diff options
| -rw-r--r-- | drivers/gpu/drm/i915/Makefile | 1 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/i915_debugfs.c | 16 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/i915_drv.h | 40 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem.c | 143 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gpu_error.c | 60 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/i915_irq.c | 20 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/intel_breadcrumbs.c | 380 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/intel_lrc.c | 7 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/intel_ringbuffer.c | 12 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/intel_ringbuffer.h | 79 |
10 files changed, 648 insertions, 110 deletions
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile index a3d2b789c9ec..618293c8c9d9 100644 --- a/drivers/gpu/drm/i915/Makefile +++ b/drivers/gpu/drm/i915/Makefile @@ -38,6 +38,7 @@ i915-y += i915_cmd_parser.o \ i915_gem_userptr.o \ i915_gpu_error.o \ i915_trace_points.o \ + intel_breadcrumbs.o \ intel_lrc.o \ intel_mocs.o \ intel_ringbuffer.o \ diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c index f664884ad27f..f522a366223d 100644 --- a/drivers/gpu/drm/i915/i915_debugfs.c +++ b/drivers/gpu/drm/i915/i915_debugfs.c @@ -788,10 +788,22 @@ static int i915_gem_request_info(struct seq_file *m, void *data) static void i915_ring_seqno_info(struct seq_file *m, struct intel_engine_cs *engine) { + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct rb_node *rb; + seq_printf(m, "Current sequence (%s): %x\n", engine->name, engine->get_seqno(engine)); seq_printf(m, "Current user interrupts (%s): %x\n", engine->name, READ_ONCE(engine->user_interrupts)); + + spin_lock(&b->lock); + for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) { + struct intel_wait *w = container_of(rb, typeof(*w), node); + + seq_printf(m, "Waiting (%s): %s [%d] on %x\n", + engine->name, w->tsk->comm, w->tsk->pid, w->seqno); + } + spin_unlock(&b->lock); } static int i915_gem_seqno_info(struct seq_file *m, void *data) @@ -1428,6 +1440,8 @@ static int i915_hangcheck_info(struct seq_file *m, void *unused) engine->hangcheck.seqno, seqno[id], engine->last_submitted_seqno); + seq_printf(m, "\twaiters? %d\n", + intel_engine_has_waiter(engine)); seq_printf(m, "\tuser interrupts = %x [current %x]\n", engine->hangcheck.user_interrupts, READ_ONCE(engine->user_interrupts)); @@ -2415,7 +2429,7 @@ static int count_irq_waiters(struct drm_i915_private *i915) int count = 0; for_each_engine(engine, i915) - count += engine->irq_refcount; + count += intel_engine_has_waiter(engine); return count; } diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 0d0e4ac4dadb..1fefa8c495f2 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -506,6 +506,7 @@ struct drm_i915_error_state { bool valid; /* Software tracked state */ bool waiting; + int num_waiters; int hangcheck_score; enum intel_ring_hangcheck_action hangcheck_action; int num_requests; @@ -551,6 +552,12 @@ struct drm_i915_error_state { u32 tail; } *requests; + struct drm_i915_error_waiter { + char comm[TASK_COMM_LEN]; + pid_t pid; + u32 seqno; + } *waiters; + struct { u32 gfx_mode; union { @@ -1429,7 +1436,7 @@ struct i915_gpu_error { #define I915_STOP_RING_ALLOW_WARN (1 << 30) /* For missed irq/seqno simulation. */ - unsigned int test_irq_rings; + unsigned long test_irq_rings; }; enum modeset_restore { @@ -3064,7 +3071,6 @@ ibx_disable_display_interrupt(struct drm_i915_private *dev_priv, uint32_t bits) ibx_display_interrupt_update(dev_priv, bits, 0); } - /* i915_gem.c */ int i915_gem_create_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv); @@ -3975,4 +3981,34 @@ static inline void i915_trace_irq_get(struct intel_engine_cs *engine, i915_gem_request_assign(&engine->trace_irq_req, req); } +static inline bool __i915_request_irq_complete(struct drm_i915_gem_request *req) +{ + /* Ensure our read of the seqno is coherent so that we + * do not "miss an interrupt" (i.e. if this is the last + * request and the seqno write from the GPU is not visible + * by the time the interrupt fires, we will see that the + * request is incomplete and go back to sleep awaiting + * another interrupt that will never come.) + * + * Strictly, we only need to do this once after an interrupt, + * but it is easier and safer to do it every time the waiter + * is woken. + */ + if (i915_gem_request_completed(req, false)) + return true; + + /* We need to check whether any gpu reset happened in between + * the request being submitted and now. If a reset has occurred, + * the seqno will have been advance past ours and our request + * is complete. If we are in the process of handling a reset, + * the request is effectively complete as the rendering will + * be discarded, but we need to return in order to drop the + * struct_mutex. + */ + if (i915_reset_in_progress(&req->i915->gpu_error)) + return true; + + return false; +} + #endif diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index b5278d117ea0..c9814572e346 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1343,17 +1343,6 @@ i915_gem_check_wedge(unsigned reset_counter, bool interruptible) return 0; } -static void fake_irq(unsigned long data) -{ - wake_up_process((struct task_struct *)data); -} - -static bool missed_irq(struct drm_i915_private *dev_priv, - struct intel_engine_cs *engine) -{ - return test_bit(engine->id, &dev_priv->gpu_error.missed_irq_rings); -} - static unsigned long local_clock_us(unsigned *cpu) { unsigned long t; @@ -1386,7 +1375,7 @@ static bool busywait_stop(unsigned long timeout, unsigned cpu) return this_cpu != cpu; } -static int __i915_spin_request(struct drm_i915_gem_request *req, int state) +static bool __i915_spin_request(struct drm_i915_gem_request *req, int state) { unsigned long timeout; unsigned cpu; @@ -1401,17 +1390,14 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state) * takes to sleep on a request, on the order of a microsecond. */ - if (req->engine->irq_refcount) - return -EBUSY; - /* Only spin if we know the GPU is processing this request */ if (!i915_gem_request_started(req, true)) - return -EAGAIN; + return false; timeout = local_clock_us(&cpu) + 5; - while (!need_resched()) { + do { if (i915_gem_request_completed(req, true)) - return 0; + return true; if (signal_pending_state(state, current)) break; @@ -1420,12 +1406,9 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state) break; cpu_relax_lowlatency(); - } - - if (i915_gem_request_completed(req, false)) - return 0; + } while (!need_resched()); - return -EAGAIN; + return false; } /** @@ -1450,18 +1433,14 @@ int __i915_wait_request(struct drm_i915_gem_request *req, s64 *timeout, struct intel_rps_client *rps) { - struct intel_engine_cs *engine = i915_gem_request_get_engine(req); - struct drm_i915_private *dev_priv = req->i915; - const bool irq_test_in_progress = - ACCESS_ONCE(dev_priv->gpu_error.test_irq_rings) & intel_engine_flag(engine); int state = interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE; DEFINE_WAIT(reset); - DEFINE_WAIT(wait); - unsigned long timeout_expire; + struct intel_wait wait; + unsigned long timeout_remain; s64 before = 0; /* Only to silence a compiler warning. */ - int ret; + int ret = 0; - WARN(!intel_irqs_enabled(dev_priv), "IRQs disabled"); + might_sleep(); if (list_empty(&req->list)) return 0; @@ -1469,7 +1448,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, if (i915_gem_request_completed(req, true)) return 0; - timeout_expire = 0; + timeout_remain = MAX_SCHEDULE_TIMEOUT; if (timeout) { if (WARN_ON(*timeout < 0)) return -EINVAL; @@ -1477,7 +1456,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, if (*timeout == 0) return -ETIME; - timeout_expire = jiffies + nsecs_to_jiffies_timeout(*timeout); + timeout_remain = nsecs_to_jiffies_timeout(*timeout); /* * Record current time in case interrupted by signal, or wedged. @@ -1485,55 +1464,32 @@ int __i915_wait_request(struct drm_i915_gem_request *req, before = ktime_get_raw_ns(); } - if (INTEL_INFO(dev_priv)->gen >= 6) - gen6_rps_boost(dev_priv, rps, req->emitted_jiffies); - trace_i915_gem_request_wait_begin(req); - /* Optimistic spin for the next jiffie before touching IRQs */ - ret = __i915_spin_request(req, state); - if (ret == 0) - goto out; + if (INTEL_INFO(req->i915)->gen >= 6) + gen6_rps_boost(req->i915, rps, req->emitted_jiffies); - if (!irq_test_in_progress && WARN_ON(!engine->irq_get(engine))) { - ret = -ENODEV; - goto out; - } + /* Optimistic spin for the next ~jiffie before touching IRQs */ + if (__i915_spin_request(req, state)) + goto complete; - add_wait_queue(&dev_priv->gpu_error.wait_queue, &reset); - for (;;) { - struct timer_list timer; + set_current_state(state); + add_wait_queue(&req->i915->gpu_error.wait_queue, &reset); - prepare_to_wait(&engine->irq_queue, &wait, state); - - /* We need to check whether any gpu reset happened in between - * the request being submitted and now. If a reset has occurred, - * the seqno will have been advance past ours and our request - * is complete. If we are in the process of handling a reset, - * the request is effectively complete as the rendering will - * be discarded, but we need to return in order to drop the - * struct_mutex. + intel_wait_init(&wait, req->seqno); + if (intel_engine_add_wait(req->engine, &wait)) + /* In order to check that we haven't missed the interrupt + * as we enabled it, we need to kick ourselves to do a + * coherent check on the seqno before we sleep. */ - if (i915_reset_in_progress(&dev_priv->gpu_error)) { - ret = 0; - break; - } - - if (i915_gem_request_completed(req, false)) { - ret = 0; - break; - } + goto wakeup; + for (;;) { if (signal_pending_state(state, current)) { ret = -ERESTARTSYS; break; } - if (timeout && time_after_eq(jiffies, timeout_expire)) { - ret = -ETIME; - break; - } - /* Ensure that even if the GPU hangs, we get woken up. * * However, note that if no one is waiting, we never notice @@ -1541,32 +1497,33 @@ int __i915_wait_request(struct drm_i915_gem_request *req, * held by the GPU and so trigger a hangcheck. In the most * pathological case, this will be upon memory starvation! */ - i915_queue_hangcheck(dev_priv); - - timer.function = NULL; - if (timeout || missed_irq(dev_priv, engine)) { - unsigned long expire; + i915_queue_hangcheck(req->i915); - setup_timer_on_stack(&timer, fake_irq, (unsigned long)current); - expire = missed_irq(dev_priv, engine) ? jiffies + 1 : timeout_expire; - mod_timer(&timer, expire); + timeout_remain = io_schedule_timeout(timeout_remain); + if (timeout_remain == 0) { + ret = -ETIME; + break; } - io_schedule(); - - if (timer.function) { - del_singleshot_timer_sync(&timer); - destroy_timer_on_stack(&timer); - } - } - remove_wait_queue(&dev_priv->gpu_error.wait_queue, &reset); + if (intel_wait_complete(&wait)) + break; - if (!irq_test_in_progress) - engine->irq_put(engine); + set_current_state(state); - finish_wait(&engine->irq_queue, &wait); +wakeup: + /* Carefully check if the request is complete, giving time + * for the seqno to be visible following the interrupt. + * We also have to check in case we are kicked by the GPU + * reset in order to drop the struct_mutex. + */ + if (__i915_request_irq_complete(req)) + break; + } + remove_wait_queue(&req->i915->gpu_error.wait_queue, &reset); -out: + intel_engine_remove_wait(req->engine, &wait); + __set_current_state(TASK_RUNNING); +complete: trace_i915_gem_request_wait_end(req); if (timeout) { @@ -2796,6 +2753,12 @@ i915_gem_init_seqno(struct drm_i915_private *dev_priv, u32 seqno) } i915_gem_retire_requests(dev_priv); + /* If the seqno wraps around, we need to clear the breadcrumb rbtree */ + if (!i915_seqno_passed(seqno, dev_priv->next_seqno)) { + while (intel_kick_waiters(dev_priv)) + yield(); + } + /* Finally reset hw state */ for_each_engine(engine, dev_priv) intel_ring_init_seqno(engine, seqno); diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c index 34ff2459ceea..250f0b818099 100644 --- a/drivers/gpu/drm/i915/i915_gpu_error.c +++ b/drivers/gpu/drm/i915/i915_gpu_error.c @@ -463,6 +463,18 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m, } } + if (error->ring[i].num_waiters) { + err_printf(m, "%s --- %d waiters\n", + dev_priv->engine[i].name, + error->ring[i].num_waiters); + for (j = 0; j < error->ring[i].num_waiters; j++) { + err_printf(m, " seqno 0x%08x for %s [%d]\n", + error->ring[i].waiters[j].seqno, + error->ring[i].waiters[j].comm, + error->ring[i].waiters[j].pid); + } + } + if ((obj = error->ring[i].ringbuffer)) { err_printf(m, "%s --- ringbuffer = 0x%08x\n", dev_priv->engine[i].name, @@ -605,8 +617,9 @@ static void i915_error_state_free(struct kref *error_ref) i915_error_object_free(error->ring[i].ringbuffer); i915_error_object_free(error->ring[i].hws_page); i915_error_object_free(error->ring[i].ctx); - kfree(error->ring[i].requests); i915_error_object_free(error->ring[i].wa_ctx); + kfree(error->ring[i].requests); + kfree(error->ring[i].waiters); } i915_error_object_free(error->semaphore_obj); @@ -892,6 +905,48 @@ static void gen6_record_semaphore_state(struct drm_i915_private *dev_priv, } } +static void engine_record_waiters(struct intel_engine_cs *engine, + struct drm_i915_error_ring *ering) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct drm_i915_error_waiter *waiter; + struct rb_node *rb; + int count; + + ering->num_waiters = 0; + ering->waiters = NULL; + + spin_lock(&b->lock); + count = 0; + for (rb = rb_first(&b->waiters); rb != NULL; rb = rb_next(rb)) + count++; + spin_unlock(&b->lock); + + waiter = NULL; + if (count) + waiter = kmalloc_array(count, + sizeof(struct drm_i915_error_waiter), + GFP_ATOMIC); + if (!waiter) + return; + + ering->waiters = waiter; + + spin_lock(&b->lock); + for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) { + struct intel_wait *w = container_of(rb, typeof(*w), node); + + strcpy(waiter->comm, w->tsk->comm); + waiter->pid = w->tsk->pid; + waiter->seqno = w->seqno; + waiter++; + + if (++ering->num_waiters == count) + break; + } + spin_unlock(&b->lock); +} + static void i915_record_ring_state(struct drm_i915_private *dev_priv, struct drm_i915_error_state *error, struct intel_engine_cs *engine, @@ -926,7 +981,7 @@ static void i915_record_ring_state(struct drm_i915_private *dev_priv, ering->instdone = I915_READ(GEN2_INSTDONE); } - ering->waiting = waitqueue_active(&engine->irq_queue); + ering->waiting = intel_engine_has_waiter(engine); ering->instpm = I915_READ(RING_INSTPM(engine->mmio_base)); ering->acthd = intel_ring_get_active_head(engine); ering->seqno = engine->get_seqno(engine); @@ -1032,6 +1087,7 @@ static void i915_gem_record_rings(struct drm_i915_private *dev_priv, error->ring[i].valid = true; i915_record_ring_state(dev_priv, error, engine, &error->ring[i]); + engine_record_waiters(engine, &error->ring[i]); request = i915_gem_find_active_request(engine); if (request) { diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 6c17596d75dd..a11ab00cdee0 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -976,13 +976,10 @@ static void ironlake_rps_change_irq_handler(struct drm_i915_private *dev_priv) static void notify_ring(struct intel_engine_cs *engine) { - if (!intel_engine_initialized(engine)) - return; - - trace_i915_gem_request_notify(engine); - engine->user_interrupts++; - - wake_up_all(&engine->irq_queue); + if (intel_engine_wakeup(engine)) { + trace_i915_gem_request_notify(engine); + engine->user_interrupts++; + } } static void vlv_c0_read(struct drm_i915_private *dev_priv, @@ -1063,7 +1060,7 @@ static bool any_waiters(struct drm_i915_private *dev_priv) struct intel_engine_cs *engine; for_each_engine(engine, dev_priv) - if (engine->irq_refcount) + if (intel_engine_has_waiter(engine)) return true; return false; @@ -3074,13 +3071,14 @@ static unsigned kick_waiters(struct intel_engine_cs *engine) if (engine->hangcheck.user_interrupts == user_interrupts && !test_and_set_bit(engine->id, &i915->gpu_error.missed_irq_rings)) { - if (!