/* * Copyright © 2015 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. * */ #include #include "i915_drv.h" static unsigned int __intel_breadcrumbs_wakeup(struct intel_breadcrumbs *b) { struct intel_wait *wait; unsigned int result = 0; wait = b->first_wait; if (wait) { result = ENGINE_WAKEUP_WAITER; if (wake_up_process(wait->tsk)) result |= ENGINE_WAKEUP_ASLEEP; } return result; } unsigned int intel_engine_wakeup(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; unsigned long flags; unsigned int result; spin_lock_irqsave(&b->lock, flags); result = __intel_breadcrumbs_wakeup(b); spin_unlock_irqrestore(&b->lock, flags); return result; } static unsigned long wait_timeout(void) { return round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES); } static noinline void missed_breadcrumb(struct intel_engine_cs *engine) { DRM_DEBUG_DRIVER("%s missed breadcrumb at %pF, irq posted? %s\n", engine->name, __builtin_return_address(0), yesno(test_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted))); set_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings); } static void intel_breadcrumbs_hangcheck(unsigned long data) { struct intel_engine_cs *engine = (struct intel_engine_cs *)data; struct intel_breadcrumbs *b = &engine->breadcrumbs; if (!b->irq_armed) return; if (b->hangcheck_interrupts != atomic_read(&engine->irq_count)) { b->hangcheck_interrupts = atomic_read(&engine->irq_count); mod_timer(&b->hangcheck, wait_timeout()); return; } /* We keep the hangcheck time alive until we disarm the irq, even * if there are no waiters at present. * * If the waiter was currently running, assume it hasn't had a chance * to process the pending interrupt (e.g, low priority task on a loaded * system) and wait until it sleeps before declaring a missed interrupt. * * If the waiter was asleep (and not even pending a wakeup), then we * must have missed an interrupt as the GPU has stopped advancing * but we still have a waiter. Assuming all batches complete within * DRM_I915_HANGCHECK_JIFFIES [1.5s]! */ if (intel_engine_wakeup(engine) & ENGINE_WAKEUP_ASLEEP) { missed_breadcrumb(engine); mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1); } else { mod_timer(&b->hangcheck, wait_timeout()); } } static void intel_breadcrumbs_fake_irq(unsigned long data) { struct intel_engine_cs *engine = (struct intel_engine_cs *)data; struct intel_breadcrumbs *b = &engine->breadcrumbs; unsigned long flags; /* * The timer persists in case we cannot enable interrupts, * or if we have previously seen seqno/interrupt incoherency * ("missed interrupt" syndrome). Here the worker will wake up * every jiffie in order to kick the oldest waiter to do the * coherent seqno check. */ spin_lock_irqsave(&b->lock, flags); if (!__intel_breadcrumbs_wakeup(b)) __intel_engine_disarm_breadcrumbs(engine); spin_unlock_irqrestore(&b->lock, flags); if (!b->irq_armed) return; mod_timer(&b->fake_irq, jiffies + 1); /* Ensure that even if the GPU hangs, we get woken up. * * However, note that if no one is waiting, we never notice * a gpu hang. Eventually, we will have to wait for a resource * held by the GPU and so trigger a hangcheck. In the most * pathological case, this will be upon memory starvation! To * prevent this, we also queue the hangcheck from the retire * worker. */ i915_queue_hangcheck(engine->i915); } static void irq_enable(struct intel_engine_cs *engine) { /* Enabling the IRQ may miss the generation of the interrupt, but * we still need to force the barrier before reading the seqno, * just in case. */ set_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted); /* Caller disables interrupts */ spin_lock(&engine->i915->irq_lock); engine->irq_enable(engine); spin_unlock(&engine->i915->irq_lock); } static void irq_disable(struct intel_engine_cs *engine) { /* Caller disables interrupts */ spin_lock(&engine->i915->irq_lock); engine->irq_disable(engine); spin_unlock(&engine->i915->irq_lock); } void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; lockdep_assert_held(&b->lock); if (b->irq_enabled) { irq_disable(engine); b->irq_enabled = false; } b->irq_armed = false; } void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; unsigned long flags; if (!b->irq_armed) return; spin_lock_irqsave(&b->lock, flags); /* We only disarm the irq when we are idle (all requests completed), * so if there remains a sleeping waiter, it missed the request * completion. */ if (__intel_breadcrumbs_wakeup(b) & ENGINE_WAKEUP_ASLEEP) missed_breadcrumb(engine); __intel_engine_disarm_breadcrumbs(engine); spin_unlock_irqrestore(&b->lock, flags); } static bool use_fake_irq(const struct intel_breadcrumbs *b) { const struct intel_engine_cs *engine = container_of(b, struct intel_engine_cs, breadcrumbs); if (!test_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings)) return false; /* Only start with the heavy weight fake irq timer if we have not * seen any interrupts since enabling it the first time. If the * interrupts are still arriving, it means we made a mistake in our * engine->seqno_barrier(), a timing error that should be transient * and unlikely to reoccur. */ return atomic_read(&engine->irq_count) == b->hangcheck_interrupts; } static void enable_fake_irq(struct intel_breadcrumbs *b) { /* Ensure we never sleep indefinitely */ if (!b->irq_enabled || use_fake_irq(b)) mod_timer(&b->fake_irq, jiffies + 1); else mod_timer(&b->hangcheck, wait_timeout()); } static void __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b) { struct intel_engine_cs *engine = container_of(b, struct intel_engine_cs, breadcrumbs); struct drm_i915_private *i915 = engine->i915; lockdep_assert_held(&b->lock); if (b->irq_armed) return; /* The breadcrumb irq will be disarmed on the interrupt after the * waiters are signaled. This gives us a single interrupt window in * which we can add a new waiter and avoid the cost of re-enabling * the irq. */ b->irq_armed = true; GEM_BUG_ON(b->irq_enabled); if (I915_SELFTEST_ONLY(b->mock)) { /* For our mock objects we want to avoid interaction * with the real hardware (which is not set up). So * we simply pretend we have enabled the powerwell * and the irq, and leave it up to the mock * implementation to call intel_engine_wakeup() * itself when it wants to simulate a user interrupt, */ return; } /* Since we are waiting on a request, the GPU should be busy * and should have its own rpm reference. This is tracked * by i915->gt.awake, we can forgo holding our own wakref * for the interrupt as before i915->gt.awake is released (when * the driver is idle) we disarm the breadcrumbs. */ /* No interrupts? Kick the waiter every jiffie! */ if (intel_irqs_enabled(i915)) { if (!test_bit(engine->id, &i915->gpu_error.test_irq_rings)) irq_enable(engine); b->irq_enabled = true; } enable_fake_irq(b); } static inline struct intel_wait *to_wait(struct rb_node *node) { return rb_entry(node, struct intel_wait, node); } static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b, struct intel_wait *wait) { lockdep_assert_held(&b->lock); /* This request is completed, so remove it from the tree, mark it as * complete, and *then* wake up the associated task. */ rb_erase(&wait->node, &b->waiters); RB_CLEAR_NODE(&wait->node); wake_up_process(wait->tsk); /* implicit smp_wmb() */ } static bool __intel_engine_add_wait(struct intel_engine_cs *engine, struct intel_wait *wait) { struct intel_breadcrumbs *b = &engine->breadcrumbs; struct rb_node **p, *parent, *completed; bool first; u32 seqno; /* Insert the request into the retirement ordered list * of waiters by walking the rbtree. If we are the oldest * seqno in the tree (the first to be retired), then * set ourselves as the bottom-half. * * As we descend the tree, prune completed branches since we hold the * spinlock we know that the first_waiter must be delayed and can * reduce some of the sequential wake up latency if we take action * ourselves and wake up the completed tasks in parallel. Also, by * removing stale elements in the tree, we may be able to reduce the * ping-pong between the old bottom-half and ourselves as first-waiter. */ first = true; parent = NULL; completed = NULL; seqno = intel_engine_get_seqno(engine); /* If the request completed before we managed to grab the spinlock, * return now before adding ourselves to the rbtree. We let the * current bottom-half handle any pending wakeups and instead * try and get out of the way quickly. */ if (i915_seqno_passed(seqno, wait->seqno)) { RB_CLEAR_NODE(&wait->node); return first; } p = &b->waiters.rb_node; while (*p) { parent = *p; if (wait->seqno == to_wait(parent)->seqno) { /* We have multiple waiters on the same seqno, select * the highest priority task (that with the smallest * task->prio) to serve as the bottom-half for this * group. */ if (wait->tsk->prio > to_wait(parent)->tsk->prio) { p = &parent->rb_right; first = false; } else { p = &parent->rb_left; } } else if (i915_seqno_passed(wait->seqno, to_wait(parent)->seqno)) { p = &parent->rb_right; if (i915_seqno_passed(seqno, to_wait(parent)->seqno)) completed = parent; else first = false; } else { p = &parent->rb_left; } } rb_link_node(&wait->node, parent, p); rb_insert_color(&wait->node, &b->waiters); if (completed) { struct rb_node *next = rb_next(completed); GEM_BUG_ON(!next && !first); if (next && next != &wait->node) { GEM_BUG_ON(first); b->first_wait = to_wait(next); /* As there is a delay between reading the current * seqno, processing the completed tasks and selecting * the next waiter, we may have missed the interrupt * and so need for the next bottom-half to wakeup. * * Also as we enable the IRQ, we may miss the * interrupt for that seqno, so we have to wake up * the next bottom-half in order to do a coherent check * in case the seqno passed. */ __intel_breadcrumbs_enable_irq(b); if (test_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted)) wake_up_process(to_wait(next)->tsk); } do { struct intel_wait *crumb = to_wait(completed); completed = rb_prev(completed); __intel_breadcrumbs_finish(b, crumb); } while (completed); } if (first) { GEM_BUG_ON(rb_first(&b->waiters) != &wait->node); b->first_wait = wait; /* After assigning ourselves as the new bottom-half, we must * perform a cursory check to prevent a missed interrupt. * Either we miss the interrupt whilst programming the hardware, * or if there was a previous waiter (for a later seqno) they * may be woken instead of us (due to the inherent race * in the unlocked read of b->irq_seqno_bh in the irq handler) * and so we miss the wake up. */ __intel_breadcrumbs_enable_irq(b); } GEM_BUG_ON(!b->first_wait); GEM_BUG_ON(rb_first(&b->waiters) != &b->first_wait->node); return first; } bool intel_engine_add_wait(struct intel_engine_cs *engine, struct intel_wait *wait) { struct intel_breadcrumbs *b = &engine->breadcrumbs; bool first; spin_lock_irq(&b->lock); first = __intel_engine_add_wait(engine, wait); spin_unlock_irq(&b->lock); return first; } static inline bool chain_wakeup(struct rb_node *rb, int priority) { return rb && to_wait(rb)->tsk->prio <= priority; } static inline int wakeup_priority(struct intel_breadcrumbs *b, struct task_struct *tsk) { if (tsk == b->signaler) return INT_MIN; else return tsk->prio; } static void __intel_engine_remove_wait(struct intel_engine_cs *engine, struct intel_wait *wait) { struct intel_breadcrumbs *b = &engine->breadcrumbs; lockdep_assert_held(&b->lock); if (RB_EMPTY_NODE(&wait->node)) goto out; if (b->first_wait == wait) { const int priority = wakeup_priority(b, wait->tsk); struct rb_node *next; /* We are the current bottom-half. Find the next candidate, * the first waiter in the queue on the remaining oldest * request. As multiple seqnos may complete in the time it * takes us to wake up and find the next waiter, we have to * wake up that waiter for it to perform its own coherent * completion check. */ next = rb_next(&wait->node); if (chain_wakeup(next, priority)) { /* If the next waiter is already complete, * wake it up and continue onto the next waiter. So * if have a small herd, they will wake up in parallel * rather than sequentially, which should reduce * the overall latency in waking all the completed * clients. * * However, waking up a chain adds extra latency to * the first_waiter. This is undesirable if that * waiter is a high priority task. */ u32 seqno = intel_engine_get_seqno(engine); while (i915_seqno_passed(seqno, to_wait(next)->seqno)) { struct rb_node *n = rb_next(next); __intel_breadcrumbs_finish(b, to_wait(next)); next = n; if (!chain_wakeup(next, priority)) break; } } if (next) { /* In our haste, we may have completed the first waiter * before we enabled the interrupt. Do so now as we * have a second waiter for a future seqno. Afterwards, * we have to wake up that waiter in case we missed * the interrupt, or if we have to handle an * exception rather than a seqno completion. */ b->first_wait = to_wait(next); if (b->first_wait->seqno != wait->seqno) __intel_breadcrumbs_enable_irq(b); wake_up_process(b->first_wait->tsk); } else { b->first_wait = NULL; } } else { GEM_BUG_ON(rb_first(&b->waiters) == &wait->node); } GEM_BUG_ON(RB_EMPTY_NODE(&wait->node)); rb_erase(&wait->node, &b->waiters); out: GEM_BUG_ON(b->first_wait == wait); GEM_BUG_ON(rb_first(&b->waiters) != (b->first_wait ? &b->first_wait->node : NULL)); } void intel_engine_remove_wait(struct intel_engine_cs *engine, struct intel_wait *wait) { struct intel_breadcrumbs *b = &engine->breadcrumbs; /* Quick check to see if this waiter was already decoupled from * the tree by the bottom-half to avoid contention on the spinlock * by the herd. */ if (RB_EMPTY_NODE(&wait->node)) return; spin_lock_irq(&b->lock); __intel_engine_remove_wait(engine, wait); spin_unlock_irq(&b->lock); } static bool signal_valid(const struct drm_i915_gem_request *request) { return intel_wait_check_request(&request->signaling.wait, request); } static bool signal_complete(const struct drm_i915_gem_request *request) { if (!request) return false; /* If another process served as the bottom-half it may have already * signalled that this wait is already completed. */ if (intel_wait_complete(&request->signaling.wait)) return signal_valid(request); /* Carefully check if the request is complete, giving time for the * seqno to be visible or if the GPU hung. */ if (__i915_request_irq_complete(request)) return true; return false; } static struct drm_i915_gem_request *to_signaler(struct rb_node *rb) { return rb_entry(rb, struct drm_i915_gem_request, signaling.node); } static void signaler_set_rtpriority(void) { struct sched_param param = { .sched_priority = 1 }; sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m); } static int intel_breadcrumbs_signaler(void *arg) { struct intel_engine_cs *engine = arg; struct intel_breadcrumbs *b = &engine->breadcrumbs; struct drm_i915_gem_request *request; /* Install ourselves with high priority to reduce signalling latency */ signaler_set_rtpriority(); do { set_current_state(TASK_INTERRUPTIBLE); /* We are either woken up by the interrupt bottom-half, * or by a client adding a new signaller. In both cases, * the GPU seqno may have advanced beyond our oldest signal. * If it has, propagate the signal, remove the waiter and * check again with the next oldest signal. Otherwise we * need to wait for a new interrupt from the GPU or for * a new client. */ rcu_read_lock(); request = rcu_dereference(b->first_signal); if (request) request = i915_gem_request_get_rcu(request); rcu_read_unlock(); if (signal_complete(request)) { local_bh_disable(); dma_fence_signal(&request->fence); local_bh_enable(); /* kick start the tasklets */ spin_lock_irq(&b->lock); /* Wake up all other completed waiters and select the * next bottom-half for the next user interrupt. */ __intel_engine_remove_wait(engine, &request->signaling.wait); /* Find the next oldest signal. Note that as we have * not been holding the lock, another client may * have installed an even older signal than the one * we just completed - so double check we are still * the oldest before picking the next one. */ if (request == rcu_access_pointer(b->first_signal)) { struct rb_node *rb = rb_next(&request->signaling.node); rcu_assign_pointer(b->first_signal, rb ? to_signaler(rb) : NULL); } rb_erase(&request->signaling.node, &b->signals); RB_CLEAR_NODE(&request->signaling.node); spin_unlock_irq(&b->lock); i915_gem_request_put(request); } else { DEFINE_WAIT(exec); if (kthread_should_stop()) { GEM_BUG_ON(request); break; } if (request) add_wait_queue(&request->execute, &exec); schedule(); if (request) remove_wait_queue(&request->execute, &exec); if (kthread_should_park()) kthread_parkme(); } i915_gem_request_put(request); } while (1); __set_current_state(TASK_RUNNING); return 0; } void intel_engine_enable_signaling(struct drm_i915_gem_request *request) { struct intel_engine_cs *engine = request->engine; struct intel_breadcrumbs *b = &engine->breadcrumbs; struct rb_node *parent, **p; bool first, wakeup; u32 seqno; /* Note that we may be called from an interrupt handler on another * device (e.g. nouveau signaling a fence completion causing us * to submit a request, and so enable signaling). As such, * we need to make sure that all other users of b->lock protect * against interrupts, i.e. use spin_lock_irqsave. */ /* locked by dma_fence_enable_sw_signaling() (irqsafe fence->lock) */ GEM_BUG_ON(!irqs_disabled()); lockdep_assert_held(&request->lock); seqno = i915_gem_request_global_seqno(request); if (!seqno) return; request->signaling.wait.tsk = b->signaler; request->signaling.wait.request = request; request->signaling.wait.seqno = seqno; i915_gem_request_get(request); spin_lock(&b->lock); /* First