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1/*2 * SPDX-License-Identifier: MIT3 *4 * Copyright © 2018 Intel Corporation5 */6 7#include <linux/mutex.h>8 9#include "i915_drv.h"10#include "i915_request.h"11#include "i915_scheduler.h"12 13static struct kmem_cache *slab_dependencies;14static struct kmem_cache *slab_priorities;15 16static DEFINE_SPINLOCK(schedule_lock);17 18static const struct i915_request *19node_to_request(const struct i915_sched_node *node)20{21 return container_of(node, const struct i915_request, sched);22}23 24static inline bool node_started(const struct i915_sched_node *node)25{26 return i915_request_started(node_to_request(node));27}28 29static inline bool node_signaled(const struct i915_sched_node *node)30{31 return i915_request_completed(node_to_request(node));32}33 34static inline struct i915_priolist *to_priolist(struct rb_node *rb)35{36 return rb_entry(rb, struct i915_priolist, node);37}38 39static void assert_priolists(struct i915_sched_engine * const sched_engine)40{41 struct rb_node *rb;42 long last_prio;43 44 if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))45 return;46 47 GEM_BUG_ON(rb_first_cached(&sched_engine->queue) !=48 rb_first(&sched_engine->queue.rb_root));49 50 last_prio = INT_MAX;51 for (rb = rb_first_cached(&sched_engine->queue); rb; rb = rb_next(rb)) {52 const struct i915_priolist *p = to_priolist(rb);53 54 GEM_BUG_ON(p->priority > last_prio);55 last_prio = p->priority;56 }57}58 59struct list_head *60i915_sched_lookup_priolist(struct i915_sched_engine *sched_engine, int prio)61{62 struct i915_priolist *p;63 struct rb_node **parent, *rb;64 bool first = true;65 66 lockdep_assert_held(&sched_engine->lock);67 assert_priolists(sched_engine);68 69 if (unlikely(sched_engine->no_priolist))70 prio = I915_PRIORITY_NORMAL;71 72find_priolist:73 /* most positive priority is scheduled first, equal priorities fifo */74 rb = NULL;75 parent = &sched_engine->queue.rb_root.rb_node;76 while (*parent) {77 rb = *parent;78 p = to_priolist(rb);79 if (prio > p->priority) {80 parent = &rb->rb_left;81 } else if (prio < p->priority) {82 parent = &rb->rb_right;83 first = false;84 } else {85 return &p->requests;86 }87 }88 89 if (prio == I915_PRIORITY_NORMAL) {90 p = &sched_engine->default_priolist;91 } else {92 p = kmem_cache_alloc(slab_priorities, GFP_ATOMIC);93 /* Convert an allocation failure to a priority bump */94 if (unlikely(!p)) {95 prio = I915_PRIORITY_NORMAL; /* recurses just once */96 97 /* To maintain ordering with all rendering, after an98 * allocation failure we have to disable all scheduling.99 * Requests will then be executed in fifo, and schedule100 * will ensure that dependencies are emitted in fifo.101 * There will be still some reordering with existing102 * requests, so if userspace lied about their103 * dependencies that reordering may be visible.104 */105 sched_engine->no_priolist = true;106 goto find_priolist;107 }108 }109 110 p->priority = prio;111 INIT_LIST_HEAD(&p->requests);112 113 rb_link_node(&p->node, rb, parent);114 rb_insert_color_cached(&p->node, &sched_engine->queue, first);115 116 return &p->requests;117}118 119void __i915_priolist_free(struct i915_priolist *p)120{121 kmem_cache_free(slab_priorities, p);122}123 124struct sched_cache {125 struct list_head *priolist;126};127 128static struct i915_sched_engine *129lock_sched_engine(struct i915_sched_node *node,130 struct i915_sched_engine *locked,131 struct sched_cache *cache)132{133 const struct i915_request *rq = node_to_request(node);134 struct i915_sched_engine *sched_engine;135 136 GEM_BUG_ON(!locked);137 138 /*139 * Virtual engines complicate