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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>
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1 parent 8174f15 commit dc52ddc0e6f45b04780b26fc0813509f8e798c42 Matt Helsley committed with torvalds Oct 19, 2008
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@@ -70,6 +70,7 @@ config AUTO_IRQ_AFFINITY
default y
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
menu "System setup"
View
@@ -192,6 +192,8 @@ config VECTORS_BASE
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "System Type"
choice
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@@ -72,6 +72,8 @@ config GENERIC_BUG
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "System Type and features"
source "kernel/time/Kconfig"
View
@@ -64,8 +64,11 @@ config HARDWARE_PM
depends on OPROFILE
source "init/Kconfig"
+
source "kernel/Kconfig.preempt"
+source "kernel/Kconfig.freezer"
+
menu "Blackfin Processor Options"
comment "Processor and Board Settings"
View
@@ -62,6 +62,8 @@ config HZ
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "General setup"
source "fs/Kconfig.binfmt"
View
@@ -66,6 +66,8 @@ mainmenu "Fujitsu FR-V Kernel Configuration"
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Fujitsu FR-V system setup"
View
@@ -90,6 +90,8 @@ config HZ
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
source "arch/h8300/Kconfig.cpu"
menu "Executable file formats"
View
@@ -7,6 +7,8 @@ mainmenu "IA-64 Linux Kernel Configuration"
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Processor type and features"
config IA64
View
@@ -42,6 +42,8 @@ config HZ
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Processor type and features"
View
@@ -62,6 +62,8 @@ mainmenu "Linux/68k Kernel Configuration"
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Platform dependent setup"
config EISA
View
@@ -75,6 +75,8 @@ config NO_IOPORT
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Processor type and features"
choice
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@@ -1885,6 +1885,8 @@ config PROBE_INITRD_HEADER
add initrd or initramfs image to the kernel image.
Otherwise, say N.
+source "kernel/Kconfig.freezer"
+
menu "Bus options (PCI, PCMCIA, EISA, ISA, TC)"
config HW_HAS_EISA
View
@@ -68,6 +68,8 @@ mainmenu "Matsushita MN10300/AM33 Kernel Configuration"
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Matsushita MN10300 system setup"
View
@@ -90,6 +90,8 @@ config ARCH_MAY_HAVE_PC_FDC
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Processor type and features"
View
@@ -230,6 +230,8 @@ config PPC_OF_PLATFORM_PCI
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
source "arch/powerpc/sysdev/Kconfig"
source "arch/powerpc/platforms/Kconfig"
View
@@ -78,6 +78,8 @@ config S390
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "Base setup"
comment "Processor type and features"
View
@@ -106,6 +106,8 @@ config IO_TRAPPED
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "System type"
#
View
@@ -37,6 +37,8 @@ config HZ
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
menu "General machine setup"
config SMP
View
@@ -96,6 +96,7 @@ config GENERIC_HARDIRQS_NO__DO_IRQ
def_bool y
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
menu "Processor type and features"
View
@@ -229,6 +229,8 @@ endmenu
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
+
source "drivers/block/Kconfig"
source "arch/um/Kconfig.char"
View
@@ -193,6 +193,7 @@ config X86_TRAMPOLINE
config KTIME_SCALAR
def_bool X86_32
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
menu "Processor type and features"
View
@@ -55,6 +55,7 @@ config HZ
default 100
source "init/Kconfig"
+source "kernel/Kconfig.freezer"
menu "Processor type and features"
@@ -48,3 +48,9 @@ SUBSYS(devices)
#endif
/* */
+
+#ifdef CONFIG_CGROUP_FREEZER
+SUBSYS(freezer)
+#endif
+
+/* */
View
@@ -46,26 +46,11 @@ static inline bool should_send_signal(struct task_struct *p)
/*
* Wake up a frozen process
- *
- * task_lock() is taken to prevent the race with refrigerator() which may
- * occur if the freezing of tasks fails. Namely, without the lock, if the
- * freezing of tasks failed, thaw_tasks() might have run before a task in
- * refrigerator() could call frozen_process(), in which case the task would be
- * frozen and no one would thaw it.
*/
-static inline int thaw_process(struct task_struct *p)
-{
- task_lock(p);
- if (frozen(p)) {
- p->flags &= ~PF_FROZEN;
- task_unlock(p);
- wake_up_process(p);
- return 1;
- }
- clear_freeze_flag(p);
- task_unlock(p);
- return 0;
-}
+extern int __thaw_process(struct task_struct *p);
+
+/* Takes and releases task alloc lock using task_lock() */
+extern int thaw_process(struct task_struct *p);
extern void refrigerator(void);
extern int freeze_processes(void);
@@ -83,6 +68,12 @@ static inline int try_to_freeze(void)
extern bool freeze_task(struct task_struct *p, bool sig_only);
extern void cancel_freezing(struct task_struct *p);
+#ifdef CONFIG_CGROUP_FREEZER
+extern int cgroup_frozen(struct task_struct *task);
+#else /* !CONFIG_CGROUP_FREEZER */
+static inline int cgroup_frozen(struct task_struct *task) { return 0; }
+#endif /* !CONFIG_CGROUP_FREEZER */
+
/*
* The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
* calls wait_for_completion(&vfork) and reset right after it returns from this
View
@@ -299,6 +299,13 @@ config CGROUP_NS
for instance virtual servers and checkpoint/restart
jobs.
+config CGROUP_FREEZER
+ bool "control group freezer subsystem"
+ depends on CGROUPS
+ help
+ Provides a way to freeze and unfreeze all tasks in a
+ cgroup.
+
config CGROUP_DEVICE
bool "Device controller for cgroups"
depends on CGROUPS && EXPERIMENTAL
View
@@ -0,0 +1,2 @@
+config FREEZER
+ def_bool PM_SLEEP || CGROUP_FREEZER
View
@@ -56,6 +56,7 @@ obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup.o
obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
+obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o
obj-$(CONFIG_CPUSETS) += cpuset.o
obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
obj-$(CONFIG_UTS_NS) += utsname.o
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