Merge tag 'drm-next-5.5-2019-11-22' of git://people.freedesktop.org/~agd5f/linux...
[sfrench/cifs-2.6.git] / drivers / gpu / drm / i915 / i915_active.c
1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2019 Intel Corporation
5  */
6
7 #include <linux/debugobjects.h>
8
9 #include "gt/intel_engine_pm.h"
10 #include "gt/intel_ring.h"
11
12 #include "i915_drv.h"
13 #include "i915_active.h"
14 #include "i915_globals.h"
15
16 /*
17  * Active refs memory management
18  *
19  * To be more economical with memory, we reap all the i915_active trees as
20  * they idle (when we know the active requests are inactive) and allocate the
21  * nodes from a local slab cache to hopefully reduce the fragmentation.
22  */
23 static struct i915_global_active {
24         struct i915_global base;
25         struct kmem_cache *slab_cache;
26 } global;
27
28 struct active_node {
29         struct i915_active_fence base;
30         struct i915_active *ref;
31         struct rb_node node;
32         u64 timeline;
33 };
34
35 static inline struct active_node *
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
43 static inline bool is_barrier(const struct i915_active_fence *active)
44 {
45         return IS_ERR(rcu_access_pointer(active->fence));
46 }
47
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 *
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 *
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
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
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 struct debug_obj_descr active_debug_desc = {
83         .name = "i915_active",
84         .debug_hint = active_debug_hint,
85 };
86
87 static void debug_active_init(struct i915_active *ref)
88 {
89         debug_object_init(ref, &active_debug_desc);
90 }
91
92 static void debug_active_activate(struct i915_active *ref)
93 {
94         spin_lock_irq(&ref->tree_lock);
95         if (!atomic_read(&ref->count)) /* before the first inc */
96                 debug_object_activate(ref, &active_debug_desc);
97         spin_unlock_irq(&ref->tree_lock);
98 }
99
100 static void debug_active_deactivate(struct i915_active *ref)
101 {
102         lockdep_assert_held(&ref->tree_lock);
103         if (!atomic_read(&ref->count)) /* after the last dec */
104                 debug_object_deactivate(ref, &active_debug_desc);
105 }
106
107 static void debug_active_fini(struct i915_active *ref)
108 {
109         debug_object_free(ref, &active_debug_desc);
110 }
111
112 static void debug_active_assert(struct i915_active *ref)
113 {
114         debug_object_assert_init(ref, &active_debug_desc);
115 }
116
117 #else
118
119 static inline void debug_active_init(struct i915_active *ref) { }
120 static inline void debug_active_activate(struct i915_active *ref) { }
121 static inline void debug_active_deactivate(struct i915_active *ref) { }
122 static inline void debug_active_fini(struct i915_active *ref) { }
123 static inline void debug_active_assert(struct i915_active *ref) { }
124
125 #endif
126
127 static void
128 __active_retire(struct i915_active *ref)
129 {
130         struct active_node *it, *n;
131         struct rb_root root;
132         unsigned long flags;
133
134         GEM_BUG_ON(i915_active_is_idle(ref));
135
136         /* return the unused nodes to our slabcache -- flushing the allocator */
137         if (!atomic_dec_and_lock_irqsave(&ref->count, &ref->tree_lock, flags))
138                 return;
139
140         GEM_BUG_ON(rcu_access_pointer(ref->excl.fence));
141         debug_active_deactivate(ref);
142
143         root = ref->tree;
144         ref->tree = RB_ROOT;
145         ref->cache = NULL;
146
147         spin_unlock_irqrestore(&ref->tree_lock, flags);
148
149         /* After the final retire, the entire struct may be freed */
150         if (ref->retire)
151                 ref->retire(ref);
152
153         /* ... except if you wait on it, you must manage your own references! */
154         wake_up_var(ref);
155
156         rbtree_postorder_for_each_entry_safe(it, n, &root, node) {
157                 GEM_BUG_ON(i915_active_fence_isset(&it->base));
158                 kmem_cache_free(global.slab_cache, it);
159         }
160 }
161
162 static void
163 active_work(struct work_struct *wrk)
164 {
165         struct i915_active *ref = container_of(wrk, typeof(*ref), work);
166
167         GEM_BUG_ON(!atomic_read(&ref->count));
168         if (atomic_add_unless(&ref->count, -1, 1))
169                 return;
170
171         __active_retire(ref);
172 }
173
174 static void
175 active_retire(struct i915_active *ref)
176 {
177         GEM_BUG_ON(!atomic_read(&ref->count));
178         if (atomic_add_unless(&ref->count, -1, 1))
