blob: b074f3d6d127fded56cdc49ea9326ced2407d51a [file] [log] [blame]
/*
* 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 <linux/kthread.h>
#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)
{
/* 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.
*/
engine->breadcrumbs.irq_posted = true;
spin_lock_irq(&engine->i915->irq_lock);
engine->irq_enable(engine);
spin_unlock_irq(&engine->i915->irq_lock);
}
static void irq_disable(struct intel_engine_cs *engine)
{
spin_lock_irq(&engine->i915->irq_lock);
engine->irq_disable(engine);
spin_unlock_irq(&engine->i915->irq_lock);
engine->breadcrumbs.irq_posted = false;
}
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;
assert_spin_locked(&b->lock);
if (b->rpm_wakelock)
return;
/* 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);
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);
/* 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!
*/
i915_queue_hangcheck(i915);
}
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 = 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);
GEM_BUG_ON(!first && !b->irq_seqno_bh);
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->irq_seqno_bh, 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);
if (READ_ONCE(b->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;
smp_store_mb(b->irq_seqno_bh, wait->tsk);
/* 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->irq_seqno_bh);
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;
}
static inline int wakeup_priority(struct intel_breadcrumbs *b,
struct task_struct *tsk)
{
if (tsk == b->signaler)
return INT_MIN;
else
return tsk->prio;
}
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) {
const int priority = wakeup_priority(b, wait->tsk);
struct rb_node *next;
GEM_BUG_ON(b->irq_seqno_bh != 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 = 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);
smp_store_mb(b->irq_seqno_bh, b->first_wait->tsk);
if (b->first_wait->seqno != wait->seqno)
__intel_breadcrumbs_enable_irq(b);
wake_up_process(b->irq_seqno_bh);
} else {
b->first_wait = NULL;
WRITE_ONCE(b->irq_seqno_bh, 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->irq_seqno_bh ^ RB_EMPTY_ROOT(&b->waiters));
spin_unlock(&b->lock);
}
static bool signal_complete(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 true;
/* 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 container_of(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, &param);
}
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.
*/
request = READ_ONCE(b->first_signal);
if (signal_complete(request)) {
/* 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.
*/
spin_lock(&b->lock);
if (request == b->first_signal) {
struct rb_node *rb =
rb_next(&request->signaling.node);
b->first_signal = rb ? to_signaler(rb) : NULL;
}
rb_erase(&request->signaling.node, &b->signals);
spin_unlock(&b->lock);
i915_gem_request_unreference(request);
} else {
if (kthread_should_stop())
break;
schedule();
}
} 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;
if (unlikely(READ_ONCE(request->signaling.wait.tsk)))
return;
spin_lock(&b->lock);
if (unlikely(request->signaling.wait.tsk)) {
wakeup = false;
goto unlock;
}
request->signaling.wait.tsk = b->signaler;
request->signaling.wait.seqno = request->seqno;
i915_gem_request_reference(request);
/* 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(request->seqno,
to_signaler(parent)->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)
smp_store_mb(b->first_signal, request);
unlock:
spin_unlock(&b->lock);
if (wakeup)
wake_up_process(b->signaler);
}
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);
/* 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;
}
void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
{
struct intel_breadcrumbs *b = &engine->breadcrumbs;
if (!IS_ERR_OR_NULL(b->signaler))
kthread_stop(b->signaler);
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;
}
unsigned int intel_kick_signalers(struct drm_i915_private *i915)
{
struct intel_engine_cs *engine;
unsigned int mask = 0;
for_each_engine(engine, i915) {
if (unlikely(READ_ONCE(engine->breadcrumbs.first_signal))) {
wake_up_process(engine->breadcrumbs.signaler);
mask |= intel_engine_flag(engine);
}
}
return mask;
}