Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Refactor the common task of updating the first_waiter, serialised with
> the interrupt handler. When we update the first_waiter, we also need to
> wakeup the new bottom-half in order to complete the actions that we may
> have delegated to it (such as checking the irq-seqno coherency or waking
> up other lower priority concurrent waiters).
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_breadcrumbs.c | 48 +++++++++++++-------------------
> 1 file changed, 19 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> index 235d4645a5cf..1cc50304f824 100644
> --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
> +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> @@ -287,6 +287,21 @@ static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b,
> wake_up_process(wait->tsk); /* implicit smp_wmb() */
> }
>
> +static inline void __intel_breadcrumbs_next(struct intel_engine_cs *engine,
> + struct rb_node *next)
> +{
> + struct intel_breadcrumbs *b = &engine->breadcrumbs;
> +
> + GEM_BUG_ON(!b->irq_armed);
> + b->first_wait = to_wait(next);
> +
> + /* We always wake up the next waiter that takes over as the bottom-half
> + * as we may delegate not only the irq-seqno barrier to the next waiter
> + * but also the task of waking up concurrent waiters.
> + */
> + wake_up_process(to_wait(next)->tsk);
> +}
> +
> static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
> struct intel_wait *wait)
> {
> @@ -357,21 +372,7 @@ static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
> 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);
> + __intel_breadcrumbs_next(engine, next);
> }
>
> do {
> @@ -473,21 +474,10 @@ static void __intel_engine_remove_wait(struct intel_engine_cs *engine,
> }
> }
>
> - 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 {
> + if (next)
> + __intel_breadcrumbs_next(engine, next);
> + else
> b->first_wait = NULL;
> - }
> } else {
> GEM_BUG_ON(rb_first(&b->waiters) == &wait->node);
> }
> --
> 2.11.0
>
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> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
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