linux/drivers/gpu/drm/i915/i915_active.c
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   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 */
  25static struct i915_global_active {
  26        struct i915_global base;
  27        struct kmem_cache *slab_cache;
  28} global;
  29
  30struct 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
  39static inline struct active_node *
  40node_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
  47static inline bool is_barrier(const struct i915_active_fence *active)
  48{
  49        return IS_ERR(rcu_access_pointer(active->fence));
  50}
  51
  52static 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
  58static 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
  64static inline struct intel_engine_cs *
  65barrier_to_engine(struct active_node *node)
  66{
  67        GEM_BUG_ON(!is_barrier(&node->base));
  68        return __barrier_to_engine(node);
  69}
  70
  71static 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
  79static 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
  86static const struct debug_obj_descr active_debug_desc = {
  87        .name = "i915_active",
  88        .debug_hint = active_debug_hint,
  89};
  90
  91static void debug_active_init(struct i915_active *ref)
  92{
  93        debug_object_init(ref, &active_debug_desc);
  94}
  95
  96static 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
 103static 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
 110static void debug_active_fini(struct i915_active *ref)
 111{
 112        debug_object_free(ref, &active_debug_desc);
 113}
 114
 115static void debug_active_assert(struct i915_active *ref)
 116{
 117        debug_object_assert_init(ref, &active_debug_desc);
 118}
 119
 120#else
 121
 122static inline void debug_active_init(struct i915_active *ref) { }
 123static inline void debug_active_activate(struct i915_active *ref) { }
 124static inline void debug_active_deactivate(struct i915_active *ref) { }
 125static inline void debug_active_fini(struct i915_active *ref) { }
 126static inline void debug_active_assert(struct i915_active *ref) { }
 127
 128#endif
 129
 130static 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
 181static void
 182active_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
 193static void
 194active_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
 208static inline struct dma_fence **
 209__active_fence_slot(struct i915_active_fence *active)
 210{
 211        return (struct dma_fence ** __force)&active->fence;
 212}
 213
 214static inline bool
 215active_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
 223static void
 224node_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
 230static void
 231excl_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
 237static 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
 293static struct i915_active_fence *
 294active_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
 336out:
 337        WRITE_ONCE(ref->cache, node);
 338        spin_unlock_irq(&ref->tree_lock);
 339
 340        return &node->base;
 341}
 342
 343void __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
 370static 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
 412static 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
 418static bool
 419replace_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
 433int 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
 456out:
 457        i915_active_release(ref);
 458        return err;
 459}
 460
 461static 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
 484static 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
 500struct 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
 507struct dma_fence *
 508i915_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
 514bool 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
 520static 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
 528int 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
 555int 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
 573void i915_active_release(struct i915_active *ref)
 574{
 575        debug_active_assert(ref);
 576        active_retire(ref);
 577}
 578
 579static 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
 594static 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
 609static 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
 626int __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
 652static 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
 674struct wait_barrier {
 675        struct wait_queue_entry base;
 676        struct i915_active *ref;
 677};
 678
 679static int
 680barrier_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
 693static 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
 716static 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
 753out:
 754        i915_active_release(ref);
 755        return err;
 756}
 757
 758static int rq_await_fence(void *arg, struct dma_fence *fence)
 759{
 760        return i915_request_await_dma_fence(arg, fence);
 761}
 762
 763int 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
 770static 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
 776int 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
 783void 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
 794static 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
 799static 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
 872match:
 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
 882int 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
 950unwind:
 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
 964void 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
1007static struct dma_fence **ll_to_fence_slot(struct llist_node *node)
1008{
1009        return __active_fence_slot(&barrier_from_ll(node)->base);
1010}
1011
1012void 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 */
1051struct 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
1097int 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
1117void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
1118{
1119        active_fence_cb(fence, cb);
1120}
1121
1122struct auto_active {
1123        struct i915_active base;
1124        struct kref ref;
1125};
1126
1127struct 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
1135static 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
1143void 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
1150static int auto_active(struct i915_active *ref)
1151{
1152        i915_active_get(ref);
1153        return 0;
1154}
1155
1156static void auto_retire(struct i915_active *ref)
1157{
1158        i915_active_put(ref);
1159}
1160
1161struct 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
1179static void i915_global_active_shrink(void)
1180{
1181        kmem_cache_shrink(global.slab_cache);
1182}
1183
1184static void i915_global_active_exit(void)
1185{
1186        kmem_cache_destroy(global.slab_cache);
1187}
1188
1189static struct i915_global_active global = { {
1190        .shrink = i915_global_active_shrink,
1191        .exit = i915_global_active_exit,
1192} };
1193
1194int __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}
1203