acquiring the engine timeline lock,140 * as their rq->engine pointer is not stable until under that141 * engine lock. The simple ploy we use is to take the lock then142 * check that the rq still belongs to the newly locked engine.143 */144 while (locked != (sched_engine = READ_ONCE(rq->engine)->sched_engine)) {145 spin_unlock(&locked->lock);146 memset(cache, 0, sizeof(*cache));147 spin_lock(&sched_engine->lock);148 locked = sched_engine;149 }150 151 GEM_BUG_ON(locked != sched_engine);152 return locked;153}154 155static void __i915_schedule(struct i915_sched_node *node,156 const struct i915_sched_attr *attr)157{158 const int prio = max(attr->priority, node->attr.priority);159 struct i915_sched_engine *sched_engine;160 struct i915_dependency *dep, *p;161 struct i915_dependency stack;162 struct sched_cache cache;163 LIST_HEAD(dfs);164 165 /* Needed in order to use the temporary link inside i915_dependency */166 lockdep_assert_held(&schedule_lock);167 GEM_BUG_ON(prio == I915_PRIORITY_INVALID);168 169 if (node_signaled(node))170 return;171 172 stack.signaler = node;173 list_add(&stack.dfs_link, &dfs);174 175 /*176 * Recursively bump all dependent priorities to match the new request.177 *178 * A naive approach would be to use recursion:179 * static void update_priorities(struct i915_sched_node *node, prio) {180 * list_for_each_entry(dep, &node->signalers_list, signal_link)181 * update_priorities(dep->signal, prio)182 * queue_request(node);183 * }184 * but that may have unlimited recursion depth and so runs a very185 * real risk of overunning the kernel stack. Instead, we build186 * a flat list of all dependencies starting with the current request.187 * As we walk the list of dependencies, we add all of its dependencies188 * to the end of the list (this may include an already visited189 * request) and continue to walk onwards onto the new dependencies. The190 * end result is a topological list of requests in reverse order, the191 * last element in the list is the request we must execute first.192 */193 list_for_each_entry(dep, &dfs, dfs_link) {194 struct i915_sched_node *node = dep->signaler;195 196 /* If we are already flying, we know we have no signalers */197 if (node_started(node))198 continue;199 200 /*201 * Within an engine, there can be no cycle, but we may202 * refer to the same dependency chain multiple times203 * (redundant dependencies are not eliminated) and across204 * engines.205 */206 list_for_each_entry(p, &node->signalers_list, signal_link) {207 GEM_BUG_ON(p == dep); /* no cycles! */208 209 if (node_signaled(p->signaler))210 continue;211 212 if (prio > READ_ONCE(p->signaler->attr.priority))213 list_move_tail(&p->dfs_link, &dfs);214 }215 }216 217 /*218 * If we didn't need to bump any existing priorities, and we haven't219 * yet submitted this request (i.e. there is no potential race with220 * execlists_submit_request()), we can set our own priority and skip221 * acquiring the engine locks.222 */223 if (node->attr.priority == I915_PRIORITY_INVALID) {224 GEM_BUG_ON(!list_empty(&node->link));225 node->attr = *attr;226 227 if (stack.dfs_link.next == stack.dfs_link.prev)228 return;229 230 __list_del_entry(&stack.dfs_link);231 }232 233 memset(&cache, 0, sizeof(cache));234 sched_engine = node_to_request(node)->engine->sched_engine;235 spin_lock(&sched_engine->lock);236 237 /* Fifo and depth-first replacement ensure our deps execute before us */238 sched_engine = lock_sched_engine(node, sched_engine, &cache);239 list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) {240 struct i915_request *from = container_of(dep->signaler,241 struct i915_request,242 sched);243 INIT_LIST_HEAD(&dep->dfs_link);244 245 node = dep->signaler;246 sched_engine = lock_sched_engine(node, sched_engine, &cache);247 lockdep_assert_held(&sched_engine->lock);248 249 /* Recheck after acquiring the engine->timeline.lock */250 if (prio <= node->attr.priority || node_signaled(node))251 continue;252 253 GEM_BUG_ON(node_to_request(node)->engine->sched_engine !