[PATCH] Introduce ActivePid: in /proc/self/status (v2, was Vpid:)

[Oleg Nesterov]

On 06/16, Eric W. Biederman wrote:
>
> I remember there were a few very weird things with pids when ptracing
> a process in another pid namespace.

The only problems is pids. PTRACE_EVENT_FORK/etc reports the global pid.
This is fixable. Some tracers look at syscall_get_return_value() register
and get the "local" pid which they do not want.

> It may be that ActivePid is enough
> to allow the tracer to figure out the confusing information it is
> getting.

I don't think so. ActivePid doesn't help unless you know all pids in
this container.

> I would be surprised if using ptrace to send signals is how you
> want to do things.

Yes, yes, this is hack.

Oleg.