I encouraged the reporter to file this bug before I found on my own Matrox 550
Stretch installation exhibiting same lockups but accessible via remote login
that blacklisting mga kernel module and rebuilding initrd stopped the lockups.
The same machine booted to Mageia 5 kernel 4.4 never had, and openSUSE kernel
4.9 ceased to have[1], this problem, and neither tried to load any mga kernel
module as Stretch was doing.
Broken mailing list thread originated by this bug's reporter:
https://lists.debian.org/debian-user/2017/04/msg00031.html
https://lists.debian.org/debian-user/2017/03/msg01272.html
https://lists.debian.org/debian-user/2017/03/msg01283.html
[1] https://bugzilla.opensuse.org/show_bug.cgi?id=1004453
