeline */
 162                 ref->cache->timeline = 0; /* needs cmpxchg(u64) */
 163         }
 164
 165         spin_unlock_irqrestore(&ref->tree_lock, flags);
 166
 167         /* After the final retire, the entire struct may be freed */
 168         if (ref->retire)
 169                 ref->retire(ref);
 170
 171         /* ... except if you wait on it, you must manage your own references! */
 172         wake_up_var(ref);
 173
 174         /* Finally free the discarded timeline tree  */
 175         rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
 176                 GEM_BUG_ON(i915_active_fence_isset(&it->base));
 177                 kmem_cache_free(global.slab_cache, it);
 178         }
 179 }
 180
 181 static void
 182 active_work(struct work_struct *wrk)
 183 {
 184         struct i915_active *ref = container_of(wrk, typeof(*ref), work);
 185
 186         GEM_BUG_ON(!atomic_read(&ref->count));
 187         if (atomic_add_unless(&ref->count, -1, 1))
 188                 return;
 189
 190         __active_retire(ref);
 191 }
 192
 193 static void
 194 active_retire(struct i915_active *ref)
 195 {
 196         GEM_BUG_ON(!atomic_read(&ref->count));
 197         if (atomic_add_unless(&ref->count, -1, 1))
 198                 return;
 199
 200         if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {
 201                 queue_work(system_unbound_wq, &ref->work);
 202                 return;
 203         }
 204
 205         __active_retire(ref);
 206 }
 207
 208 static inline struct dma_fence **
 209 __active_fence_slot(struct i915_active_fence *active)
 210 {
 211         return (struct dma_fence ** __force)&active->fence;
 212 }
 213
 214 static inline bool
 215 active_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
 216 {
 217         struct i915_active_fence *active =
 218                 container_of(cb, typeof(*active), cb);
 219
 220         return cmpxchg(__active_fence_slot(active), fence, NULL) == fence;
 221 }
 222
 223 static void
 224 node_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
 225 {
 226         if (active_fence_cb(fence, cb))
 227                 active_retire(container_of(cb, struct active_node, base.cb)->ref);
 228 }
 229
 230 static void
 231 excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
 232 {
 233         if (active_fence_cb(fence, cb))
 234                 active_retire(container_of(cb, struct i915_active, excl.cb));
 235 }
 236
 237 static struct active_node *__active_lookup(struct i915_active *ref, u64 idx)
 238 {
 239         struct active_node *it;
 240
 241         GEM_BUG_ON(idx == 0); /* 0 is the unordered timeline, rsvd for cache */
 242
 243         /*
 244          * We track the most recently used timeline to skip a rbtree search
 245          * for the common case, under typical loads we never need the rbtree
 246          * at all. We can reuse the last slot if it is empty, that is
 247          * after the previous activity has been retired, or if it matches the
 248          * current timeline.
 249          */
 250         it = READ_ONCE(ref->cache);
 251         if (it) {
 252                 u64 cached = READ_ONCE(it->timeline);
 253
 254                 /* Once claimed, this slot will only belong to this idx */
 255                 if (cached == idx)
 256                         return it;
 257
 258                 /*
 259                  * An unclaimed cache [.timeline=0] can only be claimed once.
 260                  *
 261                  * If the value is already non-zero, some other thread has
 262                  * claimed the cache and we know that is does not match our
 263                  * idx. If, and only if, the timeline is currently zero is it
 264                  * worth competing to claim it atomically for ourselves (for
 265                  * only the winner of that race will cmpxchg return the old
 266                  * value of 0).
