CHROMIUM: drm/i915: Replace pin count BUG_ON with warning

This patch reduces the BUG_ON when pin_count reaches max to a warning.
The reason we want to just warn is because the unpin_work_fn work
function can get starved out during soft lockup. When the unpin worker
is starved, the pin_count rises, and the gem BUG_ON races the soft
lockup crash reporter.

The original intent of this BUG was to catch overflow cases when all of
the small bitfields in drm_i915_gem_object were combined into one
bitfield (commit 778c35444). Since pin leaks aren't an issue in steady
state, it should be fine to downgrade the error.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
BUG=chrome-os-partner:8552,chromium-os:30733
TEST=Tested on lumpy

Change-Id: Ibd7377385f36a722b588cfe4989b3e26d2647bd2
Reviewed-on: https://gerrit.chromium.org/gerrit/22829
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Tested-by: Sean Paul <seanpaul@chromium.org>
Commit-Ready: Sean Paul <seanpaul@chromium.org>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ee51890..686e5f1 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3317,7 +3317,10 @@ i915_gem_object_pin(struct drm_i915_gem_object *obj,
        struct drm_i915_private *dev_priv = dev->dev_private;
        int ret;
 
-       BUG_ON(obj->pin_count == DRM_I915_GEM_OBJECT_MAX_PIN_COUNT);
+       if (obj->pin_count == DRM_I915_GEM_OBJECT_MAX_PIN_COUNT) {
+               WARN(obj->pin_count, "pin count has reached its max\n");
+               return -ENOSPC;
+       }
        WARN_ON(i915_verify_lists(dev));
 
        if (obj->gtt_space != NULL) {