add ourselves into the list of waiters, but register our * bottom-half as the signaller thread. As per usual, only the oldest * waiter (not just signaller) is tasked as the bottom-half waking * up all completed waiters after the user interrupt. * * If we are the oldest waiter, enable the irq (after which we * must double check that the seqno did not complete). */ wakeup = __intel_engine_add_wait(engine, &request->signaling.wait); /* Now insert ourselves into the retirement ordered list of signals * on this engine. We track the oldest seqno as that will be the * first signal to complete. */ parent = NULL; first = true; p = &b->signals.rb_node; while (*p) { parent = *p; if (i915_seqno_passed(seqno, to_signaler(parent)->signaling.wait.seqno)) { p = &parent->rb_right; first = false; } else { p = &parent->rb_left; } } rb_link_node(&request->signaling.node, parent, p); rb_insert_color(&request->signaling.node, &b->signals); if (first) rcu_assign_pointer(b->first_signal, request); spin_unlock(&b->lock); if (wakeup) wake_up_process(b->signaler); } void intel_engine_cancel_signaling(struct drm_i915_gem_request *request) { struct intel_engine_cs *engine = request->engine; struct intel_breadcrumbs *b = &engine->breadcrumbs; GEM_BUG_ON(!irqs_disabled()); lockdep_assert_held(&request->lock); GEM_BUG_ON(!request->signaling.wait.seqno); spin_lock(&b->lock); if (!RB_EMPTY_NODE(&request->signaling.node)) { if (request == rcu_access_pointer(b->first_signal)) { struct rb_node *rb = rb_next(&request->signaling.node); rcu_assign_pointer(b->first_signal, rb ? to_signaler(rb) : NULL); } rb_erase(&request->signaling.node, &b->signals); RB_CLEAR_NODE(&request->signaling.node); i915_gem_request_put(request); } __intel_engine_remove_wait(engine, &request->signaling.wait); spin_unlock(&b->lock); request->signaling.wait.seqno = 0; } int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; struct task_struct *tsk; spin_lock_init(&b->lock); setup_timer(&b->fake_irq, intel_breadcrumbs_fake_irq, (unsigned long)engine); setup_timer(&b->hangcheck, intel_breadcrumbs_hangcheck, (unsigned long)engine); /* Spawn a thread to provide a common bottom-half for all signals. * As this is an asynchronous interface we cannot steal the current * task for handling the bottom-half to the user interrupt, therefore * we create a thread to do the coherent seqno dance after the * interrupt and then signal the waitqueue (via the dma-buf/fence). */ tsk = kthread_run(intel_breadcrumbs_signaler, engine, "i915/signal:%d", engine->id); if (IS_ERR(tsk)) return PTR_ERR(tsk); b->signaler = tsk; return 0; } static void cancel_fake_irq(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; del_timer_sync(&b->hangcheck); del_timer_sync(&b->fake_irq); clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings); } void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; cancel_fake_irq(engine); spin_lock_irq(&b->lock); if (b->irq_enabled) irq_enable(engine); else irq_disable(engine); /* We set the IRQ_BREADCRUMB bit when we enable the irq presuming the * GPU is active and may have already executed the MI_USER_INTERRUPT * before the CPU is ready to receive. However, the engine is currently * idle (we haven't started it yet), there is no possibility for a * missed interrupt as we enabled the irq and so we can clear the * immediate wakeup (until a real interrupt arrives for the waiter). */ clear_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted); if (b->irq_armed) enable_fake_irq(b); spin_unlock_irq(&b->lock); } void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; /* The engines should be idle and all requests accounted for! */ WARN_ON(READ_ONCE(b->first_wait)); WARN_ON(!RB_EMPTY_ROOT(&b->waiters)); WARN_ON(rcu_access_pointer(b->first_signal)); WARN_ON(!RB_EMPTY_ROOT(&b->signals)); if (!IS_ERR_OR_NULL(b->signaler)) kthread_stop(b->signaler); cancel_fake_irq(engine); } bool intel_breadcrumbs_busy(struct intel_engine_cs *engine) { struct intel_breadcrumbs *b = &engine->breadcrumbs; bool busy = false; spin_lock_irq(&b->lock); if (b->first_wait) { wake_up_process(b->first_wait->tsk); busy |= intel_engine_flag(engine); } if (rcu_access_pointer(b->first_signal)) { wake_up_process(b->signaler); busy |= intel_engine_flag(engine); } spin_unlock_irq(&b->lock); return busy; } #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST) #include "selftests/intel_breadcrumbs.c" #endif