On Thu, 21 May 2015 12:30:21 +0200 Alban Crequy <alban.crequy@xxxxxxxxx> wrote:
> commit 818411616baf ("fs, proc: introduce
> /proc/<pid>/task/<tid>/children entry") introduced the children entry
> for checkpoint restore and the file is only available on kernels
> configured with CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE.
>
> This is available in most distributions (Fedora, Debian, Ubuntu, CoreOS)
> because they usually enable CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE.
> But Arch does not enable CONFIG_EXPERT or CONFIG_CHECKPOINT_RESTORE.
>
> However, the children proc file is useful outside of checkpoint restore.
> I would like to use it in rkt. The rkt process exec() another program it
> does not control, and that other program will fork()+exec() a child
> process. I would like to find the pid of the child process from an
> external tool without iterating in /proc over all processes to find
> which one has a parent pid equal to rkt.
>
> Since the children proc file is useful outside of checkpoint-restore,
> I am removing the guard on CONFIG_CHECKPOINT_RESTORE.
This will add a lump of code to kernels which don't need it.
It's a bit of a pain, but I suppose we should still keep the presence
of get_children_pid() configurable. That would be by adding a new
CONFIG_PROC_CHILDREN (or similar) and making CONFIG_CHECKPOINT_RESTORE
select that.
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