Re: [PATCHv7 01/33] ns: Introduce Time Namespace

On 10/17/19 10:20 AM, Thomas Gleixner wrote:

[...]

The architectures which implement VDSO are:

    arm, arm64, mips, nds32, powerpc, riscv, s390, sparc, x86, um

arm64, mips, x86 use the generic VDSO. Patches for arm are floating
around. UM is special as it just traps into the syscalls. No idea about the
rest. Vincenzo might know.

There a couple of cases: hexagon and csky that have vDSOs for signal trampolines
if I recall correctly, but they do not fall into the category we are exploring
at the moment.

The bad news is that we have no information (except on arm which has a
config switch for VDSO) whether an architecture provides VDSO support or
not.

So unless you add something like

   config HAS_VDSO
   	  bool

which is selected by all architectures which provide VDSO support, the only
sane solution is to depend on GENERIC_VDSO_TIME_NS.

TBH, I would not even bother. The architectures which matter and are going
to use time namespaces already support VDSO and they need to move to the
generic implementation anyway as we discussed and agreed on in Vancouver.

Providing time name spaces for the non VDSO archs is a purely academic
exercise.

I totally agree with this.

-- 
Regards,
Vincenzo