Comment # 1 on bug 104306 from eric vz

Similar experience here on Arch Linux with a Radeon HD 8870M / R9 M270X/M370X. 
Firefox hangs on launch before drawing a window, and Chromium won't start
either unless I --disable-gpu.  Similar strace results, no amdkfd errors.

Archive package 2017/12/15/extra/os/x86_64/mesa-17.2.6-1 works fine,
2017/12/16/extra/os/x86_64/mesa-17.3.0-2 doesn't.  Kernel 4.9.69-1-lts #1 SMP
Thu Dec 14 19:51:07 CET 2017 x86_64 GNU/Linux, if it matters.

I notice the Arch maintainer changed the build arg --enable-omx to
--enable-omx-bellagio in this release.  I know nothing of Mesa's build process,
this being my first encounter, but I thought that might be useful to mention in
case it's relevant.