2 * Copyright © 2015 Intel Corporation
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:
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
25 #include <linux/kthread.h>
29 static void intel_breadcrumbs_hangcheck(unsigned long data)
31 struct intel_engine_cs *engine = (struct intel_engine_cs *)data;
32 struct intel_breadcrumbs *b = &engine->breadcrumbs;
37 if (time_before(jiffies, b->timeout)) {
38 mod_timer(&b->hangcheck, b->timeout);
42 DRM_DEBUG("Hangcheck timer elapsed... %s idle\n", engine->name);
43 set_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
44 mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1);
46 /* Ensure that even if the GPU hangs, we get woken up.
48 * However, note that if no one is waiting, we never notice
49 * a gpu hang. Eventually, we will have to wait for a resource
50 * held by the GPU and so trigger a hangcheck. In the most
51 * pathological case, this will be upon memory starvation! To
52 * prevent this, we also queue the hangcheck from the retire
55 i915_queue_hangcheck(engine->i915);
58 static unsigned long wait_timeout(void)
60 return round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES);
63 static void intel_breadcrumbs_fake_irq(unsigned long data)
65 struct intel_engine_cs *engine = (struct intel_engine_cs *)data;
68 * The timer persists in case we cannot enable interrupts,
69 * or if we have previously seen seqno/interrupt incoherency
70 * ("missed interrupt" syndrome). Here the worker will wake up
71 * every jiffie in order to kick the oldest waiter to do the
72 * coherent seqno check.
74 if (intel_engine_wakeup(engine))
75 mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1);
78 static void irq_enable(struct intel_engine_cs *engine)
80 /* Enabling the IRQ may miss the generation of the interrupt, but
81 * we still need to force the barrier before reading the seqno,
84 engine->breadcrumbs.irq_posted = true;
86 spin_lock_irq(&engine->i915->irq_lock);
87 engine->irq_enable(engine);
88 spin_unlock_irq(&engine->i915->irq_lock);
91 static void irq_disable(struct intel_engine_cs *engine)
93 spin_lock_irq(&engine->i915->irq_lock);
94 engine->irq_disable(engine);
95 spin_unlock_irq(&engine->i915->irq_lock);
97 engine->breadcrumbs.irq_posted = false;
100 static void __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b)
102 struct intel_engine_cs *engine =
103 container_of(b, struct intel_engine_cs, breadcrumbs);
104 struct drm_i915_private *i915 = engine->i915;
106 assert_spin_locked(&b->lock);
110 /* Since we are waiting on a request, the GPU should be busy
111 * and should have its own rpm reference. For completeness,
112 * record an rpm reference for ourselves to cover the
113 * interrupt we unmask.
115 intel_runtime_pm_get_noresume(i915);
116 b->rpm_wakelock = true;
118 /* No interrupts? Kick the waiter every jiffie! */
119 if (intel_irqs_enabled(i915)) {
120 if (!test_bit(engine->id, &i915->gpu_error.test_irq_rings))
122 b->irq_enabled = true;
125 if (!b->irq_enabled ||
126 test_bit(engine->id, &i915->gpu_error.missed_irq_rings)) {
127 mod_timer(&b->fake_irq, jiffies + 1);
129 /* Ensure we never sleep indefinitely */
130 GEM_BUG_ON(!time_after(b->timeout, jiffies));
131 mod_timer(&b->hangcheck, b->timeout);
135 static void __intel_breadcrumbs_disable_irq(struct intel_breadcrumbs *b)
137 struct intel_engine_cs *engine =
138 container_of(b, struct intel_engine_cs, breadcrumbs);
140 assert_spin_locked(&b->lock);
141 if (!b->rpm_wakelock)
144 if (b->irq_enabled) {
146 b->irq_enabled = false;
149 intel_runtime_pm_put(engine->i915);
150 b->rpm_wakelock = false;
153 static inline struct intel_wait *to_wait(struct rb_node *node)
155 return container_of(node, struct intel_wait, node);
158 static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b,
159 struct intel_wait *wait)
161 assert_spin_locked(&b->lock);
163 /* This request is completed, so remove it from the tree, mark it as
164 * complete, and *then* wake up the associated task.
166 rb_erase(&wait->node, &b->waiters);
167 RB_CLEAR_NODE(&wait->node);
169 wake_up_process(wait->tsk); /* implicit smp_wmb() */
172 static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
173 struct intel_wait *wait)
175 struct intel_breadcrumbs *b = &engine->breadcrumbs;
176 struct rb_node **p, *parent, *completed;
180 /* Insert the request into the retirement ordered list
181 * of waiters by walking the rbtree. If we are the oldest
182 * seqno in the tree (the first to be retired), then
183 * set ourselves as the bottom-half.
