1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2019 Intel Corporation
5  */
6 
7 #include <linux/debugobjects.h>
8 
9 #include "gt/intel_context.h"
10 #include "gt/intel_engine_heartbeat.h"
11 #include "gt/intel_engine_pm.h"
12 #include "gt/intel_ring.h"
13 
14 #include "i915_drv.h"
15 #include "i915_active.h"
16 
17 /*
18  * Active refs memory management
19  *
20  * To be more economical with memory, we reap all the i915_active trees as
21  * they idle (when we know the active requests are inactive) and allocate the
22  * nodes from a local slab cache to hopefully reduce the fragmentation.
23  */
24 static struct kmem_cache *slab_cache;
25 
26 struct active_node {
27 	struct rb_node node;
28 	struct i915_active_fence base;
29 	struct i915_active *ref;
30 	u64 timeline;
31 };
32 
33 #define fetch_node(x) rb_entry(READ_ONCE(x), typeof(struct active_node), node)
34 
35 static inline struct active_node *
node_from_active(struct i915_active_fence * active)36 node_from_active(struct i915_active_fence *active)
37 {
38 	return container_of(active, struct active_node, base);
39 }
40 
41 #define take_preallocated_barriers(x) llist_del_all(&(x)->preallocated_barriers)
42 
is_barrier(const struct i915_active_fence * active)43 static inline bool is_barrier(const struct i915_active_fence *active)
44 {
45 	return IS_ERR(rcu_access_pointer(active->fence));
46 }
47 
barrier_to_ll(struct active_node * node)48 static inline struct llist_node *barrier_to_ll(struct active_node *node)
49 {
50 	GEM_BUG_ON(!is_barrier(&node->base));
51 	return (struct llist_node *)&node->base.cb.node;
52 }
53 
54 static inline struct intel_engine_cs *
__barrier_to_engine(struct active_node * node)55 __barrier_to_engine(struct active_node *node)
56 {
57 	return (struct intel_engine_cs *)READ_ONCE(node->base.cb.node.prev);
58 }
59 
60 static inline struct intel_engine_cs *
barrier_to_engine(struct active_node * node)61 barrier_to_engine(struct active_node *node)
62 {
63 	GEM_BUG_ON(!is_barrier(&node->base));
64 	return __barrier_to_engine(node);
65 }
66 
barrier_from_ll(struct llist_node * x)67 static inline struct active_node *barrier_from_ll(struct llist_node *x)
68 {
69 	return container_of((struct list_head *)x,
70 			    struct active_node, base.cb.node);
71 }
72 
73 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && IS_ENABLED(CONFIG_DEBUG_OBJECTS)
74 
active_debug_hint(void * addr)75 static void *active_debug_hint(void *addr)
76 {
77 	struct i915_active *ref = addr;
78 
79 	return (void *)ref->active ?: (void *)ref->retire ?: (void *)ref;
80 }
81 
82 static const struct debug_obj_descr active_debug_desc = {
83 	.name = "i915_active",
84 	.debug_hint = active_debug_hint,
85 };
86 
debug_active_init(struct i915_active * ref)87 static void debug_active_init(struct i915_active *ref)
88 {
89 	debug_object_init(ref, &active_debug_desc);
90 }
91 
debug_active_activate(struct i915_active * ref)92 static void debug_active_activate(struct i915_active *ref)
93 {
94 	lockdep_assert_held(&ref->tree_lock);
95 	if (!atomic_read(&ref->count)) /* before the first inc */
96 		debug_object_activate(ref, &active_debug_desc);
97 }
98 
debug_active_deactivate(struct i915_active * ref)99 static void debug_active_deactivate(struct i915_active *ref)
100 {
101 	lockdep_assert_held(&ref->tree_lock);
102 	if (!atomic_read(&ref->count)) /* after the last dec */
103 		debug_object_deactivate(ref, &active_debug_desc);
104 }
105 
debug_active_fini(struct i915_active * ref)106 static void debug_active_fini(struct i915_active *ref)
107 {
108 	debug_object_free(ref, &active_debug_desc);
109 }
110 
debug_active_assert(struct i915_active * ref)111 static void debug_active_assert(struct i915_active *ref)
112 {
113 	debug_object_assert_init(ref, &active_debug_desc);
114 }
115 
116 #else
117 
debug_active_init(struct i915_active * ref)118 static inline void debug_active_init(struct i915_active *ref) { }
debug_active_activate(struct i915_active * ref)119 static inline void debug_active_activate(struct i915_active *ref) { }
debug_active_deactivate(struct i915_active * ref)120 static inline void debug_active_deactivate(struct i915_active *ref) { }
debug_active_fini(struct i915_active * ref)121 static inline void debug_active_fini(struct i915_active *ref) { }
debug_active_assert(struct i915_active * ref)122 static inline void debug_active_assert(struct i915_active *ref) { }
123 
124 #endif
125 
126 static void
__active_retire(struct i915_active * ref)127 __active_retire(struct i915_active *ref)
128 {
129 	struct rb_root root = RB_ROOT;
130 	struct active_node *it, *n;
