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(node: &ref->cache->node, NULL, rb_link: &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(lock: &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(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(s: slab_cache, objp: 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(v: &ref->count, a: -1, u: 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(v: &ref->count, a: -1, u: 1))
193 return;
194
195 if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {
196 queue_work(wq: system_unbound_wq, work: &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 succeed).
261 */
262 if (!cached && try_cmpxchg64(&it->timeline, &cached, idx))
263 return it;
264 }
265
266 BUILD_BUG_ON(offsetof(typeof(*it), node));
267
268 /* While active, the tree can only be built; not destroyed */
269 GEM_BUG_ON(i915_active_is_idle(ref));
270
271 it = fetch_node(ref->tree.rb_node);
272 while (it) {
273 if (it->timeline < idx) {
274 it = fetch_node(it->node.rb_right);
275 } else if (it->timeline > idx) {
276 it = fetch_node(it->node.rb_left);
277 } else {
278 WRITE_ONCE(ref->cache, it);
279 break;
280 }
281 }
282
283 /* NB: If the tree rotated beneath us, we may miss our target. */
284 return it;
285}
286
287static struct i915_active_fence *
288active_instance(struct i915_active *ref, u64 idx)
289{
290 struct active_node *node;
291 struct rb_node **p, *parent;
292
293 node = __active_lookup(ref, idx);
294 if (likely(node))
295 return &node->base;
296
297 spin_lock_irq(lock: &ref->tree_lock);
298 GEM_BUG_ON(i915_active_is_idle(ref));
299
300 parent = NULL;
301 p = &ref->tree.rb_node;
302 while (*p) {
303 parent = *p;
304
305 node = rb_entry(parent, struct active_node, node);
306 if (node->timeline == idx)
307 goto out;
308
309 if (node->timeline < idx)
310 p = &parent->rb_right;
311 else
312 p = &parent->rb_left;
313 }
314
315 /*
316 * XXX: We should preallocate this before i915_active_ref() is ever
317 * called, but we cannot call into fs_reclaim() anyway, so use GFP_ATOMIC.
318 */
319 node = kmem_cache_alloc(slab_cache, GFP_ATOMIC);
320 if (!node)
321 goto out;
322
323 __i915_active_fence_init(active: &node->base, NULL, fn: node_retire);
324 node->ref = ref;
325 node->timeline = idx;
326
327 rb_link_node(node: &node->node, parent, rb_link: p);
328 rb_insert_color(&node->node, &ref->tree);
329
330out:
331 WRITE_ONCE(ref->cache, node);
332 spin_unlock_irq(lock: &ref->tree_lock);
333
334 return &node->base;
335}
336
337void __i915_active_init(struct i915_active *ref,
338 int (*active)(struct i915_active *ref),
339 void (*retire)(struct i915_active *ref),
340 unsigned long flags,
341 struct lock_class_key *mkey,
342 struct lock_class_key *wkey)
343{
344 debug_active_init(ref);
345
346 ref->flags = flags;
347 ref->active = active;
348 ref->retire = retire;
349
350 spin_lock_init(&ref->tree_lock);
351 ref->tree = RB_ROOT;
352 ref->cache = NULL;
353
354 init_llist_head(list: &ref->preallocated_barriers);
355 atomic_set(v: &ref->count, i: 0);
356 __mutex_init(lock: &ref->mutex, name: "i915_active", key: mkey);
357 __i915_active_fence_init(active: &ref->excl, NULL, fn: excl_retire);
358 INIT_WORK(&ref->work, active_work);
359#if IS_ENABLED(CONFIG_LOCKDEP)
360 lockdep_init_map(lock: &ref->work.lockdep_map, name: "i915_active.work", key: wkey, subclass: 0);
361#endif
362}
363
364static bool ____active_del_barrier(struct i915_active *ref,
365 struct active_node *node,
366 struct intel_engine_cs *engine)
367
368{
369 struct llist_node *head = NULL, *tail = NULL;
370 struct llist_node *pos, *next;
371
372 GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context);
373
374 /*
375 * Rebuild the llist excluding our node. We may perform this
376 * outside of the kernel_context timeline mutex and so someone
377 * else may be manipulating the engine->barrier_tasks, in
378 * which case either we or they will be upset :)
379 *
380 * A second __active_del_barrier() will report failure to claim
381 * the active_node and the caller will just shrug and know not to
382 * claim ownership of its node.
