Split out process check as separate function.

This will allow the checks to be changed for different operating systems.

Issue #260 is related to this, but this does not change any current behaviour.

lock.go

@@ -12,7 +12,6 @@ import (
 	"github.com/restic/restic/backend"
 	"github.com/restic/restic/debug"
 	"github.com/restic/restic/repository"
-	"runtime"
 )
 
 // Lock represents a process locking the repository for an operation.
@@ -195,22 +194,12 @@ func (l *Lock) Stale() bool {
 		return true
 	}
 
-	proc, err := os.FindProcess(l.PID)
-	if err != nil {
-		debug.Log("Lock.Stale", "error searching for process %d: %v\n", l.PID, err)
+	// check if we can reach the process retaining the lock
+	exists := l.processExists()
+	if !exists {
+		debug.Log("Lock.Stale", "could not reach process, %d, lock is probably stale\n", l.PID)
 		return true
 	}
-	defer proc.Release()
-
-	// Windows does not have SIGHUP
-	if runtime.GOOS != "windows" {
-		debug.Log("Lock.Stale", "sending SIGHUP to process %d\n", l.PID)
-		err = proc.Signal(syscall.SIGHUP)
-		if err != nil {
-			debug.Log("Lock.Stale", "signal error: %v, lock is probably stale\n", err)
-			return true
-		}
-	}
 
 	debug.Log("Lock.Stale", "lock not stale\n")
 	return false

lock_unix.go

@@ -3,8 +3,12 @@
 package restic
 
 import (
+	"os"
 	"os/user"
 	"strconv"
+	"syscall"
+
+	"github.com/restic/restic/debug"
 )
 
 // uidGidInt returns uid, gid of the user as a number.
@@ -22,3 +26,23 @@ func uidGidInt(u user.User) (uid, gid uint32, err error) {
 	gid = uint32(gi)
 	return
 }
+
+// checkProcess will check if the process retaining the lock
+// exists and responds to SIGHUP signal.
+// Returns true if the process exists and responds.
+func (l Lock) processExists() bool {
+	proc, err := os.FindProcess(l.PID)
+	if err != nil {
+		debug.Log("Lock.Stale", "error searching for process %d: %v\n", l.PID, err)
+		return false
+	}
+	defer proc.Release()
+
+	debug.Log("Lock.Stale", "sending SIGHUP to process %d\n", l.PID)
+	err = proc.Signal(syscall.SIGHUP)
+	if err != nil {
+		debug.Log("Lock.Stale", "signal error: %v, lock is probably stale\n", err)
+		return false
+	}
+	return true
+}

lock_windows.go

@@ -1,10 +1,25 @@
 package restic
 
 import (
+	"os"
 	"os/user"
+
+	"github.com/restic/restic/debug"
 )
 
 // uidGidInt always returns 0 on Windows, since uid isn't numbers
 func uidGidInt(u user.User) (uid, gid uint32, err error) {
 	return 0, 0, nil
 }
+
+// checkProcess will check if the process retaining the lock exists.
+// Returns true if the process exists.
+func (l Lock) processExists() bool {
+	proc, err := os.FindProcess(l.PID)
+	if err != nil {
+		debug.Log("Lock.Stale", "error searching for process %d: %v\n", l.PID, err)
+		return false
+	}
+	proc.Release()
+	return true
+}