131 	unsigned long flags;
132 
133 	GEM_BUG_ON(i915_active_is_idle(ref));
134 
135 	/* return the unused nodes to our slabcache -- flushing the allocator */
136 	if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags))
137 		return;
138 
139 	GEM_BUG_ON(rcu_access_pointer(ref->excl.fence));
140 	debug_active_deactivate(ref);
141 
142 	/* Even if we have not used the cache, we may still have a barrier */
143 	if (!ref->cache)
144 		ref->cache = fetch_node(ref->tree.rb_node);
145 
146 	/* Keep the MRU cached node for reuse */
147 	if (ref->cache) {
148 		/* Discard all other nodes in the tree */
149 		rb_erase(&ref->cache->node, &ref->tree);
150 		root = ref->tree;
151 
152 		/* Rebuild the tree with only the cached node */
153 		rb_link_node(&ref->cache->node, NULL, &ref->tree.rb_node);
154 		rb_insert_color(&ref->cache->node, &ref->tree);
155 		GEM_BUG_ON(ref->tree.rb_node != &ref->cache->node);
156 
157 		/* Make the cached node available for reuse with any timeline */
158 		ref->cache->timeline = 0; /* needs cmpxchg(u64) */
159 	}
160 
161 	spin_unlock_irqrestore(&ref->tree_lock, flags);
162 
163 	/* After the final retire, the entire struct may be freed */
164 	if (ref->retire)
165 		ref->retire(ref);
166 
167 	/* ... except if you wait on it, you must manage your own references! */
168 	wake_up_var(ref);
169 
170 	/* Finally free the discarded timeline tree  */
171 	rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
172 		GEM_BUG_ON(i915_active_fence_isset(&it->base));
173 		kmem_cache_free(slab_cache, it);
174 	}
175 }
176 
177 static void
active_work(struct work_struct * wrk)178 active_work(struct work_struct *wrk)
179 {
180 	struct i915_active *ref = container_of(wrk, typeof(*ref), work);
181 
182 	GEM_BUG_ON(!atomic_read(&ref->count));
183 	if (atomic_add_unless(&ref->count, -1, 1))
184 		return;
185 
186 	__active_retire(ref);
187 }
188 
189 static void
active_retire(struct i915_active * ref)190 active_retire(struct i915_active *ref)
191 {
192 	GEM_BUG_ON(!atomic_read(&ref->count));
193 	if (atomic_add_unless(&ref->count, -1, 1))
194 		return;
195 
196 	if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {
197 		queue_work(system_unbound_wq, &ref->work);
198 		return;
199 	}
200 
201 	__active_retire(ref);
202 }
203 
204 static inline struct dma_fence **
__active_fence_slot(struct i915_active_fence * active)205 __active_fence_slot(struct i915_active_fence *active)
206 {
207 	return (struct dma_fence ** __force)&active->fence;
208 }
209 
210 static inline bool
active_fence_cb(struct dma_fence * fence,struct dma_fence_cb * cb)211 active_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
212 {
213 	struct i915_active_fence *active =
214 		container_of(cb, typeof(*active), cb);
215 
216 	return cmpxchg(__active_fence_slot(active), fence, NULL) == fence;
217 }
218 
219 static void
node_retire(struct dma_fence * fence,struct dma_fence_cb * cb)220 node_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
221 {
222 	if (active_fence_cb(fence, cb))
223 		active_retire(container_of(cb, struct active_node, base.cb)->ref);
224 }
225 
226 static void
excl_retire(struct dma_fence * fence,struct dma_fence_cb * cb)227 excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
228 {
229 	if (active_fence_cb(fence, cb))
230 		active_retire(container_of(cb, struct i915_active, excl.cb));
231 }
232 
__active_lookup(struct i915_active * ref,u64 idx)233 static struct active_node *__active_lookup(struct i915_active *ref, u64 idx)
234 {
235 	struct active_node *it;
236 
237 	GEM_BUG_ON(idx == 0); /* 0 is the unordered timeline, rsvd for cache */
238 
239 	/*
240 	 * We track the most recently used timeline to skip a rbtree search
241 	 * for the common case, under typical loads we never need the rbtree
242 	 * at all. We can reuse the last slot if it is empty, that is
243 	 * after the previous activity has been retired, or if it matches the
244 	 * current timeline.
245 	 */
246 	it = READ_ONCE(ref->cache);
247 	if (it) {
248 		u64 cached = READ_ONCE(it->timeline);
249 
250 		/* Once claimed, this slot will only belong to this idx */
251 		if (cached == idx)
252 			return it;
253 
254 		/*
255 		 * An unclaimed cache [.timeline=0] can only be claimed once.
256 		 *
257 		 * If the value is already non-zero, some other thread has
258 		 * claimed the cache and we know that is does not match our
259 		 * idx. If, and only if, the timeline is currently zero is it
260 		 * worth competing to claim it atomically for ourselves (for
261 		 * only the winner of that race will cmpxchg return the old
262 		 * value of 0).