179                 return;
180
181         if (ref->flags & I915_ACTIVE_RETIRE_SLEEPS) {
182                 queue_work(system_unbound_wq, &ref->work);
183                 return;
184         }
185
186         __active_retire(ref);
187 }
188
189 static void
190 node_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
191 {
192         i915_active_fence_cb(fence, cb);
193         active_retire(container_of(cb, struct active_node, base.cb)->ref);
194 }
195
196 static void
197 excl_retire(struct dma_fence *fence, struct dma_fence_cb *cb)
198 {
199         i915_active_fence_cb(fence, cb);
200         active_retire(container_of(cb, struct i915_active, excl.cb));
201 }
202
203 static struct i915_active_fence *
204 active_instance(struct i915_active *ref, struct intel_timeline *tl)
205 {
206         struct active_node *node, *prealloc;
207         struct rb_node **p, *parent;
208         u64 idx = tl->fence_context;
209
210         /*
211          * We track the most recently used timeline to skip a rbtree search
212          * for the common case, under typical loads we never need the rbtree
213          * at all. We can reuse the last slot if it is empty, that is
214          * after the previous activity has been retired, or if it matches the
215          * current timeline.
216          */
217         node = READ_ONCE(ref->cache);
218         if (node && node->timeline == idx)
219                 return &node->base;
220
221         /* Preallocate a replacement, just in case */
222         prealloc = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
223         if (!prealloc)
224                 return NULL;
225
226         spin_lock_irq(&ref->tree_lock);
227         GEM_BUG_ON(i915_active_is_idle(ref));
228
229         parent = NULL;
230         p = &ref->tree.rb_node;
231         while (*p) {
232                 parent = *p;
233
234                 node = rb_entry(parent, struct active_node, node);
235                 if (node->timeline == idx) {
236                         kmem_cache_free(global.slab_cache, prealloc);
237                         goto out;
238                 }
239
240                 if (node->timeline < idx)
241                         p = &parent->rb_right;
242                 else
243                         p = &parent->rb_left;
244         }
245
246         node = prealloc;
247         __i915_active_fence_init(&node->base, &tl->mutex, NULL, node_retire);
248         node->ref = ref;
249         node->timeline = idx;
250
251         rb_link_node(&node->node, parent, p);
252         rb_insert_color(&node->node, &ref->tree);
253
254 out:
255         ref->cache = node;
256         spin_unlock_irq(&ref->tree_lock);
257
258         BUILD_BUG_ON(offsetof(typeof(*node), base));
259         return &node->base;
260 }
261
262 void __i915_active_init(struct i915_active *ref,
263                         int (*active)(struct i915_active *ref),
264                         void (*retire)(struct i915_active *ref),
265                         struct lock_class_key *key)
266 {
267         unsigned long bits;
268
269         debug_active_init(ref);
270
271         ref->flags = 0;
272         ref->active = active;
273         ref->retire = ptr_unpack_bits(retire, &bits, 2);
274         if (bits & I915_ACTIVE_MAY_SLEEP)
275                 ref->flags |= I915_ACTIVE_RETIRE_SLEEPS;
276
277         spin_lock_init(&ref->tree_lock);
278         ref->tree = RB_ROOT;
279         ref->cache = NULL;
280
281         init_llist_head(&ref->preallocated_barriers);
282         atomic_set(&ref->count, 0);
283         __mutex_init(&ref->mutex, "i915_active", key);
284         __i915_active_fence_init(&ref->excl, &ref->mutex, NULL, excl_retire);
285         INIT_WORK(&ref->work, active_work);
286 }
287
288 static bool ____active_del_barrier(struct i915_active *ref,
289                                    struct active_node *node,
290                                    struct intel_engine_cs *engine)
291
292 {
293         struct llist_node *head = NULL, *tail = NULL;
294         struct llist_node *pos, *next;
295
296         GEM_BUG_ON(node->timeline != engine->kernel_context->timeline->fence_context);
297
298         /*
299          * Rebuild the llist excluding our node. We may perform this
300          * outside of the kernel_context timeline mutex and so someone
301          * else may be manipulating the engine->barrier_tasks, in
302          * which case either we or they will be upset :)
303          *
304          * A second __active_del_barrier() will report failure to claim
305          * the active_node and the caller will just shrug and know not to
306          * claim ownership of its node.
