Messages in this thread | | | From | Bill Davidsen <> | Subject | Re: init's children list is long and slows reaping children. | Date | Wed, 11 Apr 2007 17:24:13 -0400 |
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Eric W. Biederman wrote: > Bill Davidsen <davidsen@tmr.com> writes: > >> As long as the original parent is preserved for getppid(). There are programs >> out there which communicate between the parent and child with signals, and if >> the original parent dies, it undesirable to have the child getppid() and start >> sending signals to a program not expecting them. Invites undefined behavior. > > Then the programs are broken. getppid is defined to change if the process > is reparented to init. > The short answer is that kthreads don't do this so it doesn't matter.
But user programs are NOT broken, currently getppid returns either the original parent or init, and a program can identify init. Reparenting to another pid would not be easily noted, and as SUS notes, no values are reserved to error. So there's no way to check, and no neeed for kthreads, I was prematurely paranoid.
Presumably user processes will still be reparented to init so that's not an issue. Since there's no atomic signal_parent() the ppid could change between getppid() and signal(), but that's never actually been a problem AFAIK.
Related: Is there a benefit from having separate queues for original children of init and reparented (to init) tasks? Even in a server would there be enough to save anything?
-- Bill Davidsen <davidsen@tmr.com> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot
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