Re: [PATCH] prctl.2: PR_{SET,GET}_CHILD_SUBREAPER

[Lennart Poettering <lennart-mdGvqq1h2p+GdvJs77BJ7Q@public.gmane.org>]

On Fri, 08.02.13 10:35, Michael Kerrisk (man-pages) (mtk.manpages@gmail.com) wrote:

> 
> Shawn, Lennart, Kay,
> 
> On Wed, Feb 6, 2013 at 7:33 PM, Shawn Landden <shawnlandden-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > Signed-off-by: Shawn Landden <shawnlandden-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > ---
> >  man2/prctl.2 |   17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/man2/prctl.2 b/man2/prctl.2
> > index e4a1030..fd78f48 100644
> > --- a/man2/prctl.2
> > +++ b/man2/prctl.2
> > @@ -379,6 +379,23 @@ if the kernel is configured with
> >  .B CONFIG_SECCOMP
> >  enabled.
> >  .TP
> > +.BR PR_SET_CHILD_SUBREAPER " (since Linux 3.3)"
> > +Designates this process as a service manager for its' (immediate and
> > +indirect) offspring processes. Any process whose immediate parent
> > +dies and whose ancestry includes a process where this flag is set will
> > +be reparented to the closest process with this flag set, instead of PID
> > +1. A 'subreaper' hence receives
> > +.B SIGHCLD
> > +signals for any orphaned
> > +offspring processes, that otherwise would be received by
> > +.BR init (8).
> > +.TP
> > +.BR PR_GET_CHILD_SUBREAPER " (since Linux 3.3)"
> > +Returns whether calling process is a child subreaper (see
> > +.BR PR_SET_CHILD_SUBREAPER ),
> > +in the location pointed to by
> > +.IR "(int\ *) arg2" .
> > +.TP
> >  .BR PR_SET_SECUREBITS " (since Linux 2.6.26)"
> >  Set the "securebits" flags of the calling thread to the value supplied in
> >  .IR arg2 .
> 
> Shawn, there was some imprecision in your patch. I've instead come up
> with an alternative.
> 
> Kay, Lennart, is the following correct?
> 
>        PR_SET_CHILD_SUBREAPER (since Linux 3.4)
>               If  arg2 is nonzero, set the "child subreaper" attribute
>               of the calling process;  if  arg2  is  zero,  unset  the
>               attribute.   When  a  process  is marked as a child sub‐
>               reaper, all of the children that it creates,  and  their
>               descendants,  will  be marked as having a subreaper.  in
>               effect, a subreaper fulfills the role of init(1) for its
>               descendant  processes.   Upon  termination  of a process
>               that is orphaned (i.e., its immediate parent has already
>               terminated)  and marked as having a subreaper, the near‐
>               est still  living  ancestor  subreaper  will  receive  a
>               SIGCHLD  signal and be able to wait(2) on the process to
>               diiscover its termination status.
> 
>        PR_GET_CHILD_SUBREAPER (since Linux 3.4)
>               Return the "child subreaper" setting of the  caller,  in
>               the location pointed to by (int *) arg2.
> 

Sounds good to me! Though s/in/In/ once in there.

Thanks for putting this together, sorry for never having done this
myself.

Oh, yeah, and I still need to do that book review for you, too!

Lennart

-- 
Lennart Poettering - Red Hat, Inc.
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html