307          *
308          * A concurrent i915_request_add_active_barriers() will miss adding
309          * any of the tasks, but we will try again on the next -- and since
310          * we are actively using the barrier, we know that there will be
311          * at least another opportunity when we idle.
312          */
313         llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {
314                 if (node == barrier_from_ll(pos)) {
315                         node = NULL;
316                         continue;
317                 }
318
319                 pos->next = head;
320                 head = pos;
321                 if (!tail)
322                         tail = pos;
323         }
324         if (head)
325                 llist_add_batch(head, tail, &engine->barrier_tasks);
326
327         return !node;
328 }
329
330 static bool
331 __active_del_barrier(struct i915_active *ref, struct active_node *node)
332 {
333         return ____active_del_barrier(ref, node, barrier_to_engine(node));
334 }
335
336 int i915_active_ref(struct i915_active *ref,
337                     struct intel_timeline *tl,
338                     struct dma_fence *fence)
339 {
340         struct i915_active_fence *active;
341         int err;
342
343         lockdep_assert_held(&tl->mutex);
344
345         /* Prevent reaping in case we malloc/wait while building the tree */
346         err = i915_active_acquire(ref);
347         if (err)
348                 return err;
349
350         active = active_instance(ref, tl);
351         if (!active) {
352                 err = -ENOMEM;
353                 goto out;
354         }
355
356         if (is_barrier(active)) { /* proto-node used by our idle barrier */
357                 /*
358                  * This request is on the kernel_context timeline, and so
359                  * we can use it to substitute for the pending idle-barrer
360                  * request that we want to emit on the kernel_context.
361                  */
362                 __active_del_barrier(ref, node_from_active(active));
363                 RCU_INIT_POINTER(active->fence, NULL);
364                 atomic_dec(&ref->count);
365         }
366         if (!__i915_active_fence_set(active, fence))
367                 atomic_inc(&ref->count);
368
369 out:
370         i915_active_release(ref);
371         return err;
372 }
373
374 void i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f)
375 {
376         /* We expect the caller to manage the exclusive timeline ordering */
377         GEM_BUG_ON(i915_active_is_idle(ref));
378
379         /*
380          * As we don't know which mutex the caller is using, we told a small
381          * lie to the debug code that it is using the i915_active.mutex;
382          * and now we must stick to that lie.
383          */
384         mutex_acquire(&ref->mutex.dep_map, 0, 0, _THIS_IP_);
385         if (!__i915_active_fence_set(&ref->excl, f))
386                 atomic_inc(&ref->count);
387         mutex_release(&ref->mutex.dep_map, 0, _THIS_IP_);
388 }
389
390 bool i915_active_acquire_if_busy(struct i915_active *ref)
391 {
392         debug_active_assert(ref);
393         return atomic_add_unless(&ref->count, 1, 0);
394 }
395
396 int i915_active_acquire(struct i915_active *ref)
397 {
398         int err;
399
400         if (i915_active_acquire_if_busy(ref))
401                 return 0;
402
403         err = mutex_lock_interruptible(&ref->mutex);
404         if (err)
405                 return err;
406
407         if (!atomic_read(&ref->count) && ref->active)
408                 err = ref->active(ref);
409         if (!err) {
410                 debug_active_activate(ref);
411                 atomic_inc(&ref->count);
412         }
413
414         mutex_unlock(&ref->mutex);
415
416         return err;
417 }
418
419 void i915_active_release(struct i915_active *ref)
420 {
421         debug_active_assert(ref);
422         active_retire(ref);
423 }
424
425 static void enable_signaling(struct i915_active_fence *active)
426 {
427         struct dma_fence *fence;
428
429         fence = i915_active_fence_get(active);
430         if (!fence)
431                 return;
432
433         dma_fence_enable_sw_signaling(fence);
434         dma_fence_put(fence);
435 }
436
437 int i915_active_wait(struct i915_active *ref)
438 {
439         struct active_node *it, *n;
440         int err = 0;
441
442         might_sleep();
443
444         if (!i915_active_acquire_if_busy(ref))
445                 return 0;
446
447         /* Flush lazy signals */
448         enable_signaling(&ref->excl);
449         rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
450                 if (is_barrier(&it->base)) /* unconnected idle barrier */
451                         continue;
452
453                 enable_signaling(&it->base);
454         }
455         /* Any fence added after the wait begins will not be auto-signaled */
456
457         i915_active_release(ref);
458         if (err)
459                 return err;
460
461         if (wait_var_event_interruptible(ref, i915_active_is_idle(ref)))
