drm/i915/gt: Shrink the critical section for irq signaling

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@chris-wilson.co.uk>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201224135544.1713-6-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index 8f7c859..2eabb9a 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -234,6 +234,7 @@ 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;
 
@@ -269,6 +270,7 @@ 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 d85a6f7..3a084ce 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs_types.h
@@ -34,6 +34,7 @@ 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_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index 1f6e9fe..ba8229c 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -594,7 +594,8 @@ 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();
        }
 
        if (READ_ONCE(ve->request))