Wily: Mesa 11.0 causes hang in Intel Xorg driver, reverting to 10.6.3 fixes

[Wladimir Mutel]

I am testing Wily on Kubuntu package set with SDDM display manager.
After upgrading Mesa packages from 10.6.3 to 11.0.0 I found that graphical logon screen does not appear, and the system freezes with black screen, non-blinking cursor and non-responding keyboard&touchpad
I disabled SDDM service in systemctl and could log in to text console.
Then I found that 'startx' command freezes the system as well.
In dpkg.log I found that Mesa packages were updated last, from v. 10.6.3 to 11.0.0.
I downloaded older versions from Ubuntu pool mirror and installed them by dpkg -i.
After that, GUI operation was fixed, and I re-enabled SDDM and continue using my system without more significant problems.

My system is Acer 1830T, made in 2010, CPU is Core i3-380UM with integrated GPU (Westmere/Ironlake/Arrandale, reported as gen5 in Xorg.0.log).

Please investigate and fix this issue. Please ask me if you need more testing or more details.

[Wladimir Mutel (mwg)]

apparently fixed after kernel upgrade from 4.2.0-10 to -11
now Mesa 11.0.0 works as well as 10.6.3 before.
probably the bug may be closed