1 /* 2 * SPDX-License-Identifier: MIT 3 * 4 * Copyright © 2018 Intel Corporation 5 */ 6 7 #include <linux/mutex.h> 8 9 #include "i915_drv.h" 10 #include "i915_globals.h" 11 #include "i915_request.h" 12 #include "i915_scheduler.h" 13 14 static struct i915_global_scheduler { 15 struct i915_global base; 16 struct kmem_cache *slab_dependencies; 17 struct kmem_cache *slab_priorities; 18 } global; 19 20 static DEFINE_SPINLOCK(schedule_lock); 21 22 static const struct i915_request * 23 node_to_request(const struct i915_sched_node *node) 24 { 25 return container_of(node, const struct i915_request, sched); 26 } 27 28 static inline bool node_started(const struct i915_sched_node *node) 29 { 30 return i915_request_started(node_to_request(node)); 31 } 32 33 static inline bool node_signaled(const struct i915_sched_node *node) 34 { 35 return i915_request_completed(node_to_request(node)); 36 } 37 38 void i915_sched_node_init(struct i915_sched_node *node) 39 { 40 INIT_LIST_HEAD(&node->signalers_list); 41 INIT_LIST_HEAD(&node->waiters_list); 42 INIT_LIST_HEAD(&node->link); 43 node->attr.priority = I915_PRIORITY_INVALID; 44 node->semaphores = 0; 45 node->flags = 0; 46 } 47 48 static struct i915_dependency * 49 i915_dependency_alloc(void) 50 { 51 return kmem_cache_alloc(global.slab_dependencies, GFP_KERNEL); 52 } 53 54 static void 55 i915_dependency_free(struct i915_dependency *dep) 56 { 57 kmem_cache_free(global.slab_dependencies, dep); 58 } 59 60 bool __i915_sched_node_add_dependency(struct i915_sched_node *node, 61 struct i915_sched_node *signal, 62 struct i915_dependency *dep, 63 unsigned long flags) 64 { 65 bool ret = false; 66 67 spin_lock_irq(&schedule_lock); 68 69 if (!node_signaled(signal)) { 70 INIT_LIST_HEAD(&dep->dfs_link); 71 list_add(&dep->wait_link, &signal->waiters_list); 72 list_add(&dep->signal_link, &node->signalers_list); 73 dep->signaler = signal; 74 dep->flags = flags; 75 76 /* Keep track of whether anyone on this chain has a semaphore */ 77 if (signal->flags & I915_SCHED_HAS_SEMAPHORE_CHAIN && 78 !node_started(signal)) 79 node->flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN; 80 81 ret = true; 82 } 83 84 spin_unlock_irq(&schedule_lock); 85 86 return ret; 87 } 88 89 int i915_sched_node_add_dependency(struct i915_sched_node *node, 90 struct i915_sched_node *signal) 91 { 92 struct i915_dependency *dep; 93 94 dep = i915_dependency_alloc(); 95 if (!dep) 96 return -ENOMEM; 97 98 if (!__i915_sched_node_add_dependency(node, signal, dep, 99 I915_DEPENDENCY_ALLOC)) 100 i915_dependency_free(dep); 101 102 return 0; 103 } 104 105 void i915_sched_node_fini(struct i915_sched_node *node) 106 { 107 struct i915_dependency *dep, *tmp; 108 109 GEM_BUG_ON(!list_empty(&node->link)); 110 111 spin_lock_irq(&schedule_lock); 112 113 /* 114 * Everyone we depended upon (the fences we wait to be signaled) 115 * should retire before us and remove themselves from our list. 116 * However, retirement is run independently on each timeline and 117 * so we may be called out-of-order. 