[PATCH 0/1] signals: introduce send_sigkill() helper

[Oleg Nesterov <oleg@redhat.com>]

On 06/08, Oleg Nesterov wrote:
>
> > @@ -399,7 +399,7 @@ static int __oom_kill_process(struct task_struct *p, struct mem_cgroup *mem)
> >  	p->rt.time_slice = HZ;
> >  	set_tsk_thread_flag(p, TIF_MEMDIE);
> >
> > -	force_sig(SIGKILL, p);
> > +	send_sig(SIGKILL, p, 1);
>
> This is not right, we need send_sig(SIGKILL, p, 0). Better yet,
> send_sig_info(SIGKILL, SEND_SIG_NOINFO). I think send_sig() should
> die.
>
> The reason is that si_fromuser() must be true, otherwise we can't kill
> the SIGNAL_UNKILLABLE (sub-namespace inits) tasks.
>
> Oh. This reminds me, we really need the trivial (but annoying) cleanups
> here. The usage of SEND_SIG_ constants is messy, and they should be
> renamed at least.
>
> And in fact, we need the new one which acts like SEND_SIG_FORCED but
> si_fromuser(). We do not want to allocate the memory when the caller
> is oom_kill or zap_pid_ns_processes().

I tried to make some simple cleanups right now, but this really needs
time and discussion.

So. If we are going to remove force_sig() in mm/oom_kill.c (and I think
we should), I'd like to add the trivial helper first.

Oleg.