383 *
384 * A concurrent i915_request_add_active_barriers() will miss adding
385 * any of the tasks, but we will try again on the next -- and since
386 * we are actively using the barrier, we know that there will be
387 * at least another opportunity when we idle.
388 */
389 llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {
390 if (node == barrier_from_ll(x: pos)) {
391 node = NULL;
392 continue;
393 }
394
395 pos->next = head;
396 head = pos;
397 if (!tail)
398 tail = pos;
399 }
400 if (head)
401 llist_add_batch(new_first: head, new_last: tail, head: &engine->barrier_tasks);
402
403 return !node;
404}
405
406static bool
407__active_del_barrier(struct i915_active *ref, struct active_node *node)
408{
409 return ____active_del_barrier(ref, node, engine: barrier_to_engine(node));
410}
411
412static bool
413replace_barrier(struct i915_active *ref, struct i915_active_fence *active)
414{
415 if (!is_barrier(active)) /* proto-node used by our idle barrier? */
416 return false;
417
418 /*
419 * This request is on the kernel_context timeline, and so
420 * we can use it to substitute for the pending idle-barrer
421 * request that we want to emit on the kernel_context.
422 */
423 return __active_del_barrier(ref, node: node_from_active(active));
424}
425
426int i915_active_add_request(struct i915_active *ref, struct i915_request *rq)
427{
428 u64 idx = i915_request_timeline(rq)->fence_context;
429 struct dma_fence *fence = &rq->fence;
430 struct i915_active_fence *active;
431 int err;
432
433 /* Prevent reaping in case we malloc/wait while building the tree */
434 err = i915_active_acquire(ref);
435 if (err)
436 return err;
437
438 do {
439 active = active_instance(ref, idx);
440 if (!active) {
441 err = -ENOMEM;
442 goto out;
443 }
444
445 if (replace_barrier(ref, active)) {
446 RCU_INIT_POINTER(active->fence, NULL);
447 atomic_dec(v: &ref->count);
448 }
449 } while (unlikely(is_barrier(active)));
450
451 fence = __i915_active_fence_set(active, fence);
452 if (!fence)
453 __i915_active_acquire(ref);
454 else
455 dma_fence_put(fence);
456
457out:
458 i915_active_release(ref);
459 return err;
460}
461
462static struct dma_fence *
463__i915_active_set_fence(struct i915_active *ref,
464 struct i915_active_fence *active,
465 struct dma_fence *fence)
466{
467 struct dma_fence *prev;
468
469 if (replace_barrier(ref, active)) {
470 RCU_INIT_POINTER(active->fence, fence);
471 return NULL;
472 }
473
474 prev = __i915_active_fence_set(active, fence);
475 if (!prev)
476 __i915_active_acquire(ref);
477
478 return prev;
479}
480
481struct dma_fence *
482i915_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, active: &ref->excl, fence: f);
486}
487
488bool i915_active_acquire_if_busy(struct i915_active *ref)
489{
490 debug_active_assert(ref);
491 return atomic_add_unless(v: &ref->count, a: 1, u: 0);
492}
493
494static void __i915_active_activate(struct i915_active *ref)
495{
496 spin_lock_irq(lock: &ref->tree_lock); /* __active_retire() */
497 if (!atomic_fetch_inc(v: &ref->count))
498 debug_active_activate(ref);
499 spin_unlock_irq(lock: &ref->tree_lock);
500}
501
502int 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(lock: &ref->mutex);
525
526 return err;
527}
528
529void i915_active_release(struct i915_active *ref)
530{
531 debug_active_assert(ref);
532 active_retire(ref);
533}
534
535static void enable_signaling(struct i915_active_fence *active)
536{
537 struct dma_fence *fence;
538
539 if (unlikely(is_barrier(active)))
