Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> writes: > Cc: Oleg, Eric > > Oren Laadan [orenl@xxxxxxxxxxxxxxx] wrote: > | > | What happens when a container-init calls clone() with the > | CLONE_PARENT flag set ? > | > | Since CLONE_PARENT can be used to create a sibling, I'd > | think that this will create a sibling, in particular, a > | new task in the same container whose parent is the parent > | of the container. From a quick look in the code I can't > | see why this would be impossible. > | > | Is this so ? Is this the desired behavior ? > > Good question. CLONE_PARENT was discussed recently on lkml but did > not look obvious to me who uses it or what the semantics are. > Some observations. > > - the "reaper" for this sibling would be the reaper of the > parent container, not the init of the new container. > > - if container-init exits, this sibling will also be killed since > it has a pid in this container. > > Not sure if it needs to be prevented though. An using CLONE_PARENT > may want to run as a container-init :-) And if CLONE_PARENT is used > with CLONE_THREAD, we don't want to preclude threaded container-inits. Fascinating. We have a way of generating processes that breaks the unix process tree. In the initial pid namespace a init that calls CLONE_PARENT will be the reaper of that child, because the idle thread is in the same pid namespace. I hadn't even thought about CLONE_PARENT in the context of a pid namespace. CLONE_PARENT is a rare uncommon case a left over from the first experiments of threading in linux. So I would not work hard at getting it to do the right thing. If it is a problem I would kill it. However if we can support processes who don't have init as their parent it makes entering a pid namespace a much more realistic proposition. Eric _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
