xref: /linux/drivers/gpu/drm/scheduler/sched_entity.c (revision 24b10e5f8e0d2bee1a10fc67011ea5d936c1a389)
1 /*
2  * Copyright 2015 Advanced Micro Devices, Inc.
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included in
12  * all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
17  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
18  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
19  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
20  * OTHER DEALINGS IN THE SOFTWARE.
21  *
22  */
23 
24 #include <linux/kthread.h>
25 #include <linux/slab.h>
26 #include <linux/completion.h>
27 
28 #include <drm/drm_print.h>
29 #include <drm/gpu_scheduler.h>
30 
31 #include "gpu_scheduler_trace.h"
32 
33 #define to_drm_sched_job(sched_job)		\
34 		container_of((sched_job), struct drm_sched_job, queue_node)
35 
36 /**
37  * drm_sched_entity_init - Init a context entity used by scheduler when
38  * submit to HW ring.
39  *
40  * @entity: scheduler entity to init
41  * @priority: priority of the entity
42  * @sched_list: the list of drm scheds on which jobs from this
43  *           entity can be submitted
44  * @num_sched_list: number of drm sched in sched_list
45  * @guilty: atomic_t set to 1 when a job on this queue
46  *          is found to be guilty causing a timeout
47  *
48  * Note that the &sched_list must have at least one element to schedule the entity.
49  *
50  * For changing @priority later on at runtime see
51  * drm_sched_entity_set_priority(). For changing the set of schedulers
52  * @sched_list at runtime see drm_sched_entity_modify_sched().
53  *
54  * An entity is cleaned up by callind drm_sched_entity_fini(). See also
55  * drm_sched_entity_destroy().
56  *
57  * Returns 0 on success or a negative error code on failure.
58  */
59 int drm_sched_entity_init(struct drm_sched_entity *entity,
60 			  enum drm_sched_priority priority,
61 			  struct drm_gpu_scheduler **sched_list,
62 			  unsigned int num_sched_list,
63 			  atomic_t *guilty)
64 {
65 	if (!(entity && sched_list && (num_sched_list == 0 || sched_list[0])))
66 		return -EINVAL;
67 
68 	memset(entity, 0, sizeof(struct drm_sched_entity));
69 	INIT_LIST_HEAD(&entity->list);
70 	entity->rq = NULL;
71 	entity->guilty = guilty;
72 	entity->num_sched_list = num_sched_list;
73 	entity->priority = priority;
74 	entity->sched_list = num_sched_list > 1 ? sched_list : NULL;
75 	RCU_INIT_POINTER(entity->last_scheduled, NULL);
76 	RB_CLEAR_NODE(&entity->rb_tree_node);
77 
78 	if (!sched_list[0]->sched_rq) {
79 		/* Warn drivers not to do this and to fix their DRM
80 		 * calling order.
81 		 */
82 		pr_warn("%s: called with uninitialized scheduler\n", __func__);
83 	} else if (num_sched_list) {
84 		/* The "priority" of an entity cannot exceed the number of run-queues of a
85 		 * scheduler. Protect against num_rqs being 0, by converting to signed. Choose
86 		 * the lowest priority available.
87 		 */
88 		if (entity->priority >= sched_list[0]->num_rqs) {
89 			drm_err(sched_list[0], "entity with out-of-bounds priority:%u num_rqs:%u\n",
90 				entity->priority, sched_list[0]->num_rqs);
91 			entity->priority = max_t(s32, (s32) sched_list[0]->num_rqs - 1,
92 						 (s32) DRM_SCHED_PRIORITY_KERNEL);
93 		}
94 		entity->rq = sched_list[0]->sched_rq[entity->priority];
95 	}
96 
97 	init_completion(&entity->entity_idle);
98 
99 	/* We start in an idle state. */
100 	complete_all(&entity->entity_idle);
101 
102 	spin_lock_init(&entity->rq_lock);
103 	spsc_queue_init(&entity->job_queue);
104 
105 	atomic_set(&entity->fence_seq, 0);
106 	entity->fence_context = dma_fence_context_alloc(2);
107 
108 	return 0;
109 }
110 EXPORT_SYMBOL(drm_sched_entity_init);
111 
112 /**
113  * drm_sched_entity_modify_sched - Modify sched of an entity
114  * @entity: scheduler entity to init
115  * @sched_list: the list of new drm scheds which will replace
116  *		 existing entity->sched_list
117  * @num_sched_list: number of drm sched in sched_list
118  *
119  * Note that this must be called under the same common lock for @entity as
120  * drm_sched_job_arm() and drm_sched_entity_push_job(), or the driver needs to
121  * guarantee through some other means that this is never called while new jobs
122  * can be pushed to @entity.
