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1/*2 * SPDX-License-Identifier: MIT3 *4 * Copyright © 2019 Intel Corporation5 */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 management19 *20 * To be more economical with memory, we reap all the i915_active trees as21 * they idle (when we know the active requests are inactive) and allocate the22 * nodes from a local slab cache to hopefully reduce the fragmentation.23 */24static struct kmem_cache *slab_cache;25 26struct 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 35static inline struct active_node *36node_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 43static inline bool is_barrier(const struct i915_active_fence *active)44{45 return IS_ERR(rcu_access_pointer(active->fence));46}47 48static 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 54static 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 60static inline struct intel_engine_cs *61barrier_to_engine(struct active_node *node)62{63 GEM_BUG_ON(!is_barrier(&node->base));64 return __barrier_to_engine(node);65}66 67static 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 75static 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 82static const struct debug_obj_descr active_debug_desc = {83 .name = "i915_active",84 .debug_hint = active_debug_hint,85};86 87static void debug_active_init(struct i915_active *ref)88{89 debug_object_init(ref, &active_debug_desc);90}91 92static void debug_active_activate(struct i915_active *ref)93{94 lockdep_assert_held(&ref->tree_lock);95 debug_object_activate(ref, &active_debug_desc);96}97 98static void debug_active_deactivate(struct i915_active *ref)99{100 lockdep_assert_held(&ref->tree_lock);101 if (!atomic_read(&ref->count)) /* after the last dec */102 debug_object_deactivate(ref, &active_debug_desc);103}104 105static void debug_active_fini(struct i915_active *ref)106{107 debug_object_free(ref, &active_debug_desc);108}109 110static void debug_active_assert(struct i915_active *ref)111{112 debug_object_assert_init(ref, &active_debug_desc);113}114 115#else116 117static inline void debug_active_init(struct i915_active *ref) { }118static inline void debug_active_activate(struct i915_active *ref) { }119static inline void debug_active_deactivate(struct i915_active *ref) { }120static inline void debug_active_fini(struct i915_active *ref) { }121static inline void debug_active_assert(struct i915_active *ref) { }122 123#endif124 125static void126__active_retire(struct i915_active *ref)127{128 struct rb_root root = RB_ROOT;129 struct active_node *it, *n;130 unsigned long flags;131 132 GEM_BUG_ON(i915_active_is_idle(ref));133 134 /* return the unused nodes to our slabcache -- flushing the allocator */135 if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags))136 return;137 138 GEM_BUG_ON(rcu_access_pointer(ref->excl.fence));139 debug_active_deactivate(ref);140 141 /* Even if we have not used the cache, we may still have a barrier */142 if (!ref->cache)143 ref->cache = fetch_node(ref->tree.rb_node);144 145 /* Keep the MRU cached node for reuse */146 if (ref->cache) {147 /* Discard all other nodes in the tree */148 rb_erase(&ref->cache->node, &ref->tree);149 root = ref->tree;150 151 /* Rebuild the tree with only the cached node */152 rb_link_node(&ref->cache->node, NULL, &ref->tree.rb_node);153 rb_insert_color(&ref->cache->node, &ref->tree);154 GEM_BUG_ON(ref->tree.rb_node != &ref->cache->node);155 156 /* Make the cached node available for reuse with any timeline */157 ref->cache->timeline = 0; /* needs cmpxchg(u64) */158 }159 160 spin_unlock_irqrestore(&ref->tree_lock, flags);161 162 /* After the final retire, the entire struct may be freed */163 if (ref->retire)164 ref->retire(ref);165 166 /* ... except if you wait on it, you must manage your own references! */167 wake_up_var(ref);168 169 /* Finally free the discarded timeline tree */170 rbtree_postorder_for_each_entry_safe(it, n, &root, node) {171 GEM_BUG_ON(i915_active_fence_isset(&it->base));172 