263 		 */
264 		if (!cached && !cmpxchg64(&it->timeline, 0, idx))
265 			return it;
266 	}
267 
268 	BUILD_BUG_ON(offsetof(typeof(*it), node));
269 
270 	/* While active, the tree can only be built; not destroyed */
271 	GEM_BUG_ON(i915_active_is_idle(ref));
272 
273 	it = fetch_node(ref->tree.rb_node);
274 	while (it) {
275 		if (it->timeline < idx) {
276 			it = fetch_node(it->node.rb_right);
277 		} else if (it->timeline > idx) {
278 			it = fetch_node(it->node.rb_left);
279 		} else {
280 			WRITE_ONCE(ref->cache, it);
281 			break;
282 		}
283 	}
284 
285 	/* NB: If the tree rotated beneath us, we may miss our target. */
286 	return it;
287 }
288 
289 static struct i915_active_fence *
active_instance(struct i915_active * ref,u64 idx)290 active_instance(struct i915_active *ref, u64 idx)
291 {
292 	struct active_node *node;
293 	struct rb_node **p, *parent;
294 
295 	node = __active_lookup(ref, idx);
296 	if (likely(node))
297 		return &node->base;
298 
299 	spin_lock_irq(&ref->tree_lock);
300 	GEM_BUG_ON(i915_active_is_idle(ref));
301 
302 	parent = NULL;
303 	p = &ref->tree.rb_node;
304 	while (*p) {
305 		parent = *p;
306 
307 		node = rb_entry(parent, struct active_node, node);
308 		if (node->timeline == idx)
309 			goto out;
310 
311 		if (node->timeline < idx)
312 			p = &parent->rb_right;
313 		else
314 			p = &parent->rb_left;
315 	}
316 
317 	/*
318 	 * XXX: We should preallocate this before i915_active_ref() is ever
319 	 *  called, but we cannot call into fs_reclaim() anyway, so use GFP_ATOMIC.
320 	 */
321 	node = kmem_cache_alloc(slab_cache, GFP_ATOMIC);
322 	if (!node)
323 		goto out;
324 
325 	__i915_active_fence_init(&node->base, NULL, node_retire);
326 	node->ref = ref;
327 	node->timeline = idx;
328 
329 	rb_link_node(&node->node, parent, p);
330 	rb_insert_color(&node->node, &ref->tree);
331 
332 out:
333 	WRITE_ONCE(ref->cache, node);
334 	spin_unlock_irq(&ref->tree_lock);
335 
336 	return &node->base;
337 }
338 
__i915_active_init(struct i915_active * ref,int (* active)(struct i915_active * ref),void (* retire)(struct i915_active * ref),unsigned long flags,struct lock_class_key * mkey,struct lock_class_key * wkey)339 void __i915_active_init(struct i915_active *ref,
340 			int (*active)(struct i915_active *ref),
341 			void (*retire)(struct i915_active *ref),
342 			unsigned long flags,
343 			struct lock_class_key *mkey,
344 			struct lock_class_key *wkey)
345 {
346 	debug_active_init(ref);
347 
348 	ref->flags = flags;
349 	ref->active = active;
350 	ref->retire = retire;
351 
352 	spin_lock_init(&ref->tree_lock);
353 	ref->tree = RB_ROOT;
354 	ref->cache = NULL;
355 
356 	init_llist_head(&ref->preallocated_barriers);
357 	atomic_set(&ref->count, 0);
358 	__mutex_init(&ref->mutex, "i915_active", mkey);
359 	__i915_active_fence_init(&ref->excl, NULL, excl_retire);
360 	INIT_WORK(&ref->work, active_work);
361 #if IS_ENABLED(CONFIG_LOCKDEP)
362 	lockdep_init_map(&ref->work.lockdep_map, "i915_active.work", wkey, 0);
363 #endif
364 }
365 
____active_del_barrier(struct i915_active * ref,struct active_node * node,struct intel_engine_cs * engine)366 static bool ____active_del_barrier(struct i915_active *ref,
367 				   struct active_node *node,
368 				   struct intel_engine_cs *engine)
369 
370 {
371 	struct llist_node *head = NULL, *tail = NULL;
372 	struct llist_node *pos, *next;
373 
374 	GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context);
375 
376 	/*
377 	 * Rebuild the llist excluding our node. We may perform this
378 	 * outside of the kernel_context timeline mutex and so someone
379 	 * else may be manipulating the engine->barrier_tasks, in
380 	 * which case either we or they will be upset :)
381 	 *
382 	 * A second __active_del_barrier() will report failure to claim
383 	 * the active_node and the caller will just shrug and know not to
384 	 * claim ownership of its node.
385 	 *
386 	 * A concurrent i915_request_add_active_barriers() will miss adding
387 	 * any of the tasks, but we will try again on the next -- and since
388 	 * we are actively using the barrier, we know that there will be
389 	 * at least another opportunity when we idle.
390 	 */
391 	llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {
392 		if (node == barrier_from_ll(pos)) {
393 			node = NULL;
394 			continue;
395 		}
396 
397 		pos->next = head;
398 		head = pos;
399 		if (!tail)
400 			tail = pos;
401 	}
402 	if (head)
403 		llist_add_batch(head, tail, &engine->barrier_tasks);
404 
405 	return !node;
406 }
407 
408 static bool
__active_del_barrier(struct i915_active * ref,struct active_node * node)409 __active_del_barrier(struct i915_active *ref, struct active_node *node)
410 {
411 	return ____active_del_barrier(ref, node, barrier_to_engine(node));
412 }
413 
414 static bool
replace_barrier(struct i915_active * ref,struct i915_active_fence * active)415 replace_barrier(struct i915_active *ref, struct i915_active_fence *active)
416 {
417 	if (!is_barrier(active)) /* proto-node used by our idle barrier? */
418 		return false;
419 
420 	/*
421 	 * This request is on the kernel_context timeline, and so
422 	 * we can use it to substitute for the pending idle-barrer
423 	 * request that we want to emit on the kernel_context.
