[Devel] [RFC][PATCH] Add child reaper to struct pspace

[Eric W. Biederman]

"Serge E. Hallyn" <serue at us.ibm.com> writes:

> Quoting Eric W. Biederman (ebiederm at xmission.com):
>> Yes.  We all so need something like that list to support kill -1.
>> Although walking the list of all processes may be sufficient for a first
>> pass.
>> 
>> The real trick is handing nested pid namespaces, properly.
>
> Not if, as you've suggested in the past, pid_ns 5 has valid pids in its
> own pid_ns for every process in pid_namespaces nested under it.
>
> It should be simple to implement, should not impact the non-container
> cases, and should only start to impact performance as the nesting gets
> deep, which AFAIK we all believe won't happen (max nesting of 2 AFAICS,
> one checkpointable application container under one vserver-thingie)
>
> And it makes kill -1 trivial, as in pid_ns 5 we just kill all processes
> in pid_ns 5, without worrying about finding the ones in it's decendent
> pid namespaces.

If you do it correctly I agree.  But you have to be very careful where
you put the list.  

My point being not that we can't get this correct with simple code, but
that it is easy to get it wrong.

Eric
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