[Devel] Re: [PATCH 0/7][v7] Container-init signal semantics

[Serge E. Hallyn]

Quoting Sukadev Bhattiprolu (sukadev at linux.vnet.ibm.com):
> KAMEZAWA Hiroyuki [kamezawa.hiroyu at jp.fujitsu.com] wrote:
> | On Sat, 17 Jan 2009 12:26:38 -0800
> | Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com> wrote:
> | 
> | > 
> | > Container-init must behave like global-init to processes within the
> | > container and hence it must be immune to unhandled fatal signals from
> | > within the container (i.e SIG_DFL signals that terminate the process).
> | > 
> | > But the same container-init must behave like a normal process to 
> | > processes in ancestor namespaces and so if it receives the same fatal
> | > signal from a process in ancestor namespace, the signal must be
> | > processed.
> | > 
> | > Implementing these semantics requires that send_signal() determine pid
> | > namespace of the sender but since signals can originate from workqueues/
> | > interrupt-handlers, determining pid namespace of sender may not always
> | > be possible or safe.
> | > 
> | 
> | Is this feature is for blocking signals from children to name-space
> | creator(owner) ?  And automatically used when namespace/cgroup is created ?
> | IOW, Container-init is Namespace-Cgroup-init ? 
> 
> I am not sure what "Namespace-cgroup-init refers" to.

It sounds like he means the first task in a newly created
ns cgroup.  In which case he would mean any task which has
done an unshare with any of CLONE_NEWNS, CLONE_NEWIPC, etc,
or is the result of clone with the same.

> But, yes, this patchset applies to the first process in a pid namespace
> i.e the child of clone(NEWPID) call.
> 
> | 
> | I'm glad if you add some documentation updates about how-it-works to patch set.
> 
> Yes,  when the patchset is accepted, I am planning to add some notes to
> /sbin/init man page. 
> 
> Thanks,
> 
> Sukadev
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