drm/i915/gem: Try to flush pending unbind events

If we cannot handle a vma within the unbind loop, try to flush the
pending events (i915_vma_parked, i915_vm_release) and try again. This
avoids a round trip to userspace that is not guaranteed to make forward
progress, as the events we wait upon require being idle.

References: cb6c3d45f948 ("drm/i915/gem: Avoid parking the vma as we unbind")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191204123556.3740002-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 07b7a8a671d0b7aab98cd2d9e4722043ae4aa8f9..cc8c6960b689ddde3636d59375e3fe9d6c1d16bb 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -124,7 +124,7 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj,
        LIST_HEAD(still_in_list);
        intel_wakeref_t wakeref;
        struct i915_vma *vma;
-       int ret = 0;
+       int ret;
 
        if (!atomic_read(&obj->bind_count))
                return 0;
@@ -137,6 +137,8 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj,
         */
        wakeref = intel_runtime_pm_get(rpm);
 
+try_again:
+       ret = 0;
        spin_lock(&obj->vma.lock);
        while (!ret && (vma = list_first_entry_or_null(&obj->vma.list,
                                                       struct i915_vma,
@@ -154,6 +156,7 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj,
                } else {
                        if (i915_vma_is_closed(vma)) {
                                spin_unlock(&obj->vma.lock);
+                               i915_vma_parked(vm->gt);
                                goto err_vm;
                        }
                }
@@ -175,6 +178,11 @@ err_vm:
        list_splice(&still_in_list, &obj->vma.list);
        spin_unlock(&obj->vma.lock);
 
+       if (ret == -EAGAIN && flags & I915_GEM_OBJECT_UNBIND_ACTIVE) {
+               rcu_barrier(); /* flush the i915_vm_release() */
+               goto try_again;
+       }
+
        intel_runtime_pm_put(rpm, wakeref);
 
        return ret;