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add some doc for shim reap orphan process #10002
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ningmingxiao
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Suggestion:
containerd-shim-runc-v2 as sub-reaper
The shim process takes responsibility as a sub-reaper to cleanup exited containers or setns(2) processes.
When container is running in new PID namespace, the container should cleanup orphaned processes before it exits.
If container uses the same PID namespace with shim process, its descendant processes will be reparented to shim process. The shim process will reap them when they exit.
However, [PATCH] exit: fix the setns() && PR_SET_CHILD_SUBREAPER interaction prevents any cross-namespace reparenting in kernel. Assume that container is in X-namespace and P in root-namespace setns into X-namespace. P forks child
C
. The childC
forks a grandchildG
and exits. TheG
will be reparented to X instead of P's reaper.If the PID namespace is different from shim process, the container init process should cleanup any orphaned reparented processes created by setns process (exec operation).
cc @AkihiroSuda @dmcgowan