[pbs-devel] [PATCH proxmox] daemon: clean up middle process of double fork

[Thomas Lamprecht]

Am 29.11.24 um 16:37 schrieb Dominik Csapak:
> so we don't leave around a zombie process when the old daemon still
> needs to run, because of e.g. a running task.
> 
> Since this is mostly a cosmetic issue though, only try a clean up
> once, so we don't unnecessarily block or run into other issues here.
> (It could happen that it didn't exit at that point, but it's very
> unlikely.)
> 
> Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
> ---
> maybe the comment could be improved, but i tried to be not overly
> verbose there, since it's not really an issue anyway
> 
>  proxmox-daemon/src/server.rs | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/proxmox-daemon/src/server.rs b/proxmox-daemon/src/server.rs
> index efea9078..edc64795 100644
> --- a/proxmox-daemon/src/server.rs
> +++ b/proxmox-daemon/src/server.rs
> @@ -165,10 +165,12 @@ impl Reloader {
>                  // No matter how we managed to get here, this is the time where we bail out quickly:
>                  unsafe { libc::_exit(-1) }
>              }
> -            Ok(ForkResult::Parent { child }) => {
> +            Ok(ForkResult::Parent {
> +                child: middle_child,
> +            }) => {
>                  log::debug!(
>                      "forked off a new server (first pid: {}), waiting for 2nd pid",
> -                    child
> +                    middle_child
>                  );
>                  std::mem::drop(pnew);
>                  let mut pold = std::fs::File::from(pold);
> @@ -211,6 +213,13 @@ impl Reloader {
>                      log::error!("child vanished during reload: {}", e);
>                  }
>  
> +                // try exactly once to get rid of the zombie process of middle_child, but
> +                // non blocking and without error handling, since it's just cosmetic
> +                let _ = nix::sys::wait::waitpid(
> +                    middle_child,
> +                    Some(nix::sys::wait::WaitPidFlag::WNOHANG),
> +                );

why not blocking though? If that does not work something would be seriously
wrong. But not _that_ hard feelings, as long as the old process exits this
will be cleaned up by systemd anyway, but I really would like to have some
error handling here, as that definitively can only help.

> +
>                  Ok(())
>              }
>              Err(e) => {