mirror of
https://github.com/Druthulu/BFM-decomp
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Drew T
49 lines
2.3 KiB
Bash
49 lines
2.3 KiB
Bash
#!/usr/bin/env bash
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# treelock.sh — THE mutex for tree-writing campaigns. Source it or wrap a command with it.
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#
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# tools/treelock.sh <name> <command…> # acquire, run, release (even on failure/kill)
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# tools/treelock.sh --status # who holds it
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#
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# WHY (P30, twice in one session — the second time I caused it myself):
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# `src/`, `config/`, `asm/` and `build/` are ONE shared mutable state. Any two of {gate_stage,
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# dedup_propagate, family_sweep, jtbl_family_bank, make clean/extract/check} running at once can
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# interleave writes and leave the fleet incoherent — and a killed writer performs NO undo, so the
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# damage outlives the process.
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#
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# The first attempt at a guard was `while pgrep -f dedup_propagate; do sleep; done`. That is
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# STRUCTURALLY WRONG and it failed within the hour: a CAMPAIGN is a LOOP of short-lived processes
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# (15 sequential dedup_propagate invocations), so between every pair there is a window with no
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# matching process. A parallel gate polled during one of those windows, saw "clear", and started —
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# then a `make clean` deleted asm/ under the still-running campaign. Result: 63 of 140 binaries
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# failed check-all and every uncommitted bank had to be reverted.
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#
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# The lesson, stated generally: **guard the CAMPAIGN, not the process.** Presence-of-a-process is a
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# sampling test on a gappy signal; a lock file is a statement of intent that spans the gaps.
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# Uses flock(1) — held for the WHOLE wrapped command, released by the kernel on exit or kill.
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set -uo pipefail
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REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
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LOCK="$REPO/.run/tree.lock"
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mkdir -p "$(dirname "$LOCK")"
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if [ "${1:-}" = "--status" ]; then
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if flock -n "$LOCK" true 2>/dev/null; then echo "tree lock: FREE"; else
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echo "tree lock: HELD by -> $(cat "$LOCK.owner" 2>/dev/null || echo '(unknown)')"; fi
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exit 0
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fi
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NAME="${1:?usage: treelock.sh <name> <command...>}"; shift
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[ $# -gt 0 ] || { echo "treelock: no command given" >&2; exit 2; }
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exec 9>"$LOCK"
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if ! flock -w "${TREELOCK_WAIT:-14400}" 9; then
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echo "treelock: timed out waiting for the tree (held by $(cat "$LOCK.owner" 2>/dev/null))" >&2
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exit 75
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fi
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echo "$NAME pid=$$ since=$(date +%H:%M:%S)" > "$LOCK.owner"
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trap 'rm -f "$LOCK.owner"' EXIT
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echo "[treelock] acquired by $NAME"
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"$@"
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rc=$?
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echo "[treelock] released by $NAME (rc=$rc)"
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exit $rc
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