Struct KillTarget 

pub struct KillTarget { /* private fields */ }

A bundle of identifiers for killing a child process.

On Linux, holds a pidfd for race-free direct-child signalling. On other unix targets, just the raw PID — kills go through kill(pid, sig). Process-group signals always use the PID as PGID (we set pgid = pid in the child via setpgid at spawn) and accept the killpg PID-reuse window.

Implementations

impl KillTarget

pub fn from_child(child: &Child) -> Option<Self>

Build a kill target from a freshly spawned tokio::process::Child.

Returns None if the child has no PID (already reaped). On Linux, attempts to open a pidfd; if that fails (old kernel, permission denied), the target falls back to PID-based kill — the caller still gets a usable target, just without the reuse-race protection.

pub fn from_pid(pid: Pid) -> Self

Build a target from a raw PID (the JC watcher uses this — it can’t borrow the original target across the spawn boundary, so it re-opens). On Linux, a fresh pidfd is opened; if it fails (e.g. the child was reaped between spawn and reopen, leaving the PID free for reuse), returns a target that falls back to PID-based kill — best-effort.

pub fn signal(&self, sig: Signal)

Send sig to the direct child. On Linux uses pidfd if available (immune to PID reuse), otherwise falls back to kill(pid, sig).

pub fn signal_pg(&self, sig: Signal)

Send sig to the child’s process group (PGID == child PID since we setpgid(0, 0) in the child’s pre_exec). No pidfd-equivalent for PGIDs; this retains the small reuse window for grandchildren.

pub fn pid(&self) -> Pid

Raw PID, for paths that still need it (logging, JC waitpid, etc.).