kmem_cache_free(slab_cache, it);173 }174}175 176static void177active_work(struct work_struct *wrk)178{179 struct i915_active *ref = container_of(wrk, typeof(*ref), work);180 181 GEM_BUG_ON(!atomic_read(&ref->count));182 if (atomic_add_unless(&ref->count, -1, 1))183 return;184 185 __active_retire(ref);186}187 188static void189active_retire(struct i915_active *ref)190{191 GEM_BUG_ON(!atomic_read(&ref->count));192 if (atomic_add_unless(&ref->count, -1, 1))193 return;194 195 if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {196 queue_work(system_unbound_wq, &ref->work);197 return;198 }199 200 __active_retire(ref);201}202 203static inline struct dma_fence **204__active_fence_slot(struct i915_active_fence *active)205{206 return (struct dma_fence ** __force)&active->fence;207}208 209static inline bool210active_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb)211{212 struct i915_active_fence *active =213 container_of(cb, typeof(*active), cb);214 215 return cmpxchg(__active_fence_slot(active), fence, NULL) == fence;216}217 218static void219node_retire(struct dma_fence *fence, struct dma_fence_cb *cb)220{221 if (active_fence_cb(fence, cb))222 active_retire(container_of(cb, struct active_node, base.cb)->ref);223}224 225static void226excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb)227{228 if (active_fence_cb(fence, cb))229 active_retire(container_of(cb, struct i915_active, excl.cb));230}231 232static struct active_node *__active_lookup(struct i915_active *ref, u64 idx)233{234 struct active_node *it;235 236 GEM_BUG_ON(idx == 0); /* 0 is the unordered timeline, rsvd for cache */237 238 /*239 * We track the most recently used timeline to skip a rbtree search240 * for the common case, under typical loads we never need the rbtree241 * at all. We can reuse the last slot if it is empty, that is242 * after the previous activity has been retired, or if it matches the243 * current timeline.244 */245 it = READ_ONCE(ref->cache);246 if (it) {247 u64 cached = READ_ONCE(it->timeline);248 249 /* Once claimed, this slot will only belong to this idx */250 if (cached == idx)251 return it;252 253 /*254 * An unclaimed cache [.timeline=0] can only be claimed once.255 *256 * If the value is already non-zero, some other thread has257 * claimed the cache and we know that is does not match our258 * idx. If, and only if, the timeline is currently zero is it259 * worth competing to claim it atomically for ourselves (for260 * only the winner of that race will cmpxchg return the old261 * value of 0).262 */263 if (!cached && !cmpxchg64(&it->timeline, 0, idx))264 return it;265 }266 267 BUILD_BUG_ON(offsetof(typeof(*it), node));268 269 /* While active, the tree can only be built; not destroyed */270 GEM_BUG_ON(i915_active_is_idle(ref));271 272 it = fetch_node(ref->tree.rb_node);273 while (it) {274 if (it->timeline < idx) {275 it = fetch_node(it->node.rb_right);276 } else if (it->timeline > idx) {277 it = fetch_node(it->node.rb_left);278 } else {279 WRITE_ONCE(ref->cache, it);280 break;281 }282 }283 284 /* NB: If the tree rotated beneath us, we may miss our target. */285 return it;286}287 288static struct i915_active_fence *289active_instance(struct i915_active *ref, u64 idx)290{291 struct active_node *node;292 struct rb_node **p, *parent;293 294 node = __active_lookup(ref, idx);295 if (likely(node))296 return &node->base;297 298 spin_lock_irq(&ref->tree_lock);299 GEM_BUG_ON(i915_active_is_idle(ref));300 301 parent = NULL;302 p = &ref->tree.rb_node;303 while (*p) {304 parent = *p;305 306 node = rb_entry(parent, struct active_node, node);307 if (node->timeline == idx)308 goto out;309 310 if (node->timeline < idx)311 p = &parent->rb_right;312 else313 p = &parent->rb_left;314 }315 316 /*317 * XXX: We should preallocate this before i915_active_ref() is ever318 * called, but we cannot call into fs_reclaim() anyway, so use GFP_ATOMIC.319 */320 node = kmem_cache_alloc(slab_cache, GFP_ATOMIC);321 if (!node)322 goto out;323 324 __i915_active_fence_init(&node->base, NULL, node_retire);325 node->ref = ref;326 node->timeline = idx;327 328 rb_link_node(&node->node, parent, p);329 rb_insert_color(&node->node, &ref->tree);330 331out:332 WRITE_ONCE(ref->cache, node);333 spin_unlock_irq(&ref->tree_lock);334 335 return &node->base;336}337 338void __i915_active_init(struct i915_active *ref,339 int (*active)(struct i915_active *ref),340 void (*retire)(struct i915_active *ref),341 unsigned long flags,342 struct lock_class_key *mkey,343 struct lock_class_key *wkey)344{345 debug_active_init(ref);346 347 ref->flags = flags;348 ref->active = active;349 ref->retire = retire;350 351 spin_lock_init(&ref->tree_lock);352 ref->tree = RB_ROOT;353 ref->cache = NULL;354 355 init_llist_head(&ref->preallocated_barriers);356 atomic_set(&ref->count, 0);357 __mutex_init(&ref->mutex, "i915_active", mkey);358 __i915_active_fence_init(&ref->excl, NULL, excl_retire);359 INIT_WORK(&ref->work, active_work);360#if IS_ENABLED(CONFIG_LOCKDEP)361 lockdep_init_map(&ref->work.lockdep_map, "i915_active.work", wkey, 0);362#endif363}364 365static bool ____active_del_barrier(struct i915_active *ref,366 struct active_node *node,367 struct intel_engine_cs *engine)368 369{370 struct llist_node *head = NULL, *tail = NULL;371 struct llist_node *pos, *next;372 373 GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context);374 375 /*376 * Rebuild the llist excluding our node. We may perform this377 * outside of the kernel_context timeline mutex and so someone378 * else may be manipulating the engine->barrier_tasks, in379 * which case either we or they will be upset :)380 *381 * A second __active_del_barrier() will report failure to claim382 * the active_node and the caller will just shrug and know not to383 * claim ownership of its node.384 *385 * A concurrent i915_request_add_active_barriers() will miss adding386 * any of the tasks, but we will try again on the next -- and since387 * we are actively using the barrier, we know that there will be388 * at least another opportunity when we idle.389 */390 llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {391 if (node == barrier_from_ll(pos)) {392 node = NULL;393 continue;394 }395 396 pos->next = head;397 head = pos;398 if (!tail)399 tail = pos;400 }401 if (head)402 llist_add_batch(head, tail, &engine->barrier_tasks);403 404 return !node;405}406 407static bool408__active_del_barrier(struct i915_active *ref, struct active_node *node)409{410 return ____active_del_barrier(ref, node, barrier_to_engine(node));411}412 413static bool414replace_barrier(struct i915_active *ref, struct i915_active_fence *active)415{416 if (!is_barrier(active)) /* proto-node used by our idle barrier? */417 return false;418 419 /*420 * This request is on the kernel_context timeline, and so421 * we can use it to substitute for the pending idle-barrer422 * request that we want to emit on the kernel_context.423 */424 return __active_del_barrier(ref, node_from_active(active));425}426 427int i915_active_add_request(struct i915_active *ref, struct i915_request *rq)428{429 u64 idx = i915_request_timeline(rq)->fence_context;430 struct dma_fence *fence = &rq->fence;431 struct i915_active_fence *active;432 int err;433 434 /* Prevent reaping in case we malloc/wait while building the tree */435 err = i915_active_acquire(ref);436 if (err)437 return err;438 439 do {440 active = active_instance(ref, idx);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 } while (unlikely(is_barrier(active)));451 452 fence = __i915_active_fence_set(active, fence);453 if (!fence)454 __i915_active_acquire(ref);455 else456 dma_fence_put(fence);457 458out:459 i915_active_release(ref);460 return err;461}462 463static struct dma_fence *464__i915_active_set_fence(struct i915_active *ref,465 struct i915_active_fence *active,466 struct dma_fence *fence)467{468 struct dma_fence *prev;469 470 if (replace_barrier(ref, active)) {471 RCU_INIT_POINTER(active->fence, fence);472 