Use process groups to avoid delay-loops when waiting for child PIDs #104
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Porges
commented
Sep 5, 2023
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| cmd.pre_exec(|| match setsid() { | ||
| Ok(_pid) => Ok(()), | ||
| Err(e) => Err(io::Error::from(e)), | ||
| }); |
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First change: setsid when spawning
Porges
commented
Sep 5, 2023
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| let pgid = nix::unistd::getpgid(Some(pid)) | ||
| .expect("tracee should have a process group due to pre-exec"); | ||
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| match wait::waitpid(pid, Some(flag)) { | ||
| // negative pid means treat it as a pgid | ||
| match wait::waitpid(Pid::from_raw(-pgid.as_raw()), Some(flag)) { |
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Second change: get PGID for tracee and wait on that instead.
Porges
commented
Sep 5, 2023
| /// Known tracees, and their state. | ||
| tracees: BTreeMap<i32, State>, | ||
| } | ||
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| const DEFAULT_POLL_DELAY: Duration = Duration::from_millis(100); |
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This is a bit of a proof-of-concept that it works:
setsidin pre-exec when spawning a new processpgidinstead ofpidThe loop inside
wait_for_traceesis a bit of a lie, really we expect there to be onepgidso we are only ever going to visit the first tracee and get thepgidthere, but doing it this way involved less code churn.This assumes that no tracee is going to mess with its own process group. If they do, then we'd need to go back to a loop over multiple process groups like before… perhaps:
(Apologies for the messy diff but it got rustfmt'd.)