khive_runtime/
process_group.rs

1//! One guarded signal to a whole process group.
2
3/// Send `signal` to every member of the process group `pgid`.
4///
5/// A group id of 0 or 1, or any negative id, is refused with an
6/// [`std::io::ErrorKind::InvalidInput`] error before the OS is called. Negated,
7/// 0 names the caller's own group, 1 names every process the caller may signal,
8/// and a negative id names a single process rather than a group. Any other
9/// failure is the OS error, unchanged: `ESRCH` once the group has no member left.
10///
11/// Which group to signal, whether a missing group is an error, and what to do
12/// after the signal all stay with the caller.
13#[cfg(unix)]
14pub fn signal_process_group(pgid: i32, signal: i32) -> std::io::Result<()> {
15    if pgid <= 1 {
16        return Err(std::io::Error::new(
17            std::io::ErrorKind::InvalidInput,
18            format!("refusing to signal process group {pgid}"),
19        ));
20    }
21    // SAFETY: `kill` borrows no Rust memory or descriptors, and `pgid > 1`
22    // keeps `-pgid` clear of the "own group" (0) and "every process" (-1)
23    // forms, so the signal reaches the one group the caller named.
24    if unsafe { libc::kill(-pgid, signal) } == 0 {
25        Ok(())
26    } else {
27        Err(std::io::Error::last_os_error())
28    }
29}
30
31#[cfg(all(test, unix))]
32mod tests {
33    use std::os::unix::process::{CommandExt, ExitStatusExt};
34    use std::process::Command;
35
36    use super::signal_process_group;
37
38    #[test]
39    fn signal_process_group_kills_a_child_group_then_reports_esrch() {
40        let mut child = Command::new("/bin/sleep")
41            .arg("30")
42            .process_group(0)
43            .spawn()
44            .expect("spawn a child into its own process group");
45        let pgid = child.id() as i32;
46
47        signal_process_group(pgid, libc::SIGKILL).expect("signal the live group");
48        let status = child.wait().expect("reap the killed child");
49        assert_eq!(
50            status.signal(),
51            Some(libc::SIGKILL),
52            "the child must die to the group signal"
53        );
54
55        // Probe with signal 0: nothing is delivered if the id has been reused.
56        let error = signal_process_group(pgid, 0).expect_err("the group is gone");
57        assert_eq!(error.raw_os_error(), Some(libc::ESRCH));
58    }
59
60    #[test]
61    fn signal_process_group_refuses_ids_that_do_not_name_one_group() {
62        for pgid in [0, 1, -5] {
63            // Signal 0 delivers nothing, so a missing guard cannot harm the host.
64            match signal_process_group(pgid, 0) {
65                Ok(()) => panic!("process group id {pgid} reached the OS"),
66                Err(error) => {
67                    assert_eq!(
68                        error.kind(),
69                        std::io::ErrorKind::InvalidInput,
70                        "process group id {pgid} must be refused as invalid input"
71                    );
72                    assert_eq!(
73                        error.raw_os_error(),
74                        None,
75                        "process group id {pgid} must be refused without an OS call"
76                    );
77                }
78            }
79        }
80    }
81}
khive_runtime/process_group.rs

khive_runtime/
process_group.rs