 267                  */
 268                 if (!cached && !cmpxchg64(&it->timeline, 0, idx))
 269                         return it;
 270         }
 271
 272         BUILD_BUG_ON(offsetof(typeof(*it), node));
 273
 274         /* While active, the tree can only be built; not destroyed */
 275         GEM_BUG_ON(i915_active_is_idle(ref));
 276
 277         it = fetch_node(ref->tree.rb_node);
 278         while (it) {
 279                 if (it->timeline < idx) {
 280                         it = fetch_node(it->node.rb_right);
 281                 } else if (it->timeline > idx) {
 282                         it = fetch_node(it->node.rb_left);
 283                 } else {
 284                         WRITE_ONCE(ref->cache, it);
 285                         break;
 286                 }
 287         }
 288
 289         /* NB: If the tree rotated beneath us, we may miss our target. */
 290         return it;
 291 }
 292
 293 static struct i915_active_fence *
 294 active_instance(struct i915_active *ref, u64 idx)
 295 {
 296         struct active_node *node;
 297         struct rb_node **p, *parent;
 298
 299         node = __active_lookup(ref, idx);
 300         if (likely(node))
 301                 return &node->base;
 302
 303         spin_lock_irq(&ref->tree_lock);
 304         GEM_BUG_ON(i915_active_is_idle(ref));
 305
 306         parent = NULL;
 307         p = &ref->tree.rb_node;
 308         while (*p) {
 309                 parent = *p;
 310
 311                 node = rb_entry(parent, struct active_node, node);
 312                 if (node->timeline == idx)
 313                         goto out;
 314
 315                 if (node->timeline < idx)
 316                         p = &parent->rb_right;
 317                 else
 318                         p = &parent->rb_left;
 319         }
 320
 321         /*
 322          * XXX: We should preallocate this before i915_active_ref() is ever
 323          *  called, but we cannot call into fs_reclaim() anyway, so use GFP_ATOMIC.
 324          */
 325         node = kmem_cache_alloc(global.slab_cache, GFP_ATOMIC);
 326         if (!node)
 327                 goto out;
 328
 329         __i915_active_fence_init(&node->base, NULL, node_retire);
 330         node->ref = ref;
 331         node->timeline = idx;
 332
 333         rb_link_node(&node->node, parent, p);
 334         rb_insert_color(&node->node, &ref->tree);
 335
 336 out:
 337         WRITE_ONCE(ref->cache, node);
 338         spin_unlock_irq(&ref->tree_lock);
 339
 340         return &node->base;
 341 }
 342
 343 void __i915_active_init(struct i915_active *ref,
 344                         int (*active)(struct i915_active *ref),
 345                         void (*retire)(struct i915_active *ref),
 346                         unsigned long flags,
 347                         struct lock_class_key *mkey,
 348                         struct lock_class_key *wkey)
 349 {
 350         debug_active_init(ref);
 351
 352         ref->flags = flags;
 353         ref->active = active;
 354         ref->retire = retire;
 355
 356         spin_lock_init(&ref->tree_lock);
 357         ref->tree = RB_ROOT;
 358         ref->cache = NULL;
 359
 360         init_llist_head(&ref->preallocated_barriers);
 361         atomic_set(&ref->count, 0);
 362         __mutex_init(&ref->mutex, "i915_active", mkey);
 363         __i915_active_fence_init(&ref->excl, NULL, excl_retire);
 364         INIT_WORK(&ref->work, active_work);
 365 #if IS_ENABLED(CONFIG_LOCKDEP)
 366         lockdep_init_map(&ref->work.lockdep_map, "i915_active.work", wkey, 0);
 367 #endif
 368 }
 369
 370 static bool ____active_del_barrier(struct i915_active *ref,
 371                                    struct active_node *node,
 372                                    struct intel_engine_cs *engine)
 373
 374 {
 375         struct llist_node *head = NULL, *tail = NULL;
 376         struct llist_node *pos, *next;
 377
 378         GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context);
 379
 380         /*
 381          * Rebuild the llist excluding our node. We may perform this
 382          * outside of the kernel_context timeline mutex and so someone
 383          * else may be manipulating the engine->barrier_tasks, in
 384          * which case either we or they will be upset :)
 385          *
 386          * A second __active_del_barrier() will report failure to claim
 387          * the active_node and the caller will just shrug and know not to
 388          * claim ownership of its node.
 389          *
 390          * A concurrent i915_request_add_active_barriers() will miss adding
 391          * any of the tasks, but we will try again on the next -- and since
 392          * we are actively using the barrier, we know that there will be
 393          * at least another opportunity when we idle.
 394          */
 395         llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {
 396                 if (node == barrier_from_ll(pos)) {
 397                         node = NULL;
 398                         continue;
 399                 }
 400
 401                 pos->next = head;
 402                 head = pos;
 403                 if (!tail)
 404                         tail = pos;
 405         }
 406         if (head)
 407                 llist_add_batch(head, tail, &engine->barrier_tasks);
 408
 409         return !node;
 410 }
 411
 412 static bool
 413 __active_del_barrier(struct i915_active *ref, struct active_node *node)
 414 {
 415         return ____active_del_barrier(ref, node, barrier_to_engine(node));
 416 }
 417
 418 static bool
 419 replace_barrier(struct i915_active *ref, struct i915_active_fence *active)
 420 {
 421         if (!is_barrier(active)) /* proto-node used by our idle barrier? */
 422                 return false;
 423
 424         /*
 425          * This request is on the kernel_context timeline, and so
 426          * we can use it to substitute for the pending idle-barrer
 427          * request that we want to emit on the kernel_context.
