hardreboot.c 

linux kernel module 

    Itīs done for systems that having some D prozesses 
    (Interuptable Sleep e.g. waiting for IO that is never comming)
    
    such a system is never rebootable via shutdown -r now 
    cause reboot will wait till all prozesses are done
    but fucking D prozesses (e.g. caused by a hardware disk fault)
    will never be done .....