return NULL;473 }474 475 prev = __i915_active_fence_set(active, fence);476 if (!prev)477 __i915_active_acquire(ref);478 479 return prev;480}481 482struct dma_fence *483i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)484{485 /* We expect the caller to manage the exclusive timeline ordering */486 return __i915_active_set_fence(ref, &ref->excl, f);487}488 489bool i915_active_acquire_if_busy(struct i915_active *ref)490{491 debug_active_assert(ref);492 return atomic_add_unless(&ref->count, 1, 0);493}494 495static void __i915_active_activate(struct i915_active *ref)496{497 spin_lock_irq(&ref->tree_lock); /* __active_retire() */498 if (!atomic_fetch_inc(&ref->count))499 debug_active_activate(ref);500 spin_unlock_irq(&ref->tree_lock);501}502 503int i915_active_acquire(struct i915_active *ref)504{505 int err;506 507 if (i915_active_acquire_if_busy(ref))508 return 0;509 510 if (!ref->active) {511 __i915_active_activate(ref);512 return 0;513 }514 515 err = mutex_lock_interruptible(&ref->mutex);516 if (err)517 return err;518 519 if (likely(!i915_active_acquire_if_busy(ref))) {520 err = ref->active(ref);521 if (!err)522 __i915_active_activate(ref);523 }524 525 mutex_unlock(&ref->mutex);526 527 return err;528}529 530int i915_active_acquire_for_context(struct i915_active *ref, u64 idx)531{532 struct i915_active_fence *active;533 int err;534 535 err = i915_active_acquire(ref);536 if (err)537 return err;538 539 active = active_instance(ref, idx);540 if (!active) {541 i915_active_release(ref);542 return -ENOMEM;543 }544 545 return 0; /* return with active ref */546}547 548void i915_active_release(struct i915_active *ref)549{550 debug_active_assert(ref);551 active_retire(ref);552}553 554static void enable_signaling(struct i915_active_fence *active)555{556 struct dma_fence *fence;557 558 if (unlikely(is_barrier(active)))559 return;560 561 fence = i915_active_fence_get(active);562 if (!fence)563 return;564 565 dma_fence_enable_sw_signaling(fence);566 dma_fence_put(fence);567}568 569static int flush_barrier(struct active_node *it)570{571 struct intel_engine_cs *engine;572 573 if (likely(!is_barrier(&it->base)))574 return 0;575 576 engine = __barrier_to_engine(it);577 smp_rmb(); /* serialise with add_active_barriers */578 if (!is_barrier(&it->base))579 return 0;580 581 return intel_engine_flush_barriers(engine);582}583 584static int flush_lazy_signals(struct i915_active *ref)585{586 struct active_node *it, *n;587 int err = 0;588 589 enable_signaling(&ref->excl);590 rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {591 err = flush_barrier(it); /* unconnected idle barrier? */592 if (err)593 break;594 595 enable_signaling(&it->base);596 }597 598 return err;599}600 601int __i915_active_wait(struct i915_active *ref, int state)602{603 might_sleep();604 605 /* Any fence added after the wait begins will not be auto-signaled */606 if (i915_active_acquire_if_busy(ref)) {607 int err;608 609 err = flush_lazy_signals(ref);610 i915_active_release(ref);611 if (err)612 return err;613 614 if (___wait_var_event(ref, i915_active_is_idle(ref),615 state, 0, 0, schedule()))616 return -EINTR;617 }618 619 /*620 * After the wait is complete, the caller may free the active.621 * We have to flush any concurrent retirement before returning.622 */623 flush_work(&ref->work);624 return 0;625}626 627static int __await_active(struct i915_active_fence *active,628 int (*fn)(void *arg, struct dma_fence *fence),629 void *arg)630{631 struct dma_fence *fence;632 633 if (is_barrier(active)) /* XXX flush the barrier? */634 return 0;635 636 fence = i915_active_fence_get(active);637 if (fence) {638 int err;639 640 err = fn(arg, fence);641 dma_fence_put(fence);642 if (err < 0)643 return err;644 }645 646 return 0;647}648 649struct wait_barrier {650 struct wait_queue_entry base;651 struct i915_active *ref;652};653 654static int655barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key)656{657 struct wait_barrier *wb = container_of(wq, typeof(*wb), base);658 659 if (i915_active_is_idle(wb->ref)) {660 list_del(&wq->entry);661 i915_sw_fence_complete(wq->private);662 kfree(wq);663 }664 665 return 0;666}667 668static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence)669{670 struct wait_barrier *wb;671 672 wb = kmalloc(sizeof(*wb), GFP_KERNEL);673 if (unlikely(!wb))674 return -ENOMEM;675 676 GEM_BUG_ON(i915_active_is_idle(ref));677 if (!i915_sw_fence_await(fence)) {678 kfree(wb);679 return -EINVAL;680 }681 682 wb->base.flags = 0;683 wb->base.func = barrier_wake;684 wb->base.private = fence;685 wb->ref = ref;686 687 add_wait_queue(__var_waitqueue(ref), &wb->base);688 return 0;689}690 691static int await_active(struct i915_active *ref,692 unsigned int flags,693 int (*fn)(void *arg, struct dma_fence *fence),694 void *arg, struct i915_sw_fence *barrier)695{696 int err = 0;697 698 if (!i915_active_acquire_if_busy(ref))699 return 0;700 701 if (flags & I915_ACTIVE_AWAIT_EXCL &&702 rcu_access_pointer(ref->excl.fence)) {703 err = __await_active(&ref->excl, fn, arg);704 if (err)705 goto out;706 }707 708 if (flags & I915_ACTIVE_AWAIT_ACTIVE) {709 struct active_node *it, *n;710 711 rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {712 err = __await_active(&it->base, fn, arg);713 if (err)714 goto out;715 }716 }717 718 if (flags & I915_ACTIVE_AWAIT_BARRIER) {719 err = flush_lazy_signals(ref);720 if (err)721 goto out;722 723 err = __await_barrier(ref, barrier);724 if (err)725 goto out;726 }727 728out:729 i915_active_release(ref);730 return err;731}732 733static int rq_await_fence(void *arg, struct dma_fence *fence)734{735 return i915_request_await_dma_fence(arg, fence);736}737 738int i915_request_await_active(struct i915_request *rq,739 struct i915_active *ref,740 unsigned int flags)741{742 return await_active(ref, flags, rq_await_fence, rq, &rq->submit);743}744 745static int sw_await_fence(void *arg, struct dma_fence *fence)746{747 return i915_sw_fence_await_dma_fence(arg, fence, 0,748 GFP_NOWAIT | __GFP_NOWARN);749}750 751int i915_sw_fence_await_active(struct i915_sw_fence *fence,752 struct i915_active *ref,753 unsigned int flags)754{755 return await_active(ref, flags, sw_await_fence, fence, fence);756}757 758void i915_active_fini(struct i915_active *ref)759{760 debug_active_fini(ref);761 GEM_BUG_ON(atomic_read(&ref->count));762 GEM_BUG_ON(work_pending(&ref->work));763 mutex_destroy(&ref->mutex);764 765 if (ref->cache)766 kmem_cache_free(slab_cache, ref->cache);767}768 769static inline bool is_idle_barrier(struct active_node *node, u64 idx)770{771 return node->timeline == idx && !i915_active_fence_isset(&node->base);772}773 774static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)775{776 struct rb_node *prev, *p;777 778 if (RB_EMPTY_ROOT(&ref->tree))779 return NULL;780 781 GEM_BUG_ON(i915_active_is_idle(ref));782 783 /*784 * Try to reuse any existing barrier nodes already allocated for this785 * i915_active, due to overlapping active phases there is likely a786 * node kept alive (as we reuse before parking). We prefer to reuse787 * completely idle barriers (less hassle in manipulating the llists),788 * but otherwise any will do.789 */790 if (ref->cache && is_idle_barrier(ref->cache, idx)) {791 p = &ref->cache->node;792 goto match;793 }794 795 prev = NULL;796 p = ref->tree.rb_node;797 while (p) {798 struct active_node *node =799 rb_entry(p, struct active_node, node);800 801 if (is_idle_barrier(node, idx))802 goto match;803 804 prev = p;805 if (node->timeline < idx)806 p = READ_ONCE(p->rb_right);807 else808 p = READ_ONCE(p->rb_left);809 }810 811 /*812 * No quick match, but we did find the leftmost rb_node for the813 * kernel_context. Walk the rb_tree in-order to see if there were814 * any idle-barriers on this timeline that we missed, or just use815 * the first pending barrier.816 */817 for (p = prev; p; p = rb_next(p)) {818 struct active_node *node =819 rb_entry(p, struct active_node, node);820 struct intel_engine_cs *engine;821 822 if (node->timeline > idx)823 break;824 825 if (node->timeline < idx)826 continue;827 828 if (is_idle_barrier(node, idx))829 goto match;830 831 /*832 * The list of pending barriers is protected by the833 * kernel_context timeline, which notably we do not hold834 * here. i915_request_add_active_barriers() may consume835 * the barrier before we claim it, so we have to check836 * for success.837 */838 engine = __barrier_to_engine(node);839 smp_rmb(); /* serialise with add_active_barriers */840 if (is_barrier(&node->base) &&841 ____active_del_barrier(ref, node, engine))842 goto match;843 }844 845 return NULL;846 847match:848 spin_lock_irq(&ref->tree_lock);849 rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */850 if (p == &ref->cache->node)851 WRITE_ONCE(ref->cache, NULL);852 spin_unlock_irq(&ref->tree_lock);853 854 return rb_entry(p, struct active_node, node);855}856 857int i915_active_acquire_preallocate_barrier(struct i915_active *ref,858 struct intel_engine_cs *engine)859{860 intel_engine_mask_t tmp, mask = engine->mask;861 struct llist_node *first = NULL, *last = NULL;862 struct intel_gt *gt = engine->gt;863 864 GEM_BUG_ON(i915_active_is_idle(ref));865 866 /* Wait until the previous preallocation is completed */867 while (!llist_empty(&ref->preallocated_barriers))868 cond_resched();869 870 /*871 * Preallocate a node for each physical engine supporting the target872 * engine (remember virtual engines have more than one sibling).873 * We can then use the preallocated nodes in874 * i915_active_acquire_barrier()875 */876 GEM_BUG_ON(!mask);877 for_each_engine_masked(engine, gt, mask, tmp) {878 u64 idx = engine->kernel_context->timeline->fence_context;879 struct llist_node *prev = first;880 struct active_node *node;881 882 rcu_read_lock();883 node = reuse_idle_barrier(ref, idx);884 rcu_read_unlock();885 if (!node) {886 node = kmem_cache_alloc(slab_cache, GFP_KERNEL);887 if (!node)888 goto unwind;889 890 RCU_INIT_POINTER(node->base.fence, NULL);891 node->base.cb.func = node_retire;892 node->timeline = idx;893 node->ref = ref;894 }895 896 if (!i915_active_fence_isset(&node->base)) {897 /*898 * Mark this as being *our* unconnected proto-node.899 *900 * Since this node is not in any list, and we have901 * decoupled it from the rbtree, we can reuse the902 * request to indicate this is an idle-barrier node903 * and then we can use the rb_node and list pointers904 * for our tracking of the pending barrier.905 */906 RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN));907 node->base.cb.node.prev = (void *)engine;908 __i915_active_acquire(ref);909 }910 GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));911 912 GEM_BUG_ON(barrier_to_engine(node) != engine);913 first = barrier_to_ll(node);914 first->next = prev;915 if (!last)916 last = first;917 intel_engine_pm_get(engine);918 }919 920 GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));921 llist_add_batch(first, last, &ref->preallocated_barriers);922 923 return 0;924 925unwind:926 while (first) {927 struct active_node *node = barrier_from_ll(first);928 929 first = first->next;930 931 atomic_dec(&ref->count);932 intel_engine_pm_put(barrier_to_engine(node));933 934 kmem_cache_free(slab_cache, node);935 }936 return -ENOMEM;937}938 939void i915_active_acquire_barrier(struct i915_active *ref)940{941 struct llist_node *pos, *next;942 unsigned long flags;943 944 GEM_BUG_ON(i915_active_is_idle(ref));945 946 /*947 * Transfer the list of preallocated barriers into the948 * i915_active rbtree, but only as proto-nodes. They will be949 * populated by i915_request_add_active_barriers() to point to the950 * request that will eventually release them.951 */952 llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {953 struct active_node *node = barrier_from_ll(pos);954 struct intel_engine_cs *engine = barrier_to_engine(node);955 struct rb_node **p, *parent;956 957 spin_lock_irqsave_nested(&ref->tree_lock, flags,958 SINGLE_DEPTH_NESTING);959 