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
..
boot	FRV: Drop 'TOPDIR' from Makefiles	2008-01-28 23:14:37 +01:00
kernel	sysctl: simplify ->strategy	2008-10-16 11:21:47 -07:00
lib	move frv docs one level up	2008-02-03 15:54:28 +02:00
mb93090-mb00	FRV: Provide dma_map_page() for NOMMU and fix comments	2008-10-16 15:06:54 -07:00
mm	FRV: Eliminate NULL test and memset after alloc_bootmem	2008-10-16 15:06:54 -07:00
defconfig
Kconfig	container freezer: implement freezer cgroup subsystem	2008-10-20 08:52:34 -07:00
Kconfig.debug	[PATCH] frv: drop unsupported debugging features	2006-01-08 20:13:36 -08:00
Makefile	kbuild: enable 'make AFLAGS=...' to add additional options to AS	2007-10-15 21:59:31 +02:00