48 lines
2.0 KiB
Bash
Executable File
48 lines
2.0 KiB
Bash
Executable File
#!/bin/sh
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# Is SIGINT deliverable to this process tree?
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#
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# WHY THIS EXISTS. A shell running a command in the background without
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# job control sets SIGINT (and SIGQUIT) to SIG_IGN in the child; nohup
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# adds SIGHUP. SIG_IGN is inherited across fork AND survives exec, so
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# the disposition reaches every descendant --- cargo, a test binary, and
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# anything either of them spawns. Tests that signal a child then wait
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# for it to die will hang until their own deadline and report that as a
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# teardown defect. One lane spent nine framing revisions on exactly that
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# misreading; see docs/gpu-probe-sigint-framing.md §4c.
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#
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# INTERFACE (docs/gpu-probe-sigint-framing.md §7c). Callers rely on
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# these three statuses and MUST NOT re-derive the classification:
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#
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# 0 safe SIGINT is deliverable. No diagnostic.
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# 1 ignored SIGINT is inherited SIG_IGN. Canonical diagnostic.
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# 2 error Undecidable. Distinct diagnostic.
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#
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# `error` is never folded into `ignored`. "Your environment ignores
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# SIGINT" and "the guard could not run" are different problems, and
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# conflating them fails callers for the wrong reason.
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#
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# THE PROBE. A child sends itself SIGINT. Deliverable => the trap runs
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# => 23. Ignored => the kill is a no-op => the child falls through to
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# `exit 0`. The `|| exit 24` arms matter: without them a FAILED kill
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# would also fall through to `exit 0` and be misread as `ignored`,
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# which is the one wrong answer this helper exists to avoid.
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#
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# POSIX shell only --- trap, kill, $$ --- so no /proc and no sigaction:
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# the mechanism is not Linux-specific and adds no unsafe code.
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probe_status=0
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sh -c 'trap "exit 23" 2 || exit 24; kill -INT "$$" || exit 24; exit 0' \
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|| probe_status=$?
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case "$probe_status" in
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23) exit 0 ;;
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0)
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echo 'pmacs: SIGINT is ignored; run this command with SIGINT deliverable' >&2
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exit 1
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;;
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*)
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echo "pmacs: could not determine whether SIGINT is deliverable (probe status $probe_status)" >&2
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exit 2
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;;
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esac
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