Hello Pavel, On 27 January 2017 at 23:11, Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx> wrote: > old semantics was non deterministic and worked differently > depending on the external factors, but nothing changes if > process first sets itself subreaper and only after forks When did the kernel behavior change? Cheers, Michael > Signed-off-by: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx> > --- > man2/prctl.2 | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/man2/prctl.2 b/man2/prctl.2 > index 97cf21a..84fbd7e 100644 > --- a/man2/prctl.2 > +++ b/man2/prctl.2 > @@ -162,20 +162,30 @@ if > is zero, unset the attribute. > > When a process is marked as a child subreaper, > -all of the children that it creates, and their descendants, > +all of the children that it creates or have created already, and their descendants, > will be marked as having a subreaper. > In effect, a subreaper fulfills the role of > .BR 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 nearest still living ancestor subreaper > -will receive a > +Upon termination of a process having a subreaper, > +all its children become orphaned > +and will be reparented to the nearest still living ancestor subreaper. > +So that on it's adopted child termination > +these subreaper will receive a > .BR SIGCHLD > signal and will be able to > .BR wait (2) > -on the process to discover its termination status. > +on the child to discover its termination status. > + > +Note, that on older kernels these prctl works slightly different. > +Child subreaper process was not actualy the > +.BR init (1) > +for all its descendants. > +If process forks a child while not been a child subreaper, > +and after sets himself child subreaper, > +sub-tree of the child might or might not reparent to the subreaper, > +depending on the configuration of ancestors of the subreaper, > +at the time of forking our subtree. > .TP > .BR PR_GET_CHILD_SUBREAPER " (since Linux 3.4)" > Return the "child subreaper" setting of the caller, > -- > 2.9.3 > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
