3 files changed, 34 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 4461336205ed..00c836154725 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3106,7 +3106,7 @@ i915_find_fence_reg(struct drm_device *dev)
         }
 
         if (avail == NULL)
-                return NULL;
+                goto deadlock;
 
         /* None available, try to steal one or wait for a user to finish */
         list_for_each_entry(reg, &dev_priv->mm.fence_list, lru_list) {
@@ -3116,7 +3116,12 @@ i915_find_fence_reg(struct drm_device *dev)
                 return reg;
         }
 
-        return NULL;
+deadlock:
+        /* Wait for completion of pending flips which consume fences */
+        if (intel_has_pending_fb_unpin(dev))
+                return ERR_PTR(-EAGAIN);
+
+        return ERR_PTR(-EDEADLK);
 }
 
 /**
@@ -3161,8 +3166,8 @@ i915_gem_object_get_fence(struct drm_i915_gem_object *obj)
                 }
         } else if (enable) {
                 reg = i915_find_fence_reg(dev);
-                if (reg == NULL)
-                        return -EDEADLK;
+                if (IS_ERR(reg))
+                        return PTR_ERR(reg);
 
                 if (reg->obj) {
                         struct drm_i915_gem_object *old = reg->obj;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 14b024becb91..98371eeac77c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2982,6 +2982,30 @@ static bool intel_crtc_has_pending_flip(struct drm_crtc *crtc)
         return pending;
 }
 
+bool intel_has_pending_fb_unpin(struct drm_device *dev)
+{
+        struct intel_crtc *crtc;
+
+        /* Note that we don't need to be called with mode_config.lock here
+         * as our list of CRTC objects is static for the lifetime of the
+         * device and so cannot disappear as we iterate. Similarly, we can
+         * happily treat the predicates as racy, atomic checks as userspace
+         * cannot claim and pin a new fb without at least acquring the
+         * struct_mutex and so serialising with us.
+         */
+        list_for_each_entry(crtc, &dev->mode_config.crtc_list, base.head) {
+                if (atomic_read(&crtc->unpin_work_count) == 0)
+                        continue;
+
+                if (crtc->unpin_work)
+                        intel_wait_for_vblank(dev, crtc->pipe);
+
+                return true;
+        }
+
+        return false;
+}
+
 static void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc)
 {
         struct drm_device *dev = crtc->dev;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 8754db9e3d52..fbfaaba5cc3b 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -626,6 +626,7 @@ void intel_ddi_get_config(struct intel_encoder *encoder,
 
 /* intel_display.c */
 const char *intel_output_name(int output);
+bool intel_has_pending_fb_unpin(struct drm_device *dev);
 int intel_pch_rawclk(struct drm_device *dev);
 void intel_mark_busy(struct drm_device *dev);
 void intel_mark_fb_busy(struct drm_i915_gem_object *obj,