[Intel-gfx] [PATCH 2/3] drm/i915/gt: Allow temporary suspension of inflight requests
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Wed Jan 15 10:58:39 UTC 2020
On 15/01/2020 08:33, Chris Wilson wrote:
> In order to support out-of-line error capture, we need to remove the
> active request from HW and put it to one side while a worker compresses
> and stores all the details associated with that request. (As that
> compression may take an arbitrary user-controlled amount of time, we
> want to let the engine continue running on other workloads while the
> hanging request is dumped.) Not only do we need to remove the active
> request, but we also have to remove its context and all requests that
> were dependent on it (both in flight, queued and future submission).
>
> Finally once the capture is complete, we need to be able to resubmit the
> request and its dependents and allow them to execute.
>
> v2: Replace stack recursion with a simple list.
>
> References: https://gitlab.freedesktop.org/drm/intel/issues/738
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
> drivers/gpu/drm/i915/gt/intel_engine_cs.c | 1 +
> drivers/gpu/drm/i915/gt/intel_engine_types.h | 1 +
> drivers/gpu/drm/i915/gt/intel_lrc.c | 159 ++++++++++++++++++-
> drivers/gpu/drm/i915/gt/selftest_lrc.c | 103 ++++++++++++
> drivers/gpu/drm/i915/i915_request.h | 22 +++
> 5 files changed, 282 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index f451ef376548..c296aaf381e7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -671,6 +671,7 @@ void
> intel_engine_init_active(struct intel_engine_cs *engine, unsigned int subclass)
> {
> INIT_LIST_HEAD(&engine->active.requests);
> + INIT_LIST_HEAD(&engine->active.hold);
>
> spin_lock_init(&engine->active.lock);
> lockdep_set_subclass(&engine->active.lock, subclass);
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> index 00287515e7af..77e68c7643de 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> @@ -295,6 +295,7 @@ struct intel_engine_cs {
> struct {
> spinlock_t lock;
> struct list_head requests;
> + struct list_head hold; /* ready requests, but on hold */
> } active;
>
> struct llist_head barrier_tasks;
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index f0cbd240a8c2..43c19dc9c0c7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -2353,6 +2353,145 @@ static void __execlists_submission_tasklet(struct intel_engine_cs *const engine)
> }
> }
>
> +static void __execlists_hold(struct i915_request *rq)
> +{
> + LIST_HEAD(list);
> +
> + do {
> + struct i915_dependency *p;
> +
> + if (i915_request_is_active(rq))
> + __i915_request_unsubmit(rq);
> +
> + RQ_TRACE(rq, "on hold\n");
> + clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
> + list_move_tail(&rq->sched.link, &rq->engine->active.hold);
> + i915_request_set_hold(rq);
> +
> + list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {
> + struct i915_request *w =
> + container_of(p->waiter, typeof(*w), sched);
> +
> + /* Leave semaphores spinning on the other engines */
> + if (w->engine != rq->engine)
> + continue;
> +
> + if (list_empty(&w->sched.link))
> + continue; /* Not yet submitted */
> +
> + if (i915_request_completed(w))
> + continue;
> +
> + if (i915_request_has_hold(rq))
> + continue;
> +
> + list_move_tail(&w->sched.link, &list);
> + }
> +
> + rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
> + } while(rq);
> +}
> +
> +__maybe_unused
> +static void execlists_hold(struct intel_engine_cs *engine,
> + struct i915_request *rq)
> +{
> + spin_lock_irq(&engine->active.lock);
> +
> + /*
> + * Transfer this request onto the hold queue to prevent it
> + * being resumbitted to HW (and potentially completed) before we have
> + * released it. Since we may have already submitted following
> + * requests, we need to remove those as well.
> + */
> + GEM_BUG_ON(i915_request_completed(rq));
> + GEM_BUG_ON(i915_request_has_hold(rq));
> + GEM_BUG_ON(rq->engine != engine);
> + __execlists_hold(rq);
> +
> + spin_unlock_irq(&engine->active.lock);
> +}
> +
> +static bool hold_request(const struct i915_request *rq)
> +{
> + struct i915_dependency *p;
> +
> + /*
> + * If one of our ancestors is still on hold, we must also still be on
> + * hold, otherwise we will bypass it and execute before it.
> + */
> + list_for_each_entry(p, &rq->sched.signalers_list, signal_link) {
> + const struct i915_request *s =
> + container_of(p->signaler, typeof(*s), sched);
> +
> + if (s->engine != rq->engine)
> + continue;
> +
> + return i915_request_has_hold(s);
It shouldn't be:
if (i915_request_has_hold(s))
return true;
?
