I think that a loadable builtin might be overkill for the second case,
because one could write a wrapper program to set PDEATHSIG and call
execve on the command-line arguments.
This way you'd just have to run "noreparent foo" instead of writing a
shell function that calls the noreparent builtin and exec into the child
afterwards. It wouldn't allow to unset the flag though, but I can't
think of a use-case for that.
It would also eliminate the need for a "fork_noreparent" builtin because
"noreparent foo &" would do just that.
On the other hand, the shell option to automatically set PDEATHSIG on
all newly created children allows to enable this behavior without
prefixing every line with "noreparent". I would understand if this
use-case was considered too narrow though.
On 11/11/2023 21:32, Corto Beau wrote:
Do you mean something like a "fork_noreparent" builtin that would call
make_child and set PDEATHSIG afterwards, or a "noreparent" builtin
that the child would have to call ? I do agree that it wouldn't make
sense to implement the later as a shell option, but this particular
use of prctl is subject to a race condition that can only be avoided
by comparing the PID of the parent before calling fork and after
calling prctl (in case the process got reparented before setting
PDEATHSIG), because checking for ppid = 1 is not enough on systems
like Linux where the process might have been reparented by a subreaper.
On 11/11/2023 20:49, Oğuz wrote:
On Saturday, November 11, 2023, Corto Beau <corto.b...@laposte.net>
wrote:
Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2
uname output: Linux zinc 6.6.1-arch1-1 #1 SMP PREEMPT_DYNAMIC
Wed, 08 Nov 2023 16:05:38 +0000 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu
Bash Version: 5.2 Patch
Level: 21
Release Status: release
Description:
Hi,
I would like to suggest a new shell option to ensure child
processes are automatically killed when the parent dies.
Right now, it's already possible to emulate this feature by
setting a trap to kill all child processes on exit (trap "kill 0"
EXIT), but obviously it doesn't work if the process is terminated
by a signal that cannot be caught (like SIGKILL).
On Linux, it can be done by setting the PR_SET_PDEATHSIG flag to
propagate the parent termination signal to the child, regardless
of whether the signal can be caught or not.
The rationale for this feature is that scripts spawning
background processes to listen to various events (udev events,
window manager events, etc) often leave orphan processes behind
when terminated forcefully.
I've attached a proof-of-concept patch.
I think it'd make more sense to implement this as a loadable builtin.
--
Oğuz
