Comment 6 for bug 1648122

FWIW, here some investigation results on the multi-user support for amdgpu-pro 17.10 on Mint/MATE 18.1.

0) The problem: Only the first user that logs in gets GLX, the second user gets errors (/dev/dri/card0 permission denied, see above).
1) The amdgpu-pro driver works fine in Ubuntu 16.04: first user logs in, second user logs in, both have GLX.
2) So I installed mate-session on Ubuntu to get at least a MATE environment, but the problem reappeared when both users log in on MATE. No problem when the second user logs in on unity or xfce4. (I didn't try to vary the session manager of the first user.)
3) However, when the second user logs in with unity,xfce4 or mate, logs out, and logs back in with mate, then everything is fine and both users have GLX.
4) So installed xfce4 on Mint-MATE to test this workaround, but no luck: GLX is not available to the second user no matter whether he/she logs into xfce4 first.

So my plan is to give up on Mint MATE 18.1 for now, and use Ubuntu 16.04 with MATE because there the second user can use MATE+GLX with the login-logout-login workaround.