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

Christoph Lameter
2005-06-25T06:13:50Z

On Sat, 25 Jun 2005, Pavel Machek wrote:

> It includes whitespace changes and most of patch is nice cleanup that
> should probably go in separately. (Hint hint :-).

> Previous code had important property: try_to_freeze was optimized away
> in !CONFIG_PM case. Please keep that.
>
> Best way is to introduce macros and cleanup the code to use the
> macros, without actually changing any object code. That can go in very
> fast. Then we can switch to atomic_t ... yeah I think that's
> neccessary, but I'd like cleanups first.

Here is such a patch:

---
Cleanup patch for freezing against 2.6.12-git5.

1. Establish a simple API for process freezing defined in linux/include/sched.h:

frozen(process) Check for frozen process
freezing(process) Check if a process is being frozen
freeze(process) Tell a process to freeze (go to refrigerator)
thaw_process(process) Restart process
frozen_process(process) Process is frozen now

2. Remove all references to PF_FREEZE and PF_FROZEN from all
kernel sources except sched.h

3. Fix numerous locations where try_to_freeze is manually done by a driver

4. Remove the argument that is no longer necessary from two function calls.

5. Some whitespace cleanup

6. Clear potential race in refrigerator (provides an open window of PF_FREEZE
cleared before setting PF_FROZEN, recalc_sigpending does not check
PF_FROZEN).

This patch does not address the problem of freeze_processes() violating the rule
that a task may only modify its own flags by setting PF_FREEZE. This is not clean
in an SMP environment. freeze(process) is therefore not SMP safe!

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

Index: linux-2.6.12/drivers/block/pktcdvd.c
===================================================================
--- linux-2.6.12.orig/drivers/block/pktcdvd.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/block/pktcdvd.c 2005-06-25 05:01:28.000000000 +0000
@@ -1251,8 +1251,7 @@ static int kcdrwd(void *foobar)
VPRINTK("kcdrwd: wake up\n");

/* make swsusp happy with our thread */
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
if (!pkt->sleep_time)
Index: linux-2.6.12/kernel/power/process.c
===================================================================
--- linux-2.6.12.orig/kernel/power/process.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/kernel/power/process.c 2005-06-25 05:33:16.000000000 +0000
@@ -32,7 +32,7 @@ static inline int freezeable(struct task
}

/* Refrigerator is place where frozen processes are stored :-). */
-void refrigerator(unsigned long flag)
+void refrigerator(void)
{
/* Hmm, should we be allowed to suspend when there are realtime
processes around? */
@@ -41,14 +41,13 @@ void refrigerator(unsigned long flag)
current->state = TASK_UNINTERRUPTIBLE;
pr_debug("%s entered refrigerator\n", current->comm);
printk("=");
- current->flags &= ~PF_FREEZE;

+ frozen_process(current);
spin_lock_irq(&current->sighand->siglock);
recalc_sigpending(); /* We sent fake signal, clean it up */
spin_unlock_irq(&current->sighand->siglock);

- current->flags |= PF_FROZEN;
- while (current->flags & PF_FROZEN)
+ while (frozen(current))
schedule();
pr_debug("%s left refrigerator\n", current->comm);
current->state = save;
@@ -57,10 +56,10 @@ void refrigerator(unsigned long flag)
/* 0 = success, else # of processes that we failed to stop */
int freeze_processes(void)
{
- int todo;
- unsigned long start_time;
+ int todo;
+ unsigned long start_time;
struct task_struct *g, *p;
-
+
printk( "Stopping tasks: " );
start_time = jiffies;
do {
@@ -70,14 +69,12 @@ int freeze_processes(void)
unsigned long flags;
if (!freezeable(p))
continue;
- if ((p->flags & PF_FROZEN) ||
+ if ((frozen(p)) ||
(p->state == TASK_TRACED) ||
(p->state == TASK_STOPPED))
continue;

- /* FIXME: smp problem here: we may not access other process' flags
- without locking */
- p->flags |= PF_FREEZE;
+ freeze(p);
spin_lock_irqsave(&p->sighand->siglock, flags);
signal_wake_up(p, 0);
spin_unlock_irqrestore(&p->sighand->siglock, flags);
@@ -91,7 +88,7 @@ int freeze_processes(void)
return todo;
}
} while(todo);
-
+
printk( "|\n" );
BUG_ON(in_atomic());
return 0;
@@ -106,10 +103,7 @@ void thaw_processes(void)
do_each_thread(g, p) {
if (!freezeable(p))
continue;
- if (p->flags & PF_FROZEN) {
- p->flags &= ~PF_FROZEN;
- wake_up_process(p);
- } else
+ if (!thaw_process(p))
printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
} while_each_thread(g, p);