parent = NULL;960 p = &ref->tree.rb_node;961 while (*p) {962 struct active_node *it;963 964 parent = *p;965 966 it = rb_entry(parent, struct active_node, node);967 if (it->timeline < node->timeline)968 p = &parent->rb_right;969 else970 p = &parent->rb_left;971 }972 rb_link_node(&node->node, parent, p);973 rb_insert_color(&node->node, &ref->tree);974 spin_unlock_irqrestore(&ref->tree_lock, flags);975 976 GEM_BUG_ON(!intel_engine_pm_is_awake(engine));977 llist_add(barrier_to_ll(node), &engine->barrier_tasks);978 intel_engine_pm_put_delay(engine, 2);979 }980}981 982static struct dma_fence **ll_to_fence_slot(struct llist_node *node)983{984 return __active_fence_slot(&barrier_from_ll(node)->base);985}986 987void i915_request_add_active_barriers(struct i915_request *rq)988{989 struct intel_engine_cs *engine = rq->engine;990 struct llist_node *node, *next;991 unsigned long flags;992 993 GEM_BUG_ON(!intel_context_is_barrier(rq->context));994 GEM_BUG_ON(intel_engine_is_virtual(engine));995 GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline);996 997 node = llist_del_all(&engine->barrier_tasks);998 if (!node)999 return;1000 /*1001 * Attach the list of proto-fences to the in-flight request such1002 * that the parent i915_active will be released when this request1003 * is retired.1004 */1005 spin_lock_irqsave(&rq->lock, flags);1006 llist_for_each_safe(node, next, node) {1007 /* serialise with reuse_idle_barrier */1008 smp_store_mb(*ll_to_fence_slot(node), &rq->fence);1009 list_add_tail((struct list_head *)node, &rq->fence.cb_list);1010 }1011 spin_unlock_irqrestore(&rq->lock, flags);1012}1013 1014/*1015 * __i915_active_fence_set: Update the last active fence along its timeline1016 * @active: the active tracker1017 * @fence: the new fence (under construction)1018 *1019 * Records the new @fence as the last active fence along its timeline in1020 * this active tracker, moving the tracking callbacks from the previous1021 * fence onto this one. Gets and returns a reference to the previous fence1022 * (if not already completed), which the caller must put after making sure1023 * that it is executed before the new fence. To ensure that the order of1024 * fences within the timeline of the i915_active_fence is understood, it1025 * should be locked by the caller.1026 */1027struct dma_fence *1028__i915_active_fence_set(struct i915_active_fence *active,1029 struct dma_fence *fence)1030{1031 struct dma_fence *prev;1032 unsigned long flags;1033 1034 /*1035 * In case of fences embedded in i915_requests, their memory is1036 * SLAB_FAILSAFE_BY_RCU, then it can be reused right after release1037 * by new requests. Then, there is a risk of passing back a pointer1038 * to a new, completely unrelated fence that reuses the same memory1039 * while tracked under a different active tracker. Combined with i9151040 * perf open/close operations that build await dependencies between1041 * engine kernel context requests and user requests from different1042 * timelines, this can lead to dependency loops and infinite waits.1043 *1044 * As a countermeasure, we try to get a reference to the active->fence1045 * first, so if we succeed and pass it back to our user then it is not1046 * released and potentially reused by an unrelated request before the1047 * user has a chance to set up an await dependency on it.1048 */1049 prev = i915_active_fence_get(active);1050 if (fence == prev)1051 return fence;1052 1053 GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));1054 1055 /*1056 * Consider that we have two threads arriving (A and B), with1057 * C already resident as the active->fence.1058 *1059 * Both A and B have got a reference to C or NULL, depending on the1060 * timing of the interrupt handler. Let's assume that if A has got C1061 * then it has locked C first (before B).1062 *1063 * Note the strong ordering of the timeline also provides consistent1064 * nesting rules for the fence->lock; the inner lock is always the1065 * older