cf giveback -f

hi, expert: 

      introduce my  environment:

     hardware : NETAPP FAS3220 ,     version :    NetApp Release 8.1.3P3 7-Mode:

     the  following is issue .

     when i execute the command ,

      cf giveback , notice me , because of the CIFS process is alive, dont agree with me to continute , the command failed.

 so that  i  execute the command cf giveback -f  .  finished the command -f option,

  both of the controller  is reboot,   what's wrong the controller ?  I read many document about  FAS3220.

  but the dont  explain  directly   ,  so the command  cf giveback -f , will reboot  controller ?