540 return;
541
542 fence = i915_active_fence_get(active);
543 if (!fence)
544 return;
545
546 dma_fence_enable_sw_signaling(fence);
547 dma_fence_put(fence);
548}
549
550static int flush_barrier(struct active_node *it)
551{
552 struct intel_engine_cs *engine;
553
554 if (likely(!is_barrier(&it->base)))
555 return 0;
556
557 engine = __barrier_to_engine(node: it);
558 smp_rmb(); /* serialise with add_active_barriers */
559 if (!is_barrier(active: &it->base))
560 return 0;
561
562 return intel_engine_flush_barriers(engine);
563}
564
565static int flush_lazy_signals(struct i915_active *ref)
566{
567 struct active_node *it, *n;
568 int err = 0;
569
570 enable_signaling(active: &ref->excl);
571 rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
572 err = flush_barrier(it); /* unconnected idle barrier? */
573 if (err)
574 break;
575
576 enable_signaling(active: &it->base);
577 }
578
579 return err;
580}
581
582int __i915_active_wait(struct i915_active *ref, int state)
583{
584 might_sleep();
585
586 /* Any fence added after the wait begins will not be auto-signaled */
587 if (i915_active_acquire_if_busy(ref)) {
588 int err;
589
590 err = flush_lazy_signals(ref);
591 i915_active_release(ref);
592 if (err)
593 return err;
594
595 if (___wait_var_event(ref, i915_active_is_idle(ref),
596 state, 0, 0, schedule()))
597 return -EINTR;
598 }
599
600 /*
601 * After the wait is complete, the caller may free the active.
602 * We have to flush any concurrent retirement before returning.
603 */
604 flush_work(work: &ref->work);
605 return 0;
606}
607
608static int __await_active(struct i915_active_fence *active,
609 int (*fn)(void *arg, struct dma_fence *fence),
610 void *arg)
611{
612 struct dma_fence *fence;
613
614 if (is_barrier(active)) /* XXX flush the barrier? */
615 return 0;
616
617 fence = i915_active_fence_get(active);
618 if (fence) {
619 int err;
620
621 err = fn(arg, fence);
622 dma_fence_put(fence);
623 if (err < 0)
624 return err;
625 }
626
627 return 0;
628}
629
630struct wait_barrier {
631 struct wait_queue_entry base;
632 struct i915_active *ref;
633};
634
635static int
636barrier_wake(wait_queue_entry_t *wq, unsigned int mode, int flags, void *key)
637{
638 struct wait_barrier *wb = container_of(wq, typeof(*wb), base);
639
640 if (i915_active_is_idle(ref: wb->ref)) {
641 list_del(entry: &wq->entry);
642 i915_sw_fence_complete(fence: wq->private);
643 kfree(objp: wq);
644 }
645
646 return 0;
647}
648
649static int __await_barrier(struct i915_active *ref, struct i915_sw_fence *fence)
650{
651 struct wait_barrier *wb;
652
653 wb = kmalloc(sizeof(*wb), GFP_KERNEL);
654 if (unlikely(!wb))
655 return -ENOMEM;
656
657 GEM_BUG_ON(i915_active_is_idle(ref));
658 if (!i915_sw_fence_await(fence)) {
659 kfree(objp: wb);
660 return -EINVAL;
661 }
662
663 wb->base.flags = 0;
664 wb->base.func = barrier_wake;
665 wb->base.private = fence;
666 wb->ref = ref;
667
668 add_wait_queue(wq_head: __var_waitqueue(p: ref), wq_entry: &wb->base);
669 return 0;
670}
671
672static int await_active(struct i915_active *ref,
673 unsigned int flags,
674 int (*fn)(void *arg, struct dma_fence *fence),
675 void *arg, struct i915_sw_fence *barrier)
676{
677 int err = 0;
678
679 if (!i915_active_acquire_if_busy(ref))
680 return 0;
681
682 if (flags & I915_ACTIVE_AWAIT_EXCL &&
683 rcu_access_pointer(ref->excl.fence)) {
684 err = __await_active(active: &ref->excl, fn, arg);
685 if (err)
686 goto out;
687 }
688
689 if (flags & I915_ACTIVE_AWAIT_ACTIVE) {