 428          */
 429         __active_del_barrier(ref, node_from_active(active));
 430         return true;
 431 }
 432
 433 int i915_active_ref(struct i915_active *ref, u64 idx, struct dma_fence *fence)
 434 {
 435         struct i915_active_fence *active;
 436         int err;
 437
 438         /* Prevent reaping in case we malloc/wait while building the tree */
 439         err = i915_active_acquire(ref);
 440         if (err)
 441                 return err;
 442
 443         active = active_instance(ref, idx);
 444         if (!active) {
 445                 err = -ENOMEM;
 446                 goto out;
 447         }
 448
 449         if (replace_barrier(ref, active)) {
 450                 RCU_INIT_POINTER(active->fence, NULL);
 451                 atomic_dec(&ref->count);
 452         }
 453         if (!__i915_active_fence_set(active, fence))
 454                 __i915_active_acquire(ref);
 455
 456 out:
 457         i915_active_release(ref);
 458         return err;
 459 }
 460
 461 static struct dma_fence *
 462 __i915_active_set_fence(struct i915_active *ref,
 463                         struct i915_active_fence *active,
 464                         struct dma_fence *fence)
 465 {
 466         struct dma_fence *prev;
 467
 468         if (replace_barrier(ref, active)) {
 469                 RCU_INIT_POINTER(active->fence, fence);
 470                 return NULL;
 471         }
 472
 473         rcu_read_lock();
 474         prev = __i915_active_fence_set(active, fence);
 475         if (prev)
 476                 prev = dma_fence_get_rcu(prev);
 477         else
 478                 __i915_active_acquire(ref);
 479         rcu_read_unlock();
 480
 481         return prev;
 482 }
 483
 484 static struct i915_active_fence *
 485 __active_fence(struct i915_active *ref, u64 idx)
 486 {
 487         struct active_node *it;
 488
 489         it = __active_lookup(ref, idx);
 490         if (unlikely(!it)) { /* Contention with parallel tree builders! */
 491                 spin_lock_irq(&ref->tree_lock);
 492                 it = __active_lookup(ref, idx);
 493                 spin_unlock_irq(&ref->tree_lock);
 494         }
 495         GEM_BUG_ON(!it); /* slot must be preallocated */
 496
 497         return &it->base;
 498 }
 499
 500 struct dma_fence *
 501 __i915_active_ref(struct i915_active *ref, u64 idx, struct dma_fence *fence)
 502 {
 503         /* Only valid while active, see i915_active_acquire_for_context() */
 504         return __i915_active_set_fence(ref, __active_fence(ref, idx), fence);
 505 }
 506
 507 struct dma_fence *
 508 i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
 509 {
 510         /* We expect the caller to manage the exclusive timeline ordering */
 511         return __i915_active_set_fence(ref, &ref->excl, f);
 512 }
 513
 514 bool i915_active_acquire_if_busy(struct i915_active *ref)
 515 {
 516         debug_active_assert(ref);
 517         return atomic_add_unless(&ref->count, 1, 0);
 518 }
 519
 520 static void __i915_active_activate(struct i915_active *ref)
 521 {
 522         spin_lock_irq(&ref->tree_lock); /* __active_retire() */
 523         if (!atomic_fetch_inc(&ref->count))
 524                 debug_active_activate(ref);
 525         spin_unlock_irq(&ref->tree_lock);
 526 }
 527
 528 int i915_active_acquire(struct i915_active *ref)
 529 {
 530         int err;
 531
 532         if (i915_active_acquire_if_busy(ref))
 533                 return 0;
 534
 535         if (!ref->active) {
 536                 __i915_active_activate(ref);
 537                 return 0;
 538         }
 539
 540         err = mutex_lock_interruptible(&ref->mutex);
 541         if (err)
 542                 return err;
 543
 544         if (likely(!i915_active_acquire_if_busy(ref))) {
 545                 err = ref->active(ref);
 546                 if (!err)
 547                         __i915_active_activate(ref);
 548         }
 549
 550         mutex_unlock(&ref->mutex);
 551
 552         return err;
 553 }
 554
 555 int i915_active_acquire_for_context(struct i915_active *ref, u64 idx)
 556 {
 557         struct i915_active_fence *active;
 558         int err;
 559
 560         err = i915_active_acquire(ref);
 561         if (err)
 562                 return err;
 563
 564         active = active_instance(ref, idx);
 565         if (!active) {
 566                 i915_active_release(ref);
 567                 return -ENOMEM;
 568         }
