drm/i915/execlists: Lock the request while validating it during promotion

Since the request is already on the HW as we perform its validation, it
and even its subsequent barrier may be concurrently retired before we
process the assertions. If it is retired already and so off the HW, our
assertions become void and we need to ignore them.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112363
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191121103546.146487-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index b65bc06855b0b94bb3039531aa2fb9142932fafb..da72794f3707958660f71ede6adb37043d76577d 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1291,38 +1291,53 @@ assert_pending_valid(const struct intel_engine_execlists *execlists,
        }
 
        for (port = execlists->pending; (rq = *port); port++) {
+               unsigned long flags;
+               bool ok = true;
+
                if (ce == rq->hw_context) {
                        GEM_TRACE_ERR("Dup context:%llx in pending[%zd]\n",
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
                        return false;
                }
-
                ce = rq->hw_context;
+
+               /* Hold tightly onto the lock to prevent concurrent retires! */
+               spin_lock_irqsave_nested(&rq->lock, flags,
+                                        SINGLE_DEPTH_NESTING);
+
                if (i915_request_completed(rq))
-                       continue;
+                       goto unlock;
 
                if (i915_active_is_idle(&ce->active) &&
                    !i915_gem_context_is_kernel(ce->gem_context)) {
                        GEM_TRACE_ERR("Inactive context:%llx in pending[%zd]\n",
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
-                       return false;
+                       ok = false;
+                       goto unlock;
                }
 
                if (!i915_vma_is_pinned(ce->state)) {
                        GEM_TRACE_ERR("Unpinned context:%llx in pending[%zd]\n",
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
-                       return false;
+                       ok = false;
+                       goto unlock;
                }
 
                if (!i915_vma_is_pinned(ce->ring->vma)) {
                        GEM_TRACE_ERR("Unpinned ring:%llx in pending[%zd]\n",
                                      ce->timeline->fence_context,
                                      port - execlists->pending);
-                       return false;
+                       ok = false;
+                       goto unlock;
                }
+
+unlock:
+               spin_unlock_irqrestore(&rq->lock, flags);
+               if (!ok)
+                       return false;
        }
 
        return ce;