118 */ 119 list_for_each_entry_safe(dep, tmp, &node->signalers_list, signal_link) { 120 GEM_BUG_ON(!node_signaled(dep->signaler)); 121 GEM_BUG_ON(!list_empty(&dep->dfs_link)); 122 123 list_del(&dep->wait_link); 124 if (dep->flags & I915_DEPENDENCY_ALLOC) 125 i915_dependency_free(dep); 126 } 127 128 /* Remove ourselves from everyone who depends upon us */ 129 list_for_each_entry_safe(dep, tmp, &node->waiters_list, wait_link) { 130 GEM_BUG_ON(dep->signaler != node); 131 GEM_BUG_ON(!list_empty(&dep->dfs_link)); 132 133 list_del(&dep->signal_link); 134 if (dep->flags & I915_DEPENDENCY_ALLOC) 135 i915_dependency_free(dep); 136 } 137 138 spin_unlock_irq(&schedule_lock); 139 } 140 141 static inline struct i915_priolist *to_priolist(struct rb_node *rb) 142 { 143 return rb_entry(rb, struct i915_priolist, node); 144 } 145 146 static void assert_priolists(struct intel_engine_execlists * const execlists) 147 { 148 struct rb_node *rb; 149 long last_prio, i; 150 151 if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)) 152 return; 153 154 GEM_BUG_ON(rb_first_cached(&execlists->queue) != 155 rb_first(&execlists->queue.rb_root)); 156 157 last_prio = (INT_MAX >> I915_USER_PRIORITY_SHIFT) + 1; 158 for (rb = rb_first_cached(&execlists->queue); rb; rb = rb_next(rb)) { 159 const struct i915_priolist *p = to_priolist(rb); 160 161 GEM_BUG_ON(p->priority >= last_prio); 162 last_prio = p->priority; 163 164 GEM_BUG_ON(!p->used); 165 for (i = 0; i < ARRAY_SIZE(p->requests); i++) { 166 if (list_empty(&p->requests[i])) 167 continue; 168 169 GEM_BUG_ON(!(p->used & BIT(i))); 170 } 171 } 172 } 173 174 struct list_head * 175 i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio) 176 { 177 struct intel_engine_execlists * const execlists = &engine->execlists; 178 struct i915_priolist *p; 179 struct rb_node **parent, *rb; 180 bool first = true; 181 int idx, i; 182 183 lockdep_assert_held(&engine->timeline.lock); 184 assert_priolists(execlists); 185 186 /* buckets sorted from highest [in slot 0] to lowest priority */ 187 idx = I915_PRIORITY_COUNT - (prio & I915_PRIORITY_MASK) - 1; 188 prio >>= I915_USER_PRIORITY_SHIFT; 189 if (unlikely(execlists->no_priolist)) 190 prio = I915_PRIORITY_NORMAL; 191 192 find_priolist: 193 /* most positive priority is scheduled first, equal priorities fifo */ 194 rb = NULL; 195 parent = &execlists->queue.rb_root.rb_node; 196 while (*parent) { 197 rb = *parent; 198 p = to_priolist(rb); 199 if (prio > p->priority) { 200 parent = &rb->rb_left; 201 } else if (prio < p->priority) { 202 parent = &rb->rb_right; 203 first = false; 204 } else { 205 goto out; 206 } 207 } 208 209 if (prio == I915_PRIORITY_NORMAL) { 210 p = &execlists->default_priolist; 211 } else { 212 p = kmem_cache_alloc(global.slab_priorities, GFP_ATOMIC); 213 /* Convert an allocation failure to a priority bump */ 214 if (unlikely(!p)) { 215 prio = I915_PRIORITY_NORMAL; /* recurses just once */ 216 217 /* To maintain ordering with all rendering, after an 218 * allocation failure we have to disable all scheduling. 219 * Requests will then be executed in fifo, and schedule 220 * will ensure that dependencies are emitted in fifo. 221 * There will be still some reordering with existing 222 * requests, so if userspace lied about their 223 * dependencies that reordering may be visible. 224 */ 225 execlists->no_priolist = true; 226 goto find_priolist; 227 } 228 } 229 230 p->priority = prio; 231 for (i = 0; i < ARRAY_SIZE(p->requests); i++) 232 INIT_LIST_HEAD(&p->requests[i]); 233 rb_link_node(&p->node, rb, parent); 234 rb_insert_color_cached(&p->node, &execlists->queue, first); 235 p->used = 0; 236 237 out: 238 p->used |= BIT(idx); 239 return &p->requests[idx]; 240 } 241 242 struct sched_cache { 243 struct list_head *priolist; 244 }; 245 246 static struct intel_engine_cs * 247 sched_lock_engine(const struct i915_sched_node *node, 248 struct intel_engine_cs *locked, 249 