123  */
124 void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
125 				    struct drm_gpu_scheduler **sched_list,
126 				    unsigned int num_sched_list)
127 {
128 	WARN_ON(!num_sched_list || !sched_list);
129 
130 	entity->sched_list = sched_list;
131 	entity->num_sched_list = num_sched_list;
132 }
133 EXPORT_SYMBOL(drm_sched_entity_modify_sched);
134 
135 static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
136 {
137 	rmb(); /* for list_empty to work without lock */
138 
139 	if (list_empty(&entity->list) ||
140 	    spsc_queue_count(&entity->job_queue) == 0 ||
141 	    entity->stopped)
142 		return true;
143 
144 	return false;
145 }
146 
147 /* Return true if entity could provide a job. */
148 bool drm_sched_entity_is_ready(struct drm_sched_entity *entity)
149 {
150 	if (spsc_queue_peek(&entity->job_queue) == NULL)
151 		return false;
152 
153 	if (READ_ONCE(entity->dependency))
154 		return false;
155 
156 	return true;
157 }
158 
159 /**
160  * drm_sched_entity_error - return error of last scheduled job
161  * @entity: scheduler entity to check
162  *
163  * Opportunistically return the error of the last scheduled job. Result can
164  * change any time when new jobs are pushed to the hw.
165  */
166 int drm_sched_entity_error(struct drm_sched_entity *entity)
167 {
168 	struct dma_fence *fence;
169 	int r;
170 
171 	rcu_read_lock();
172 	fence = rcu_dereference(entity->last_scheduled);
173 	r = fence ? fence->error : 0;
174 	rcu_read_unlock();
175 
176 	return r;
177 }
178 EXPORT_SYMBOL(drm_sched_entity_error);
179 
180 static void drm_sched_entity_kill_jobs_work(struct work_struct *wrk)
181 {
182 	struct drm_sched_job *job = container_of(wrk, typeof(*job), work);
183 
184 	drm_sched_fence_finished(job->s_fence, -ESRCH);
185 	WARN_ON(job->s_fence->parent);
186 	job->sched->ops->free_job(job);
187 }
188 
189 /* Signal the scheduler finished fence when the entity in question is killed. */
190 static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f,
191 					  struct dma_fence_cb *cb)
192 {
193 	struct drm_sched_job *job = container_of(cb, struct drm_sched_job,
194 						 finish_cb);
195 	unsigned long index;
196 
197 	dma_fence_put(f);
198 
199 	/* Wait for all dependencies to avoid data corruptions */
200 	xa_for_each(&job->dependencies, index, f) {
201 		struct drm_sched_fence *s_fence = to_drm_sched_fence(f);
202 
203 		if (s_fence && f == &s_fence->scheduled) {
204 			/* The dependencies array had a reference on the scheduled
205 			 * fence, and the finished fence refcount might have
206 			 * dropped to zero. Use dma_fence_get_rcu() so we get
207 			 * a NULL fence in that case.
208 			 */
209 			f = dma_fence_get_rcu(&s_fence->finished);
210 
211 			/* Now that we have a reference on the finished fence,
212 			 * we can release the reference the dependencies array
213 			 * had on the scheduled fence.
214 			 */
215 			dma_fence_put(&s_fence->scheduled);
216 		}
217 
218 		xa_erase(&job->dependencies, index);
219 		if (f && !dma_fence_add_callback(f, &job->finish_cb,
220 						 drm_sched_entity_kill_jobs_cb))
221 			return;
222 
223 		dma_fence_put(f);
224 	}
225 
226 	INIT_WORK(&job->work, drm_sched_entity_kill_jobs_work);
227 	schedule_work(&job->work);
228 }
229 
230 /* Remove the entity from the scheduler and kill all pending jobs */
231 static void drm_sched_entity_kill(struct drm_sched_entity *entity)
232 {
233 	struct drm_sched_job *job;
234 	struct dma_fence *prev;
235 
236 	if (!entity->rq)
237 		return;
238 
239 	spin_lock(&entity->rq_lock);
240 	entity->stopped = true;
241 	drm_sched_rq_remove_entity(entity->rq, entity);
242 	spin_unlock(&entity->rq_lock);
243 
244 	/* Make sure this entity is not used by the scheduler at the moment */
245 	wait_for_completion(&entity->entity_idle);
246 
247 	/* The entity is guaranteed to not be used by the scheduler */
248 	prev = rcu_dereference_check(entity->last_scheduled, true);
249 	dma_fence_get(prev);
250 	while ((job = to_drm_sched_job(spsc_queue_pop(&entity->job_queue)))) {
251 		struct drm_sched_fence *s_fence = job->s_fence;
252 
253 		dma_fence_get(&s_fence->finished);
254 		if (!prev || dma_fence_add_callback(prev, &job->finish_cb,
255 					   drm_sched_entity_kill_jobs_cb))
256 			drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb);
257 
258 		prev = &s_fence->finished;
259 	}
260 	dma_fence_put(prev);
261 }
262 
263 /**
264  * drm_sched_entity_flush - Flush a context entity
265  *
266  * @entity: scheduler entity
267  * @timeout: time to wait in for Q to become empty in jiffies.
