session and process group IDs

quoted : professional linux kernel architecture by Wolfgang Mauerer, page 55.

The session and process group IDs are NOT directly contained in the task structure itself, but in the structure used for signal handling.

task_struct->signal->__session : global SID
task_struct->signal->__pgrp : global PGID

set_task_session() and set_task_pgrp() are provided to modify the values.

http://www.win.tue.nl/~aeb/linux/lk/lk-10.html

http://www.gnu.org/s/libc/manual/html_node/Process-Group-Functions.html

http://man.he.net/man7/credentials