container freezer: add TIF_FREEZE flag to all architectures

This patch series introduces a cgroup subsystem that utilizes the swsusp
freezer to freeze a group of tasks.  It's immediately useful for batch job
management scripts.  It should also be useful in the future for
implementing container checkpoint/restart.

The freezer subsystem in the container filesystem defines a cgroup file
named freezer.state.  Reading freezer.state will return the current state
of the cgroup.  Writing "FROZEN" to the state file will freeze all tasks
in the cgroup.  Subsequently writing "RUNNING" will unfreeze the tasks in
the cgroup.

* Examples of usage :

   # mkdir /containers/freezer
   # mount -t cgroup -ofreezer freezer  /containers
   # mkdir /containers/0
   # echo $some_pid > /containers/0/tasks

to get status of the freezer subsystem :

   # cat /containers/0/freezer.state
   RUNNING

to freeze all tasks in the container :

   # echo FROZEN > /containers/0/freezer.state
   # cat /containers/0/freezer.state
   FREEZING
   # cat /containers/0/freezer.state
   FROZEN

to unfreeze all tasks in the container :

   # echo RUNNING > /containers/0/freezer.state
   # cat /containers/0/freezer.state
   RUNNING

This patch:

The first step in making the refrigerator() available to all
architectures, even for those without power management.

The purpose of such a change is to be able to use the refrigerator() in a
new control group subsystem which will implement a control group freezer.

[[email protected]: fix sparc]
Signed-off-by: Cedric Le Goater <[email protected]>
Signed-off-by: Matt Helsley <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Acked-by: Serge E. Hallyn <[email protected]>
Acked-by: Rafael J. Wysocki <[email protected]>
Acked-by: Nigel Cunningham <[email protected]>
Tested-by: Matt Helsley <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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