462                 return -EINTR;
463
464         return 0;
465 }
466
467 int i915_request_await_active(struct i915_request *rq, struct i915_active *ref)
468 {
469         int err = 0;
470
471         if (rcu_access_pointer(ref->excl.fence)) {
472                 struct dma_fence *fence;
473
474                 rcu_read_lock();
475                 fence = dma_fence_get_rcu_safe(&ref->excl.fence);
476                 rcu_read_unlock();
477                 if (fence) {
478                         err = i915_request_await_dma_fence(rq, fence);
479                         dma_fence_put(fence);
480                 }
481         }
482
483         /* In the future we may choose to await on all fences */
484
485         return err;
486 }
487
488 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
489 void i915_active_fini(struct i915_active *ref)
490 {
491         debug_active_fini(ref);
492         GEM_BUG_ON(atomic_read(&ref->count));
493         GEM_BUG_ON(work_pending(&ref->work));
494         GEM_BUG_ON(!RB_EMPTY_ROOT(&ref->tree));
495         mutex_destroy(&ref->mutex);
496 }
497 #endif
498
499 static inline bool is_idle_barrier(struct active_node *node, u64 idx)
500 {
501         return node->timeline == idx && !i915_active_fence_isset(&node->base);
502 }
503
504 static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
505 {
506         struct rb_node *prev, *p;
507
508         if (RB_EMPTY_ROOT(&ref->tree))
509                 return NULL;
510
511         spin_lock_irq(&ref->tree_lock);
512         GEM_BUG_ON(i915_active_is_idle(ref));
513
514         /*
515          * Try to reuse any existing barrier nodes already allocated for this
516          * i915_active, due to overlapping active phases there is likely a
517          * node kept alive (as we reuse before parking). We prefer to reuse
518          * completely idle barriers (less hassle in manipulating the llists),
519          * but otherwise any will do.
520          */
521         if (ref->cache && is_idle_barrier(ref->cache, idx)) {
522                 p = &ref->cache->node;
523                 goto match;
524         }
525
526         prev = NULL;
527         p = ref->tree.rb_node;
528         while (p) {
529                 struct active_node *node =
530                         rb_entry(p, struct active_node, node);
531
532                 if (is_idle_barrier(node, idx))
533                         goto match;
534
535                 prev = p;
536                 if (node->timeline < idx)
537                         p = p->rb_right;
538                 else
539                         p = p->rb_left;
540         }
541
542         /*
543          * No quick match, but we did find the leftmost rb_node for the
544          * kernel_context. Walk the rb_tree in-order to see if there were
545          * any idle-barriers on this timeline that we missed, or just use
546          * the first pending barrier.
547          */
548         for (p = prev; p; p = rb_next(p)) {
549                 struct active_node *node =
550                         rb_entry(p, struct active_node, node);
551                 struct intel_engine_cs *engine;
552
553                 if (node->timeline > idx)
554                         break;
555
556                 if (node->timeline < idx)
557                         continue;
558
559                 if (is_idle_barrier(node, idx))
560                         goto match;
561
562                 /*
563                  * The list of pending barriers is protected by the
564                  * kernel_context timeline, which notably we do not hold
565                  * here. i915_request_add_active_barriers() may consume
566                  * the barrier before we claim it, so we have to check
567                  * for success.
568                  */
569                 engine = __barrier_to_engine(node);
570                 smp_rmb(); /* serialise with add_active_barriers */
571                 if (is_barrier(&node->base) &&
572                     ____active_del_barrier(ref, node, engine))
573                         goto match;
574         }
575
576         spin_unlock_irq(&ref->tree_lock);
577
578         return NULL;
579
580 match:
581         rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
582         if (p == &ref->cache->node)
583                 ref->cache = NULL;
584         spin_unlock_irq(&ref->tree_lock);
585
586         return rb_entry(p, struct active_node, node);
587 }
588
589 int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
590                                             struct intel_engine_cs *engine)
591 {
592         intel_engine_mask_t tmp, mask = engine->mask;
593         struct intel_gt *gt = engine->gt;
594         struct llist_node *pos, *next;
595         int err;
596
597         GEM_BUG_ON(i915_active_is_idle(ref));
598         GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
599
600         /*
601          * Preallocate a node for each physical engine supporting the target
602          * engine (remember virtual engines have more than one sibling).
