drm/i915/userptr: Only flush the workqueue if required

To avoid waiting for work from other invalidate-range threads where
not required, only wait on the userptr cancel workqueue if we have added
some work to it.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170307205851.32578-2-chris@chris-wilson.co.uk
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 6ef05d5..dc9bf52 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -145,7 +145,8 @@ static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,
                del_object(mo);
        spin_unlock(&mn->lock);
 
-       flush_workqueue(mn->wq);
+       if (!list_empty(&cancelled))
+               flush_workqueue(mn->wq);
 }
 
 static const struct mmu_notifier_ops i915_gem_userptr_notifier = {