Re: [RFC] Fix SMP brokenness for PF_FREEZE and make freezing usable for other purposes

Christoph Lameter
2005-06-27T15:13:27Z

On Mon, 27 Jun 2005, Pavel Machek wrote:

> Approach seems okay... Perhaps better place is something like
> kernel/freezer.c so it stays separate file? It is not really scheduler
> core, and it is only conditionally compiled...

There is already lots of other conditional code in kernel/sched.c and this
is just one function. It is scheduler like and uses scheduler variables
since it suspends a process. So lets move it there.

I think this is as far as I can take it. Could you test this and see
if it works okay?

For suspension for migration do:

1. down(&freezer_sem)

2. Signal processes to sleep (see kernel/power/process.c). Basically
set the TIF_FREEZE and may be do the fake signal thing.

3. If all processes have PF_FROZEN set then they are asleep.

4. Do migration things

5. complete_all(&thaw)

6. up(&freezer_sem)

----
Revise handling of freezing in the suspend code

The current suspend code modifies thread flags from outside the context of process.
This creates a SMP race.

The patch fixes that by introducing a TIF_FREEZE flag (for all arches). Also

- Uses a completion handler instead of waiting in a schedule loop in the refrigerator.

- Introduces a semaphore freezer_sem to provide a way that multiple kernel
subsystems can use the freezing ability without interfering with one another.

- Include necessary definitions for the migration code if CONFIG_MIGRATE is set.

- Removes PF_FREEZE

Signed-off-by: Christoph Lameter <christoph@lameter.com>

Index: linux-2.6.12/include/linux/sched.h
===================================================================
--- linux-2.6.12.orig/include/linux/sched.h 2005-06-27 05:20:15.000000000 +0000
+++ linux-2.6.12/include/linux/sched.h 2005-06-27 05:33:46.000000000 +0000
@@ -804,7 +804,6 @@ do { if (atomic_dec_and_test(&(tsk)->usa
#define PF_MEMALLOC 0x00000800 /* Allocating memory */
#define PF_FLUSHER 0x00001000 /* responsible for disk writeback */
#define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
-#define PF_FREEZE 0x00004000 /* this task is being frozen for suspend now */
#define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
#define PF_FROZEN 0x00010000 /* frozen for system suspend */
#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
@@ -1265,78 +1264,37 @@ extern void normalize_rt_tasks(void);

#endif

-#ifdef CONFIG_PM
-/*
- * Check if a process has been frozen
- */
-static inline int frozen(struct task_struct *p)
-{
- return p->flags & PF_FROZEN;
-}
-
-/*
- * Check if there is a request to freeze a process
- */
-static inline int freezing(struct task_struct *p)
-{
- return p->flags & PF_FREEZE;
-}
+#if defined(CONFIG_PM) || defined(CONFIG_MIGRATE)
+extern struct semaphore freezer_sem;
+extern struct completion thaw;

-/*
- * Request that a process be frozen
- * FIXME: SMP problem. We may not modify other process' flags!
- */
-static inline void freeze(struct task_struct *p)
-{
- p->flags |= PF_FREEZE;
-}
-
-/*
- * Wake up a frozen process
- */
-static inline int thaw_process(struct task_struct *p)
-{
- if (frozen(p)) {
- p->flags &= ~PF_FROZEN;
- wake_up_process(p);
- return 1;
- }
- return 0;
-}
+extern void refrigerator(void);

-/*
- * freezing is complete, mark process as frozen
- */
-static inline void frozen_process(struct task_struct *p)
+static inline int freezing(struct task_struct *p)
{
- p->flags = (p->flags & ~PF_FREEZE) | PF_FROZEN;
+ return test_ti_thread_flag(p->thread_info, TIF_FREEZE);
}

-extern void refrigerator(void);
-extern int freeze_processes(void);
-extern void thaw_processes(void);
-
static inline int try_to_freeze(void)
{
- if (freezing(current)) {
+ if (test_thread_flag(TIF_FREEZE)) {
refrigerator();
return 1;
} else
return 0;
}
#else
-static inline int frozen(struct task_struct *p) { return 0; }
+static inline void refrigerator(void) {}
static inline int freezing(struct task_struct *p) { return 0; }
-static inline void freeze(struct task_struct *p) { BUG(); }
-static inline int thaw_process(struct task_struct *p) { return 1; }
-static inline void frozen_process(struct task_struct *p) { BUG(); }
+static inline int try_to_freeze(void) { return 0; }
+#endif

