On Thu, Mar 07, 2019 at 09:02:07PM +0100, Eugene Syromyatnikov wrote:
> On Thu, Mar 7, 2019 at 8:05 PM Eugene Syromyatnikov <evgsyr@xxxxxxxxx> wrote:
> >
> > The POSIX-mandated behaviour of sending SIGCONT/SIGHUP to stopped processes
> > of an orphaned process group is not observed inside PID namespaces, as
> > can be verified by running [1] inside a PID namespace, for example.
> >
> > The derivation is (presumably) introduced by Linux commit
> s/derivation/deviation/
>
> > v2.6.24-rc1~237 ("pid namespaces: define is_global_init() and
> > is_container_init()").
> >
> > [1] https://gitlab.com/strace/strace/commit/4278e6613f48273e7da0989712f1c18aaffefd84
> >
> > Reported-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
> > Signed-off-by: Eugene Syromyatnikov <evgsyr@xxxxxxxxx>
>
> It should probably also be noted that the behaviour is also described
> in TLPI, Section 34.8 ("Process groups, sessions, and job control:
> Summary"), so it also likely has to be updated.
Strictly speaking, whether orphaned process group semantics works in
a PID namespace or not depends on the session ID. If the session ID is
the same as the session ID of init (which happens quite often in case
of a PID namespace), then orphaned process group semantics doesn't work.
If they differ, then the POSIX-mandated behaviour is supported.
For example:
$ unshare -fprU sh -c './orphaned_process_group >/dev/null' && echo good || echo bad
Orphaned process group semantics is not supported by the kernel
bad
$ unshare -fprU sh -c 'setsid ./orphaned_process_group >/dev/null' && echo good || echo bad
good
What can I say? The very least that could be done to fix this is
to replace is_global_init() invocation with is_container_init()
in will_become_orphaned_pgrp() as suggested in
https://lkml.org/lkml/2007/12/8/208
--
ldv
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