In kernel-programming we should avoid doing call_usermodehelper() which allows to execute a command from kernel-space. And sometimes we even want to call this function within a systemcall. Normally, we really don't wanna do this. But, desperate times require extraordinary methods.
When I first tried to execute call_usermodehelper() within a systemcall() I got a kernel failure. So I googled and what I found was: