[debug] find out why signal is called on create

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/container_linux.go

@@ -10,6 +10,7 @@ import (
 	"path"
 	"path/filepath"
 	"reflect"
+	"runtime/debug"
 	"slices"
 	"strconv"
 	"strings"
@@ -389,6 +390,7 @@ func (c *Container) Signal(s os.Signal) error {
 	if s == unix.SIGKILL && !c.config.Namespaces.IsPrivate(configs.NEWPID) {
 		if err := signalAllProcesses(c.cgroupManager, unix.SIGKILL); err != nil {
 			if c.config.RootlessCgroups { // may not have an access to cgroup
+				logrus.Warn(debug.Stack())
 				logrus.WithError(err).Warn("failed to kill all processes, possibly due to lack of cgroup (Hint: enable cgroup v2 delegation)")
 				// Some processes may leak when cgroup is not delegated
 				// https://github.com/opencontainers/runc/pull/4395#pullrequestreview-2291179652