Re: [meta-arm] [PATCH v2] runfvp: Ensure new process group is in the foreground

[Jon Mason <jdmason@kudzu.us>]

On Mon, Nov 01, 2021 at 03:50:15PM +0000, Peter Hoyes wrote:
> Hi,
> 
> I'm seeing the same issue on honister - is it possible to backport this patch?

Done

> 
> Cheers,
> Peter
> 
> ________________________________
> From: meta-arm@lists.yoctoproject.org <meta-arm@lists.yoctoproject.org> on behalf of Ross Burton via lists.yoctoproject.org <ross=burtonini.com@lists.yoctoproject.org>
> Sent: 21 October 2021 12:16
> To: meta-arm@lists.yoctoproject.org <meta-arm@lists.yoctoproject.org>
> Subject: [meta-arm] [PATCH v2] runfvp: Ensure new process group is in the foreground
> 
> From: Peter Hoyes <Peter.Hoyes@arm.com>
> 
> When a new process group is created, it is launched in the background
> and any attempt to access the session terminal triggers a SIGTTIN (for
> stdin) or SIGTTOU (for stdout) signal. These are ignored in an
> interactive shell, but the default signal behavior in a new job is to
> send a SIGTSTP to the whole process group. This causes runfvp to hang
> when executed via a subprocess when stdin is accessed.
> 
> After creating a new process group, use tcsetpgrp to make the new group
> the foreground process for the terminal associated with stdin/stdout,
> but only if stdin is a tty.
> 
> The documentation for tcsetgrp states that tcsetpgrp itself raises a
> SIGTTOU signal, so set this signal to SIG_IGN.
> 
> Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
> Change-Id: I349a825df7fcb8a3cedb81762b901c6f50fa53b5
> ---
>  scripts/runfvp | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/scripts/runfvp b/scripts/runfvp
> index 97836726..66a76cc5 100755
> --- a/scripts/runfvp
> +++ b/scripts/runfvp
> @@ -4,6 +4,7 @@ import asyncio
>  import json
>  import os
>  import re
> +import signal
>  import sys
>  import subprocess
>  import pathlib
> @@ -220,6 +221,9 @@ if __name__ == "__main__":
>          # Set the process group so that it's possible to kill runfvp and
>          # everything it spawns easily.
>          os.setpgid(0, 0)
> +        if sys.stdin.isatty():
> +            signal.signal(signal.SIGTTOU, signal.SIG_IGN)
> +            os.tcsetpgrp(sys.stdin.fileno(), os.getpgrp())
>          runfvp(sys.argv[1:])
>      except KeyboardInterrupt:
>          pass
> --
> 2.25.1
> 

> 
> -=-=-=-=-=-=-=-=-=-=-=-
> Links: You receive all messages sent to this group.
> View/Reply Online (#2328): https://lists.yoctoproject.org/g/meta-arm/message/2328
> Mute This Topic: https://lists.yoctoproject.org/mt/86487012/3616920
> Group Owner: meta-arm+owner@lists.yoctoproject.org
> Unsubscribe: https://lists.yoctoproject.org/g/meta-arm/unsub [jdmason@kudzu.us]
> -=-=-=-=-=-=-=-=-=-=-=-
>