fix: lock-mgr release meta-lock before exiting

lock-mgr/main.go

@@ -5,7 +5,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"os/signal"
 	"path/filepath"
+	"sync"
+	"syscall"
 	"time"
 )
 
@@ -17,6 +20,51 @@ type LockEntry struct {
 
 type LockFile map[string]*LockEntry
 
+// heldLock tracks the meta-lock currently held by this process so it can be
+// released on panic, signal, or any other unexpected exit.
+var (
+	heldMu      sync.Mutex
+	heldMgrPath string
+	heldMgrKey  string
+)
+
+func setHeldLock(path, key string) {
+	heldMu.Lock()
+	heldMgrPath = path
+	heldMgrKey = key
+	heldMu.Unlock()
+}
+
+func clearHeldLock() {
+	heldMu.Lock()
+	heldMgrPath = ""
+	heldMgrKey = ""
+	heldMu.Unlock()
+}
+
+// cleanupMgrLock releases the meta-lock if this process still holds it.
+// Safe to call multiple times.
+func cleanupMgrLock() {
+	heldMu.Lock()
+	path := heldMgrPath
+	key := heldMgrKey
+	heldMu.Unlock()
+
+	if path == "" || key == "" {
+		return
+	}
+	lf, err := readLockFile(path)
+	if err != nil {
+		return
+	}
+	entry := lf[path]
+	if entry != nil && entry.Key == key {
+		delete(lf, path)
+		_ = writeLockFile(path, lf)
+	}
+	clearHeldLock()
+}
+
 func generateUUID() (string, error) {
 	b := make([]byte, 16)
 	if _, err := rand.Read(b); err != nil {
@@ -105,6 +153,7 @@ func acquireMgrLock(mgrPath string) (string, error) {
 			return "", err
 		}
 		if lf2[mgrPath] != nil && lf2[mgrPath].Key == mgrKey {
+			setHeldLock(mgrPath, mgrKey)
 			return mgrKey, nil
 		}
 		// Lost the race; go back to step 4 (keep same mgrKey, reset timer)
@@ -118,7 +167,11 @@ func releaseMgrLock(mgrPath string) error {
 		return err
 	}
 	delete(lf, mgrPath)
-	return writeLockFile(mgrPath, lf)
+	err = writeLockFile(mgrPath, lf)
+	if err == nil {
+		clearHeldLock()
+	}
+	return err
 }
 
 func cmdAcquire(mgrPath, filePath, key string) error {
@@ -176,7 +229,7 @@ func cmdAcquire(mgrPath, filePath, key string) error {
 		if err := writeLockFile(mgrPath, lf); err != nil {
 			return err
 		}
-
+		clearHeldLock()
 		return nil
 	}
 }
@@ -213,7 +266,11 @@ func cmdRelease(mgrPath, filePath, key string) error {
 	// Step 15: delete file lock and meta-lock, write
 	delete(lf, filePath)
 	delete(lf, mgrPath)
-	return writeLockFile(mgrPath, lf)
+	err = writeLockFile(mgrPath, lf)
+	if err == nil {
+		clearHeldLock()
+	}
+	return err
 }
 
 func cmdForceUnlock(mgrPath, filePath string) error {
@@ -231,29 +288,31 @@ func cmdForceUnlock(mgrPath, filePath string) error {
 	// Remove file lock and meta-lock unconditionally
 	delete(lf, filePath)
 	delete(lf, mgrPath)
-	return writeLockFile(mgrPath, lf)
+	err = writeLockFile(mgrPath, lf)
+	if err == nil {
+		clearHeldLock()
+	}
+	return err
 }
 
-func main() {
+func run() error {
+	// cleanupMgrLock runs on normal return AND on panic (defer unwinds through panics).
+	// os.Exit bypasses defer, so we keep os.Exit only in main() after run() returns.
+	defer cleanupMgrLock()
+
 	action := ""
 	if len(os.Args) >= 2 {
 		action = os.Args[1]
 	}
 
-	// force-unlock only needs 2 args
 	if action == "force-unlock" && len(os.Args) < 3 {
-		fmt.Fprintln(os.Stderr, "Usage: lock-mgr force-unlock <file>")
-		os.Exit(1)
+		return fmt.Errorf("usage: lock-mgr force-unlock <file>")
 	}
-	// acquire and release need 3 args
 	if (action == "acquire" || action == "release") && len(os.Args) < 4 {
-		fmt.Fprintf(os.Stderr, "Usage: lock-mgr %s <file> <key>\n", action)
-		os.Exit(1)
+		return fmt.Errorf("usage: lock-mgr %s <file> <key>", action)
 	}
 	if action == "" || (action != "acquire" && action != "release" && action != "force-unlock") {
-		fmt.Fprintln(os.Stderr, "Usage: lock-mgr <acquire|release> <file> <key>")
-		fmt.Fprintln(os.Stderr, "       lock-mgr force-unlock <file>")
-		os.Exit(1)
+		return fmt.Errorf("usage: lock-mgr <acquire|release> <file> <key>\n       lock-mgr force-unlock <file>")
 	}
 
 	fileArg := os.Args[2]
@@ -265,8 +324,7 @@ func main() {
 	// Step 1: resolve tool directory and locate (or create) the lock file
 	execPath, err := os.Executable()
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "error: cannot determine executable path: %v\n", err)
-		os.Exit(1)
+		return fmt.Errorf("cannot determine executable path: %w", err)
 	}
 
 	toolDir := filepath.Dir(execPath)
@@ -275,34 +333,44 @@ func main() {
 	// Step 2: get absolute paths
 	mgrPath, err := filepath.Abs(rawMgrPath)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "error: cannot resolve lock file path: %v\n", err)
-		os.Exit(1)
+		return fmt.Errorf("cannot resolve lock file path: %w", err)
 	}
 
 	filePath, err := filepath.Abs(fileArg)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "error: cannot resolve file path: %v\n", err)
-		os.Exit(1)
+		return fmt.Errorf("cannot resolve file path: %w", err)
 	}
 
 	// Ensure lock file exists
 	if _, statErr := os.Stat(mgrPath); os.IsNotExist(statErr) {
 		if writeErr := os.WriteFile(mgrPath, []byte("{}"), 0644); writeErr != nil {
-			fmt.Fprintf(os.Stderr, "error: cannot create lock file: %v\n", writeErr)
-			os.Exit(1)
+			return fmt.Errorf("cannot create lock file: %w", writeErr)
 		}
 	}
 
 	switch action {
 	case "acquire":
-		err = cmdAcquire(mgrPath, filePath, key)
+		return cmdAcquire(mgrPath, filePath, key)
 	case "release":
-		err = cmdRelease(mgrPath, filePath, key)
+		return cmdRelease(mgrPath, filePath, key)
 	case "force-unlock":
-		err = cmdForceUnlock(mgrPath, filePath)
+		return cmdForceUnlock(mgrPath, filePath)
+	}
+	return nil
 }
 
-	if err != nil {
+func main() {
+	// Signal handler: release meta-lock on SIGINT / SIGTERM before exiting.
+	// This covers Ctrl+C and process termination while the lock is held.
+	sigCh := make(chan os.Signal, 1)
+	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		<-sigCh
+		cleanupMgrLock()
+		os.Exit(130)
+	}()
+
+	if err := run(); err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}