690 struct active_node *it, *n;
691
692 rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
693 err = __await_active(active: &it->base, fn, arg);
694 if (err)
695 goto out;
696 }
697 }
698
699 if (flags & I915_ACTIVE_AWAIT_BARRIER) {
700 err = flush_lazy_signals(ref);
701 if (err)
702 goto out;
703
704 err = __await_barrier(ref, fence: barrier);
705 if (err)
706 goto out;
707 }
708
709out:
710 i915_active_release(ref);
711 return err;
712}
713
714static int rq_await_fence(void *arg, struct dma_fence *fence)
715{
716 return i915_request_await_dma_fence(rq: arg, fence);
717}
718
719int i915_request_await_active(struct i915_request *rq,
720 struct i915_active *ref,
721 unsigned int flags)
722{
723 return await_active(ref, flags, fn: rq_await_fence, arg: rq, barrier: &rq->submit);
724}
725
726static int sw_await_fence(void *arg, struct dma_fence *fence)
727{
728 return i915_sw_fence_await_dma_fence(fence: arg, dma: fence, timeout: 0,
729 GFP_NOWAIT | __GFP_NOWARN);
730}
731
732int i915_sw_fence_await_active(struct i915_sw_fence *fence,
733 struct i915_active *ref,
734 unsigned int flags)
735{
736 return await_active(ref, flags, fn: sw_await_fence, arg: fence, barrier: fence);
737}
738
739void i915_active_fini(struct i915_active *ref)
740{
741 debug_active_fini(ref);
742 GEM_BUG_ON(atomic_read(&ref->count));
743 GEM_BUG_ON(work_pending(&ref->work));
744 mutex_destroy(lock: &ref->mutex);
745
746 if (ref->cache)
747 kmem_cache_free(s: slab_cache, objp: ref->cache);
748}
749
750static inline bool is_idle_barrier(struct active_node *node, u64 idx)
751{
752 return node->timeline == idx && !i915_active_fence_isset(active: &node->base);
753}
754
755static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
756{
757 struct rb_node *prev, *p;
758
759 if (RB_EMPTY_ROOT(&ref->tree))
760 return NULL;
761
762 GEM_BUG_ON(i915_active_is_idle(ref));
763
764 /*
765 * Try to reuse any existing barrier nodes already allocated for this
766 * i915_active, due to overlapping active phases there is likely a
767 * node kept alive (as we reuse before parking). We prefer to reuse
768 * completely idle barriers (less hassle in manipulating the llists),
769 * but otherwise any will do.
770 */
771 if (ref->cache && is_idle_barrier(node: ref->cache, idx)) {
772 p = &ref->cache->node;
773 goto match;
774 }
775
776 prev = NULL;
777 p = ref->tree.rb_node;
778 while (p) {
779 struct active_node *node =
780 rb_entry(p, struct active_node, node);
781
782 if (is_idle_barrier(node, idx))
783 goto match;
784
785 prev = p;
786 if (node->timeline < idx)
787 p = READ_ONCE(p->rb_right);
788 else
789 p = READ_ONCE(p->rb_left);
790 }
791
792 /*
793 * No quick match, but we did find the leftmost rb_node for the
794 * kernel_context. Walk the rb_tree in-order to see if there were
795 * any idle-barriers on this timeline that we missed, or just use
796 * the first pending barrier.
797 */
798 for (p = prev; p; p = rb_next(p)) {
799 struct active_node *node =
800 rb_entry(p, struct active_node, node);
801 struct intel_engine_cs *engine;
802
803 if (node->timeline > idx)
804 break;
805
806 if (node->timeline < idx)
807 continue;
808
809 if (is_idle_barrier(node, idx))
810 goto match;
811
812 /*
813 * The list of pending barriers is protected by the
814 * kernel_context timeline, which notably we do not hold
815 * here. i915_request_add_active_barriers() may consume
816 * the barrier before we claim it, so we have to check
817 * for success.