Index: linux-2.6.12/mm/vmscan.c
===================================================================
--- linux-2.6.12.orig/mm/vmscan.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/mm/vmscan.c 2005-06-25 05:01:28.000000000 +0000
@@ -1216,8 +1216,8 @@ static int kswapd(void *p)
order = 0;
for ( ; ; ) {
unsigned long new_order;
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+
+ try_to_freeze();

prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
new_order = pgdat->kswapd_max_order;
Index: linux-2.6.12/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -213,7 +213,7 @@ static inline int has_pending_signals(si
fastcall void recalc_sigpending_tsk(struct task_struct *t)
{
if (t->signal->group_stop_count > 0 ||
- (t->flags & PF_FREEZE) ||
+ (freezing(t)) ||
PENDING(&t->pending, &t->blocked) ||
PENDING(&t->signal->shared_pending, &t->blocked))
set_tsk_thread_flag(t, TIF_SIGPENDING);
@@ -2231,8 +2231,7 @@ sys_rt_sigtimedwait(const sigset_t __use
current->state = TASK_INTERRUPTIBLE;
timeout = schedule_timeout(timeout);

- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
spin_lock_irq(&current->sighand->siglock);
sig = dequeue_signal(current, &these, &info);
current->blocked = current->real_blocked;
Index: linux-2.6.12/mm/pdflush.c
===================================================================
--- linux-2.6.12.orig/mm/pdflush.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/mm/pdflush.c 2005-06-25 05:01:28.000000000 +0000
@@ -105,7 +105,7 @@ static int __pdflush(struct pdflush_work
spin_unlock_irq(&pdflush_lock);

schedule();
- if (try_to_freeze(PF_FREEZE)) {
+ if (try_to_freeze()) {
spin_lock_irq(&pdflush_lock);
continue;
}
Index: linux-2.6.12/kernel/sched.c
===================================================================
--- linux-2.6.12.orig/kernel/sched.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/kernel/sched.c 2005-06-25 05:01:28.000000000 +0000
@@ -4174,8 +4174,7 @@ static int migration_thread(void * data)
struct list_head *head;
migration_req_t *req;

- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

spin_lock_irq(&rq->lock);

Index: linux-2.6.12/drivers/pcmcia/cs.c
===================================================================
--- linux-2.6.12.orig/drivers/pcmcia/cs.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/pcmcia/cs.c 2005-06-25 05:01:28.000000000 +0000
@@ -718,7 +718,7 @@ static int pccardd(void *__skt)
}

schedule();
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

if (!skt->thread)
break;
Index: linux-2.6.12/drivers/usb/core/hub.c
===================================================================
--- linux-2.6.12.orig/drivers/usb/core/hub.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/usb/core/hub.c 2005-06-25 05:01:28.000000000 +0000
@@ -2808,7 +2808,7 @@ static int hub_thread(void *__unused)
do {
hub_events();
wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list));
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
} while (!signal_pending(current));

pr_debug ("%s: khubd exiting\n", usbcore_name);
Index: linux-2.6.12/drivers/input/serio/serio.c
===================================================================
--- linux-2.6.12.orig/drivers/input/serio/serio.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/input/serio/serio.c 2005-06-25 05:01:28.000000000 +0000
@@ -344,7 +344,7 @@ static int serio_thread(void *nothing)
do {
serio_handle_events();
wait_event_interruptible(serio_wait, !list_empty(&serio_event_list));
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
} while (!signal_pending(current));

printk(KERN_DEBUG "serio: kseriod exiting\n");
Index: linux-2.6.12/fs/jbd/journal.c
===================================================================
--- linux-2.6.12.orig/fs/jbd/journal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/jbd/journal.c 2005-06-25 05:01:28.000000000 +0000
@@ -167,7 +167,7 @@ loop:
}

wake_up(&journal->j_wait_done_commit);
- if (current->flags & PF_FREEZE) {
+ if (freezing(current)) {
/*
* The simpler the better. Flushing journal isn't a
* good idea, because that depends on threads that may
@@ -175,7 +175,7 @@ loop:
*/
jbd_debug(1, "Now suspending kjournald\n");
spin_unlock(&journal->j_state_lock);
- refrigerator(PF_FREEZE);
+ refrigerator();
spin_lock(&journal->j_state_lock);
} else {
/*
Index: linux-2.6.12/drivers/usb/storage/usb.c
===================================================================
--- linux-2.6.12.orig/drivers/usb/storage/usb.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/usb/storage/usb.c 2005-06-25 05:01:28.000000000 +0000
@@ -847,10 +847,8 @@ retry:
wait_event_interruptible_timeout(us->delay_wait,
test_bit(US_FLIDX_DISCONNECTING, &us->flags),
delay_use * HZ);
- if (current->flags & PF_FREEZE) {
- refrigerator(PF_FREEZE);
+ if (try_to_freeze())
goto retry;
- }
}