-static inline void refrigerator(void) {}
+#ifdef CONFIG_PM
+extern int freeze_processes(void);
+extern void thaw_processes(void);
+#else
static inline int freeze_processes(void) { BUG(); return 0; }
static inline void thaw_processes(void) {}
-
-static inline int try_to_freeze(void) { return 0; }
-
#endif /* CONFIG_PM */
#endif /* __KERNEL__ */

Index: linux-2.6.12/kernel/power/process.c
===================================================================
--- linux-2.6.12.orig/kernel/power/process.c 2005-06-27 05:20:15.000000000 +0000
+++ linux-2.6.12/kernel/power/process.c 2005-06-27 15:07:46.000000000 +0000
@@ -18,7 +18,6 @@
*/
#define TIMEOUT (6 * HZ)

-
static inline int freezeable(struct task_struct * p)
{
if ((p == current) ||
@@ -31,28 +30,6 @@ static inline int freezeable(struct task
return 1;
}

-/* Refrigerator is place where frozen processes are stored :-). */
-void refrigerator(void)
-{
- /* Hmm, should we be allowed to suspend when there are realtime
- processes around? */
- long save;
- save = current->state;
- current->state = TASK_UNINTERRUPTIBLE;
- pr_debug("%s entered refrigerator\n", current->comm);
- printk("=");
-
- frozen_process(current);
- spin_lock_irq(&current->sighand->siglock);
- recalc_sigpending(); /* We sent fake signal, clean it up */
- spin_unlock_irq(&current->sighand->siglock);
-
- while (frozen(current))
- schedule();
- pr_debug("%s left refrigerator\n", current->comm);
- current->state = save;
-}
-
/* 0 = success, else # of processes that we failed to stop */
int freeze_processes(void)
{
@@ -60,6 +37,7 @@ int freeze_processes(void)
unsigned long start_time;
struct task_struct *g, *p;

+ down(&freezer_sem);
printk( "Stopping tasks: " );
start_time = jiffies;
do {
@@ -69,12 +47,12 @@ int freeze_processes(void)
unsigned long flags;
if (!freezeable(p))
continue;
- if ((frozen(p)) ||
+ if ((p->flags & PF_FROZEN) ||
(p->state == TASK_TRACED) ||
(p->state == TASK_STOPPED))
continue;

- freeze(p);
+ set_thread_flag(TIF_FREEZE);
spin_lock_irqsave(&p->sighand->siglock, flags);
signal_wake_up(p, 0);
spin_unlock_irqrestore(&p->sighand->siglock, flags);
@@ -96,20 +74,6 @@ int freeze_processes(void)

void thaw_processes(void)
{
- struct task_struct *g, *p;
-
- printk( "Restarting tasks..." );
- read_lock(&tasklist_lock);
- do_each_thread(g, p) {
- if (!freezeable(p))
- continue;
- if (!thaw_process(p))
- printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
- } while_each_thread(g, p);
-
- read_unlock(&tasklist_lock);
- schedule();
- printk( " done\n" );
+ complete_all(&thaw);
+ up(&freezer_sem);
}
-
-EXPORT_SYMBOL(refrigerator);
Index: linux-2.6.12/include/asm-x86_64/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-x86_64/thread_info.h 2005-06-27 05:20:15.000000000 +0000
+++ linux-2.6.12/include/asm-x86_64/thread_info.h 2005-06-27 05:37:24.000000000 +0000
@@ -108,6 +108,7 @@ static inline struct thread_info *stack_
#define TIF_FORK 18 /* ret_from_fork */
#define TIF_ABI_PENDING 19
#define TIF_MEMDIE 20
+#define TIF_FREEZE 21 /* Freeze process */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-ia64/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-ia64/thread_info.h 2005-06-27 05:20:15.000000000 +0000
+++ linux-2.6.12/include/asm-ia64/thread_info.h 2005-06-27 05:26:12.000000000 +0000
@@ -76,6 +76,7 @@ struct thread_info {
#define TIF_SIGDELAYED 5 /* signal delayed from MCA/INIT/NMI/PMI context */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
+#define TIF_FREEZE 18 /* Freeze process */