> + }
> +
> + return false;
> +}
> +
> +static void __execlists_unhold(struct i915_request *rq)
> +{
> + LIST_HEAD(list);
> +
> + do {
> + struct i915_dependency *p;
> +
> + GEM_BUG_ON(!i915_request_has_hold(rq));
> + GEM_BUG_ON(!i915_sw_fence_signaled(&rq->submit));
> +
> + i915_request_clear_hold(rq);
> + list_move_tail(&rq->sched.link,
> + i915_sched_lookup_priolist(rq->engine,
> + rq_prio(rq)));
> + set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
> + RQ_TRACE(rq, "hold release\n");
> +
> + /* Also release any children on this engine that are ready */
> + list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {
> + struct i915_request *w =
> + container_of(p->waiter, typeof(*w), sched);
> +
> + if (w->engine != rq->engine)
> + continue;
> +
> + if (!i915_request_has_hold(rq))
is_held?
> + continue;
> +
> + /* Check that no other parents are on hold */
> + if (hold_request(rq))
> + continue;
This would be two simultaneous hangs in the interlinked hierarchy? But
since the engine must be the same, can't be possible.
Regards,
Tvrtko
> +
> + list_move_tail(&w->sched.link, &list);
> + }
> +
> + rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);
> + } while(rq);
> +}
> +
> +__maybe_unused
> +static void execlists_unhold(struct intel_engine_cs *engine,
> + struct i915_request *rq)
> +{
> + spin_lock_irq(&engine->active.lock);
> +
> + /*
> + * Move this request back to the priority queue, and all of its
> + * children and grandchildren that were suspended along with it.
> + */
> + __execlists_unhold(rq);
> +
> + if (rq_prio(rq) > engine->execlists.queue_priority_hint) {
> + engine->execlists.queue_priority_hint = rq_prio(rq);
> + tasklet_hi_schedule(&engine->execlists.tasklet);
> + }
> +
> + spin_unlock_irq(&engine->active.lock);
> +}
> +
> static noinline void preempt_reset(struct intel_engine_cs *engine)
> {
> const unsigned int bit = I915_RESET_ENGINE + engine->id;
> @@ -2465,6 +2604,13 @@ static void submit_queue(struct intel_engine_cs *engine,
> __submit_queue_imm(engine);
> }
>
> +static bool on_hold(const struct intel_engine_cs *engine,
> + const struct i915_request *rq)
> +{
> + GEM_BUG_ON(i915_request_has_hold(rq));
> + return !list_empty(&engine->active.hold) && hold_request(rq);
> +}
> +
> static void execlists_submit_request(struct i915_request *request)
> {
> struct intel_engine_cs *engine = request->engine;
> @@ -2473,12 +2619,17 @@ static void execlists_submit_request(struct i915_request *request)
> /* Will be called from irq-context when using foreign fences. */
> spin_lock_irqsave(&engine->active.lock, flags);
>
> - queue_request(engine, request);
> + if (unlikely(on_hold(engine, request))) { /* ancestor is suspended */
> + list_add_tail(&request->sched.link, &engine->active.hold);
> + i915_request_set_hold(request);
> + } else {
> + queue_request(engine, request);
>
> - GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
> - GEM_BUG_ON(list_empty(&request->sched.link));
> + GEM_BUG_ON(RB_EMPTY_ROOT(&engine->execlists.queue.rb_root));
> + GEM_BUG_ON(list_empty(&request->sched.link));
>
> - submit_queue(engine, request);
> + submit_queue(engine, request);
> + }
>
> spin_unlock_irqrestore(&engine->active.lock, flags);
> }
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index 15cda024e3e4..78501d79c0ea 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -285,6 +285,108 @@ static int live_unlite_preempt(void *arg)
> return live_unlite_restore(arg, I915_USER_PRIORITY(I915_PRIORITY_MAX));
> }
>
> +static int live_hold_reset(void *arg)
> +{
> + struct intel_gt *gt = arg;
> + struct intel_engine_cs *engine;
> + enum intel_engine_id id;
> + struct igt_spinner spin;
> + int err = 0;
> +
> + /*
> + * In order to support offline error capture for fast preempt reset,
> + * we need to decouple the guilty request and ensure that it and its
> + * descendents are not executed while the capture is in progress.