=254 sched_engine);255 256 /* Must be called before changing the nodes priority */257 if (sched_engine->bump_inflight_request_prio)258 sched_engine->bump_inflight_request_prio(from, prio);259 260 WRITE_ONCE(node->attr.priority, prio);261 262 /*263 * Once the request is ready, it will be placed into the264 * priority lists and then onto the HW runlist. Before the265 * request is ready, it does not contribute to our preemption266 * decisions and we can safely ignore it, as it will, and267 * any preemption required, be dealt with upon submission.268 * See engine->submit_request()269 */270 if (list_empty(&node->link))271 continue;272 273 if (i915_request_in_priority_queue(node_to_request(node))) {274 if (!cache.priolist)275 cache.priolist =276 i915_sched_lookup_priolist(sched_engine,277 prio);278 list_move_tail(&node->link, cache.priolist);279 }280 281 /* Defer (tasklet) submission until after all of our updates. */282 if (sched_engine->kick_backend)283 sched_engine->kick_backend(node_to_request(node), prio);284 }285 286 spin_unlock(&sched_engine->lock);287}288 289void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)290{291 spin_lock_irq(&schedule_lock);292 __i915_schedule(&rq->sched, attr);293 spin_unlock_irq(&schedule_lock);294}295 296void i915_sched_node_init(struct i915_sched_node *node)297{298 INIT_LIST_HEAD(&node->signalers_list);299 INIT_LIST_HEAD(&node->waiters_list);300 INIT_LIST_HEAD(&node->link);301 302 i915_sched_node_reinit(node);303}304 305void i915_sched_node_reinit(struct i915_sched_node *node)306{307 node->attr.priority = I915_PRIORITY_INVALID;308 node->semaphores = 0;309 node->flags = 0;310 311 GEM_BUG_ON(!list_empty(&node->signalers_list));312 GEM_BUG_ON(!list_empty(&node->waiters_list));313 GEM_BUG_ON(!list_empty(&node->link));314}315 316static struct i915_dependency *317i915_dependency_alloc(void)318{319 return kmem_cache_alloc(slab_dependencies, GFP_KERNEL);320}321 322static void323i915_dependency_free(struct i915_dependency *dep)324{325 kmem_cache_free(slab_dependencies, dep);326}327 328bool __i915_sched_node_add_dependency(struct i915_sched_node *node,329 struct i915_sched_node *signal,330 struct i915_dependency *dep,331 unsigned long flags)332{333 bool ret = false;334 335 spin_lock_irq(&schedule_lock);336 337 if (!node_signaled(signal)) {338 INIT_LIST_HEAD(&dep->dfs_link);339 dep->signaler = signal;340 dep->waiter = node;341 dep->flags = flags;342 343 /* All set, now publish. Beware the lockless walkers. */344 list_add_rcu(&dep->signal_link, &node->signalers_list);345 list_add_rcu(&dep->wait_link, &signal->waiters_list);346 347 /* Propagate the chains */348 node->flags |= signal->flags;349 ret = true;350 }351 352 spin_unlock_irq(&schedule_lock);353 354 return ret;355}356 357int i915_sched_node_add_dependency(struct i915_sched_node *node,358 struct i915_sched_node *signal,359 unsigned long flags)360{361 struct i915_dependency *dep;362 363 dep = i915_dependency_alloc();364 if (!dep)365 return -ENOMEM;366 367 if (!