I. was. blind.
Caught with vkms, which has some really slow crc computation function.
Fixes: 1882018a70e0 ("drm/crc-debugfs: User irqsafe spinlock in drm_crtc_add_crc_entry")
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190606211544.5389-1-daniel.vetter@ffwll.ch
 
        /* Caller may not have noticed yet that userspace has stopped reading */
        if (!crc->entries) {
-               spin_unlock(&crc->lock);
+               spin_unlock_irqrestore(&crc->lock, flags);
                return -EINVAL;
        }
 
                bool was_overflow = crc->overflow;
 
                crc->overflow = true;
-               spin_unlock(&crc->lock);
+               spin_unlock_irqrestore(&crc->lock, flags);
 
                if (!was_overflow)
                        DRM_ERROR("Overflow of CRC buffer, userspace reads too slow.\n");