struct sched_cache *cache) 250 { 251 struct intel_engine_cs *engine = node_to_request(node)->engine; 252 253 GEM_BUG_ON(!locked); 254 255 if (engine != locked) { 256 spin_unlock(&locked->timeline.lock); 257 memset(cache, 0, sizeof(*cache)); 258 spin_lock(&engine->timeline.lock); 259 } 260 261 return engine; 262 } 263 264 static bool inflight(const struct i915_request *rq, 265 const struct intel_engine_cs *engine) 266 { 267 const struct i915_request *active; 268 269 if (!i915_request_is_active(rq)) 270 return false; 271 272 active = port_request(engine->execlists.port); 273 return active->hw_context == rq->hw_context; 274 } 275 276 static void __i915_schedule(struct i915_request *rq, 277 const struct i915_sched_attr *attr) 278 { 279 struct intel_engine_cs *engine; 280 struct i915_dependency *dep, *p; 281 struct i915_dependency stack; 282 const int prio = attr->priority; 283 struct sched_cache cache; 284 LIST_HEAD(dfs); 285 286 /* Needed in order to use the temporary link inside i915_dependency */ 287 lockdep_assert_held(&schedule_lock); 288 GEM_BUG_ON(prio == I915_PRIORITY_INVALID); 289 290 if (i915_request_completed(rq)) 291 return; 292 293 if (prio <= READ_ONCE(rq->sched.attr.priority)) 294 return; 295 296 stack.signaler = &rq->sched; 297 list_add(&stack.dfs_link, &dfs); 298 299 /* 300 * Recursively bump all dependent priorities to match the new request. 301 * 302 * A naive approach would be to use recursion: 303 * static void update_priorities(struct i915_sched_node *node, prio) { 304 * list_for_each_entry(dep, &node->signalers_list, signal_link) 305 * update_priorities(dep->signal, prio) 306 * queue_request(node); 307 * } 308 * but that may have unlimited recursion depth and so runs a very 309 * real risk of overunning the kernel stack. Instead, we build 310 * a flat list of all dependencies starting with the current request. 311 * As we walk the list of dependencies, we add all of its dependencies 312 * to the end of the list (this may include an already visited 313 * request) and continue to walk onwards onto the new dependencies. The 314 * end result is a topological list of requests in reverse order, the 315 * last element in the list is the request we must execute first. 316 */ 317 list_for_each_entry(dep, &dfs, dfs_link) { 318 struct i915_sched_node *node = dep->signaler; 319 320 /* If we are already flying, we know we have no signalers */ 321 if (node_started(node)) 322 continue; 323 324 /* 325 * Within an engine, there can be no cycle, but we may 326 * refer to the same dependency chain multiple times 327 * (redundant dependencies are not eliminated) and across 328 * engines. 329 */ 330 list_for_each_entry(p, &node->signalers_list, signal_link) { 331 GEM_BUG_ON(p == dep); /* no cycles! */ 332 333 if (node_signaled(p->signaler)) 334 continue; 335 336 if (prio > READ_ONCE(p->signaler->attr.priority)) 337 list_move_tail(&p->dfs_link, &dfs); 338 } 339 } 340 341 /* 342 * If we didn't need to bump any existing priorities, and we haven't 343 * yet submitted this request (i.e. there is no potential race with 344 * execlists_submit_request()), we can set our own priority and skip 345 * acquiring the engine locks. 