From: Matt Helsley Date: Sun, 19 Oct 2008 03:27:21 +0000 (-0700) Subject: container freezer: implement freezer cgroup subsystem X-Git-Tag: v2.6.28-rc1~201 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=dc52ddc0e6f45b04780b26fc0813509f8e798c42 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 Signed-off-by: Matt Helsley Acked-by: Serge E. Hallyn Tested-by: Matt Helsley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index a0f642b..6110197 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -70,6 +70,7 @@ config AUTO_IRQ_AFFINITY default y source "init/Kconfig" +source "kernel/Kconfig.freezer" menu "System setup" diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 4853f9d..df39d20 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -192,6 +192,8 @@ config VECTORS_BASE source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "System Type" choice diff --git a/arch/avr32/Kconfig b/arch/avr32/Kconfig index 7c239a9..33a5b29 100644 --- a/arch/avr32/Kconfig +++ b/arch/avr32/Kconfig @@ -72,6 +72,8 @@ config GENERIC_BUG source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "System Type and features" source "kernel/time/Kconfig" diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig index 8102c79..29e71ed 100644 --- a/arch/blackfin/Kconfig +++ b/arch/blackfin/Kconfig @@ -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" diff --git a/arch/cris/Kconfig b/arch/cris/Kconfig index 9389d38..07335e7 100644 --- a/arch/cris/Kconfig +++ b/arch/cris/Kconfig @@ -62,6 +62,8 @@ config HZ source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "General setup" source "fs/Kconfig.binfmt" diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig index a5aac1b..9d1552a 100644 --- a/arch/frv/Kconfig +++ b/arch/frv/Kconfig @@ -66,6 +66,8 @@ mainmenu "Fujitsu FR-V Kernel Configuration" source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Fujitsu FR-V system setup" diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig index c796674..bd19954 100644 --- a/arch/h8300/Kconfig +++ b/arch/h8300/Kconfig @@ -90,6 +90,8 @@ config HZ source "init/Kconfig" +source "kernel/Kconfig.freezer" + source "arch/h8300/Kconfig.cpu" menu "Executable file formats" diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig index 3b7aa38..912c57d 100644 --- a/arch/ia64/Kconfig +++ b/arch/ia64/Kconfig @@ -7,6 +7,8 @@ mainmenu "IA-64 Linux Kernel Configuration" source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Processor type and features" config IA64 diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig index 00289c1..dbaed4a 100644 --- a/arch/m32r/Kconfig +++ b/arch/m32r/Kconfig @@ -42,6 +42,8 @@ config HZ source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Processor type and features" diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig index 677c93a..836fb66 100644 --- a/arch/m68k/Kconfig +++ b/arch/m68k/Kconfig @@ -62,6 +62,8 @@ mainmenu "Linux/68k Kernel Configuration" source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Platform dependent setup" config EISA diff --git a/arch/m68knommu/Kconfig b/arch/m68knommu/Kconfig index 0a89983..76b66fe 100644 --- a/arch/m68knommu/Kconfig +++ b/arch/m68knommu/Kconfig @@ -75,6 +75,8 @@ config NO_IOPORT source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Processor type and features" choice diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index b905744..5f149b0 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -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 diff --git a/arch/mn10300/Kconfig b/arch/mn10300/Kconfig index dd557c9..9a9f433 100644 --- a/arch/mn10300/Kconfig +++ b/arch/mn10300/Kconfig @@ -68,6 +68,8 @@ mainmenu "Matsushita MN10300/AM33 Kernel Configuration" source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Matsushita MN10300 system setup" diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig index 8313fcc..2bd1f6e 100644 --- a/arch/parisc/Kconfig +++ b/arch/parisc/Kconfig @@ -90,6 +90,8 @@ config ARCH_MAY_HAVE_PC_FDC source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Processor type and features" diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 380baa1..9391199 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -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" diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index