> + */
> +
> + if (!intel_has_reset_engine(gt))
> + return 0;
> +
> + if (igt_spinner_init(&spin, gt))
> + return -ENOMEM;
> +
> + for_each_engine(engine, gt, id) {
> + struct intel_context *ce;
> + unsigned long heartbeat;
> + struct i915_request *rq;
> +
> + ce = intel_context_create(engine);
> + if (IS_ERR(ce)) {
> + err = PTR_ERR(ce);
> + break;
> + }
> +
> + engine_heartbeat_disable(engine, &heartbeat);
> +
> + rq = igt_spinner_create_request(&spin, ce, MI_ARB_CHECK);
> + if (IS_ERR(rq)) {
> + err = PTR_ERR(rq);
> + goto out;
> + }
> + i915_request_add(rq);
> +
> + if (!igt_wait_for_spinner(&spin, rq)) {
> + intel_gt_set_wedged(gt);
> + err = -ETIME;
> + goto out;
> + }
> +
> + /* We have our request executing, now remove it and reset */
> +
> + if (test_and_set_bit(I915_RESET_ENGINE + id,
> + >->reset.flags)) {
> + spin_unlock_irq(&engine->active.lock);
> + intel_gt_set_wedged(gt);
> + err = -EBUSY;
> + goto out;
> + }
> + tasklet_disable(&engine->execlists.tasklet);
> +
> + engine->execlists.tasklet.func(engine->execlists.tasklet.data);
> + GEM_BUG_ON(execlists_active(&engine->execlists) != rq);
> +
> + execlists_hold(engine, rq);
> + GEM_BUG_ON(!i915_request_has_hold(rq));
> +
> + intel_engine_reset(engine, NULL);
> + GEM_BUG_ON(rq->fence.error != -EIO);
> +
> + tasklet_enable(&engine->execlists.tasklet);
> + clear_and_wake_up_bit(I915_RESET_ENGINE + id,
> + >->reset.flags);
> +
> + /* Check that we do not resubmit the held request */
> + i915_request_get(rq);
> + if (!i915_request_wait(rq, 0, HZ / 5)) {
> + pr_err("%s: on hold request completed!\n",
> + engine->name);
> + i915_request_put(rq);
> + err = -EIO;
> + goto out;
> + }
> + GEM_BUG_ON(!i915_request_has_hold(rq));
> +
> + /* But is resubmitted on release */
> + execlists_unhold(engine, rq);
> + if (i915_request_wait(rq, 0, HZ / 5) < 0) {
> + pr_err("%s: held request did not complete!\n",
> + engine->name);
> + intel_gt_set_wedged(gt);
> + err = -ETIME;
> + }
> + i915_request_put(rq);
> +
> +out:
> + engine_heartbeat_enable(engine, heartbeat);
> + intel_context_put(ce);
> + if (err)
> + break;
> + }
> +
> + igt_spinner_fini(&spin);
> + return err;
> +}
> +
> static int
> emit_semaphore_chain(struct i915_request *rq, struct i915_vma *vma, int idx)
> {
> @@ -3315,6 +3417,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
> SUBTEST(live_sanitycheck),
> SUBTEST(live_unlite_switch),
> SUBTEST(live_unlite_preempt),
> + SUBTEST(live_hold_reset),
> SUBTEST(live_timeslice_preempt),
> SUBTEST(live_timeslice_queue),
> SUBTEST(live_busywait_preempt),
> diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
> index a9f0d3c8d8b7..47fa5419c74f 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -90,6 +90,13 @@ enum {
> */
> I915_FENCE_FLAG_SIGNAL,
>
> + /*
> + * I915_FENCE_FLAG_HOLD - this request is currently on hold
> + *
> + * This request has been suspended, pending an ongoing investigation.
> + */
> + I915_FENCE_FLAG_HOLD,
> +
> /*
> * I915_FENCE_FLAG_NOPREEMPT - this request should not be preempted
> *
> @@ -500,6 +507,21 @@ static inline bool i915_request_has_sentinel(const struct i915_request *rq)
> return unlikely(test_bit(I915_FENCE_FLAG_SENTINEL, &rq->fence.flags));
> }
>
> +static inline bool i915_request_has_hold(const struct i915_request *rq)
> +{
> + return unlikely(test_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags));
> +}
> +
> +static inline void i915_request_set_hold(struct i915_request *rq)
> +{
> + set_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags);
> +}
> +
> +static inline void i915_request_clear_hold(struct i915_request *rq)
> +{
> + clear_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags);
> +}
> +
> static inline struct intel_timeline *
> i915_request_timeline(struct i915_request *rq)
> {
>
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