185 * As we descend the tree, prune completed branches since we hold the
186 * spinlock we know that the first_waiter must be delayed and can
187 * reduce some of the sequential wake up latency if we take action
188 * ourselves and wake up the completed tasks in parallel. Also, by
189 * removing stale elements in the tree, we may be able to reduce the
190 * ping-pong between the old bottom-half and ourselves as first-waiter.
195 seqno = intel_engine_get_seqno(engine);
197 /* If the request completed before we managed to grab the spinlock,
198 * return now before adding ourselves to the rbtree. We let the
199 * current bottom-half handle any pending wakeups and instead
200 * try and get out of the way quickly.
202 if (i915_seqno_passed(seqno, wait->seqno)) {
203 RB_CLEAR_NODE(&wait->node);
207 p = &b->waiters.rb_node;
210 if (wait->seqno == to_wait(parent)->seqno) {
211 /* We have multiple waiters on the same seqno, select
212 * the highest priority task (that with the smallest
213 * task->prio) to serve as the bottom-half for this
216 if (wait->tsk->prio > to_wait(parent)->tsk->prio) {
217 p = &parent->rb_right;
220 p = &parent->rb_left;
222 } else if (i915_seqno_passed(wait->seqno,
223 to_wait(parent)->seqno)) {
224 p = &parent->rb_right;
225 if (i915_seqno_passed(seqno, to_wait(parent)->seqno))
230 p = &parent->rb_left;
233 rb_link_node(&wait->node, parent, p);
234 rb_insert_color(&wait->node, &b->waiters);
235 GEM_BUG_ON(!first && !rcu_access_pointer(b->irq_seqno_bh));
238 struct rb_node *next = rb_next(completed);
240 GEM_BUG_ON(!next && !first);
241 if (next && next != &wait->node) {
243 b->timeout = wait_timeout();
244 b->first_wait = to_wait(next);
245 rcu_assign_pointer(b->irq_seqno_bh, b->first_wait->tsk);
246 /* As there is a delay between reading the current
247 * seqno, processing the completed tasks and selecting
248 * the next waiter, we may have missed the interrupt
249 * and so need for the next bottom-half to wakeup.
251 * Also as we enable the IRQ, we may miss the
252 * interrupt for that seqno, so we have to wake up
253 * the next bottom-half in order to do a coherent check
254 * in case the seqno passed.
256 __intel_breadcrumbs_enable_irq(b);
257 if (READ_ONCE(b->irq_posted))
258 wake_up_process(to_wait(next)->tsk);
262 struct intel_wait *crumb = to_wait(completed);
263 completed = rb_prev(completed);
264 __intel_breadcrumbs_finish(b, crumb);
269 GEM_BUG_ON(rb_first(&b->waiters) != &wait->node);
270 b->timeout = wait_timeout();
271 b->first_wait = wait;
272 rcu_assign_pointer(b->irq_seqno_bh, wait->tsk);
273 /* After assigning ourselves as the new bottom-half, we must
274 * perform a cursory check to prevent a missed interrupt.
275 * Either we miss the interrupt whilst programming the hardware,
276 * or if there was a previous waiter (for a later seqno) they
277 * may be woken instead of us (due to the inherent race
278 * in the unlocked read of b->irq_seqno_bh in the irq handler)
279 * and so we miss the wake up.
281 __intel_breadcrumbs_enable_irq(b);
283 GEM_BUG_ON(!rcu_access_pointer(b->irq_seqno_bh));
284 GEM_BUG_ON(!b->first_wait);
285 GEM_BUG_ON(rb_first(&b->waiters) != &b->first_wait->node);
290 bool intel_engine_add_wait(struct intel_engine_cs *engine,
291 struct intel_wait *wait)
293 struct intel_breadcrumbs *b = &engine->breadcrumbs;
297 first = __intel_engine_add_wait(engine, wait);
298 spin_unlock(&b->lock);
303 static inline bool chain_wakeup(struct rb_node *rb, int priority)
305 return rb && to_wait(rb)->tsk->prio <= priority;
308 static inline int wakeup_priority(struct intel_breadcrumbs *b,
309 struct task_struct *tsk)
311 if (tsk == b->signaler)
317 void intel_engine_remove_wait(struct intel_engine_cs *engine,
318 struct intel_wait *wait)
320 struct intel_breadcrumbs *b = &engine->breadcrumbs;
322 /* Quick check to see if this waiter was already decoupled from
323 * the tree by the bottom-half to avoid contention on the spinlock
326 if (RB_EMPTY_NODE(&wait->node))
331 if (RB_EMPTY_NODE(&wait->node))
334 if (b->first_wait == wait) {
335 const int priority = wakeup_priority(b, wait->tsk);
336 struct rb_node *next;
338 GEM_BUG_ON(rcu_access_pointer(b->irq_seqno_bh) != wait->tsk);
340 /* We are the current bottom-half. Find the next candidate,
341 * the first waiter in the queue on the remaining oldest
342 * request. As multiple seqnos may complete in the time it
343 * takes us to wake up and find the next waiter, we have to
344 * wake up that waiter for it to perform its own coherent
347 next = rb_next(&wait->node);
348 if (chain_wakeup(next, priority)) {
349 /* If the next waiter is already complete,
350 * wake it up and continue onto the next waiter. So
351 * if have a small herd, they will wake up in parallel
352 * rather than sequentially, which should reduce
353 * the overall latency in waking all the completed
356 * However, waking up a chain adds extra latency to
357 * the first_waiter. This is undesirable if that
358 * waiter is a high priority task.