603          * We can then use the preallocated nodes in
604          * i915_active_acquire_barrier()
605          */
606         for_each_engine_masked(engine, gt, mask, tmp) {
607                 u64 idx = engine->kernel_context->timeline->fence_context;
608                 struct active_node *node;
609
610                 node = reuse_idle_barrier(ref, idx);
611                 if (!node) {
612                         node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
613                         if (!node) {
614                                 err = ENOMEM;
615                                 goto unwind;
616                         }
617
618 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
619                         node->base.lock =
620                                 &engine->kernel_context->timeline->mutex;
621 #endif
622                         RCU_INIT_POINTER(node->base.fence, NULL);
623                         node->base.cb.func = node_retire;
624                         node->timeline = idx;
625                         node->ref = ref;
626                 }
627
628                 if (!i915_active_fence_isset(&node->base)) {
629                         /*
630                          * Mark this as being *our* unconnected proto-node.
631                          *
632                          * Since this node is not in any list, and we have
633                          * decoupled it from the rbtree, we can reuse the
634                          * request to indicate this is an idle-barrier node
635                          * and then we can use the rb_node and list pointers
636                          * for our tracking of the pending barrier.
637                          */
638                         RCU_INIT_POINTER(node->base.fence, ERR_PTR(-EAGAIN));
639                         node->base.cb.node.prev = (void *)engine;
640                         atomic_inc(&ref->count);
641                 }
642
643                 GEM_BUG_ON(barrier_to_engine(node) != engine);
644                 llist_add(barrier_to_ll(node), &ref->preallocated_barriers);
645                 intel_engine_pm_get(engine);
646         }
647
648         return 0;
649
650 unwind:
651         llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
652                 struct active_node *node = barrier_from_ll(pos);
653
654                 atomic_dec(&ref->count);
655                 intel_engine_pm_put(barrier_to_engine(node));
656
657                 kmem_cache_free(global.slab_cache, node);
658         }
659         return err;
660 }
661
662 void i915_active_acquire_barrier(struct i915_active *ref)
663 {
664         struct llist_node *pos, *next;
665         unsigned long flags;
666
667         GEM_BUG_ON(i915_active_is_idle(ref));
668
669         /*
670          * Transfer the list of preallocated barriers into the
671          * i915_active rbtree, but only as proto-nodes. They will be
672          * populated by i915_request_add_active_barriers() to point to the
673          * request that will eventually release them.
674          */
675         spin_lock_irqsave_nested(&ref->tree_lock, flags, SINGLE_DEPTH_NESTING);
676         llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
677                 struct active_node *node = barrier_from_ll(pos);
678                 struct intel_engine_cs *engine = barrier_to_engine(node);
679                 struct rb_node **p, *parent;
680
681                 parent = NULL;
682                 p = &ref->tree.rb_node;
683                 while (*p) {
684                         struct active_node *it;
685
686                         parent = *p;
687
688                         it = rb_entry(parent, struct active_node, node);
689                         if (it->timeline < node->timeline)
690                                 p = &parent->rb_right;
691                         else
692                                 p = &parent->rb_left;
693                 }
694                 rb_link_node(&node->node, parent, p);
695                 rb_insert_color(&node->node, &ref->tree);
696
697                 GEM_BUG_ON(!intel_engine_pm_is_awake(engine));
698                 llist_add(barrier_to_ll(node), &engine->barrier_tasks);
699                 intel_engine_pm_put(engine);
700         }
701         spin_unlock_irqrestore(&ref->tree_lock, flags);
702 }
703
704 void i915_request_add_active_barriers(struct i915_request *rq)
705 {
706         struct intel_engine_cs *engine = rq->engine;
707         struct llist_node *node, *next;
708         unsigned long flags;
709
710         GEM_BUG_ON(intel_engine_is_virtual(engine));
711         GEM_BUG_ON(i915_request_timeline(rq) != engine->kernel_context->timeline);
712
713         node = llist_del_all(&engine->barrier_tasks);
714         if (!node)
715                 return;
716         /*
717          * Attach the list of proto-fences to the in-flight request such
718          * that the parent i915_active will be released when this request
719          * is retired.
