Using DRI_PRIME=0 is just to switch between Intel and AMD Graphics.
Of course, we can omit it completely.

The system halt issue happens when executing `DRI_PRIME=1 glxgears -info`.

u@u:~$ DRI_PRIME=1 glxgears -info
Running synchronized to the vertical refresh.  The framerate should be
approximately the same as the monitor refresh rate.
GL_RENDERER   = Gallium 0.4 on AMD HAINAN (DRM 2.46.0, LLVM 3.8.0)
GL_VERSION    = 3.0 Mesa 11.2.0
GL_VENDOR     = X.Org
...
u@u:~$ DRI_PRIME=0 glxgears -info
Running synchronized to the vertical refresh.  The framerate should be
approximately the same as the monitor refresh rate.
GL_RENDERER   = Mesa DRI Intel(R) Kabylake GT1.5 
GL_VERSION    = 3.0 Mesa 11.2.0
GL_VENDOR     = Intel Open Source Technology Center
...

(In reply to Michel Dänzer from comment #1)
> Please attach the corresponding dmesg output.
> 
> (In reply to Shih-Yuan Lee from comment #0)
> > While I am doing the tests with AC plugged in by `DRI_PRIME=1 glxgears
> > -info` and `DRI_PRIME=0 glxgears -info`, the system halts and then is forced
> > to shutdown automatically.
> 
> To clarify, DRI_PRIME=1 glxgears works, the problem only occurs with
> DRI_PRIME=0 glxgears?