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linux/arch/s390
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Matt Helsley dc52ddc0e6 container freezer: implement freezer cgroup subsystem 
This patch implements a new freezer subsystem in the control groups
framework.  It provides a way to stop and resume execution of all tasks in
a cgroup by writing in the cgroup filesystem.

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

* 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 is the basic mechanism which should do the right thing for user space
task in a simple scenario.

It's important to note that freezing can be incomplete.  In that case we
return EBUSY.  This means that some tasks in the cgroup are busy doing
something that prevents us from completely freezing the cgroup at this
time.  After EBUSY, the cgroup will remain partially frozen -- reflected
by freezer.state reporting "FREEZING" when read.  The state will remain
"FREEZING" until one of these things happens:

	1) Userspace cancels the freezing operation by writing "RUNNING" to
		the freezer.state file
	2) Userspace retries the freezing operation by writing "FROZEN" to
		the freezer.state file (writing "FREEZING" is not legal
		and returns EIO)
	3) The tasks that blocked the cgroup from entering the "FROZEN"
		state disappear from the cgroup's set of tasks.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: export thaw_process]
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Tested-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-10-20 08:52:34 -07:00
..
appldata Merge branch 'generic-ipi' into generic-ipi-for-linus 2008-07-15 21:55:59 +02:00
boot [PATCH] use ${CROSS_COMPILE}installkernel in arch/*/boot/install.sh 2005-06-23 09:45:07 -07:00
crypto Merge branch 'bkl-removal' of git://git.lwn.net/linux-2.6 2008-07-14 14:48:31 -07:00
hypfs vfs: Use const for kernel parser table 2008-10-13 10:10:37 -07:00
include/asm container freezer: add TIF_FREEZE flag to all architectures 2008-10-20 08:52:33 -07:00
kernel compat: generic compat get/settimeofday 2008-10-16 11:21:33 -07:00
kvm KVM: s390: Make facility bits future-proof 2008-10-15 10:15:24 +02:00
lib [S390] Move private simple udelay function to arch/s390/lib/delay.c. 2008-10-10 21:33:58 +02:00
math-emu [S390] remove -traditional 2008-04-30 13:38:44 +02:00
mm mm: cleanup to make remove_memory() arch-neutral 2008-10-20 08:50:25 -07:00
oprofile Combine instrumentation menus in kernel/Kconfig.instrumentation 2007-10-19 11:53:54 -07:00
defconfig [S390] Update default configuration. 2008-08-21 19:46:42 +02:00
Kconfig container freezer: implement freezer cgroup subsystem 2008-10-20 08:52:34 -07:00
Kconfig.debug [S390] DEBUG_PAGEALLOC support for s390. 2008-02-05 16:50:54 +01:00
Makefile KVM: s390: arch backend for the kvm kernel module 2008-04-27 12:00:42 +03:00