__i915_sched_node_add_dependency(node, signal, dep,368 flags | I915_DEPENDENCY_ALLOC))369 i915_dependency_free(dep);370 371 return 0;372}373 374void i915_sched_node_fini(struct i915_sched_node *node)375{376 struct i915_dependency *dep, *tmp;377 378 spin_lock_irq(&schedule_lock);379 380 /*381 * Everyone we depended upon (the fences we wait to be signaled)382 * should retire before us and remove themselves from our list.383 * However, retirement is run independently on each timeline and384 * so we may be called out-of-order.385 */386 list_for_each_entry_safe(dep, tmp, &node->signalers_list, signal_link) {387 GEM_BUG_ON(!list_empty(&dep->dfs_link));388 389 list_del_rcu(&dep->wait_link);390 if (dep->flags & I915_DEPENDENCY_ALLOC)391 i915_dependency_free(dep);392 }393 INIT_LIST_HEAD(&node->signalers_list);394 395 /* Remove ourselves from everyone who depends upon us */396 list_for_each_entry_safe(dep, tmp, &node->waiters_list, wait_link) {397 GEM_BUG_ON(dep->signaler != node);398 GEM_BUG_ON(!list_empty(&dep->dfs_link));399 400 list_del_rcu(&dep->signal_link);401 if (dep->flags & I915_DEPENDENCY_ALLOC)402 i915_dependency_free(dep);403 }404 INIT_LIST_HEAD(&node->waiters_list);405 406 spin_unlock_irq(&schedule_lock);407}408 409void i915_request_show_with_schedule(struct drm_printer *m,410 const struct i915_request *rq,411 const char *prefix,412 int indent)413{414 struct i915_dependency *dep;415 416 i915_request_show(m, rq, prefix, indent);417 if (i915_request_completed(rq))418 return;419 420 rcu_read_lock();421 for_each_signaler(dep, rq) {422 const struct i915_request *signaler =423 node_to_request(dep->signaler);424 425 /* Dependencies along the same timeline are expected. */426 if (signaler->timeline == rq->timeline)427 continue;428 429 if (__i915_request_is_complete(signaler))430 continue;431 432 i915_request_show(m, signaler, prefix, indent + 2);433 }434 rcu_read_unlock();435}436 437static void default_destroy(struct kref *kref)438{439 struct i915_sched_engine *sched_engine =440 container_of(kref, typeof(*sched_engine), ref);441 442 tasklet_kill(&sched_engine->tasklet); /* flush the callback */443 kfree(sched_engine);444}445 446static bool default_disabled(struct i915_sched_engine *sched_engine)447{448 return false;449}450 451struct i915_sched_engine *452i915_sched_engine_create(unsigned int subclass)453{454 struct i915_sched_engine *sched_engine;455 456 sched_engine = kzalloc(sizeof(*sched_engine), GFP_KERNEL);457 if (!sched_engine)458 return NULL;459 460 kref_init(&sched_engine->ref);461 462 sched_engine->queue = RB_ROOT_CACHED;463 sched_engine->queue_priority_hint = INT_MIN;464 sched_engine->destroy = default_destroy;465 sched_engine->disabled = default_disabled;466 467 INIT_LIST_HEAD(&sched_engine->requests);468 INIT_LIST_HEAD(&sched_engine->hold);469 470 spin_lock_init(&sched_engine->lock);471 lockdep_set_subclass(&sched_engine->lock, subclass);472 473 /*474 * Due to an interesting quirk in lockdep's internal debug tracking,475 * after setting a subclass we must ensure the lock is used. Otherwise,476 * nr_unused_locks is incremented once too often.477 */478#ifdef CONFIG_DEBUG_LOCK_ALLOC479 local_irq_disable();480 lock_map_acquire(&sched_engine->lock.dep_map);481 lock_map_release(&sched_engine->lock.dep_map);482 local_irq_enable();483#endif484 485 return sched_engine;486}487 488void i915_scheduler_module_exit(void)489{490 kmem_cache_destroy(slab_dependencies);491 kmem_cache_destroy(slab_priorities);492}493 494int __init i915_scheduler_module_init(void)495{496 slab_dependencies = KMEM_CACHE(i915_dependency,497 SLAB_HWCACHE_ALIGN |498 SLAB_TYPESAFE_BY_RCU);499 if (!slab_dependencies)500 return -ENOMEM;501 502 slab_priorities = KMEM_CACHE(i915_priolist, 0);503 if (!slab_priorities)504 goto err_priorities;505 506 return 0;507 508err_priorities:509 kmem_cache_destroy(slab_priorities);510 return -ENOMEM;511}512