On Mon, Dec 07, 2020 at 07:38:11PM +0000, Chris Wilson wrote:
> Let's only wait for the list iterator when decoupling the virtual
> breadcrumb, as the signaling of all the requests may take a long time,
> during which we do not want to keep the tasklet spinning.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 2 ++
> drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h | 1 +
> drivers/gpu/drm/i915/gt/intel_lrc.c | 3 ++-
> 3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
> index 63900edbde88..ac1e5f6c3c2c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
> @@ -239,6 +239,7 @@ static void signal_irq_work(struct irq_work *work)
> intel_breadcrumbs_disarm_irq(b);
>
> rcu_read_lock();
> + atomic_inc(&b->signaler_active);
> list_for_each_entry_rcu(ce, &b->signalers, signal_link) {
> struct i915_request *rq;
>
> @@ -274,6 +275,7 @@ static void signal_irq_work(struct irq_work *work)
> }
> }
> }
> + atomic_dec(&b->signaler_active);
> rcu_read_unlock();
>
> llist_for_each_safe(signal, sn, signal) {
> diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
> index a74bb3062bd8..f672053d694d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
> @@ -35,6 +35,7 @@ struct intel_breadcrumbs {
> spinlock_t signalers_lock; /* protects the list of signalers */
> struct list_head signalers;
> struct llist_head signaled_requests;
> + atomic_t signaler_active;
>
> spinlock_t irq_lock; /* protects the interrupt from hardirq context */
> struct irq_work irq_work; /* for use from inside irq_lock */
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index b3db16b2a5a4..35cded25c6c1 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1401,7 +1401,8 @@ static void kick_siblings(struct i915_request *rq, struct intel_context *ce)
> * ce->signal_link.
> */
> i915_request_cancel_breadcrumb(rq);
> - irq_work_sync(&engine->breadcrumbs->irq_work);
> + while (atomic_read(&engine->breadcrumbs->signaler_active))
> + cpu_relax();
Would a 'cond_resched' be better here? I trust your opinion on which to
use but thought I'd mention it.
With that:
Reviewed-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> }
>
> if (READ_ONCE(ve->request))
> --
> 2.20.1
>
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