bc581d8..70b7645 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -78,6 +78,8 @@ config S390 source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "Base setup" comment "Processor type and features" diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index 5131d50..2ed5713 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -106,6 +106,8 @@ config IO_TRAPPED source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "System type" # diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 97671da..e594559 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -37,6 +37,8 @@ config HZ source "init/Kconfig" +source "kernel/Kconfig.freezer" + menu "General machine setup" config SMP diff --git a/arch/sparc64/Kconfig b/arch/sparc64/Kconfig index 5446e2a..035b15a 100644 --- a/arch/sparc64/Kconfig +++ b/arch/sparc64/Kconfig @@ -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" diff --git a/arch/um/Kconfig b/arch/um/Kconfig index 6976812..393bccf 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -229,6 +229,8 @@ endmenu source "init/Kconfig" +source "kernel/Kconfig.freezer" + source "drivers/block/Kconfig" source "arch/um/Kconfig.char" diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index bd3c2c5..49349ba 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -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" diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index 02e417d..a213260 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -55,6 +55,7 @@ config HZ default 100 source "init/Kconfig" +source "kernel/Kconfig.freezer" menu "Processor type and features" diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h index e287745..9c22396 100644 --- a/include/linux/cgroup_subsys.h +++ b/include/linux/cgroup_subsys.h @@ -48,3 +48,9 @@ SUBSYS(devices) #endif /* */ + +#ifdef CONFIG_CGROUP_FREEZER +SUBSYS(freezer) +#endif + +/* */ diff --git a/include/linux/freezer.h b/include/linux/freezer.h index 17e3bb4..8f22533 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -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 diff --git a/init/Kconfig b/init/Kconfig index 5ceff32..8828ed0 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -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 diff --git a/kernel/Kconfig.freezer b/kernel/Kconfig.freezer new file mode 100644 index 0000000..a3bb4cb --- /dev/null +++ b/kernel/Kconfig.freezer @@ -0,0 +1,2 @@ +config FREEZER + def_bool PM_SLEEP || CGROUP_FREEZER diff --git a/kernel/Makefile b/kernel/Makefile index e8194d1..066550a 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -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 diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c new file mode 100644 index 0000000..b08722d --- /dev/null +++ b/kernel/cgroup_freezer.c @@ -0,0 +1,366 @@ +/* + * cgroup_freezer.c - control group freezer subsystem + * + * Copyright IBM Corporation, 2007 + * + * Author : Cedric Le Goater + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of version 2.1 of the GNU Lesser General Public License + * as published by the Free Software Foundation. + * + * This program is distributed in the hope that it would be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. + */ + +#include +#include +#include +#include +#include +#include + +enum freezer_state { + STATE_RUNNING = 0, + STATE_FREEZING, + STATE_FROZEN, +}; + +struct freezer { + struct cgroup_subsys_state css; + enum freezer_state state; + spinlock_t lock; /* protects _writes_ to state */ +}; + +static inline struct freezer *cgroup_freezer( + struct cgroup *cgroup) +{ + return container_of( + cgroup_subsys_state(cgroup, freezer_subsys_id), + struct freezer, css); +} + +static inline struct freezer *task_freezer(struct task_struct *task) +{ + return container_of(task_subsys_state(task, freezer_subsys_id), + struct freezer, css); +} + +int cgroup_frozen(struct task_struct *task) +{ + struct freezer *freezer; + enum freezer_state state; + + task_lock(task); + freezer = task_freezer(task); + state = freezer->state; + task_unlock(task); + + return state == STATE_FROZEN; +} + +/* + * cgroups_write_string() limits the size of freezer state strings to + * CGROUP_LOCAL_BUFFER_SIZE + */ +static const char *freezer_state_strs[] = { + "RUNNING", + "FREEZING", + "FROZEN", +}; + +/* + * State diagram + * Transitions are caused by userspace writes to the freezer.state file. + * The values in parenthesis are state labels. The rest are edge labels. + * + * (RUNNING) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN) + * ^ ^ | | + * | \_______RUNNING_______/ | + * \_____________________________RUNNING___________/ + */ + +struct cgroup_subsys freezer_subsys; + +/* Locks taken and their ordering + * ------------------------------ + * css_set_lock + * cgroup_mutex (AKA cgroup_lock) + * task->alloc_lock (AKA task_lock) + * freezer->lock + * task->sighand->siglock + * + * cgroup code forces css_set_lock to be taken before task->alloc_lock + * + * freezer_create(), freezer_destroy(): + * cgroup_mutex [ by cgroup core ] + * + * can_attach(): + * cgroup_mutex + * + * cgroup_frozen(): + * task->alloc_lock (to get task's cgroup) + * + * freezer_fork() (preserving fork() performance means can't take cgroup_mutex): + * task->alloc_lock (to get task's cgroup) + * freezer->lock + * sighand->siglock (if the cgroup is freezing) + * + * freezer_read(): + * cgroup_mutex + * freezer->lock + * read_lock css_set_lock (cgroup iterator start) + * + * freezer_write() (freeze): + * cgroup_mutex + * freezer->lock + * read_lock css_set_lock (cgroup iterator start) + * sighand->siglock + * + * freezer_write() (unfreeze): + * cgroup_mutex + * freezer->lock + * read_lock css_set_lock (cgroup iterator start) + * task->alloc_lock (to prevent races with freeze_task()) + * sighand->siglock + */ +static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss, + struct cgroup *cgroup) +{ + struct freezer *freezer; + + freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); + if (!freezer) + return ERR_PTR(-ENOMEM); + + spin_lock_init(&freezer->lock); + freezer->state = STATE_RUNNING; + return &freezer->css; +} + +static void freezer_destroy(struct cgroup_subsys *ss, + struct cgroup *cgroup) +{ + kfree(cgroup_freezer(cgroup)); +} + + +static int freezer_can_attach(struct cgroup_subsys *ss, + struct cgroup *new_cgroup, + struct task_struct *task) +{ + struct freezer *freezer; + int retval = 0; + + /* + * The call to cgroup_lock() in the freezer.state write method prevents + * a write to that file racing against an attach, and hence the + * can_attach() result will remain valid until the attach completes. + */ + freezer = cgroup_freezer(new_cgroup); + if (freezer->state == STATE_FROZEN) + retval = -EBUSY; + return retval; +} + +static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) +{ + struct freezer *freezer; + + task_lock(task); + freezer = task_freezer(task); + task_unlock(task); + + BUG_ON(freezer->state == STATE_FROZEN); + spin_lock_irq(&freezer->lock); + /* Locking avoids race with FREEZING -> RUNNING transitions. */ + if (freezer->state == STATE_FREEZING) + freeze_task(task, true); + spin_unlock_irq(&freezer->lock); +} + +/* + * caller must hold freezer->lock + */ +static void check_if_frozen(struct cgroup *cgroup, + struct freezer *freezer) +{ + struct cgroup_iter it; + struct task_struct *task; + unsigned int nfrozen = 0, ntotal = 0; + + cgroup_iter_start(cgroup, &it); + while ((task = cgroup_iter_next(cgroup, &it))) { + ntotal++; + /* + * Task is frozen or will freeze immediately when next it gets + * woken + */ + if (frozen(task) || + (task_is_stopped_or_traced(task) && freezing(task))) + nfrozen++; + } + + /* + * Transition to FROZEN when no new tasks can be added ensures + * that we never exist in the FROZEN state while there are unfrozen + * tasks. + */ + if (nfrozen == ntotal) + freezer->state = STATE_FROZEN; + cgroup_iter_end(cgroup, &it); +} + +static int freezer_read(struct cgroup *cgroup, struct cftype *cft, + struct seq_file *m) +{ + struct freezer *freezer; + enum freezer_state state; + + if (!cgroup_lock_live_group(cgroup)) + return -ENODEV; + + freezer = cgroup_freezer(cgroup); + spin_lock_irq(&freezer->lock); + state = freezer->state; + if (state == STATE_FREEZING) { + /* We change from FREEZING to FROZEN lazily if the cgroup was + * only partially frozen when we exitted write. */ + check_if_frozen(cgroup, freezer); + state = freezer->state; + } + spin_unlock_irq(&freezer->lock); + cgroup_unlock(); + + seq_puts(m, freezer_state_strs[state]); + seq_putc(m, '\n'); + return 0; +} + +static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) +{ + struct cgroup_iter it; + struct task_struct *task; + unsigned int num_cant_freeze_now = 0; + + freezer->state = STATE_FREEZING; + cgroup_iter_start(cgroup, &it); + while ((task = cgroup_iter_next(cgroup, &it))) { + if (!freeze_task(task, true)) + continue; + if (task_is_stopped_or_traced(task) && freezing(task)) + /* + * The freeze flag is set so these tasks will + * immediately go into the fridge upon waking. + */ + continue; + if (!freezing(task) && !freezer_should_skip(task)) + num_cant_freeze_now++; + } + cgroup_iter_end(cgroup, &it); + + return num_cant_freeze_now ? -EBUSY : 0; +} + +static int unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) +{ + struct cgroup_iter it; + struct task_struct *task; + + cgroup_iter_start(cgroup, &it); + while ((task = cgroup_iter_next(cgroup, &it))) { + int do_wake; + + task_lock(task); + do_wake = __thaw_process(task); + task_unlock(task); + if (do_wake) + wake_up_process(task); + } + cgroup_iter_end(cgroup, &it); + freezer->state = STATE_RUNNING; + + return 0; +} + +static int freezer_change_state(struct cgroup *cgroup, + enum freezer_state goal_state) +{ + struct freezer *freezer; + int retval = 0; + + freezer = cgroup_freezer(cgroup); + spin_lock_irq(&freezer->lock); + check_if_frozen(cgroup, freezer); /* may update freezer->state */ + if (goal_state == freezer->state) + goto out; + switch (freezer->state) { + case STATE_RUNNING: + retval = try_to_freeze_cgroup(cgroup, freezer); + break; + case STATE_FREEZING: + if (goal_state == STATE_FROZEN) { + /* Userspace is retrying after + * "/bin/echo FROZEN > freezer.state" returned -EBUSY */ + retval = try_to_freeze_cgroup(cgroup, freezer); + break; + } + /* state == FREEZING and goal_state == RUNNING, so unfreeze */ + case STATE_FROZEN: + retval = unfreeze_cgroup(cgroup, freezer); + break; + default: + break; + } +out: + spin_unlock_irq(&freezer->lock); + + return retval; +} + +static int freezer_write(struct cgroup *cgroup, + struct cftype *cft, + const char *buffer) +{ + int retval; + enum freezer_state goal_state; + + if (strcmp(buffer, freezer_state_strs[STATE_RUNNING]) == 0) + goal_state = STATE_RUNNING; + else if (strcmp(buffer, freezer_state_strs[STATE_FROZEN]) == 0) + goal_state = STATE_FROZEN; + else + return -EIO; + + if (!cgroup_lock_live_group(cgroup)) + return -ENODEV; + retval = freezer_change_state(cgroup, goal_state); + cgroup_unlock(); + return retval; +} + +static struct cftype files[] = { + { + .name = "state", + .read_seq_string = freezer_read, + .write_string = freezer_write, + }, +}; + +static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup) +{ + return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files)); +} + +struct cgroup_subsys freezer_subsys = { + .name = "freezer", + .create = freezer_create, + .destroy = freezer_destroy, + .populate = freezer_populate, + .subsys_id = freezer_subsys_id, + .can_attach = freezer_can_attach, + .attach = NULL, + .fork = freezer_fork, + .exit = NULL, +}; diff --git a/kernel/freezer.c b/kernel/freezer.c index cb0931f..ba6248b 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -120,3 +120,35 @@ void cancel_freezing(struct task_struct *p) spin_unlock_irqrestore(&p->sighand->siglock, flags); } } + +/* + * Wake up a frozen process + * + * task_lock() is needed 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. + */ +int __thaw_process(struct task_struct *p) +{ + if (frozen(p)) { + p->flags &= ~PF_FROZEN; + return 1; + } + clear_freeze_flag(p); + return 0; +} + +int thaw_process(struct task_struct *p) +{ + task_lock(p); + if (__thaw_process(p) == 1) { + task_unlock(p); + wake_up_process(p); + return 1; + } + task_unlock(p); + return 0; +} +EXPORT_SYMBOL(thaw_process); diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index ebdd7f5..dcd165f 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -85,9 +85,6 @@ config PM_SLEEP depends on SUSPEND || HIBERNATION || XEN_SAVE_RESTORE default y -config FREEZER - def_bool PM_SLEEP - config SUSPEND bool "Suspend to RAM and standby" depends on PM && ARCH_SUSPEND_POSSIBLE