lock.1066 */1067 spin_lock_irqsave(fence->lock, flags);1068 if (prev)1069 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);1070 1071 /*1072 * A does the cmpxchg first, and so it sees C or NULL, as before, or1073 * something else, depending on the timing of other threads and/or1074 * interrupt handler. If not the same as before then A unlocks C if1075 * applicable and retries, starting from an attempt to get a new1076 * active->fence. Meanwhile, B follows the same path as A.1077 * Once A succeeds with cmpxch, B fails again, retires, gets A from1078 * active->fence, locks it as soon as A completes, and possibly1079 * succeeds with cmpxchg.1080 */1081 while (cmpxchg(__active_fence_slot(active), prev, fence) != prev) {1082 if (prev) {1083 spin_unlock(prev->lock);1084 dma_fence_put(prev);1085 }1086 spin_unlock_irqrestore(fence->lock, flags);1087 1088 prev = i915_active_fence_get(active);1089 GEM_BUG_ON(prev == fence);1090 1091 spin_lock_irqsave(fence->lock, flags);1092 if (prev)1093 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);1094 }1095 1096 /*1097 * If prev is NULL then the previous fence must have been signaled1098 * and we know that we are first on the timeline. If it is still1099 * present then, having the lock on that fence already acquired, we1100 * serialise with the interrupt handler, in the process of removing it1101 * from any future interrupt callback. A will then wait on C before1102 * executing (if present).1103 *1104 * As B is second, it sees A as the previous fence and so waits for1105 * it to complete its transition and takes over the occupancy for1106 * itself -- remembering that it needs to wait on A before executing.1107 */1108 if (prev) {1109 __list_del_entry(&active->cb.node);1110 spin_unlock(prev->lock); /* serialise with prev->cb_list */1111 }1112 list_add_tail(&active->cb.node, &fence->cb_list);1113 spin_unlock_irqrestore(fence->lock, flags);1114 1115 return prev;1116}1117 1118int i915_active_fence_set(struct i915_active_fence *active,1119 struct i915_request *rq)1120{1121 struct dma_fence *fence;1122 int err = 0;1123 1124 /* Must maintain timeline ordering wrt previous active requests */1125 fence = __i915_active_fence_set(active, &rq->fence);1126 if (fence) {1127 err = i915_request_await_dma_fence(rq, fence);1128 dma_fence_put(fence);1129 }1130 1131 return err;1132}1133 1134void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)1135{1136 active_fence_cb(fence, cb);1137}1138 1139struct auto_active {1140 struct i915_active base;1141 struct kref ref;1142};1143 1144struct i915_active *i915_active_get(struct i915_active *ref)1145{1146 struct auto_active *aa = container_of(ref, typeof(*aa), base);1147 1148 kref_get(&aa->ref);1149 return &aa->base;1150}1151 1152static void auto_release(struct kref *ref)1153{1154 struct auto_active *aa = container_of(ref, typeof(*aa), ref);1155 1156 i915_active_fini(&aa->base);1157 kfree(aa);1158}1159 1160void i915_active_put(struct i915_active *ref)1161{1162 struct auto_active *aa = container_of(ref, typeof(*aa), base);1163 1164 kref_put(&aa->ref, auto_release);1165}1166 1167static int auto_active(struct i915_active *ref)1168{1169 i915_active_get(ref);1170 return 0;1171}1172 1173static void auto_retire(struct i915_active *ref)1174{1175 i915_active_put(ref);1176}1177 1178struct i915_active *i915_active_create(void)1179{1180 struct auto_active *aa;1181 1182 aa = kmalloc(sizeof(*aa), GFP_KERNEL);1183 if (!aa)1184 return NULL;1185 1186 kref_init(&aa->ref);1187 i915_active_init(&aa->base, auto_active, auto_retire, 0);1188 1189 return &aa->base;1190}1191 1192#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)1193#include "selftests/i915_active.c"1194#endif1195 1196void i915_active_module_exit(void)1197{1198 kmem_cache_destroy(slab_cache);1199}1200 1201int __init i915_active_module_init(void)1202{1203 slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);1204 if (!slab_cache)1205 return -ENOMEM;1206 1207 return 0;1208}1209