(In reply to Alexander Tsoy from comment #0)
> With 4.14 kernels the game process is unkillable so it hangs somewhere 
> in the kernel space. With 4.17 kernels it can be killed but this
> takes some time.
The process actually can be killed in a while loop.

Perf report:

$ sudo perf report | grep metro | head
    33.33%  metro            metro                          [.]
cbackend_OGL::delayed_upload
    31.56%  metro            [kernel.vmlinux]               [k] rb_prev
     2.07%  metro            [kernel.vmlinux]               [k] alloc_iova
     0.20%  metro            [kernel.vmlinux]               [k] __switch_to
     0.18%  metro            [kernel.vmlinux]               [k]
native_load_gs_index
     0.13%  metro            [kernel.vmlinux]               [k]
__x86_indirect_thunk_rax
     0.12%  metro            [kernel.vmlinux]               [k]
entry_SYSCALL_64
     0.08%  metro            [kernel.vmlinux]               [k] __schedule
     0.08%  metro            [kernel.vmlinux]               [k] read_tsc
     0.07%  metro            libc-2.26.so                   [.] __nanosleep