169 lines
3.8 KiB
Bash
Executable File
169 lines
3.8 KiB
Bash
Executable File
#!/usr/bin/env bash
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# loop_lock.sh — Atomic race-free loop lock acquisition and marker ownership (O-2)
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# Manages .mam/loop-guard-active with atomic hard links and pid+lstart identity validation.
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MAM_LOCK_STEAL_RETRIES="${MAM_LOCK_STEAL_RETRIES:-3}"
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mam_lstart() {
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local pid="${1:-$$}"
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ps -p "$pid" -o lstart= 2>/dev/null | tr -s ' ' | sed 's/^ *//;s/ *$//'
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}
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_mam_lock_field() {
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local file="$1" key="$2"
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if [ ! -f "$file" ]; then
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return 1
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fi
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grep "^${key}=" "$file" 2>/dev/null | head -n 1 | cut -d'=' -f2- || true
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}
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_mam_lock_holder_state() {
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local marker="$1"
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if [ ! -f "$marker" ]; then
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printf 'stale'
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return 0
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fi
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local rec_pid rec_lstart cur_lstart own_lstart
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rec_pid=$(_mam_lock_field "$marker" "pid")
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rec_lstart=$(_mam_lock_field "$marker" "lstart")
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if [ -z "$rec_pid" ] || ! [[ "$rec_pid" =~ ^[0-9]+$ ]]; then
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printf 'stale'
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return 0
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fi
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own_lstart=$(mam_lstart "$$")
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if [ -z "$own_lstart" ]; then
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printf 'unknown'
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return 0
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fi
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cur_lstart=$(mam_lstart "$rec_pid")
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if [ -z "$cur_lstart" ]; then
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printf 'stale'
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return 0
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fi
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if [ -n "$rec_lstart" ]; then
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if [ "$cur_lstart" != "$rec_lstart" ]; then
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printf 'stale'
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return 0
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fi
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fi
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printf 'live'
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return 0
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}
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_mam_lock_publish() {
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local marker="$1"
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local parent_dir
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parent_dir=$(dirname "$marker")
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mkdir -p "$parent_dir" 2>/dev/null || true
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local tmp_marker="${marker}.tmp.${$}.${RANDOM:-0}"
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local lstart_val
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lstart_val=$(mam_lstart "$$")
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printf 'pid=%s\nlstart=%s\nstarted=%s\n' \
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"$$" "$lstart_val" "$(date -u +%Y-%m-%dT%H:%M:%SZ 2>/dev/null || date)" > "$tmp_marker"
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local rc=0
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ln "$tmp_marker" "$marker" 2>/dev/null || rc=$?
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rm -f "$tmp_marker" 2>/dev/null || true
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return $rc
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}
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mam_acquire_loop_lock() {
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local marker="${1:-}"
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if [ -z "$marker" ]; then
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return 2
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fi
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local steal_lock="${marker}.steal"
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local retries=0
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while [ "$retries" -le "$MAM_LOCK_STEAL_RETRIES" ]; do
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# Upgrade path: clean up legacy directory at steal_lock if present
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if [ -d "$steal_lock" ]; then
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rmdir "$steal_lock" 2>/dev/null || true
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fi
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# Try publishing primary marker
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if _mam_lock_publish "$marker"; then
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return 0
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fi
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# Check primary marker holder state
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local state
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state=$(_mam_lock_holder_state "$marker")
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if [ "$state" = "live" ]; then
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return 3
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fi
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if [ "$state" = "unknown" ]; then
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return 4
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fi
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# Primary marker is stale! Try publishing steal_lock
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if _mam_lock_publish "$steal_lock"; then
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if [ "$(_mam_lock_holder_state "$marker")" = "stale" ]; then
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rm -f "$marker" 2>/dev/null || true
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fi
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rm -f "$steal_lock" 2>/dev/null || true
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if _mam_lock_publish "$marker"; then
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return 0
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fi
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fi
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# Check steal_lock holder state
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local steal_state
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steal_state=$(_mam_lock_holder_state "$steal_lock")
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case "$steal_state" in
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live)
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return 3
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;;
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unknown)
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return 4
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;;
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stale)
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rm -f "$steal_lock" 2>/dev/null || true
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retries=$((retries + 1))
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continue
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;;
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esac
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sleep 1
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retries=$((retries + 1))
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done
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return 3
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}
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mam_release_loop_lock() {
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local marker="${1:-}"
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if [ -z "$marker" ] || [ ! -f "$marker" ]; then
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return 0
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fi
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local rec_pid rec_lstart cur_lstart
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rec_pid=$(_mam_lock_field "$marker" "pid")
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rec_lstart=$(_mam_lock_field "$marker" "lstart")
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cur_lstart=$(mam_lstart "$$")
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if [ "$rec_pid" = "$$" ] && [ "$rec_lstart" = "$cur_lstart" ]; then
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rm -f "$marker" 2>/dev/null || true
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return 0
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fi
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return 1
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}
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if [ "${BASH_SOURCE[0]}" = "$0" ]; then
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case "${1:-}" in
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acquire) mam_acquire_loop_lock "${2:-}" ;;
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release) mam_release_loop_lock "${2:-}" ;;
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*) echo "Usage: $0 {acquire|release} <marker-path>" ; exit 1 ;;
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esac
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fi
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