 569
 570         return 0; /* return with active ref */
 571 }
 572
 573 void i915_active_release(struct i915_active *ref)
 574 {
 575         debug_active_assert(ref);
 576         active_retire(ref);
 577 }
 578
 579 static void enable_signaling(struct i915_active_fence *active)
 580 {
 581         struct dma_fence *fence;
 582
 583         if (unlikely(is_barrier(active)))
 584                 return;
 585
 586         fence = i915_active_fence_get(active);
 587         if (!fence)
 588                 return;
 589
 590         dma_fence_enable_sw_signaling(fence);
 591         dma_fence_put(fence);
 592 }
 593
 594 static int flush_barrier(struct active_node *it)
 595 {
 596         struct intel_engine_cs *engine;
 597
 598         if (likely(!is_barrier(&it->base)))
 599                 return 0;
 600
 601         engine = __barrier_to_engine(it);
 602         smp_rmb(); /* serialise with add_active_barriers */
 603         if (!is_barrier(&it->base))
 604                 return 0;
 605
 606         return intel_engine_flush_barriers(engine);
 607 }
 608
 609 static int flush_lazy_signals(struct i915_active *ref)
 610 {
 611         struct active_node *it, *n;
 612         int err = 0;
 613
 614         enable_signaling(&ref->excl);
 615         rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 616                 err = flush_barrier(it); /* unconnected idle barrier? */
 617                 if (err)
 618                         break;
 619
 620                 enable_signaling(&it->base);
 621         }
 622
 623         return err;
 624 }
 625
 626 int __i915_active_wait(struct i915_active *ref, int state)
 627 {
 628         might_sleep();
 629
 630         /* Any fence added after the wait begins will not be auto-signaled */
 631         if (i915_active_acquire_if_busy(ref)) {
 632                 int err;
 633
 634                 err = flush_lazy_signals(ref);
 635                 i915_active_release(ref);
 636                 if (err)
 637                         return err;
 638
 639                 if (___wait_var_event(ref, i915_active_is_idle(ref),
 640                                       state, 0, 0, schedule()))
 641                         return -EINTR;
 642         }
 643
 644         /*
 645          * After the wait is complete, the caller may free the active.
 646          * We have to flush any concurrent retirement before returning.
 647          */
 648         flush_work(&ref->work);
 649         return 0;
 650 }
 651
 652 static int __await_active(struct i915_active_fence *active,
 653                           int (*fn)(void *arg, struct dma_fence *fence),
 654                           void *arg)
 655 {
 656         struct dma_fence *fence;
 657
 658         if (is_barrier(active)) /* XXX flush the barrier? */
 659                 return 0;
 660
 661         fence = i915_active_fence_get(active);
 662         if (fence) {
 663                 int err;
 664
 665                 err = fn(arg, fence);
 666                 dma_fence_put(fence);
 667                 if (err < 0)
 668                         return err;
 669         }
 670
 671         return 0;
 672 }
 673
 674 struct wait_barrier {
 675         struct wait_queue_entry base;
 676         struct i915_active *ref;
 677 };
 678
 679 static int
 680 barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key)
 681 {
 682         struct wait_barrier *wb = container_of(wq, typeof(*wb), base);
 683
 684         if (i915_active_is_idle(wb->ref)) {
 685                 list_del(&wq->entry);
 686                 i915_sw_fence_complete(wq->private);
 687                 kfree(wq);
 688         }
 689
 690         return 0;
 691 }
 692
 693 static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence)
 694 {
 695         struct wait_barrier *wb;
 696
 697         wb = kmalloc(sizeof(*wb), GFP_KERNEL);
 698         if (unlikely(!wb))
 699                 return -ENOMEM;
 700
 701         GEM_BUG_ON(i915_active_is_idle(ref));
 702         if (!i915_sw_fence_await(fence)) {
 703                 kfree(wb);
 704                 return -EINVAL;
 705         }
 706
 707         wb->base.flags = 0;
 708         wb->base.func = barrier_wake;
 709         wb->base.private = fence;
 710         wb->ref = ref;
 711
 712         add_wait_queue(__var_waitqueue(ref), &wb->base);
 713         return 0;
 714 }
 715
 716 static int await_active(struct i915_active *ref,
 717                         unsigned int flags,
