Before we mark the virtual engine as no longer inflight, flush any
ongoing signaling that may be using the ce->signal_link along the
previous breadcrumbs. On switch to a new physical engine, that link will
be inserted into the new set of breadcrumbs, causing confusion to an
ongoing iterator.
This patch undoes a last minute mistake introduced into commit
bab0557c8dca ("drm/i915/gt: Remove virtual breadcrumb before transfer"),
to simplify later patches whereby instead of unconditionally applying the
flush, it was only applied if the request itself was going to be reused.
Fixes: bab0557c8dca ("drm/i915/gt: Remove virtual breadcrumb before transfer")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
.../drm/i915/gt/intel_execlists_submission.c | 32 ++++++++++---------
1 file changed, 17 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index a5b442683c18..db208bb59364 100644
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -581,21 +581,6 @@ resubmit_virtual_request(struct i915_request *rq, struct virtual_engine *ve)
{
struct intel_engine_cs *engine = rq->engine;
- /* Flush concurrent rcu iterators in signal_irq_work */
- if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags)) {
- /*
- * After this point, the rq may be transferred to a new
- * sibling, so before we clear ce->inflight make sure that
- * the context has been removed from the b->signalers and
- * furthermore we need to make sure that the concurrent
- * iterator in signal_irq_work is no longer following
- * ce->signal_link.
- */
- i915_request_cancel_breadcrumb(rq);
- while (atomic_read(&engine->breadcrumbs->signaler_active))
- cpu_relax();
- }
-
spin_lock_irq(&engine->active.lock);
clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
@@ -609,6 +594,19 @@ static void kick_siblings(struct i915_request *rq, struct intel_context *ce)
{
struct virtual_engine *ve = container_of(ce, typeof(*ve), context);
struct intel_engine_cs *engine = rq->engine;
+ bool signals = !list_empty(&ce->signals);
+
+ /* Flush concurrent rcu iterators in signal_irq_work */
+ if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags))
+ /*
+ * After this point, the rq may be transferred to a new
+ * sibling, so before we clear ce->inflight make sure that
+ * the context has been removed from the b->signalers and
+ * furthermore we need to make sure that the concurrent
+ * iterator in signal_irq_work is no longer following
+ * ce->signal_link.
+ */
+ i915_request_cancel_breadcrumb(rq);
/*
* This engine is now too busy to run this virtual request, so
@@ -622,6 +620,10 @@ static void kick_siblings(struct i915_request *rq, struct intel_context *ce)
if (READ_ONCE(ve->request))
tasklet_hi_schedule(&ve->base.execlists.tasklet);
+
+ /* Flush concurrent signal_irq_work before we reuse the link */
+ while (signals && atomic_read(&engine->breadcrumbs->signaler_active))
+ cpu_relax();
}
static inline void __execlists_schedule_out(struct i915_request *rq)
--
2.20.1
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