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
Index: linux-2.6.12/include/asm-i386/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-i386/thread_info.h 2005-06-27 05:20:15.000000000 +0000
+++ linux-2.6.12/include/asm-i386/thread_info.h 2005-06-27 05:25:49.000000000 +0000
@@ -143,6 +143,7 @@ register unsigned long current_stack_poi
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
+#define TIF_FREEZE 18 /* Freeze thread */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-xtensa/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-xtensa/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-xtensa/thread_info.h 2005-06-27 05:36:54.000000000 +0000
@@ -118,6 +118,7 @@ static inline struct thread_info *curren
#define TIF_SINGLESTEP 4 /* restore singlestep on return to user mode */
#define TIF_IRET 5 /* return with iret */
#define TIF_MEMDIE 6
+#define TIF_FREEZE 7
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-h8300/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-h8300/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-h8300/thread_info.h 2005-06-27 05:25:25.000000000 +0000
@@ -94,6 +94,7 @@ static inline struct thread_info *curren
#define TIF_POLLING_NRFLAG 4 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 5
+#define TIF_FREEZE 6

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-ppc/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-ppc/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-ppc/thread_info.h 2005-06-27 05:28:53.000000000 +0000
@@ -80,6 +80,7 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 5
#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */
#define TIF_SECCOMP 7 /* secure computing */
+#define TIF_FREEZE 8

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-sh64/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-sh64/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-sh64/thread_info.h 2005-06-27 05:35:02.000000000 +0000
@@ -80,6 +80,7 @@ static inline struct thread_info *curren
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_MEMDIE 4
+#define TIF_FREEZE 5

#endif /* __KERNEL__ */
Index: linux-2.6.12/include/asm-alpha/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-alpha/thread_info.h 2005-06-17 19:48:29.000000000 +0000
+++ linux-2.6.12/include/asm-alpha/thread_info.h 2005-06-27 05:23:06.000000000 +0000
@@ -78,6 +78,7 @@ register struct thread_info *__current_t
#define TIF_UAC_NOFIX 7
#define TIF_UAC_SIGBUS 8
#define TIF_MEMDIE 9
+#define TIF_FREEZE 10

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-sparc/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-sparc/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-sparc/thread_info.h 2005-06-27 05:35:23.000000000 +0000
@@ -139,6 +139,7 @@ BTFIXUPDEF_CALL(void, free_thread_info,
#define TIF_POLLING_NRFLAG 9 /* true if poll_idle() is polling
* TIF_NEED_RESCHED */
#define TIF_MEMDIE 10
+#define TIF_FREEZE 11

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-frv/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-frv/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-frv/thread_info.h 2005-06-27 05:25:02.000000000 +0000
@@ -133,6 +133,7 @@ register struct thread_info *__current_t
#define TIF_IRET 5 /* return with iret */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17 /* OOM killer killed process */
+#define TIF_FREEZE 18

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-parisc/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-parisc/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-parisc/thread_info.h 2005-06-27 05:28:34.000000000 +0000
@@ -64,6 +64,7 @@ struct thread_info {
#define TIF_POLLING_NRFLAG 4 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_32BIT 5 /* 32 bit binary */
#define TIF_MEMDIE 6
+#define TIF_FREEZE 7

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-m68knommu/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-m68knommu/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-m68knommu/thread_info.h 2005-06-27 05:27:13.000000000 +0000
@@ -91,6 +91,7 @@ static inline struct thread_info *curren
#define TIF_POLLING_NRFLAG 4 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 5
+#define TIF_FREEZE 6

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-m68k/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-m68k/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-m68k/thread_info.h 2005-06-27 05:26:49.000000000 +0000
@@ -49,6 +49,7 @@ struct thread_info {
#define TIF_SIGPENDING 3 /* signal pending */
#define TIF_NEED_RESCHED 4 /* rescheduling necessary */
#define TIF_MEMDIE 5
+#define TIF_FREEZE 6

extern int thread_flag_fixme(void);

Index: linux-2.6.12/include/asm-sh/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-sh/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-sh/thread_info.h 2005-06-27 05:34:43.000000000 +0000
@@ -84,6 +84,7 @@ static inline struct thread_info *curren
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 18
+#define TIF_FREEZE 19
#define TIF_USERSPACE 31 /* true if FS sets userspace */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-s390/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-s390/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-s390/thread_info.h 2005-06-27 05:34:19.000000000 +0000
@@ -102,6 +102,7 @@ static inline struct thread_info *curren
TIF_NEED_RESCHED */
#define TIF_31BIT 18 /* 32bit process */
#define TIF_MEMDIE 19
+#define TIF_FREEZE 20