424 	 */
425 	__active_del_barrier(ref, node_from_active(active));
426 	return true;
427 }
428 
i915_active_add_request(struct i915_active * ref,struct i915_request * rq)429 int i915_active_add_request(struct i915_active *ref, struct i915_request *rq)
430 {
431 	struct dma_fence *fence = &rq->fence;
432 	struct i915_active_fence *active;
433 	int err;
434 
435 	/* Prevent reaping in case we malloc/wait while building the tree */
436 	err = i915_active_acquire(ref);
437 	if (err)
438 		return err;
439 
440 	active = active_instance(ref, i915_request_timeline(rq)->fence_context);
441 	if (!active) {
442 		err = -ENOMEM;
443 		goto out;
444 	}
445 
446 	if (replace_barrier(ref, active)) {
447 		RCU_INIT_POINTER(active->fence, NULL);
448 		atomic_dec(&ref->count);
449 	}
450 	if (!__i915_active_fence_set(active, fence))
451 		__i915_active_acquire(ref);
452 
453 out:
454 	i915_active_release(ref);
455 	return err;
456 }
457 
458 static struct dma_fence *
__i915_active_set_fence(struct i915_active * ref,struct i915_active_fence * active,struct dma_fence * fence)459 __i915_active_set_fence(struct i915_active *ref,
460 			struct i915_active_fence *active,
461 			struct dma_fence *fence)
462 {
463 	struct dma_fence *prev;
464 
465 	if (replace_barrier(ref, active)) {
466 		RCU_INIT_POINTER(active->fence, fence);
467 		return NULL;
468 	}
469 
470 	rcu_read_lock();
471 	prev = __i915_active_fence_set(active, fence);
472 	if (prev)
473 		prev = dma_fence_get_rcu(prev);
474 	else
475 		__i915_active_acquire(ref);
476 	rcu_read_unlock();
477 
478 	return prev;
479 }
480 
481 struct dma_fence *
i915_active_set_exclusive(struct i915_active * ref,struct dma_fence * f)482 i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
483 {
484 	/* We expect the caller to manage the exclusive timeline ordering */
485 	return __i915_active_set_fence(ref, &ref->excl, f);
486 }
487 
i915_active_acquire_if_busy(struct i915_active * ref)488 bool i915_active_acquire_if_busy(struct i915_active *ref)
489 {
490 	debug_active_assert(ref);
491 	return atomic_add_unless(&ref->count, 1, 0);
492 }
493 
__i915_active_activate(struct i915_active * ref)494 static void __i915_active_activate(struct i915_active *ref)
495 {
496 	spin_lock_irq(&ref->tree_lock); /* __active_retire() */
497 	if (!atomic_fetch_inc(&ref->count))
498 		debug_active_activate(ref);
499 	spin_unlock_irq(&ref->tree_lock);
500 }
501 
i915_active_acquire(struct i915_active * ref)502 int i915_active_acquire(struct i915_active *ref)
503 {
504 	int err;
505 
506 	if (i915_active_acquire_if_busy(ref))
507 		return 0;
508 
509 	if (!ref->active) {
510 		__i915_active_activate(ref);
511 		return 0;
512 	}
513 
514 	err = mutex_lock_interruptible(&ref->mutex);
515 	if (err)
516 		return err;
517 
518 	if (likely(!i915_active_acquire_if_busy(ref))) {
519 		err = ref->active(ref);
520 		if (!err)
521 			__i915_active_activate(ref);
522 	}
523 
524 	mutex_unlock(&ref->mutex);
525 
526 	return err;
527 }
528 
i915_active_acquire_for_context(struct i915_active * ref,u64 idx)529 int i915_active_acquire_for_context(struct i915_active *ref, u64 idx)
530 {
531 	struct i915_active_fence *active;
532 	int err;
533 
534 	err = i915_active_acquire(ref);
535 	if (err)
536 		return err;
537 
538 	active = active_instance(ref, idx);
539 	if (!active) {
540 		i915_active_release(ref);
541 		return -ENOMEM;
542 	}
543 
544 	return 0; /* return with active ref */
545 }
546 
i915_active_release(struct i915_active * ref)547 void i915_active_release(struct i915_active *ref)
548 {
549 	debug_active_assert(ref);
550 	active_retire(ref);
551 }
552 
enable_signaling(struct i915_active_fence * active)553 static void enable_signaling(struct i915_active_fence *active)
554 {
555 	struct dma_fence *fence;
556 
557 	if (unlikely(is_barrier(active)))
558 		return;
559 
560 	fence = i915_active_fence_get(active);
561 	if (!fence)
562 		return;
563 
564 	dma_fence_enable_sw_signaling(fence);
565 	dma_fence_put(fence);
566 }
567 
flush_barrier(struct active_node * it)568 static int flush_barrier(struct active_node *it)
569 {
570 	struct intel_engine_cs *engine;
571 
572 	if (likely(!is_barrier(&it->base)))
573 		return 0;
574 
575 	engine = __barrier_to_engine(it);
576 	smp_rmb(); /* serialise with add_active_barriers */
577 	if (!is_barrier(&it->base))
578 		return 0;
579 
580 	return intel_engine_flush_barriers(engine);
581 }
582 
flush_lazy_signals(struct i915_active * ref)583 static int flush_lazy_signals(struct i915_active *ref)
584 {
585 	struct active_node *it, *n;
586 	int err = 0;
587 
588 	enable_signaling(&ref->excl);
589 	rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
590 		err = flush_barrier(it); /* unconnected idle barrier? */
591 		if (err)
592 			break;
593 
594 		enable_signaling(&it->base);
595 	}
596 
597 	return err;
598 }
599 
__i915_active_wait(struct i915_active * ref,int state)600 int __i915_active_wait(struct i915_active *ref, int state)
601 {
602 	might_sleep();
603 
604 	/* Any fence added after the wait begins will not be auto-signaled */
605 	if (i915_active_acquire_if_busy(ref)) {
606 		int err;
607 
608 		err = flush_lazy_signals(ref);
609 		i915_active_release(ref);
610 		if (err)
611 			return err;
612 
613 		if (___wait_var_event(ref, i915_active_is_idle(ref),
614 				      state, 0, 0, schedule()))
615 			return -EINTR;
616 	}
617 
618 	/*
619 	 * After the wait is complete, the caller may free the active.
