drm/i915/gt: Restore ce->signal flush before releasing virtual engine

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"),
whereby instead of unconditionally applying the flush, it was only
applied if the request itself was going to be reused.

v2: Generalise and cancel all remaining ce->signals

Fixes: bab0557c8dca ("drm/i915/gt: Remove virtual breadcrumb before transfer")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210108204026.20682-4-chris@chris-wilson.co.uk

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index 2eabb9ab5d47..7137b6f24f55 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -472,6 +472,39 @@ void i915_request_cancel_breadcrumb(struct i915_request *rq)
 	i915_request_put(rq);
 }
 
+void intel_context_remove_breadcrumbs(struct intel_context *ce,
+				      struct intel_breadcrumbs *b)
+{
+	struct i915_request *rq, *rn;
+	bool release = false;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ce->signal_lock, flags);
+
+	if (list_empty(&ce->signals))
+		goto unlock;
+
+	list_for_each_entry_safe(rq, rn, &ce->signals, signal_link) {
+		GEM_BUG_ON(!__i915_request_is_complete(rq));
+		if (!test_and_clear_bit(I915_FENCE_FLAG_SIGNAL,
+					&rq->fence.flags))
+			continue;
+
+		list_del_rcu(&rq->signal_link);
+		irq_signal_request(rq, b);
+		i915_request_put(rq);
+	}
+	release = remove_signaling_context(b, ce);
+
+unlock:
+	spin_unlock_irqrestore(&ce->signal_lock, flags);
+	if (release)
+		intel_context_put(ce);
+
+	while (atomic_read(&b->signaler_active))
+		cpu_relax();
+}
+
 static void print_signals(struct intel_breadcrumbs *b, struct drm_printer *p)
 {
 	struct intel_context *ce;