268  *
269  * Splitting drm_sched_entity_fini() into two functions, The first one does the
270  * waiting, removes the entity from the runqueue and returns an error when the
271  * process was killed.
272  *
273  * Returns the remaining time in jiffies left from the input timeout
274  */
275 long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
276 {
277 	struct drm_gpu_scheduler *sched;
278 	struct task_struct *last_user;
279 	long ret = timeout;
280 
281 	if (!entity->rq)
282 		return 0;
283 
284 	sched = entity->rq->sched;
285 	/**
286 	 * The client will not queue more IBs during this fini, consume existing
287 	 * queued IBs or discard them on SIGKILL
288 	 */
289 	if (current->flags & PF_EXITING) {
290 		if (timeout)
291 			ret = wait_event_timeout(
292 					sched->job_scheduled,
293 					drm_sched_entity_is_idle(entity),
294 					timeout);
295 	} else {
296 		wait_event_killable(sched->job_scheduled,
297 				    drm_sched_entity_is_idle(entity));
298 	}
299 
300 	/* For killed process disable any more IBs enqueue right now */
301 	last_user = cmpxchg(&entity->last_user, current->group_leader, NULL);
302 	if ((!last_user || last_user == current->group_leader) &&
303 	    (current->flags & PF_EXITING) && (current->exit_code == SIGKILL))
304 		drm_sched_entity_kill(entity);
305 
306 	return ret;
307 }
308 EXPORT_SYMBOL(drm_sched_entity_flush);
309 
310 /**
311  * drm_sched_entity_fini - Destroy a context entity
312  *
313  * @entity: scheduler entity
314  *
315  * Cleanups up @entity which has been initialized by drm_sched_entity_init().
316  *
317  * If there are potentially job still in flight or getting newly queued
318  * drm_sched_entity_flush() must be called first. This function then goes over
319  * the entity and signals all jobs with an error code if the process was killed.
320  */
321 void drm_sched_entity_fini(struct drm_sched_entity *entity)
322 {
323 	/*
324 	 * If consumption of existing IBs wasn't completed. Forcefully remove
325 	 * them here. Also makes sure that the scheduler won't touch this entity
326 	 * any more.
327 	 */
328 	drm_sched_entity_kill(entity);
329 
330 	if (entity->dependency) {
331 		dma_fence_remove_callback(entity->dependency, &entity->cb);
332 		dma_fence_put(entity->dependency);
333 		entity->dependency = NULL;
334 	}
335 
336 	dma_fence_put(rcu_dereference_check(entity->last_scheduled, true));
337 	RCU_INIT_POINTER(entity->last_scheduled, NULL);
338 }
339 EXPORT_SYMBOL(drm_sched_entity_fini);
340 
341 /**
342  * drm_sched_entity_destroy - Destroy a context entity
343  * @entity: scheduler entity
344  *
345  * Calls drm_sched_entity_flush() and drm_sched_entity_fini() as a
346  * convenience wrapper.