360 u32 seqno = intel_engine_get_seqno(engine);
362 while (i915_seqno_passed(seqno, to_wait(next)->seqno)) {
363 struct rb_node *n = rb_next(next);
365 __intel_breadcrumbs_finish(b, to_wait(next));
367 if (!chain_wakeup(next, priority))
373 /* In our haste, we may have completed the first waiter
374 * before we enabled the interrupt. Do so now as we
375 * have a second waiter for a future seqno. Afterwards,
376 * we have to wake up that waiter in case we missed
377 * the interrupt, or if we have to handle an
378 * exception rather than a seqno completion.
380 b->timeout = wait_timeout();
381 b->first_wait = to_wait(next);
382 rcu_assign_pointer(b->irq_seqno_bh, b->first_wait->tsk);
383 if (b->first_wait->seqno != wait->seqno)
384 __intel_breadcrumbs_enable_irq(b);
385 wake_up_process(b->first_wait->tsk);
387 b->first_wait = NULL;
388 rcu_assign_pointer(b->irq_seqno_bh, NULL);
389 __intel_breadcrumbs_disable_irq(b);
392 GEM_BUG_ON(rb_first(&b->waiters) == &wait->node);
395 GEM_BUG_ON(RB_EMPTY_NODE(&wait->node));
396 rb_erase(&wait->node, &b->waiters);
399 GEM_BUG_ON(b->first_wait == wait);
400 GEM_BUG_ON(rb_first(&b->waiters) !=
401 (b->first_wait ? &b->first_wait->node : NULL));
402 GEM_BUG_ON(!rcu_access_pointer(b->irq_seqno_bh) ^ RB_EMPTY_ROOT(&b->waiters));
403 spin_unlock(&b->lock);
406 static bool signal_complete(struct drm_i915_gem_request *request)
411 /* If another process served as the bottom-half it may have already
412 * signalled that this wait is already completed.
414 if (intel_wait_complete(&request->signaling.wait))
417 /* Carefully check if the request is complete, giving time for the
418 * seqno to be visible or if the GPU hung.
420 if (__i915_request_irq_complete(request))
426 static struct drm_i915_gem_request *to_signaler(struct rb_node *rb)
428 return container_of(rb, struct drm_i915_gem_request, signaling.node);
431 static void signaler_set_rtpriority(void)
433 struct sched_param param = { .sched_priority = 1 };
435 sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m);
438 static int intel_breadcrumbs_signaler(void *arg)
440 struct intel_engine_cs *engine = arg;
441 struct intel_breadcrumbs *b = &engine->breadcrumbs;
442 struct drm_i915_gem_request *request;
444 /* Install ourselves with high priority to reduce signalling latency */
445 signaler_set_rtpriority();
448 set_current_state(TASK_INTERRUPTIBLE);
450 /* We are either woken up by the interrupt bottom-half,
451 * or by a client adding a new signaller. In both cases,
452 * the GPU seqno may have advanced beyond our oldest signal.
453 * If it has, propagate the signal, remove the waiter and
454 * check again with the next oldest signal. Otherwise we
455 * need to wait for a new interrupt from the GPU or for
458 request = READ_ONCE(b->first_signal);
459 if (signal_complete(request)) {
460 /* Wake up all other completed waiters and select the
461 * next bottom-half for the next user interrupt.
463 intel_engine_remove_wait(engine,
464 &request->signaling.wait);
467 fence_signal(&request->fence);
468 local_bh_enable(); /* kick start the tasklets */
470 /* Find the next oldest signal. Note that as we have
471 * not been holding the lock, another client may
472 * have installed an even older signal than the one
473 * we just completed - so double check we are still
474 * the oldest before picking the next one.