620 	 * We have to flush any concurrent retirement before returning.
621 	 */
622 	flush_work(&ref->work);
623 	return 0;
624 }
625 
__await_active(struct i915_active_fence * active,int (* fn)(void * arg,struct dma_fence * fence),void * arg)626 static int __await_active(struct i915_active_fence *active,
627 			  int (*fn)(void *arg, struct dma_fence *fence),
628 			  void *arg)
629 {
630 	struct dma_fence *fence;
631 
632 	if (is_barrier(active)) /* XXX flush the barrier? */
633 		return 0;
634 
635 	fence = i915_active_fence_get(active);
636 	if (fence) {
637 		int err;
638 
639 		err = fn(arg, fence);
640 		dma_fence_put(fence);
641 		if (err < 0)
642 			return err;
643 	}
644 
645 	return 0;
646 }
647 
648 struct wait_barrier {
649 	struct wait_queue_entry base;
650 	struct i915_active *ref;
651 };
652 
653 static int
barrier_wake(wait_queue_entry_t * wq,unsigned int mode,int flags,void * key)654 barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key)
655 {
656 	struct wait_barrier *wb = container_of(wq, typeof(*wb), base);
657 
658 	if (i915_active_is_idle(wb->ref)) {
659 		list_del(&wq->entry);
660 		i915_sw_fence_complete(wq->private);
661 		kfree(wq);
662 	}
663 
664 	return 0;
665 }
666 
__await_barrier(struct i915_active * ref,struct i915_sw_fence * fence)667 static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence)
668 {
669 	struct wait_barrier *wb;
670 
671 	wb = kmalloc(sizeof(*wb), GFP_KERNEL);
672 	if (unlikely(!wb))
673 		return -ENOMEM;
674 
675 	GEM_BUG_ON(i915_active_is_idle(ref));
676 	if (!i915_sw_fence_await(fence)) {
677 		kfree(wb);
678 		return -EINVAL;
679 	}
680 
681 	wb->base.flags = 0;
682 	wb->base.func = barrier_wake;
683 	wb->base.private = fence;
684 	wb->ref = ref;
685 
686 	add_wait_queue(__var_waitqueue(ref), &wb->base);
687 	return 0;
688 }
689 
await_active(struct i915_active * ref,unsigned int flags,int (* fn)(void * arg,struct dma_fence * fence),void * arg,struct i915_sw_fence * barrier)690 static int await_active(struct i915_active *ref,
691 			unsigned int flags,
692 			int (*fn)(void *arg, struct dma_fence *fence),
693 			void *arg, struct i915_sw_fence *barrier)
694 {
695 	int err = 0;
696 
697 	if (!i915_active_acquire_if_busy(ref))
698 		return 0;
699 
700 	if (flags & I915_ACTIVE_AWAIT_EXCL &&
701 	    rcu_access_pointer(ref->excl.fence)) {
702 		err = __await_active(&ref->excl, fn, arg);
703 		if (err)
704 			goto out;
705 	}
706 
707 	if (flags & I915_ACTIVE_AWAIT_ACTIVE) {
708 		struct active_node *it, *n;
709 
710 		rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
711 			err = __await_active(&it->base, fn, arg);
712 			if (err)
713 				goto out;
714 		}
715 	}
716 
717 	if (flags & I915_ACTIVE_AWAIT_BARRIER) {
718 		err = flush_lazy_signals(ref);
719 		if (err)
720 			goto out;
721 
722 		err = __await_barrier(ref, barrier);
723 		if (err)
724 			goto out;
725 	}
726 
727 out:
728 	i915_active_release(ref);
729 	return err;
730 }
731 
rq_await_fence(void * arg,struct dma_fence * fence)732 static int rq_await_fence(void *arg, struct dma_fence *fence)
733 {
734 	return i915_request_await_dma_fence(arg, fence);
735 }
736 
i915_request_await_active(struct i915_request * rq,struct i915_active * ref,unsigned int flags)737 int i915_request_await_active(struct i915_request *rq,
738 			      struct i915_active *ref,
739 			      unsigned int flags)
740 {
741 	return await_active(ref, flags, rq_await_fence, rq, &rq->submit);
742 }
743 
sw_await_fence(void * arg,struct dma_fence * fence)744 static int sw_await_fence(void *arg, struct dma_fence *fence)
745 {
746 	return i915_sw_fence_await_dma_fence(arg, fence, 0,
747 					     GFP_NOWAIT | __GFP_NOWARN);
748 }
749 
i915_sw_fence_await_active(struct i915_sw_fence * fence,struct i915_active * ref,unsigned int flags)750 int i915_sw_fence_await_active(struct i915_sw_fence *fence,
