[systemd-devel] Fwd: [Pkg-systemd-maintainers] Bug#732157: Want SIGSTOP-style daemon/service readiness notification

[Lennart Poettering]

On Mon, 16.12.13 06:55, Andrey Borzenkov (arvidjaar at gmail.com) wrote:

> В Sun, 15 Dec 2013 23:23:54 +0100
> Lennart Poettering <lennart at poettering.net> пишет:
> 
> > 
> > This is really not how we should do it: the admin must be capable of
> > tracing and pausing the boot process, and an init system should not make
> > that impossible. 
> >
> 
> What happens currently when service gets SIGSTOP? Does systemd ignore
> it? 

We never ask for SIGSTOP notifications, and we hence don't get them at all.

> Will it reflect this information in service state? 

No. It really doesn't care much. I am not sure reflecting this
information in the service state would really be such a good idea, as
the service concept mostly tries to reflect state that applies to all
processes of a service, except when it comese to lifecycle
decisions. Now, whether a process is stopped or not is really something
that is specific to a single process, not a service, so it probably
shouldn't be reflected in the entirety of the service.

That said, I am not against adding something to the way we display
"systemctl status" where we show explicitly for each process we list
whether it is stopped or not. (maybe just by showing unicode stop sign
or so next to stopped processes). But sofar nobody asked fr this...

Not that we when we kill a service the hard way then we will send a
SIGCONT to it, so that we can fulfill the request even if the process is
currently stopped. (Because it won't react to SIGTERM as long as it is paused.)

> Actually, what
> state service *is* in this case (it obviously is not running but is not
> failed either ...)?

Well, we don't care about whether a process is stopped or not, hence
from our perspective whether it is paused or not is indistuingishable,
it's just a process like any other, except maybe that it might not
respond anymore (which we might notice eventually if watchdog support is
enabled for it...)

Lennart

-- 
Lennart Poettering, Red Hat