(i915->gpu_error.test_irq_rings & intel_engine_flag(engine))) + if (!test_bit(engine->id, &i915->gpu_error.test_irq_rings)) DRM_ERROR("Hangcheck timer elapsed... %s idle\n", engine->name); else DRM_INFO("Fake missed irq on %s\n", engine->name); - wake_up_all(&engine->irq_queue); + + intel_engine_enable_fake_irq(engine); } return user_interrupts; @@ -3124,7 +3122,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work) intel_uncore_arm_unclaimed_mmio_detection(dev_priv); for_each_engine_id(engine, dev_priv, id) { - bool busy = waitqueue_active(&engine->irq_queue); + bool busy = intel_engine_has_waiter(engine); u64 acthd; u32 seqno; unsigned user_interrupts; diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c new file mode 100644 index 000000000000..a3bbf2d90dce --- /dev/null +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c @@ -0,0 +1,380 @@ +/* + * 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 "i915_drv.h" + +static void intel_breadcrumbs_fake_irq(unsigned long data) +{ + struct intel_engine_cs *engine = (struct intel_engine_cs *)data; + + /* + * 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. + */ + rcu_read_lock(); + if (intel_engine_wakeup(engine)) + mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1); + rcu_read_unlock(); +} + +static void irq_enable(struct intel_engine_cs *engine) +{ + WARN_ON(!engine->irq_get(engine)); +} + +static void irq_disable(struct intel_engine_cs *engine) +{ + engine->irq_put(engine); +} + +static bool __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; + bool irq_posted = false; + + assert_spin_locked(&b->lock); + if (b->rpm_wakelock) + return false; + + /* Since we are waiting on a request, the GPU should be busy + * and should have its own rpm reference. For completeness, + * record an rpm reference for ourselves to cover the + * interrupt we unmask. + */ + intel_runtime_pm_get_noresume(i915); + b->rpm_wakelock = true; + + /* 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); + irq_posted = true; + } + b->irq_enabled = true; + } + + if (!b->irq_enabled || + test_bit(engine->id, &i915->gpu_error.missed_irq_rings)) + mod_timer(&b->fake_irq, jiffies + 1); + + return irq_posted; +} + +static void __intel_breadcrumbs_disable_irq(struct intel_breadcrumbs *b) +{ + struct intel_engine_cs *engine = + container_of(b, struct intel_engine_cs, breadcrumbs); + + assert_spin_locked(&b->lock); + if (!b->rpm_wakelock) + return; + + if (b->irq_enabled) { + irq_disable(engine); + b->irq_enabled = false; + } + + intel_runtime_pm_put(engine->i915); + b->rpm_wakelock = false; +} + +static inline struct intel_wait *to_wait(struct rb_node *node) +{ + return container_of(node, struct intel_wait, node); +} + +static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b, + struct intel_wait *wait) +{ + assert_spin_locked(&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 = 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); + GEM_BUG_ON(!first && !b->tasklet); + + 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); + smp_store_mb(b->tasklet, b->first_wait->tsk); + /* 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); + 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; + smp_store_mb(b->tasklet, wait->tsk); + first = __intel_breadcrumbs_enable_irq(b); + } + GEM_BUG_ON(!b->tasklet); + 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(&b->lock); + first = __intel_engine_add_wait(engine, wait); + spin_unlock(&b->lock); + + return first; +} + +void intel_engine_enable_fake_irq(struct intel_engine_cs *engine) +{ + mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1); +} + +static