751 			       struct i915_active *ref,
752 			       unsigned int flags)
753 {
754 	return await_active(ref, flags, sw_await_fence, fence, fence);
755 }
756 
i915_active_fini(struct i915_active * ref)757 void i915_active_fini(struct i915_active *ref)
758 {
759 	debug_active_fini(ref);
760 	GEM_BUG_ON(atomic_read(&ref->count));
761 	GEM_BUG_ON(work_pending(&ref->work));
762 	mutex_destroy(&ref->mutex);
763 
764 	if (ref->cache)
765 		kmem_cache_free(slab_cache, ref->cache);
766 }
767 
is_idle_barrier(struct active_node * node,u64 idx)768 static inline bool is_idle_barrier(struct active_node *node, u64 idx)
769 {
770 	return node->timeline == idx && !i915_active_fence_isset(&node->base);
771 }
772 
reuse_idle_barrier(struct i915_active * ref,u64 idx)773 static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
774 {
775 	struct rb_node *prev, *p;
776 
777 	if (RB_EMPTY_ROOT(&ref->tree))
778 		return NULL;
779 
780 	GEM_BUG_ON(i915_active_is_idle(ref));
781 
782 	/*
783 	 * Try to reuse any existing barrier nodes already allocated for this
784 	 * i915_active, due to overlapping active phases there is likely a
785 	 * node kept alive (as we reuse before parking). We prefer to reuse
786 	 * completely idle barriers (less hassle in manipulating the llists),
787 	 * but otherwise any will do.
788 	 */
789 	if (ref->cache && is_idle_barrier(ref->cache, idx)) {
790 		p = &ref->cache->node;
791 		goto match;
792 	}
793 
794 	prev = NULL;
795 	p = ref->tree.rb_node;
796 	while (p) {
797 		struct active_node *node =
798 			rb_entry(p, struct active_node, node);
799 
800 		if (is_idle_barrier(node, idx))
801 			goto match;
802 
803 		prev = p;
804 		if (node->timeline < idx)
805 			p = READ_ONCE(p->rb_right);
806 		else
807 			p = READ_ONCE(p->rb_left);
808 	}
809 
810 	/*
811 	 * No quick match, but we did find the leftmost rb_node for the
812 	 * kernel_context. Walk the rb_tree in-order to see if there were
813 	 * any idle-barriers on this timeline that we missed, or just use
814 	 * the first pending barrier.
815 	 */
816 	for (p = prev; p; p = rb_next(p)) {
817 		struct active_node *node =
818 			rb_entry(p, struct active_node, node);
819 		struct intel_engine_cs *engine;
820 
821 		if (node->timeline > idx)
822 			break;
823 
824 		if (node->timeline < idx)
825 			continue;
826 
827 		if (is_idle_barrier(node, idx))
828 			goto match;
829 
830 		/*
831 		 * The list of pending barriers is protected by the
832 		 * kernel_context timeline, which notably we do not hold
833 		 * here. i915_request_add_active_barriers() may consume
834 		 * the barrier before we claim it, so we have to check
835 		 * for success.
836 		 */
837 		engine = __barrier_to_engine(node);
838 		smp_rmb(); /* serialise with add_active_barriers */
839 		if (is_barrier(&node->base) &&
840 		    ____active_del_barrier(ref, node, engine))
841 			goto match;
842 	}
843 
844 	return NULL;
845 
846 match:
847 	spin_lock_irq(&ref->tree_lock);
848 	rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
849 	if (p == &ref->cache->node)
850 		WRITE_ONCE(ref->cache, NULL);
851 	spin_unlock_irq(&ref->tree_lock);
852 
853 	return rb_entry(p, struct active_node, node);
854 }
855 
i915_active_acquire_preallocate_barrier(struct i915_active * ref,struct intel_engine_cs * engine)856 int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
857 					    struct intel_engine_cs *engine)
858 {
859 	intel_engine_mask_t tmp, mask = engine->mask;
860 	struct llist_node *first = NULL, *last = NULL;
861 	struct intel_gt *gt = engine->gt;
862 
863 	GEM_BUG_ON(i915_active_is_idle(ref));
864 
865 	/* Wait until the previous preallocation is completed */
866 	while (!llist_empty(&ref->preallocated_barriers))
867 		cond_resched();
868 
869 	/*
870 	 * Preallocate a node for each physical engine supporting the target
871 	 * engine (remember virtual engines have more than one sibling).