347  */
348 void drm_sched_entity_destroy(struct drm_sched_entity *entity)
349 {
350 	drm_sched_entity_flush(entity, MAX_WAIT_SCHED_ENTITY_Q_EMPTY);
351 	drm_sched_entity_fini(entity);
352 }
353 EXPORT_SYMBOL(drm_sched_entity_destroy);
354 
355 /* drm_sched_entity_clear_dep - callback to clear the entities dependency */
356 static void drm_sched_entity_clear_dep(struct dma_fence *f,
357 				       struct dma_fence_cb *cb)
358 {
359 	struct drm_sched_entity *entity =
360 		container_of(cb, struct drm_sched_entity, cb);
361 
362 	entity->dependency = NULL;
363 	dma_fence_put(f);
364 }
365 
366 /*
367  * drm_sched_entity_clear_dep - callback to clear the entities dependency and
368  * wake up scheduler
369  */
370 static void drm_sched_entity_wakeup(struct dma_fence *f,
371 				    struct dma_fence_cb *cb)
372 {
373 	struct drm_sched_entity *entity =
374 		container_of(cb, struct drm_sched_entity, cb);
375 
376 	drm_sched_entity_clear_dep(f, cb);
377 	drm_sched_wakeup(entity->rq->sched, entity);
378 }
379 
380 /**
381  * drm_sched_entity_set_priority - Sets priority of the entity
382  *
383  * @entity: scheduler entity
384  * @priority: scheduler priority
385  *
386  * Update the priority of runqueus used for the entity.
387  */
388 void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
389 				   enum drm_sched_priority priority)
390 {
391 	spin_lock(&entity->rq_lock);
392 	entity->priority = priority;
393 	spin_unlock(&entity->rq_lock);
394 }
395 EXPORT_SYMBOL(drm_sched_entity_set_priority);
396 
397 /*
398  * Add a callback to the current dependency of the entity to wake up the
399  * scheduler when the entity becomes available.
400  */
401 static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity)
402 {
403 	struct drm_gpu_scheduler *sched = entity->rq->sched;
404 	struct dma_fence *fence = entity->dependency;
405 	struct drm_sched_fence *s_fence;
406 
407 	if (fence->context == entity->fence_context ||
408 	    fence->context == entity->fence_context + 1) {
409 		/*
410 		 * Fence is a scheduled/finished fence from a job
411 		 * which belongs to the same entity, we can ignore
412 		 * fences from ourself
413 		 */
414 		dma_fence_put(entity->dependency);
415 		return false;
416 	}
417 
418 	s_fence = to_drm_sched_fence(fence);
419 	if (!fence->error && s_fence && s_fence->sched == sched &&
420 	    !test_bit(DRM_SCHED_FENCE_DONT_PIPELINE, &fence->flags)) {
421 
422 		/*
423 		 * Fence is from the same scheduler, only need to wait for
424 		 * it to be scheduled
425 		 */
426 		fence = dma_fence_get(&s_fence->scheduled);
427 		dma_fence_put(entity->dependency);
428 		entity->dependency = fence;
429 		if (!dma_fence_add_callback(fence, &entity->cb,
430 					    drm_sched_entity_clear_dep))
431 			return true;
432 
433 		/* Ignore it when it is already scheduled */
434 		dma_fence_put(fence);
435 		return false;
436 	}
437 
438 	if (!dma_fence_add_callback(entity->dependency, &entity->cb,
439 				    drm_sched_entity_wakeup))
440 		return true;
441 
442 	dma_fence_put(entity->dependency);
443 	return false;
444 }
445 
446 static struct dma_fence *
447 drm_sched_job_dependency(struct drm_sched_job *job,
448 			 struct drm_sched_entity *entity)
449 {
450 	struct dma_fence *f;
451 
452 	/* We keep the fence around, so we can iterate over all dependencies
453 	 * in drm_sched_entity_kill_jobs_cb() to ensure all deps are signaled
454 	 * before killing the job.
455 	 */
456 	f = xa_load(&job->dependencies, job->last_dependency);
457 	if (f) {
458 		job->last_dependency++;
459 		return dma_fence_get(f);
460 	}
461 
462 	if (job->sched->ops->prepare_job)
463 		return job->sched->ops->prepare_job(job, entity);
464 
465 	return NULL;
466 }
467 
468 struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
469 {
470 	struct drm_sched_job *sched_job;
471 
472 	sched_job = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
473 	if (!sched_job)
474 		return NULL;
475 
476 	while ((entity->dependency =
477 			drm_sched_job_dependency(sched_job, entity))) {
478 		trace_drm_sched_job_wait_dep(sched_job, entity->dependency);
479 
480 		if (drm_sched_entity_add_dependency_cb(entity))
481 			return NULL;
482 	}
483 
484 	/* skip jobs from entity that marked guilty */
485 	if (entity->guilty && atomic_read(entity->guilty))
486 		dma_fence_set_error(&sched_job->s_fence->finished, -ECANCELED);
487 
488 	dma_fence_put(rcu_dereference_check(entity->last_scheduled, true));
489 	rcu_assign_pointer(entity->last_scheduled,
490 			   dma_fence_get(&sched_job->s_fence->finished));
491 
492 	/*
493 	 * If the queue is empty we allow drm_sched_entity_select_rq() to
494 	 * locklessly access ->last_scheduled. This only works if we set the
495 	 * pointer before we dequeue and if we a write barrier here.