inline bool chain_wakeup(struct rb_node *rb, int priority) +{ + return rb && to_wait(rb)->tsk->prio <= priority; +} + +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(&b->lock); + + if (RB_EMPTY_NODE(&wait->node)) + goto out_unlock; + + if (b->first_wait == wait) { + struct rb_node *next; + const int priority = wait->tsk->prio; + + GEM_BUG_ON(b->tasklet != wait->tsk); + + /* 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 = 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); + smp_store_mb(b->tasklet, b->first_wait->tsk); + if (b->first_wait->seqno != wait->seqno) + __intel_breadcrumbs_enable_irq(b); + wake_up_process(b->tasklet); + } else { + b->first_wait = NULL; + WRITE_ONCE(b->tasklet, NULL); + __intel_breadcrumbs_disable_irq(b); + } + } 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_unlock: + GEM_BUG_ON(b->first_wait == wait); + GEM_BUG_ON(rb_first(&b->waiters) != + (b->first_wait ? &b->first_wait->node : NULL)); + GEM_BUG_ON(!b->tasklet ^ RB_EMPTY_ROOT(&b->waiters)); + spin_unlock(&b->lock); +} + +int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + spin_lock_init(&b->lock); + setup_timer(&b->fake_irq, + intel_breadcrumbs_fake_irq, + (unsigned long)engine); + + return 0; +} + +void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + del_timer_sync(&b->fake_irq); +} + +unsigned int intel_kick_waiters(struct drm_i915_private *i915) +{ + struct intel_engine_cs *engine; + unsigned int mask = 0; + + /* To avoid the task_struct disappearing beneath us as we wake up + * the process, we must first inspect the task_struct->state under the + * RCU lock, i.e. as we call wake_up_process() we must be holding the + * rcu_read_lock(). + */ + rcu_read_lock(); + for_each_engine(engine, i915) + if (unlikely(intel_engine_wakeup(engine))) + mask |= intel_engine_flag(engine); + rcu_read_unlock(); + + return mask; +} diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 339d8041075f..226bba22e4b4 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -1961,6 +1961,8 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *engine) i915_cmd_parser_fini_ring(engine); i915_gem_batch_pool_fini(&engine->batch_pool); + intel_engine_fini_breadcrumbs(engine); + if (engine->status_page.obj) { i915_gem_object_unpin_map(engine->status_page.obj); engine->status_page.obj = NULL; @@ -1998,7 +2000,6 @@ logical_ring_default_irqs(struct intel_engine_cs *engine, unsigned shift) { engine->irq_enable_mask = GT_RENDER_USER_INTERRUPT << shift; engine->irq_keep_mask = GT_CONTEXT_SWITCH_INTERRUPT << shift; - init_waitqueue_head(&engine->irq_queue); } static int @@ -2025,6 +2026,10 @@ logical_ring_init(struct intel_engine_cs *engine) struct i915_gem_context *dctx = engine->i915->kernel_context; int ret; + ret = intel_engine_init_breadcrumbs(engine); + if (ret) + goto error; + ret = i915_cmd_parser_init_ring(engine); if (ret) goto error; diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 24cdc920f4b4..af50aa01bcd9 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -2394,7 +2394,9 @@ static int intel_init_ring_buffer(struct drm_device *dev, memset(engine->semaphore.sync_seqno, 0, sizeof(engine->semaphore.sync_seqno)); - init_waitqueue_head(&engine->irq_queue); + ret = intel_engine_init_breadcrumbs(engine); + if (ret) + goto error; /* We may need to do things with the shrinker which * require us to immediately switch back to the default @@ -2474,6 +2476,7 @@ void intel_cleanup_engine(struct intel_engine_cs *engine) i915_cmd_parser_fini_ring(engine); i915_gem_batch_pool_fini(&engine->batch_pool); + intel_engine_fini_breadcrumbs(engine); intel_ring_context_unpin(dev_priv->kernel_context, engine); @@ -2676,6 +2679,13 @@ void intel_ring_init_seqno(struct intel_engine_cs *engine, u32 seqno) engine->last_submitted_seqno = seqno; engine->hangcheck.seqno = seqno; + + /* After manually advancing the seqno, fake the interrupt