 718                         int (*fn)(void *arg, struct dma_fence *fence),
 719                         void *arg, struct i915_sw_fence *barrier)
 720 {
 721         int err = 0;
 722
 723         if (!i915_active_acquire_if_busy(ref))
 724                 return 0;
 725
 726         if (flags & I915_ACTIVE_AWAIT_EXCL &&
 727             rcu_access_pointer(ref->excl.fence)) {
 728                 err = __await_active(&ref->excl, fn, arg);
 729                 if (err)
 730                         goto out;
 731         }
 732
 733         if (flags & I915_ACTIVE_AWAIT_ACTIVE) {
 734                 struct active_node *it, *n;
 735
 736                 rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
 737                         err = __await_active(&it->base, fn, arg);
 738                         if (err)
 739                                 goto out;
 740                 }
 741         }
 742
 743         if (flags & I915_ACTIVE_AWAIT_BARRIER) {
 744                 err = flush_lazy_signals(ref);
 745                 if (err)
 746                         goto out;
 747
 748                 err = __await_barrier(ref, barrier);
 749                 if (err)
 750                         goto out;
 751         }
 752
 753 out:
 754         i915_active_release(ref);
 755         return err;
 756 }
 757
 758 static int rq_await_fence(void *arg, struct dma_fence *fence)
 759 {
 760         return i915_request_await_dma_fence(arg, fence);
 761 }
 762
 763 int i915_request_await_active(struct i915_request *rq,
 764                               struct i915_active *ref,
 765                               unsigned int flags)
 766 {
 767         return await_active(ref, flags, rq_await_fence, rq, &rq->submit);
 768 }
 769
 770 static int sw_await_fence(void *arg, struct dma_fence *fence)
 771 {
 772         return i915_sw_fence_await_dma_fence(arg, fence, 0,
 773                                              GFP_NOWAIT | __GFP_NOWARN);
 774 }
 775
 776 int i915_sw_fence_await_active(struct i915_sw_fence *fence,
 777                                struct i915_active *ref,
 778                                unsigned int flags)
 779 {
 780         return await_active(ref, flags, sw_await_fence, fence, fence);
 781 }
 782
 783 void i915_active_fini(struct i915_active *ref)
 784 {
 785         debug_active_fini(ref);
 786         GEM_BUG_ON(atomic_read(&ref->count));
 787         GEM_BUG_ON(work_pending(&ref->work));
 788         mutex_destroy(&ref->mutex);
 789
 790         if (ref->cache)
 791                 kmem_cache_free(global.slab_cache, ref->cache);
 792 }
 793
 794 static inline bool is_idle_barrier(struct active_node *node, u64 idx)
 795 {
 796         return node->timeline == idx && !i915_active_fence_isset(&node->base);
 797 }
 798
 799 static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
 800 {
 801         struct rb_node *prev, *p;
 802
 803         if (RB_EMPTY_ROOT(&ref->tree))
 804                 return NULL;
 805
 806         GEM_BUG_ON(i915_active_is_idle(ref));
 807
 808         /*
 809          * Try to reuse any existing barrier nodes already allocated for this
 810          * i915_active, due to overlapping active phases there is likely a
 811          * node kept alive (as we reuse before parking). We prefer to reuse
 812          * completely idle barriers (less hassle in manipulating the llists),
 813          * but otherwise any will do.
 814          */
 815         if (ref->cache && is_idle_barrier(ref->cache, idx)) {
 816                 p = &ref->cache->node;
 817                 goto match;
 818         }
 819
 820         prev = NULL;
 821         p = ref->tree.rb_node;
 822         while (p) {
 823                 struct active_node *node =
 824                         rb_entry(p, struct active_node, node);
 825
 826                 if (is_idle_barrier(node, idx))
 827                         goto match;
 828
 829                 prev = p;
 830                 if (node->timeline < idx)
 831                         p = READ_ONCE(p->rb_right);
 832                 else
 833                         p = READ_ONCE(p->rb_left);
 834         }
 835
 836         /*
 837          * No quick match, but we did find the leftmost rb_node for the
 838          * kernel_context. Walk the rb_tree in-order to see if there were
 839          * any idle-barriers on this timeline that we missed, or just use
 840          * the first pending barrier.
