[PATCH] tty: make __proc_set_tty static

The aim of this patch set is to start wrapping up the struct pid conversions.
As such this patchset culminates with the removal of kill_pg, kill_pg_info,
__kill_pg_info, do_each_task_pid, and while_each_task_pid.

kill_proc, daemonize, and kernel_thread are still in my sights but there is
still work to get to them.

The first three are basic cleanups around disassociate_ctty, while working on
converting it I found several issues.  tty_old_pgrp can be a tricky concept to
wrap your head around.

 1 tty: Make __proc_set_tty static.
 2 tty: Clarify disassociate_ctty
 3 tty: Fix the locking for signal->session in disassociate_ctty

These just stop using the old helper functions.

 4 signal: Use kill_pgrp not kill_pg in the sunos compatibility code.
 5 signal: Rewrite kill_something_info so it uses newer helpers.

Then the grind to convert the tty layer and all of it's helper functions to
struct pid.

 6 pid: Make session_of_pgrp use struct pid instead of pid_t.
 7 pid: Use struct pid for talking about process groups in exit.c
 8 pid: Replace is_orphaned_pgrp with is_current_pgrp_orphaned
 9 tty: Update the tty layer to work with struct pid.

A final helper function update.

10 pid: Replace do/while_each_task_pid with do/while_each_pid_task

And the removal of the functions that are now unused.
11 pid: Remove now unused do_each_task_pid and while_each_task_pid
12 pid: Remove the now unused kill_pg kill_pg_info and __kill_pg_info

All of these should be fairly simple and to the point.

This patch:

Currently all users of __proc_set_tty are in tty_io.c so make the function
static.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>