818 */
819 engine = __barrier_to_engine(node);
820 smp_rmb(); /* serialise with add_active_barriers */
821 if (is_barrier(active: &node->base) &&
822 ____active_del_barrier(ref, node, engine))
823 goto match;
824 }
825
826 return NULL;
827
828match:
829 spin_lock_irq(lock: &ref->tree_lock);
830 rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
831 if (p == &ref->cache->node)
832 WRITE_ONCE(ref->cache, NULL);
833 spin_unlock_irq(lock: &ref->tree_lock);
834
835 return rb_entry(p, struct active_node, node);
836}
837
838int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
839 struct intel_engine_cs *engine)
840{
841 intel_engine_mask_t tmp, mask = engine->mask;
842 struct llist_node *first = NULL, *last = NULL;
843 struct intel_gt *gt = engine->gt;
844
845 GEM_BUG_ON(i915_active_is_idle(ref));
846
847 /* Wait until the previous preallocation is completed */
848 while (!llist_empty(head: &ref->preallocated_barriers))
849 cond_resched();
850
851 /*
852 * Preallocate a node for each physical engine supporting the target
853 * engine (remember virtual engines have more than one sibling).
854 * We can then use the preallocated nodes in
855 * i915_active_acquire_barrier()
856 */
857 GEM_BUG_ON(!mask);
858 for_each_engine_masked(engine, gt, mask, tmp) {
859 u64 idx = engine->kernel_context->timeline->fence_context;
860 struct llist_node *prev = first;
861 struct active_node *node;
862
863 rcu_read_lock();
864 node = reuse_idle_barrier(ref, idx);
865 rcu_read_unlock();
866 if (!node) {
867 node = kmem_cache_alloc(slab_cache, GFP_KERNEL);
868 if (!node)
869 goto unwind;
870
871 RCU_INIT_POINTER(node->base.fence, NULL);
872 node->base.cb.func = node_retire;
873 node->timeline = idx;
874 node->ref = ref;
875 }
876
877 if (!i915_active_fence_isset(active: &node->base)) {
878 /*
879 * Mark this as being *our* unconnected proto-node.
880 *
881 * Since this node is not in any list, and we have
882 * decoupled it from the rbtree, we can reuse the
883 * request to indicate this is an idle-barrier node
884 * and then we can use the rb_node and list pointers
885 * for our tracking of the pending barrier.
886 */
887 RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN));
888 node->base.cb.node.prev = (void *)engine;
889 __i915_active_acquire(ref);
890 }
891 GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));
892
893 GEM_BUG_ON(barrier_to_engine(node) != engine);
894 first = barrier_to_ll(node);
895 first->next = prev;
896 if (!last)
897 last = first;
898 intel_engine_pm_get(engine);
899 }
900
901 GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
902 llist_add_batch(new_first: first, new_last: last, head: &ref->preallocated_barriers);
903
904 return 0;
905
906unwind:
907 while (first) {
908 struct active_node *node = barrier_from_ll(x: first);
909
910 first = first->next;
911
912 atomic_dec(v: &ref->count);
913 intel_engine_pm_put(engine: barrier_to_engine(node));
914
915 kmem_cache_free(s: slab_cache, objp: node);
916 }
917 return -ENOMEM;
918}
919
920void i915_active_acquire_barrier(struct i915_active *ref)
921{
922 struct llist_node *pos, *next;
923 unsigned long flags;
924
925 GEM_BUG_ON(i915_active_is_idle(ref));
926
927 /*
928 * Transfer the list of preallocated barriers into the
929 * i915_active rbtree, but only as proto-nodes. They will be
930 * populated by i915_request_add_active_barriers() to point to the
931 * request that will eventually release them.