720          */
721         spin_lock_irqsave(&rq->lock, flags);
722         llist_for_each_safe(node, next, node) {
723                 RCU_INIT_POINTER(barrier_from_ll(node)->base.fence, &rq->fence);
724                 smp_wmb(); /* serialise with reuse_idle_barrier */
725                 list_add_tail((struct list_head *)node, &rq->fence.cb_list);
726         }
727         spin_unlock_irqrestore(&rq->lock, flags);
728 }
729
730 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
731 #define active_is_held(active) lockdep_is_held((active)->lock)
732 #else
733 #define active_is_held(active) true
734 #endif
735
736 /*
737  * __i915_active_fence_set: Update the last active fence along its timeline
738  * @active: the active tracker
739  * @fence: the new fence (under construction)
740  *
741  * Records the new @fence as the last active fence along its timeline in
742  * this active tracker, moving the tracking callbacks from the previous
743  * fence onto this one. Returns the previous fence (if not already completed),
744  * which the caller must ensure is executed before the new fence. To ensure
745  * that the order of fences within the timeline of the i915_active_fence is
746  * maintained, it must be locked by the caller.
747  */
748 struct dma_fence *
749 __i915_active_fence_set(struct i915_active_fence *active,
750                         struct dma_fence *fence)
751 {
752         struct dma_fence *prev;
753         unsigned long flags;
754
755         /* NB: must be serialised by an outer timeline mutex (active->lock) */
756         spin_lock_irqsave(fence->lock, flags);
757         GEM_BUG_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
758
759         prev = rcu_dereference_protected(active->fence, active_is_held(active));
760         if (prev) {
761                 GEM_BUG_ON(prev == fence);
762                 spin_lock_nested(prev->lock, SINGLE_DEPTH_NESTING);
763                 __list_del_entry(&active->cb.node);
764                 spin_unlock(prev->lock); /* serialise with prev->cb_list */
765
766                 /*
767                  * active->fence is reset by the callback from inside
768                  * interrupt context. We need to serialise our list
769                  * manipulation with the fence->lock to prevent the prev
770                  * being lost inside an interrupt (it can't be replaced as
771                  * no other caller is allowed to enter __i915_active_fence_set
772                  * as we hold the timeline lock). After serialising with
773                  * the callback, we need to double check which ran first,
774                  * our list_del() [decoupling prev from the callback] or
775                  * the callback...
776                  */
777                 prev = rcu_access_pointer(active->fence);
778         }
779
780         rcu_assign_pointer(active->fence, fence);
781         list_add_tail(&active->cb.node, &fence->cb_list);
782
783         spin_unlock_irqrestore(fence->lock, flags);
784
785         return prev;
786 }
787
788 int i915_active_fence_set(struct i915_active_fence *active,
789                           struct i915_request *rq)
790 {
791         struct dma_fence *fence;
792         int err = 0;
793
794 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
795         lockdep_assert_held(active->lock);
796 #endif
797
798         /* Must maintain timeline ordering wrt previous active requests */
799         rcu_read_lock();
800         fence = __i915_active_fence_set(active, &rq->fence);
801         if (fence) /* but the previous fence may not belong to that timeline! */
802                 fence = dma_fence_get_rcu(fence);
803         rcu_read_unlock();
804         if (fence) {
805                 err = i915_request_await_dma_fence(rq, fence);
806                 dma_fence_put(fence);
807         }
808
809         return err;
810 }
811
812 void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb)
813 {
814         i915_active_fence_cb(fence, cb);
815 }
816
817 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
818 #include "selftests/i915_active.c"
819 #endif
820
821 static void i915_global_active_shrink(void)
822 {
823         kmem_cache_shrink(global.slab_cache);
824 }
825
826 static void i915_global_active_exit(void)
827 {
828         kmem_cache_destroy(global.slab_cache);
829 }
830
831 static struct i915_global_active global = { {
832         .shrink = i915_global_active_shrink,
833         .exit = i915_global_active_exit,
834 } };
835
836 int __init i915_global_active_init(void)
837 {
838         global.slab_cache = KMEM_CACHE(active_node, SLAB_HWCACHE_ALIGN);
839         if (!global.slab_cache)
840                 return -ENOMEM;
841
842         i915_global_register(&global.base);
843         return 0;
844 }