346 */ 347 if (rq->sched.attr.priority == I915_PRIORITY_INVALID) { 348 GEM_BUG_ON(!list_empty(&rq->sched.link)); 349 rq->sched.attr = *attr; 350 351 if (stack.dfs_link.next == stack.dfs_link.prev) 352 return; 353 354 __list_del_entry(&stack.dfs_link); 355 } 356 357 memset(&cache, 0, sizeof(cache)); 358 engine = rq->engine; 359 spin_lock(&engine->timeline.lock); 360 361 /* Fifo and depth-first replacement ensure our deps execute before us */ 362 list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) { 363 struct i915_sched_node *node = dep->signaler; 364 365 INIT_LIST_HEAD(&dep->dfs_link); 366 367 engine = sched_lock_engine(node, engine, &cache); 368 lockdep_assert_held(&engine->timeline.lock); 369 370 /* Recheck after acquiring the engine->timeline.lock */ 371 if (prio <= node->attr.priority || node_signaled(node)) 372 continue; 373 374 node->attr.priority = prio; 375 if (!list_empty(&node->link)) { 376 if (!cache.priolist) 377 cache.priolist = 378 i915_sched_lookup_priolist(engine, 379 prio); 380 list_move_tail(&node->link, cache.priolist); 381 } else { 382 /* 383 * If the request is not in the priolist queue because 384 * it is not yet runnable, then it doesn't contribute 385 * to our preemption decisions. On the other hand, 386 * if the request is on the HW, it too is not in the 387 * queue; but in that case we may still need to reorder 388 * the inflight requests. 389 */ 390 if (!i915_sw_fence_done(&node_to_request(node)->submit)) 391 continue; 392 } 393 394 if (prio <= engine->execlists.queue_priority_hint) 395 continue; 396 397 engine->execlists.queue_priority_hint = prio; 398 399 /* 400 * If we are already the currently executing context, don't 401 * bother evaluating if we should preempt ourselves. 402 */ 403 if (inflight(node_to_request(node), engine)) 404 continue; 405 406 /* Defer (tasklet) submission until after all of our updates. */ 407 tasklet_hi_schedule(&engine->execlists.tasklet); 408 } 409 410 spin_unlock(&engine->timeline.lock); 411 } 412 413 void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr) 414 { 415 spin_lock_irq(&schedule_lock); 416 __i915_schedule(rq, attr); 417 spin_unlock_irq(&schedule_lock); 418 } 419 420 void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump) 421 { 422 struct i915_sched_attr attr; 423 unsigned long flags; 424 425 GEM_BUG_ON(bump & ~I915_PRIORITY_MASK); 426 427 if (READ_ONCE(rq->sched.attr.priority) == I915_PRIORITY_INVALID) 428 return; 429 430 spin_lock_irqsave(&schedule_lock, flags); 431 432 attr = rq->sched.attr; 433 attr.priority |= bump; 434 __i915_schedule(rq, &attr); 435 436 spin_unlock_irqrestore(&schedule_lock, flags); 437 } 438 439 void __i915_priolist_free(struct i915_priolist *p) 440 { 441 kmem_cache_free(global.slab_priorities, p); 442 } 443 444 static void i915_global_scheduler_shrink(void) 445 { 446 kmem_cache_shrink(global.slab_dependencies); 447 kmem_cache_shrink(global.slab_priorities); 448 } 449 450 static void i915_global_scheduler_exit(void) 451 { 452 kmem_cache_destroy(global.slab_dependencies); 453 kmem_cache_destroy(global.slab_priorities); 454 } 455 456 static struct i915_global_scheduler global = { { 457 .shrink = i915_global_scheduler_shrink, 458 .exit = i915_global_scheduler_exit, 459 } }; 460 461 int __init i915_global_scheduler_init(void) 462 { 463 global.slab_dependencies = KMEM_CACHE(i915_dependency, 464 SLAB_HWCACHE_ALIGN); 465 if (!global.slab_dependencies) 466 return -ENOMEM; 467 468 global.slab_priorities = KMEM_CACHE(i915_priolist, 469 SLAB_HWCACHE_ALIGN); 470 if (!global.slab_priorities) 471 goto err_priorities; 472 473 i915_global_register(&global.base); 474 return 0; 475 476 err_priorities: 477 kmem_cache_destroy(global.slab_priorities); 478 return -ENOMEM; 479 } 480