872 	 * We can then use the preallocated nodes in
873 	 * i915_active_acquire_barrier()
874 	 */
875 	GEM_BUG_ON(!mask);
876 	for_each_engine_masked(engine, gt, mask, tmp) {
877 		u64 idx = engine->kernel_context->timeline->fence_context;
878 		struct llist_node *prev = first;
879 		struct active_node *node;
880 
881 		rcu_read_lock();
882 		node = reuse_idle_barrier(ref, idx);
883 		rcu_read_unlock();
884 		if (!node) {
885 			node = kmem_cache_alloc(slab_cache, GFP_KERNEL);
886 			if (!node)
887 				goto unwind;
888 
889 			RCU_INIT_POINTER(node->base.fence, NULL);
890 			node->base.cb.func = node_retire;
891 			node->timeline = idx;
892 			node->ref = ref;
893 		}
894 
895 		if (!i915_active_fence_isset(&node->base)) {
896 			/*
897 			 * Mark this as being *our* unconnected proto-node.
898 			 *
899 			 * Since this node is not in any list, and we have
900 			 * decoupled it from the rbtree, we can reuse the
901 			 * request to indicate this is an idle-barrier node
902 			 * and then we can use the rb_node and list pointers
903 			 * for our tracking of the pending barrier.
904 			 */
905 			RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN));
906 			node->base.cb.node.prev = (void *)engine;
907 			__i915_active_acquire(ref);
908 		}
909 		GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));
910 
911 		GEM_BUG_ON(barrier_to_engine(node) != engine);
912 		first = barrier_to_ll(node);
913 		first->next = prev;
914 		if (!last)
915 			last = first;
916 		intel_engine_pm_get(engine);
917 	}
918 
919 	GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
920 	llist_add_batch(first, last, &ref->preallocated_barriers);
921 
922 	return 0;
923 
924 unwind:
925 	while (first) {
926 		struct active_node *node = barrier_from_ll(first);
927 
928 		first = first->next;
929 
930 		atomic_dec(&ref->count);
931 		intel_engine_pm_put(barrier_to_engine(node));
932 
933 		kmem_cache_free(slab_cache, node);
934 	}
935 	return -ENOMEM;
936 }
937 
i915_active_acquire_barrier(struct i915_active * ref)938 void i915_active_acquire_barrier(struct i915_active *ref)
939 {
940 	struct llist_node *pos, *next;
941 	unsigned long flags;
942 
943 	GEM_BUG_ON(i915_active_is_idle(ref));
944 
945 	/*
946 	 * Transfer the list of preallocated barriers into the
947 	 * i915_active rbtree, but only as proto-nodes. They will be
948 	 * populated by i915_request_add_active_barriers() to point to the
949 	 * request that will eventually release them.
950 	 */
951 	llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
952 		struct active_node *node = barrier_from_ll(pos);
953 		struct intel_engine_cs *engine = barrier_to_engine(node);
954 		struct rb_node **p, *parent;
955 
956 		spin_lock_irqsave_nested(&ref->tree_lock, flags,
957 					 SINGLE_DEPTH_NESTING);
958 		parent = NULL;
959 		p = &ref->tree.rb_node;
960 		while (*p) {
961 			struct active_node *it;
962 
963 			parent = *p;
964 
965 			it = rb_entry(parent, struct active_node, node);
966 			if (it->timeline < node->timeline)
967 				p = &parent->rb_right;
968 			else
969 				p = &parent->rb_left;
970 		}
971 		rb_link_node(&node->node, parent, p);
972 		rb_insert_color(&node->node, &ref->tree);
973 		spin_unlock_irqrestore(&ref->tree_lock, flags);
974 
975 		GEM_BUG_ON(!intel_engine_pm_is_awake(engine));
976 		llist_add(barrier_to_ll(node), &engine->barrier_tasks);
977 		intel_engine_pm_put_delay(engine, 2);
978 	}
979 }
980 
ll_to_fence_slot(struct llist_node * node)981 static struct dma_fence **ll_to_fence_slot(struct llist_node *node)
982 {
983 	return __active_fence_slot(&barrier_from_ll(node)->base);
984 }
985 
i915_request_add_active_barriers(struct i915_request * rq)986 void i915_request_add_active_barriers(struct i915_request *rq)
987 {
988 	struct intel_engine_cs *engine = rq->engine;
989 	struct llist_node *node, *next;
990 	unsigned long flags;
991 
992 	GEM_BUG_ON(!intel_context_is_barrier(rq->context));
993 	GEM_BUG_ON(intel_engine_is_virtual(engine));
994 	GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline);
995 
996 	node = llist_del_all(&engine->barrier_tasks);
997 	if (!node)
998 		return;
999 	/*
1000 	 * Attach the list of proto-fences to the in-flight request such
1001 	 * that the parent i915_active will be released when this request
1002 	 * is retired.
1003 	 */
1004 	spin_lock_irqsave(&rq->lock, flags);
1005 	llist_for_each_safe(node, next, node) {
1006 		/* serialise with reuse_idle_barrier */
1007 		smp_store_mb(*ll_to_fence_slot(node), &rq->fence);
1008 		list_add_tail((struct list_head *)node, &rq->fence.cb_list);
1009 	}
1010 	spin_unlock_irqrestore(&rq->lock, flags);
1011 }
1012 
1013 /*
1014  * __i915_active_fence_set: Update the last active fence along its timeline
1015  * @active: the active tracker
1016  * @fence: the new fence (under construction)
1017  *
1018  * Records the new @fence as the last active fence along its timeline in
1019  * this active tracker, moving the tracking callbacks from the previous
1020  * fence onto this one. Returns the previous fence (if not already completed),
1021  * which the caller must ensure is executed before the new fence. To ensure
1022  * that the order of fences within the timeline of the i915_active_fence is
1023  * understood, it should be locked by the caller.