in case + * there are any waiters for that seqno. + */ + rcu_read_lock(); + intel_engine_wakeup(engine); + rcu_read_unlock(); } static void gen6_bsd_ring_write_tail(struct intel_engine_cs *engine, diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 113d5230a6de..6fd70a56e219 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -148,6 +148,32 @@ struct intel_engine_cs { struct intel_ringbuffer *buffer; struct list_head buffers; + /* Rather than have every client wait upon all user interrupts, + * with the herd waking after every interrupt and each doing the + * heavyweight seqno dance, we delegate the task (of being the + * bottom-half of the user interrupt) to the first client. After + * every interrupt, we wake up one client, who does the heavyweight + * coherent seqno read and either goes back to sleep (if incomplete), + * or wakes up all the completed clients in parallel, before then + * transferring the bottom-half status to the next client in the queue. + * + * Compared to walking the entire list of waiters in a single dedicated + * bottom-half, we reduce the latency of the first waiter by avoiding + * a context switch, but incur additional coherent seqno reads when + * following the chain of request breadcrumbs. Since it is most likely + * that we have a single client waiting on each seqno, then reducing + * the overhead of waking that client is much preferred. + */ + struct intel_breadcrumbs { + spinlock_t lock; /* protects the lists of requests */ + struct rb_root waiters; /* sorted by retirement, priority */ + struct intel_wait *first_wait; /* oldest waiter by retirement */ + struct task_struct *tasklet; /* bh for user interrupts */ + struct timer_list fake_irq; /* used after a missed interrupt */ + bool irq_enabled; + bool rpm_wakelock; + } breadcrumbs; + /* * A pool of objects to use as shadow copies of client batch buffers * when the command parser is enabled. Prevents the client from @@ -296,8 +322,6 @@ struct intel_engine_cs { bool gpu_caches_dirty; - wait_queue_head_t irq_queue; - struct i915_gem_context *last_context; struct intel_ring_hangcheck hangcheck; @@ -483,4 +507,55 @@ static inline u32 intel_hws_seqno_address(struct intel_engine_cs *engine) return engine->status_page.gfx_addr + I915_GEM_HWS_INDEX_ADDR; } +/* intel_breadcrumbs.c -- user interrupt bottom-half for waiters */ +struct intel_wait { + struct rb_node node; + struct task_struct *tsk; + u32 seqno; +}; + +int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine); + +static inline void intel_wait_init(struct intel_wait *wait, u32 seqno) +{ + wait->tsk = current; + wait->seqno = seqno; +} + +static inline bool intel_wait_complete(const struct intel_wait *wait) +{ + return RB_EMPTY_NODE(&wait->node); +} + +bool intel_engine_add_wait(struct intel_engine_cs *engine, + struct intel_wait *wait); +void intel_engine_remove_wait(struct intel_engine_cs *engine, + struct intel_wait *wait); + +static inline bool intel_engine_has_waiter(struct intel_engine_cs *engine) +{ + return READ_ONCE(engine->breadcrumbs.tasklet); +} + +static inline bool intel_engine_wakeup(struct intel_engine_cs *engine) +{ + bool wakeup = false; + struct task_struct *tsk = READ_ONCE(engine->breadcrumbs.tasklet); + /* Note that for this not to dangerously chase a dangling pointer, + * the caller is responsible for ensure that the task remain valid for + * wake_up_process() i.e. that the RCU grace period cannot expire. + * + * Also note that tsk is likely to be in !TASK_RUNNING state so an + * early test for tsk->state != TASK_RUNNING before wake_up_process() + * is unlikely to be beneficial. + */ + if (tsk) + wakeup = wake_up_process(tsk); + return wakeup; +} + +void intel_engine_enable_fake_irq(struct intel_engine_cs *engine); +void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine); +unsigned int intel_kick_waiters(struct drm_i915_private *i915); + #endif /* _INTEL_RINGBUFFER_H_ */ |