 841          */
 842         for (p = prev; p; p = rb_next(p)) {
 843                 struct active_node *node =
 844                         rb_entry(p, struct active_node, node);
 845                 struct intel_engine_cs *engine;
 846
 847                 if (node->timeline > idx)
 848                         break;
 849
 850                 if (node->timeline < idx)
 851                         continue;
 852
 853                 if (is_idle_barrier(node, idx))
 854                         goto match;
 855
 856                 /*
 857                  * The list of pending barriers is protected by the
 858                  * kernel_context timeline, which notably we do not hold
 859                  * here. i915_request_add_active_barriers() may consume
 860                  * the barrier before we claim it, so we have to check
 861                  * for success.
 862                  */
 863                 engine = __barrier_to_engine(node);
 864                 smp_rmb(); /* serialise with add_active_barriers */
 865                 if (is_barrier(&node->base) &&
 866                     ____active_del_barrier(ref, node, engine))
 867                         goto match;
 868         }
 869
 870         return NULL;
 871
 872 match:
 873         spin_lock_irq(&ref->tree_lock);
 874         rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
 875         if (p == &ref->cache->node)
 876                 WRITE_ONCE(ref->cache, NULL);
 877         spin_unlock_irq(&ref->tree_lock);
 878
 879         return rb_entry(p, struct active_node, node);
 880 }
 881
 882 int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
 883                                             struct intel_engine_cs *engine)
 884 {
 885         intel_engine_mask_t tmp, mask = engine->mask;
 886         struct llist_node *first = NULL, *last = NULL;
 887         struct intel_gt *gt = engine->gt;
 888
 889         GEM_BUG_ON(i915_active_is_idle(ref));
 890
 891         /* Wait until the previous preallocation is completed */
 892         while (!llist_empty(&ref->preallocated_barriers))
 893                 cond_resched();
 894
 895         /*
 896          * Preallocate a node for each physical engine supporting the target
 897          * engine (remember virtual engines have more than one sibling).
 898          * We can then use the preallocated nodes in
 899          * i915_active_acquire_barrier()
 900          */
 901         GEM_BUG_ON(!mask);
 902         for_each_engine_masked(engine, gt, mask, tmp) {
 903                 u64 idx = engine->kernel_context->timeline->fence_context;
 904                 struct llist_node *prev = first;
 905                 struct active_node *node;
 906
 907                 rcu_read_lock();
 908                 node = reuse_idle_barrier(ref, idx);
 909                 rcu_read_unlock();
 910                 if (!node) {
 911                         node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
 912                         if (!node)
 913                                 goto unwind;
 914
 915                         RCU_INIT_POINTER(node->base.fence, NULL);
 916                         node->base.cb.func = node_retire;
 917                         node->timeline = idx;
 918                         node->ref = ref;
 919                 }
 920
 921                 if (!i915_active_fence_isset(&node->base)) {
 922                         /*
 923                          * Mark this as being *our* unconnected proto-node.
 924                          *
 925                          * Since this node is not in any list, and we have
 926                          * decoupled it from the rbtree, we can reuse the
 927                          * request to indicate this is an idle-barrier node
 928                          * and then we can use the rb_node and list pointers
 929                          * for our tracking of the pending barrier.