496 	 */
497 	smp_wmb();
498 
499 	spsc_queue_pop(&entity->job_queue);
500 
501 	/*
502 	 * Update the entity's location in the min heap according to
503 	 * the timestamp of the next job, if any.
504 	 */
505 	if (drm_sched_policy == DRM_SCHED_POLICY_FIFO) {
506 		struct drm_sched_job *next;
507 
508 		next = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
509 		if (next)
510 			drm_sched_rq_update_fifo(entity, next->submit_ts);
511 	}
512 
513 	/* Jobs and entities might have different lifecycles. Since we're
514 	 * removing the job from the entities queue, set the jobs entity pointer
515 	 * to NULL to prevent any future access of the entity through this job.
516 	 */
517 	sched_job->entity = NULL;
518 
519 	return sched_job;
520 }
521 
522 void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
523 {
524 	struct dma_fence *fence;
525 	struct drm_gpu_scheduler *sched;
526 	struct drm_sched_rq *rq;
527 
528 	/* single possible engine and already selected */
529 	if (!entity->sched_list)
530 		return;
531 
532 	/* queue non-empty, stay on the same engine */
533 	if (spsc_queue_count(&entity->job_queue))
534 		return;
535 
536 	/*
537 	 * Only when the queue is empty are we guaranteed that the scheduler
538 	 * thread cannot change ->last_scheduled. To enforce ordering we need
539 	 * a read barrier here. See drm_sched_entity_pop_job() for the other
540 	 * side.
541 	 */
542 	smp_rmb();
543 
544 	fence = rcu_dereference_check(entity->last_scheduled, true);
545 
546 	/* stay on the same engine if the previous job hasn't finished */
547 	if (fence && !dma_fence_is_signaled(fence))
548 		return;
549 
550 	spin_lock(&entity->rq_lock);
551 	sched = drm_sched_pick_best(entity->sched_list, entity->num_sched_list);
552 	rq = sched ? sched->sched_rq[entity->priority] : NULL;
553 	if (rq != entity->rq) {
554 		drm_sched_rq_remove_entity(entity->rq, entity);
555 		entity->rq = rq;
556 	}
557 	spin_unlock(&entity->rq_lock);
558 
559 	if (entity->num_sched_list == 1)
560 		entity->sched_list = NULL;
561 }
562 
563 /**
564  * drm_sched_entity_push_job - Submit a job to the entity's job queue
565  * @sched_job: job to submit
566  *
567  * Note: To guarantee that the order of insertion to queue matches the job's
568  * fence sequence number this function should be called with drm_sched_job_arm()
569  * under common lock for the struct drm_sched_entity that was set up for
570  * @sched_job in drm_sched_job_init().
571  *
572  * Returns 0 for success, negative error code otherwise.
573  */
574 void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
575 {
576 	struct drm_sched_entity *entity = sched_job->entity;
577 	bool first;
578 	ktime_t submit_ts;
579 
580 	trace_drm_sched_job(sched_job, entity);
581 	atomic_inc(entity->rq->sched->score);
582 	WRITE_ONCE(entity->last_user, current->group_leader);
583 
584 	/*
585 	 * After the sched_job is pushed into the entity queue, it may be
586 	 * completed and freed up at any time. We can no longer access it.
587 	 * Make sure to set the submit_ts first, to avoid a race.
588 	 */
589 	sched_job->submit_ts = submit_ts = ktime_get();
590 	first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node);
591 
592 	/* first job wakes up scheduler */
593 	if (first) {
594 		/* Add the entity to the run queue */
595 		spin_lock(&entity->rq_lock);
596 		if (entity->stopped) {
597 			spin_unlock(&entity->rq_lock);
598 
599 			DRM_ERROR("Trying to push to a killed entity\n");
600 			return;
601 		}
602 
603 		drm_sched_rq_add_entity(entity->rq, entity);
604 		spin_unlock(&entity->rq_lock);
605 
606 		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
607 			drm_sched_rq_update_fifo(entity, submit_ts);
608 
609 		drm_sched_wakeup(entity->rq->sched, entity);
610 	}
611 }
612 EXPORT_SYMBOL(drm_sched_entity_push_job);
613