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

Kirill Korotaev
2005-06-28T06:18:19Z

commented with <<<< inside

>>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)
<<<< why not to make a single option CONFIG_REFRIGERATOR? It looks to be
a more robust way, since there are multiple users of it.
> +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
<<<< is it intentionaly? or you just lost CONFIG_MIGRATE?
> +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;
<<<< I still think this refrigerator is racy with freeze_processes():
<<<< scenarios:
<<<< scenario 1
<<<<
task1 -> freeze_processes(): taskXXX ->refrigerator()
checked (task->flags & PF_FROZEN) == 0 cur->flags |= PF_FROZEN
clear TIF_FREEZE
<sleep on thaw>
set TIF_FREEZING
clear PF_FROZEN

<<<< so the task awakes with TIF_FREEZE flag set!!!

<<<< scenario 2
<<<< look at error path in freeze_processes (on timeout), it is broken
as well. You need to wakeup tasks there...

<<<< ------------------------------
> +}
> +EXPORT_SYMBOL(refrigerator);
> +#endif
> +
> +
> #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
> void __might_sleep(char *file, int line)
> {
> -
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