1024  */
1025 struct dma_fence *
__i915_active_fence_set(struct i915_active_fence * active,struct dma_fence * fence)1026 __i915_active_fence_set(struct i915_active_fence *active,
1027 			struct dma_fence *fence)
1028 {
1029 	struct dma_fence *prev;
1030 	unsigned long flags;
1031 
1032 	if (fence == rcu_access_pointer(active->fence))
1033 		return fence;
1034 
1035 	GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
1036 
1037 	/*
1038 	 * Consider that we have two threads arriving (A and B), with
1039 	 * C already resident as the active->fence.
1040 	 *
1041 	 * A does the xchg first, and so it sees C or NULL depending
1042 	 * on the timing of the interrupt handler. If it is NULL, the
1043 	 * previous fence must have been signaled and we know that
1044 	 * we are first on the timeline. If it is still present,
1045 	 * we acquire the lock on that fence and serialise with the interrupt
1046 	 * handler, in the process removing it from any future interrupt
1047 	 * callback. A will then wait on C before executing (if present).
1048 	 *
1049 	 * As B is second, it sees A as the previous fence and so waits for
1050 	 * it to complete its transition and takes over the occupancy for
1051 	 * itself -- remembering that it needs to wait on A before executing.
1052 	 *
1053 	 * Note the strong ordering of the timeline also provides consistent
1054 	 * nesting rules for the fence->lock; the inner lock is always the
1055 	 * older lock.
1056 	 */
1057 	spin_lock_irqsave(fence->lock, flags);
1058 	prev = xchg(__active_fence_slot(active), fence);
1059 	if (prev) {
1060 		GEM_BUG_ON(prev == fence);
1061 		spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
1062 		__list_del_entry(&active->cb.node);
1063 		spin_unlock(prev->lock); /* serialise with prev->cb_list */
1064 	}
1065 	list_add_tail(&active->cb.node, &fence->cb_list);
1066 	spin_unlock_irqrestore(fence->lock, flags);
1067 
1068 	return prev;
1069 }
1070 
i915_active_fence_set(struct i915_active_fence * active,struct i915_request * rq)1071 int i915_active_fence_set(struct i915_active_fence *active,
1072 			  struct i915_request *rq)
1073 {
1074 	struct dma_fence *fence;
1075 	int err = 0;
1076 
1077 	/* Must maintain timeline ordering wrt previous active requests */
1078 	rcu_read_lock();
1079 	fence = __i915_active_fence_set(active, &rq->fence);
1080 	if (fence) /* but the previous fence may not belong to that timeline! */
1081 		fence = dma_fence_get_rcu(fence);
1082 	rcu_read_unlock();
1083 	if (fence) {
1084 		err = i915_request_await_dma_fence(rq, fence);
1085 		dma_fence_put(fence);
1086 	}
1087 
1088 	return err;
1089 }
1090 
i915_active_noop(struct dma_fence * fence,struct dma_fence_cb * cb)1091 void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
1092 {
1093 	active_fence_cb(fence, cb);
1094 }
1095 
1096 struct auto_active {
1097 	struct i915_active base;
1098 	struct kref ref;
1099 };
1100 
i915_active_get(struct i915_active * ref)1101 struct i915_active *i915_active_get(struct i915_active *ref)
1102 {
1103 	struct auto_active *aa = container_of(ref, typeof(*aa), base);
1104 
1105 	kref_get(&aa->ref);
1106 	return &aa->base;
1107 }
1108 
auto_release(struct kref * ref)1109 static void auto_release(struct kref *ref)
1110 {
1111 	struct auto_active *aa = container_of(ref, typeof(*aa), ref);
1112 
1113 	i915_active_fini(&aa->base);
1114 	kfree(aa);
1115 }
1116 
i915_active_put(struct i915_active * ref)1117 void i915_active_put(struct i915_active *ref)
1118 {
1119 	struct auto_active *aa = container_of(ref, typeof(*aa), base);
1120 
1121 	kref_put(&aa->ref, auto_release);
1122 }
1123 
auto_active(struct i915_active * ref)1124 static int auto_active(struct i915_active *ref)
1125 {
1126 	i915_active_get(ref);
1127 	return 0;
1128 }
1129 
auto_retire(struct i915_active * ref)1130 static void auto_retire(struct i915_active *ref)
1131 {
1132 	i915_active_put(ref);
1133 }
1134 
i915_active_create(void)1135 struct i915_active *i915_active_create(void)
1136 {
1137 	struct auto_active *aa;
1138 
1139 	aa = kmalloc(sizeof(*aa), GFP_KERNEL);
1140 	if (!aa)
1141 		return NULL;
1142 
1143 	kref_init(&aa->ref);
1144 	i915_active_init(&aa->base, auto_active, auto_retire, 0);
1145 
1146 	return &aa->base;
1147 }
1148 
1149 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
1150 #include "selftests/i915_active.c"
1151 #endif
1152 
i915_active_module_exit(void)1153 void i915_active_module_exit(void)
1154 {
1155 	kmem_cache_destroy(slab_cache);
1156 }
1157 
i915_active_module_init(void)1158 int __init i915_active_module_init(void)
1159 {
1160 	slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
1161 	if (!slab_cache)
1162 		return -ENOMEM;
1163 
1164 	return 0;
1165 }
1166