restorer: implement restore of ps tree in stopped state

This patch adds implementation of --leave-stopped option
to CRIU restore cmd. If --leave-stopped is passed then
each process in ps tree gets SIGSTOP before detaching
from it.
Signed-off-by: Kravchenko Dmitrii <equivalence1@gmail.com>
Signed-off-by: Eugene Batalov <eabatalov89@gmail.com>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-restore.c

@@ -1541,7 +1541,8 @@ static void finalize_restore(void)
 
 		xfree(ctl);
 
-		if (item->pid.state == TASK_STOPPED)
+		if ((item->pid.state == TASK_STOPPED) ||
+				(opts.final_state == TASK_STOPPED))
 			kill(item->pid.real, SIGSTOP);
 	}
 }

criu/crtools.c

@@ -653,6 +653,16 @@ int main(int argc, char *argv[], char *envp[])
 			return 1;
 	}
 
+	/*
+	 * When a process group becomes an orphan,
+	 * its processes are sent a SIGHUP signal
+	 */
+	if (!strcmp(argv[optind], "restore") &&
+			opts.restore_detach &&
+			opts.final_state == TASK_STOPPED &&
+			opts.shell_job)
+		pr_warn("Stopped and detached shell job will get SIGHUP from OS.");
+
 	if (chdir(opts.work_dir)) {
 		pr_perror("Can't change directory to %s", opts.work_dir);
 		return 1;