477 if (request == b->first_signal) {
479 rb_next(&request->signaling.node);
480 b->first_signal = rb ? to_signaler(rb) : NULL;
482 rb_erase(&request->signaling.node, &b->signals);
483 spin_unlock(&b->lock);
485 i915_gem_request_put(request);
487 if (kthread_should_stop())
493 __set_current_state(TASK_RUNNING);
498 void intel_engine_enable_signaling(struct drm_i915_gem_request *request)
500 struct intel_engine_cs *engine = request->engine;
501 struct intel_breadcrumbs *b = &engine->breadcrumbs;
502 struct rb_node *parent, **p;
505 /* locked by fence_enable_sw_signaling() */
506 assert_spin_locked(&request->lock);
508 request->signaling.wait.tsk = b->signaler;
509 request->signaling.wait.seqno = request->fence.seqno;
510 i915_gem_request_get(request);
514 /* First add ourselves into the list of waiters, but register our
515 * bottom-half as the signaller thread. As per usual, only the oldest
516 * waiter (not just signaller) is tasked as the bottom-half waking
517 * up all completed waiters after the user interrupt.
519 * If we are the oldest waiter, enable the irq (after which we
520 * must double check that the seqno did not complete).
522 wakeup = __intel_engine_add_wait(engine, &request->signaling.wait);
524 /* Now insert ourselves into the retirement ordered list of signals
525 * on this engine. We track the oldest seqno as that will be the
526 * first signal to complete.
530 p = &b->signals.rb_node;
533 if (i915_seqno_passed(request->fence.seqno,
534 to_signaler(parent)->fence.seqno)) {
535 p = &parent->rb_right;
538 p = &parent->rb_left;
541 rb_link_node(&request->signaling.node, parent, p);
542 rb_insert_color(&request->signaling.node, &b->signals);
544 smp_store_mb(b->first_signal, request);
546 spin_unlock(&b->lock);
549 wake_up_process(b->signaler);
552 int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
554 struct intel_breadcrumbs *b = &engine->breadcrumbs;
555 struct task_struct *tsk;
557 spin_lock_init(&b->lock);
558 setup_timer(&b->fake_irq,
559 intel_breadcrumbs_fake_irq,
560 (unsigned long)engine);
561 setup_timer(&b->hangcheck,
562 intel_breadcrumbs_hangcheck,
563 (unsigned long)engine);
565 /* Spawn a thread to provide a common bottom-half for all signals.
566 * As this is an asynchronous interface we cannot steal the current
567 * task for handling the bottom-half to the user interrupt, therefore
568 * we create a thread to do the coherent seqno dance after the
569 * interrupt and then signal the waitqueue (via the dma-buf/fence).
571 tsk = kthread_run(intel_breadcrumbs_signaler, engine,
572 "i915/signal:%d", engine->id);
581 static void cancel_fake_irq(struct intel_engine_cs *engine)
583 struct intel_breadcrumbs *b = &engine->breadcrumbs;
585 del_timer_sync(&b->hangcheck);
586 del_timer_sync(&b->fake_irq);
587 clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
590 void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
592 struct intel_breadcrumbs *b = &engine->breadcrumbs;
594 cancel_fake_irq(engine);
597 __intel_breadcrumbs_disable_irq(b);
598 if (intel_engine_has_waiter(engine)) {
599 b->timeout = wait_timeout();
600 __intel_breadcrumbs_enable_irq(b);
601 if (READ_ONCE(b->irq_posted))
602 wake_up_process(b->first_wait->tsk);
604 /* sanitize the IMR and unmask any auxiliary interrupts */
608 spin_unlock(&b->lock);
611 void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
613 struct intel_breadcrumbs *b = &engine->breadcrumbs;
615 if (!IS_ERR_OR_NULL(b->signaler))
616 kthread_stop(b->signaler);
618 cancel_fake_irq(engine);
621 unsigned int intel_kick_waiters(struct drm_i915_private *i915)
623 struct intel_engine_cs *engine;
624 unsigned int mask = 0;
626 /* To avoid the task_struct disappearing beneath us as we wake up
627 * the process, we must first inspect the task_struct->state under the
628 * RCU lock, i.e. as we call wake_up_process() we must be holding the
631 for_each_engine(engine, i915)
632 if (unlikely(intel_engine_wakeup(engine)))
633 mask |= intel_engine_flag(engine);
638 unsigned int intel_kick_signalers(struct drm_i915_private *i915)
640 struct intel_engine_cs *engine;
641 unsigned int mask = 0;
643 for_each_engine(engine, i915) {
644 if (unlikely(READ_ONCE(engine->breadcrumbs.first_signal))) {
645 wake_up_process(engine->breadcrumbs.signaler);
646 mask |= intel_engine_flag(engine);