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-arm/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-arm/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-arm/thread_info.h 2005-06-27 05:23:34.000000000 +0000
@@ -132,6 +132,7 @@ extern void iwmmxt_task_release(struct t
#define TIF_POLLING_NRFLAG 16
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18
+#define TIF_FREEZE 19

#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
Index: linux-2.6.12/include/asm-v850/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-v850/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-v850/thread_info.h 2005-06-27 05:36:25.000000000 +0000
@@ -85,6 +85,7 @@ struct thread_info {
#define TIF_POLLING_NRFLAG 4 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
#define TIF_MEMDIE 5
+#define TIF_FREEZE 6

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-mips/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-mips/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-mips/thread_info.h 2005-06-27 05:27:41.000000000 +0000
@@ -117,6 +117,7 @@ register struct thread_info *__current_t
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 18
+#define TIF_FREEZE 19
#define TIF_SYSCALL_TRACE 31 /* syscall trace active */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-cris/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-cris/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-cris/thread_info.h 2005-06-27 05:24:28.000000000 +0000
@@ -86,6 +86,7 @@ struct thread_info {
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17
+#define TIF_FREEZE 18

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-arm26/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-arm26/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-arm26/thread_info.h 2005-06-27 05:24:02.000000000 +0000
@@ -127,6 +127,7 @@ extern void free_thread_info(struct thre
#define TIF_USED_FPU 16
#define TIF_POLLING_NRFLAG 17
#define TIF_MEMDIE 18
+#define TIF_FREEZE 19

#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
Index: linux-2.6.12/include/asm-sparc64/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-sparc64/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-sparc64/thread_info.h 2005-06-27 05:35:45.000000000 +0000
@@ -229,6 +229,7 @@ register struct thread_info *current_thr
*/
#define TIF_ABI_PENDING 12
#define TIF_MEMDIE 13
+#define TIF_FREEZE 14

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-m32r/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-m32r/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-m32r/thread_info.h 2005-06-27 05:26:33.000000000 +0000
@@ -156,6 +156,7 @@ static inline unsigned int get_thread_fa
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
/* 31..28 fault code */
#define TIF_MEMDIE 17
+#define TIF_FREEZE 18

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
Index: linux-2.6.12/include/asm-ppc64/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-ppc64/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-ppc64/thread_info.h 2005-06-27 05:29:13.000000000 +0000
@@ -102,6 +102,7 @@ static inline struct thread_info *curren
#define TIF_SINGLESTEP 9 /* singlestepping active */
#define TIF_MEMDIE 10
#define TIF_SECCOMP 11 /* secure computing */
+#define TIF_FREEZE 12

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
Index: linux-2.6.12/include/asm-um/thread_info.h
===================================================================
--- linux-2.6.12.orig/include/asm-um/thread_info.h 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/include/asm-um/thread_info.h 2005-06-27 05:36:07.000000000 +0000
@@ -72,6 +72,7 @@ static inline struct thread_info *curren
#define TIF_RESTART_BLOCK 4
#define TIF_MEMDIE 5
#define TIF_SYSCALL_AUDIT 6
+#define TIF_FREEZE 7

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
Index: linux-2.6.12/kernel/sched.c
===================================================================
--- linux-2.6.12.orig/kernel/sched.c 2005-06-27 02:23:01.000000000 +0000
+++ linux-2.6.12/kernel/sched.c 2005-06-27 15:08:19.000000000 +0000
@@ -5203,6 +5203,25 @@ void __init sched_init(void)
init_idle(current, smp_processor_id());
}

+#if defined(CONFIG_PM) || defined(CONFIG_MIGRATE)
+DECLARE_MUTEX(freezer_sem);
+DECLARE_COMPLETION(thaw);
+
+void refrigerator(void)
+{
+ current->flags |= PF_FROZEN;
+ clear_thread_flag(TIF_FREEZE);
+ /* A fake signal 0 may have been sent. Recalculate sigpending */
+ spin_lock_irq(&current->sighand->siglock);
+ recalc_sigpending();
+ spin_unlock_irq(&current->sighand->siglock);
+ wait_for_completion(&thaw);
+ current->flags &= ~PF_FROZEN;
+}
+EXPORT_SYMBOL(refrigerator);
+#endif
+
+
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
void __might_sleep(char *file, int line)
{