 930                          */
 931                         RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN));
 932                         node->base.cb.node.prev = (void *)engine;
 933                         __i915_active_acquire(ref);
 934                 }
 935                 GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));
 936
 937                 GEM_BUG_ON(barrier_to_engine(node) != engine);
 938                 first = barrier_to_ll(node);
 939                 first->next = prev;
 940                 if (!last)
 941                         last = first;
 942                 intel_engine_pm_get(engine);
 943         }
 944
 945         GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
 946         llist_add_batch(first, last, &ref->preallocated_barriers);
 947
 948         return 0;
 949
 950 unwind:
 951         while (first) {
 952                 struct active_node *node = barrier_from_ll(first);
 953
 954                 first = first->next;
 955
 956                 atomic_dec(&ref->count);
 957                 intel_engine_pm_put(barrier_to_engine(node));
 958
 959                 kmem_cache_free(global.slab_cache, node);
 960         }
 961         return -ENOMEM;
 962 }
 963
 964 void i915_active_acquire_barrier(struct i915_active *ref)
 965 {
 966         struct llist_node *pos, *next;
 967         unsigned long flags;
 968
 969         GEM_BUG_ON(i915_active_is_idle(ref));
 970
 971         /*
 972          * Transfer the list of preallocated barriers into the
 973          * i915_active rbtree, but only as proto-nodes. They will be
 974          * populated by i915_request_add_active_barriers() to point to the
 975          * request that will eventually release them.
 976          */
 977         llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
 978                 struct active_node *node = barrier_from_ll(pos);
 979                 struct intel_engine_cs *engine = barrier_to_engine(node);
 980                 struct rb_node **p, *parent;
 981
 982                 spin_lock_irqsave_nested(&ref->tree_lock, flags,
 983                                          SINGLE_DEPTH_NESTING);
 984                 parent = NULL;
 985                 p = &ref->tree.rb_node;
 986                 while (*p) {
 987                         struct active_node *it;
 988
 989                         parent = *p;
 990
 991                         it = rb_entry(parent, struct active_node, node);
 992                         if (it->timeline < node->timeline)
 993                                 p = &parent->rb_right;
 994                         else
 995                                 p = &parent->rb_left;
 996                 }
 997                 rb_link_node(&node->node, parent, p);
 998                 rb_insert_color(&node->node, &ref->tree);
 999                 spin_unlock_irqrestore(&ref->tree_lock, flags);
1000
1001                 GEM_BUG_ON(!intel_engine_pm_is_awake(engine));
1002                 llist_add(barrier_to_ll(node), &engine->barrier_tasks);
1003                 intel_engine_pm_put_delay(engine, 1);
1004         }
1005 }
1006
1007 static struct dma_fence **ll_to_fence_slot(struct llist_node *node)
1008 {
1009         return __active_fence_slot(&barrier_from_ll(node)->base);
1010 }
1011
1012 void i915_request_add_active_barriers(struct i915_request *rq)
1013 {
1014         struct intel_engine_cs *engine = rq->engine;
1015         struct llist_node *node, *next;
1016         unsigned long flags;
1017
1018         GEM_BUG_ON(!intel_context_is_barrier(rq->context));
1019         GEM_BUG_ON(intel_engine_is_virtual(engine));
1020         GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline);
1021
1022         node = llist_del_all(&engine->barrier_tasks);
1023         if (!node)
1024                 return;
1025         /*
1026          * Attach the list of proto-fences to the in-flight request such
1027          * that the parent i915_active will be released when this request
1028          * is retired.
1029          */
1030         spin_lock_irqsave(&rq->lock, flags);
1031         llist_for_each_safe(node, next, node) {
1032                 /* serialise with reuse_idle_barrier */
1033                 smp_store_mb(*ll_to_fence_slot(node), &rq->fence);
1034                 list_add_tail((struct list_head *)node, &rq->fence.cb_list);
1035         }
1036         spin_unlock_irqrestore(&rq->lock, flags);
1037 }
1038
1039 /*
1040  * __i915_active_fence_set: Update the last active fence along its timeline
1041  * @active: the active tracker
1042  * @fence: the new fence (under construction)
1043  *
1044  * Records the new @fence as the last active fence along its timeline in
1045  * this active tracker, moving the tracking callbacks from the previous
1046  * fence onto this one. Returns the previous fence (if not already completed),
1047  * which the caller must ensure is executed before the new fence. To ensure
1048  * that the order of fences within the timeline of the i915_active_fence is
1049  * understood, it should be locked by the caller.
1050  */
1051 struct dma_fence *
1052 __i915_active_fence_set(struct i915_active_fence *active,
1053                         struct dma_fence *fence)
1054 {
1055         struct dma_fence *prev;
1056         unsigned long flags;
1057
1058         if (fence == rcu_access_pointer(active->fence))
1059                 return fence;
1060
1061         GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
1062
1063         /*
1064          * Consider that we have two threads arriving (A and B), with
1065          * C already resident as the active->fence.
