[RFC][PATCH] Disable CLONE_PARENT for init
sukadev at linux.vnet.ibm.com
Wed Jul 1 01:01:06 PDT 2009
Roland McGrath [roland at redhat.com] wrote:
| > When global or container-init processes use CLONE_PARENT, they create a
| > multi-rooted process tree.
| I take this to be the real motivation for your change.
| But you don't mention it in the code comment.
Well, it was - when I started. But my understanding of the comments was that
the constraint could be extended to global init as well for the following
| > + * Swapper process sets the handler for SIGCHLD to SIG_DFL. If init
| > + * creates a sibling and the sibling exits, the SIGCHLD is sent to
| > + * the swapper (since the swapper's handler for SIGCHLD is SIG_DFL).
| > + * But since the swapper does not reap its children, the zombie will
| > + * remain forever. So prevent init from using CLONE_PARENT.
| This would be fixed by having swapper set its SIGCHLD to SIG_IGN instead,
| so such children self-reap. That seems like the better fix for that.
Yes, that would fix the global init case.
| If you want to make this change because of container-init issues, I think
| you should just say so independent of this global-init case.
So can I leave the check for SIGNAL_UNKILLABLE but simplify the comments
to refer to the multi-rooted process tree ?
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