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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
17/*
18 * Active refs memory management
19 *
20 * To be more economical with memory, we reap all the i915_active trees as
21 * they idle (when we know the active requests are inactive) and allocate the
22 * nodes from a local slab cache to hopefully reduce the fragmentation.
23 */
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#else
116
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#endif
124
125static void
126__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 void
177active_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 void
189active_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 bool
210active_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 try_cmpxchg(__active_fence_slot(active), &fence, NULL);
216}
217
218static void
219node_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 void
226excl_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 search
240 * for the common case, under typical loads we never need the rbtree
241 * at all. We can reuse the last slot if it is empty, that is
242 * after the previous activity has been retired, or if it matches the
243 * 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 has
257 * claimed the cache and we know that is does not match our
258 * idx. If, and only if, the timeline is currently zero is it
259 * worth competing to claim it atomically for ourselves (for
260 * only the winner of that race will cmpxchg return the old
261 * 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 else
313 p = &parent->rb_left;
314 }
315
316 /*
317 * XXX: We should preallocate this before i915_active_ref() is ever
318 * 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#endif
363}
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 this
377 * outside of the kernel_context timeline mutex and so someone
378 * else may be manipulating the engine->barrier_tasks, in
379 * which case either we or they will be upset :)
380 *
381 * A second __active_del_barrier() will report failure to claim
382 * the active_node and the caller will just shrug and know not to
383 * claim ownership of its node.
384 *
385 * A concurrent i915_request_add_active_barriers() will miss adding
386 * any of the tasks, but we will try again on the next -- and since
387 * we are actively using the barrier, we know that there will be
388 * 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 bool
408__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 bool
414replace_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 so
421 * we can use it to substitute for the pending idle-barrer
422 * 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 else
456 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 int
655barrier_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 this
785 * i915_active, due to overlapping active phases there is likely a
786 * node kept alive (as we reuse before parking). We prefer to reuse
787 * 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 else
808 p = READ_ONCE(p->rb_left);
809 }
810
811 /*
812 * No quick match, but we did find the leftmost rb_node for the
813 * kernel_context. Walk the rb_tree in-order to see if there were
814 * any idle-barriers on this timeline that we missed, or just use
815 * 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 the
833 * kernel_context timeline, which notably we do not hold
834 * here. i915_request_add_active_barriers() may consume
835 * the barrier before we claim it, so we have to check
836 * 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 target
872 * engine (remember virtual engines have more than one sibling).
873 * We can then use the preallocated nodes in
874 * 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 have
901 * decoupled it from the rbtree, we can reuse the
902 * request to indicate this is an idle-barrier node
903 * and then we can use the rb_node and list pointers
904 * 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 the
948 * i915_active rbtree, but only as proto-nodes. They will be
949 * populated by i915_request_add_active_barriers() to point to the
950 * 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 else
970 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 such
1002 * that the parent i915_active will be released when this request
1003 * 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 timeline
1016 * @active: the active tracker
1017 * @fence: the new fence (under construction)
1018 *
1019 * Records the new @fence as the last active fence along its timeline in
1020 * this active tracker, moving the tracking callbacks from the previous
1021 * fence onto this one. Gets and returns a reference to the previous fence
1022 * (if not already completed), which the caller must put after making sure
1023 * that it is executed before the new fence. To ensure that the order of
1024 * fences within the timeline of the i915_active_fence is understood, it
1025 * 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 is
1036 * SLAB_FAILSAFE_BY_RCU, then it can be reused right after release
1037 * by new requests. Then, there is a risk of passing back a pointer
1038 * to a new, completely unrelated fence that reuses the same memory
1039 * while tracked under a different active tracker. Combined with i915
1040 * perf open/close operations that build await dependencies between
1041 * engine kernel context requests and user requests from different
1042 * timelines, this can lead to dependency loops and infinite waits.
1043 *
1044 * As a countermeasure, we try to get a reference to the active->fence
1045 * first, so if we succeed and pass it back to our user then it is not
1046 * released and potentially reused by an unrelated request before the
1047 * 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), with
1057 * C already resident as the active->fence.
1058 *
1059 * Both A and B have got a reference to C or NULL, depending on the
1060 * timing of the interrupt handler. Let's assume that if A has got C
1061 * then it has locked C first (before B).
1062 *
1063 * Note the strong ordering of the timeline also provides consistent
1064 * nesting rules for the fence->lock; the inner lock is always the
1065 * 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, or
1073 * something else, depending on the timing of other threads and/or
1074 * interrupt handler. If not the same as before then A unlocks C if
1075 * applicable and retries, starting from an attempt to get a new
1076 * active->fence. Meanwhile, B follows the same path as A.
1077 * Once A succeeds with cmpxch, B fails again, retires, gets A from
1078 * active->fence, locks it as soon as A completes, and possibly
1079 * 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 signaled
1098 * and we know that we are first on the timeline. If it is still
1099 * present then, having the lock on that fence already acquired, we
1100 * serialise with the interrupt handler, in the process of removing it
1101 * from any future interrupt callback. A will then wait on C before
1102 * executing (if present).
1103 *
1104 * As B is second, it sees A as the previous fence and so waits for
1105 * it to complete its transition and takes over the occupancy for
1106 * 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#endif
1195
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}