1066          *
1067          * A does the xchg first, and so it sees C or NULL depending
1068          * on the timing of the interrupt handler. If it is NULL, the
1069          * previous fence must have been signaled and we know that
1070          * we are first on the timeline. If it is still present,
1071          * we acquire the lock on that fence and serialise with the interrupt
1072          * handler, in the process removing it from any future interrupt
1073          * callback. A will then wait on C before executing (if present).
1074          *
1075          * As B is second, it sees A as the previous fence and so waits for
1076          * it to complete its transition and takes over the occupancy for
1077          * itself -- remembering that it needs to wait on A before executing.
1078          *
1079          * Note the strong ordering of the timeline also provides consistent
1080          * nesting rules for the fence->lock; the inner lock is always the
1081          * older lock.
1082          */
1083         spin_lock_irqsave(fence->lock, flags);
1084         prev = xchg(__active_fence_slot(active), fence);
1085         if (prev) {
1086                 GEM_BUG_ON(prev == fence);
1087                 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
1088                 __list_del_entry(&active->cb.node);
1089                 spin_unlock(prev->lock); /* serialise with prev->cb_list */
1090         }
1091         list_add_tail(&active->cb.node, &fence->cb_list);
1092         spin_unlock_irqrestore(fence->lock, flags);
1093
1094         return prev;
1095 }
1096
1097 int i915_active_fence_set(struct i915_active_fence *active,
1098                           struct i915_request *rq)
1099 {
1100         struct dma_fence *fence;
1101         int err = 0;
1102
1103         /* Must maintain timeline ordering wrt previous active requests */
1104         rcu_read_lock();
1105         fence = __i915_active_fence_set(active, &rq->fence);
1106         if (fence) /* but the previous fence may not belong to that timeline! */
1107                 fence = dma_fence_get_rcu(fence);
1108         rcu_read_unlock();
1109         if (fence) {
1110                 err = i915_request_await_dma_fence(rq, fence);
1111                 dma_fence_put(fence);
1112         }
1113
1114         return err;
1115 }
1116
1117 void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
1118 {
1119         active_fence_cb(fence, cb);
1120 }
1121
1122 struct auto_active {
1123         struct i915_active base;
1124         struct kref ref;
1125 };
1126
1127 struct i915_active *i915_active_get(struct i915_active *ref)
1128 {
1129         struct auto_active *aa = container_of(ref, typeof(*aa), base);
1130
1131         kref_get(&aa->ref);
1132         return &aa->base;
1133 }
1134
1135 static void auto_release(struct kref *ref)
1136 {
1137         struct auto_active *aa = container_of(ref, typeof(*aa), ref);
1138
1139         i915_active_fini(&aa->base);
1140         kfree(aa);
1141 }
1142
1143 void i915_active_put(struct i915_active *ref)
1144 {
1145         struct auto_active *aa = container_of(ref, typeof(*aa), base);
1146
1147         kref_put(&aa->ref, auto_release);
1148 }
1149
1150 static int auto_active(struct i915_active *ref)
1151 {
1152         i915_active_get(ref);
1153         return 0;
1154 }
1155
1156 static void auto_retire(struct i915_active *ref)
1157 {
1158         i915_active_put(ref);
1159 }
1160
1161 struct i915_active *i915_active_create(void)
1162 {
1163         struct auto_active *aa;
1164
1165         aa = kmalloc(sizeof(*aa), GFP_KERNEL);
1166         if (!aa)
1167                 return NULL;
1168
1169         kref_init(&aa->ref);
1170         i915_active_init(&aa->base, auto_active, auto_retire, 0);
1171
1172         return &aa->base;
1173 }
1174
1175 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
1176 #include "selftests/i915_active.c"
1177 #endif
1178
1179 static void i915_global_active_shrink(void)
1180 {
1181         kmem_cache_shrink(global.slab_cache);
1182 }
1183
1184 static void i915_global_active_exit(void)
1185 {
1186         kmem_cache_destroy(global.slab_cache);
1187 }
1188
1189 static struct i915_global_active global = { {
1190         .shrink = i915_global_active_shrink,
1191         .exit = i915_global_active_exit,
1192 } };
1193
1194 int __init i915_global_active_init(void)
1195 {
1196         global.slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
1197         if (!global.slab_cache)
1198                 return -ENOMEM;
1199
1200         i915_global_register(&global.base);
1201         return 0;
1202 }