After disabling plymouth-splash I can't reproduce this anymore.
It's a race between plymouth and xorg. Plymouth holds DRM master (drm_setmaster_ioctl) while xorg tries to start (drm_setversion) and fails with EACCESS because it needs DRM_MASTER for that.
It works fine if
1. plymouth never starts
2. plymouth calls drm_dropmaster_ioctl before X starts
And another thing is the Xorg.log timestamps can't really be trusted.
After disabling plymouth-splash I can't reproduce this anymore.
It's a race between plymouth and xorg. Plymouth holds DRM master (drm_setmaster_ ioctl) while xorg tries to start (drm_setversion) and fails with EACCESS because it needs DRM_MASTER for that.
It works fine if ioctl before X starts
1. plymouth never starts
2. plymouth calls drm_dropmaster_
And another thing is the Xorg.log timestamps can't really be trusted.