932 */
933 llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
934 struct active_node *node = barrier_from_ll(x: pos);
935 struct intel_engine_cs *engine = barrier_to_engine(node);
936 struct rb_node **p, *parent;
937
938 spin_lock_irqsave_nested(&ref->tree_lock, flags,
939 SINGLE_DEPTH_NESTING);
940 parent = NULL;
941 p = &ref->tree.rb_node;
942 while (*p) {
943 struct active_node *it;
944
945 parent = *p;
946
947 it = rb_entry(parent, struct active_node, node);
948 if (it->timeline < node->timeline)
949 p = &parent->rb_right;
950 else
951 p = &parent->rb_left;
952 }
953 rb_link_node(node: &node->node, parent, rb_link: p);
954 rb_insert_color(&node->node, &ref->tree);
955 spin_unlock_irqrestore(lock: &ref->tree_lock, flags);
956
957 GEM_BUG_ON(!intel_engine_pm_is_awake(engine));
958 llist_add(new: barrier_to_ll(node), head: &engine->barrier_tasks);
959 intel_engine_pm_put_delay(engine, delay: 2);
960 }
961}
962
963static struct dma_fence **ll_to_fence_slot(struct llist_node *node)
964{
965 return __active_fence_slot(active: &barrier_from_ll(x: node)->base);
966}
967
968void i915_request_add_active_barriers(struct i915_request *rq)
969{
970 struct intel_engine_cs *engine = rq->engine;
971 struct llist_node *node, *next;
972 unsigned long flags;
973
974 GEM_BUG_ON(!intel_context_is_barrier(rq->context));
975 GEM_BUG_ON(intel_engine_is_virtual(engine));
976 GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline);
977
978 node = llist_del_all(head: &engine->barrier_tasks);
979 if (!node)
980 return;
981 /*
982 * Attach the list of proto-fences to the in-flight request such
983 * that the parent i915_active will be released when this request
984 * is retired.
985 */
986 spin_lock_irqsave(&rq->lock, flags);
987 llist_for_each_safe(node, next, node) {
988 /* serialise with reuse_idle_barrier */
989 smp_store_mb(*ll_to_fence_slot(node), &rq->fence);
990 list_add_tail(new: (struct list_head *)node, head: &rq->fence.cb_list);
991 }
992 spin_unlock_irqrestore(lock: &rq->lock, flags);
993}
994
995/*
996 * __i915_active_fence_set: Update the last active fence along its timeline
997 * @active: the active tracker
998 * @fence: the new fence (under construction)
999 *
1000 * Records the new @fence as the last active fence along its timeline in
1001 * this active tracker, moving the tracking callbacks from the previous
1002 * fence onto this one. Gets and returns a reference to the previous fence
1003 * (if not already completed), which the caller must put after making sure
1004 * that it is executed before the new fence. To ensure that the order of
1005 * fences within the timeline of the i915_active_fence is understood, it
1006 * should be locked by the caller.
1007 */
1008struct dma_fence *
1009__i915_active_fence_set(struct i915_active_fence *active,
1010 struct dma_fence *fence)
1011{
1012 struct dma_fence *prev;
1013 unsigned long flags;
1014
1015 /*
1016 * In case of fences embedded in i915_requests, their memory is
1017 * SLAB_FAILSAFE_BY_RCU, then it can be reused right after release
1018 * by new requests. Then, there is a risk of passing back a pointer
1019 * to a new, completely unrelated fence that reuses the same memory
1020 * while tracked under a different active tracker. Combined with i915
1021 * perf open/close operations that build await dependencies between
1022 * engine kernel context requests and user requests from different
1023 * timelines, this can lead to dependency loops and infinite waits.
1024 *
1025 * As a countermeasure, we try to get a reference to the active->fence
1026 * first, so if we succeed and pass it back to our user then it is not
1027 * released and potentially reused by an unrelated request before the
1028 * user has a chance to set up an await dependency on it.
1029 */
1030 prev = i915_active_fence_get(active);
1031 if (fence == prev)
1032 return fence;
1033
1034 GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
1035
1036 /*
1037 * Consider that we have two threads arriving (A and B), with
1038 * C already resident as the active->fence.
1039 *
1040 * Both A and B have got a reference to C or NULL, depending on the
1041 * timing of the interrupt handler. Let's assume that if A has got C
1042 * then it has locked C first (before B).
1043 *
1044 * Note the strong ordering of the timeline also provides consistent
1045 * nesting rules for the fence->lock; the inner lock is always the
1046 * older lock.
1047 */
1048 spin_lock_irqsave(fence->lock, flags);
1049 if (prev)
1050 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
1051
1052 /*
1053 * A does the cmpxchg first, and so it sees C or NULL, as before, or
1054 * something else, depending on the timing of other threads and/or
1055 * interrupt handler. If not the same as before then A unlocks C if
1056 * applicable and retries, starting from an attempt to get a new
1057 * active->fence. Meanwhile, B follows the same path as A.
