linux_dsm_epyc7002/drivers/gpu/drm/i915/intel_breadcrumbs.c
Chris Wilson 5590af3e11 drm/i915: Drive request submission through fence callbacks
Drive final request submission from a callback from the fence. This way
the request is queued until all dependencies are resolved, at which
point it is handed to the backend for queueing to hardware. At this
point, no dependencies are set on the request, so the callback is
immediate.

A side-effect of imposing a heavier-irqsafe spinlock for execlist
submission is that we lose the softirq enabling after scheduling the
execlists tasklet. To compensate, we manually kickstart the softirq by
disabling and enabling the bh around the fence signaling.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: John Harrison <john.c.harrison@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-14-chris@chris-wilson.co.uk
2016-09-09 14:23:05 +01:00

623 lines
18 KiB
C

/*
* 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_hangcheck(unsigned long data)
{
struct intel_engine_cs *engine = (struct intel_engine_cs *)data;
struct intel_breadcrumbs *b = &engine->breadcrumbs;
if (!b->irq_enabled)
return;
if (time_before(jiffies, b->timeout)) {
mod_timer(&b->hangcheck, b->timeout);
return;
}
DRM_DEBUG("Hangcheck timer elapsed... %s idle\n", engine->name);
set_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
mod_timer(&engine->breadcrumbs.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 unsigned long wait_timeout(void)
{
return round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES);
}
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.
*/
if (intel_engine_wakeup(engine))
mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1);
}
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);
} else {
/* Ensure we never sleep indefinitely */
GEM_BUG_ON(!time_after(b->timeout, jiffies));
mod_timer(&b->hangcheck, b->timeout);
}
}
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 && !rcu_access_pointer(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->timeout = wait_timeout();
b->first_wait = to_wait(next);
rcu_assign_pointer(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->timeout = wait_timeout();
b->first_wait = wait;
rcu_assign_pointer(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(!rcu_access_pointer(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;
}
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(rcu_access_pointer(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->timeout = wait_timeout();
b->first_wait = to_wait(next);
rcu_assign_pointer(b->irq_seqno_bh, b->first_wait->tsk);
if (b->first_wait->seqno != wait->seqno)
__intel_breadcrumbs_enable_irq(b);
wake_up_process(b->first_wait->tsk);
} else {
b->first_wait = NULL;
rcu_assign_pointer(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(!rcu_access_pointer(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);
local_bh_disable();
fence_signal(&request->fence);
local_bh_enable(); /* kick start the tasklets */
/* 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_put(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;
/* locked by fence_enable_sw_signaling() */
assert_spin_locked(&request->lock);
request->signaling.wait.tsk = b->signaler;
request->signaling.wait.seqno = request->fence.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(request->fence.seqno,
to_signaler(parent)->fence.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);
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);
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;
}
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->hangcheck);
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().
*/
for_each_engine(engine, i915)
if (unlikely(intel_engine_wakeup(engine)))
mask |= intel_engine_flag(engine);
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;
}