1058 * Once A succeeds with cmpxch, B fails again, retires, gets A from
1059 * active->fence, locks it as soon as A completes, and possibly
1060 * succeeds with cmpxchg.
1061 */
1062 while (cmpxchg(__active_fence_slot(active), prev, fence) != prev) {
1063 if (prev) {
1064 spin_unlock(lock: prev->lock);
1065 dma_fence_put(fence: prev);
1066 }
1067 spin_unlock_irqrestore(lock: fence->lock, flags);
1068
1069 prev = i915_active_fence_get(active);
1070 GEM_BUG_ON(prev == fence);
1071
1072 spin_lock_irqsave(fence->lock, flags);
1073 if (prev)
1074 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
1075 }
1076
1077 /*
1078 * If prev is NULL then the previous fence must have been signaled
1079 * and we know that we are first on the timeline. If it is still
1080 * present then, having the lock on that fence already acquired, we
1081 * serialise with the interrupt handler, in the process of removing it
1082 * from any future interrupt callback. A will then wait on C before
1083 * executing (if present).
1084 *
1085 * As B is second, it sees A as the previous fence and so waits for
1086 * it to complete its transition and takes over the occupancy for
1087 * itself -- remembering that it needs to wait on A before executing.
1088 */
1089 if (prev) {
1090 __list_del_entry(entry: &active->cb.node);
1091 spin_unlock(lock: prev->lock); /* serialise with prev->cb_list */
1092 }
1093 list_add_tail(new: &active->cb.node, head: &fence->cb_list);
1094 spin_unlock_irqrestore(lock: fence->lock, flags);
1095
1096 return prev;
1097}
1098
1099int i915_active_fence_set(struct i915_active_fence *active,
1100 struct i915_request *rq)
1101{
1102 struct dma_fence *fence;
1103 int err = 0;
1104
1105 /* Must maintain timeline ordering wrt previous active requests */
1106 fence = __i915_active_fence_set(active, fence: &rq->fence);
1107 if (fence) {
1108 err = i915_request_await_dma_fence(rq, fence);
1109 dma_fence_put(fence);
1110 }
1111
1112 return err;
1113}
1114
1115void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
1116{
1117 active_fence_cb(fence, cb);
1118}
1119
1120struct auto_active {
1121 struct i915_active base;
1122 struct kref ref;
1123};
1124
1125struct i915_active *i915_active_get(struct i915_active *ref)
1126{
1127 struct auto_active *aa = container_of(ref, typeof(*aa), base);
1128
1129 kref_get(kref: &aa->ref);
1130 return &aa->base;
1131}
1132
1133static void auto_release(struct kref *ref)
1134{
1135 struct auto_active *aa = container_of(ref, typeof(*aa), ref);
1136
1137 i915_active_fini(ref: &aa->base);
1138 kfree(objp: aa);
1139}
1140
1141void i915_active_put(struct i915_active *ref)
1142{
1143 struct auto_active *aa = container_of(ref, typeof(*aa), base);
1144
1145 kref_put(kref: &aa->ref, release: auto_release);
1146}
1147
1148static int auto_active(struct i915_active *ref)
1149{
1150 i915_active_get(ref);
1151 return 0;
1152}
1153
1154static void auto_retire(struct i915_active *ref)
1155{
1156 i915_active_put(ref);
1157}
1158
1159struct i915_active *i915_active_create(void)
1160{
1161 struct auto_active *aa;
1162
1163 aa = kmalloc(sizeof(*aa), GFP_KERNEL);
1164 if (!aa)
1165 return NULL;
1166
1167 kref_init(kref: &aa->ref);
1168 i915_active_init(&aa->base, auto_active, auto_retire, 0);
1169
1170 return &aa->base;
1171}
1172
1173#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
1174#include "selftests/i915_active.c"
1175#endif
1176
1177void i915_active_module_exit(void)
1178{
1179 kmem_cache_destroy(s: slab_cache);
1180}
1181
1182int __init i915_active_module_init(void)
1183{
1184 slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
1185 if (!slab_cache)
1186 return -ENOMEM;
1187
1188 return 0;
1189}
1190

source code of linux/drivers/gpu/drm/i915/i915_active.c