/* If the device is still connected, perform the scanning */
Index: linux-2.6.12/drivers/ieee1394/ieee1394_core.c
===================================================================
--- linux-2.6.12.orig/drivers/ieee1394/ieee1394_core.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/ieee1394/ieee1394_core.c 2005-06-25 05:01:28.000000000 +0000
@@ -1041,10 +1041,8 @@ static int hpsbpkt_thread(void *__hi)

while (1) {
if (down_interruptible(&khpsbpkt_sig)) {
- if (current->flags & PF_FREEZE) {
- refrigerator(0);
+ if (try_to_freeze())
continue;
- }
printk("khpsbpkt: received unexpected signal?!\n" );
break;
}
Index: linux-2.6.12/arch/i386/kernel/io_apic.c
===================================================================
--- linux-2.6.12.orig/arch/i386/kernel/io_apic.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/i386/kernel/io_apic.c 2005-06-25 05:01:28.000000000 +0000
@@ -573,7 +573,7 @@ static int balanced_irq(void *unused)
for ( ; ; ) {
set_current_state(TASK_INTERRUPTIBLE);
time_remaining = schedule_timeout(time_remaining);
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
if (time_after(jiffies,
prev_balance_time+balanced_irq_interval)) {
do_irq_balance();
Index: linux-2.6.12/net/sunrpc/svcsock.c
===================================================================
--- linux-2.6.12.orig/net/sunrpc/svcsock.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/net/sunrpc/svcsock.c 2005-06-25 05:01:28.000000000 +0000
@@ -1185,8 +1185,8 @@ svc_recv(struct svc_serv *serv, struct s
arg->page_len = (pages-2)*PAGE_SIZE;
arg->len = (pages-1)*PAGE_SIZE;
arg->tail[0].iov_len = 0;
-
- try_to_freeze(PF_FREEZE);
+
+ try_to_freeze();
if (signalled())
return -EINTR;

@@ -1227,7 +1227,7 @@ svc_recv(struct svc_serv *serv, struct s

schedule_timeout(timeout);

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

spin_lock_bh(&serv->sv_lock);
remove_wait_queue(&rqstp->rq_wait, &wait);
Index: linux-2.6.12/drivers/ieee1394/nodemgr.c
===================================================================
--- linux-2.6.12.orig/drivers/ieee1394/nodemgr.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/ieee1394/nodemgr.c 2005-06-25 05:01:28.000000000 +0000
@@ -1510,7 +1510,7 @@ static int nodemgr_host_thread(void *__h

if (down_interruptible(&hi->reset_sem) ||
down_interruptible(&nodemgr_serialize)) {
- if (try_to_freeze(PF_FREEZE))
+ if (try_to_freeze())
continue;
printk("NodeMgr: received unexpected signal?!\n" );
break;
Index: linux-2.6.12/drivers/md/md.c
===================================================================
--- linux-2.6.12.orig/drivers/md/md.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/md/md.c 2005-06-25 05:01:28.000000000 +0000
@@ -2976,8 +2976,7 @@ static int md_thread(void * arg)
wait_event_interruptible_timeout(thread->wqueue,
test_bit(THREAD_WAKEUP, &thread->flags),
thread->timeout);
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

clear_bit(THREAD_WAKEUP, &thread->flags);

Index: linux-2.6.12/fs/jfs/jfs_logmgr.c
===================================================================
--- linux-2.6.12.orig/fs/jfs/jfs_logmgr.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/jfs/jfs_logmgr.c 2005-06-25 05:01:28.000000000 +0000
@@ -2359,9 +2359,9 @@ int jfsIOWait(void *arg)
lbmStartIO(bp);
spin_lock_irq(&log_redrive_lock);
}
- if (current->flags & PF_FREEZE) {
+ if (freezing(current)) {
spin_unlock_irq(&log_redrive_lock);
- refrigerator(PF_FREEZE);
+ refrigerator();
} else {
add_wait_queue(&jfs_IO_thread_wait, &wq);
set_current_state(TASK_INTERRUPTIBLE);
Index: linux-2.6.12/fs/jfs/jfs_txnmgr.c
===================================================================
--- linux-2.6.12.orig/fs/jfs/jfs_txnmgr.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/jfs/jfs_txnmgr.c 2005-06-25 05:01:28.000000000 +0000
@@ -2788,9 +2788,9 @@ int jfs_lazycommit(void *arg)
/* In case a wakeup came while all threads were active */
jfs_commit_thread_waking = 0;

- if (current->flags & PF_FREEZE) {
+ if (freezing(current)) {
LAZY_UNLOCK(flags);
- refrigerator(PF_FREEZE);
+ refrigerator();
} else {
DECLARE_WAITQUEUE(wq, current);

@@ -2987,9 +2987,9 @@ int jfs_sync(void *arg)
/* Add anon_list2 back to anon_list */
list_splice_init(&TxAnchor.anon_list2, &TxAnchor.anon_list);

- if (current->flags & PF_FREEZE) {
+ if (freezing(current)) {
TXN_UNLOCK();
- refrigerator(PF_FREEZE);
+ refrigerator();
} else {
DECLARE_WAITQUEUE(wq, current);

Index: linux-2.6.12/arch/i386/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/arch/i386/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/i386/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -608,10 +608,8 @@ int fastcall do_signal(struct pt_regs *r
if (!user_mode(regs))
return 1;

- if (current->flags & PF_FREEZE) {
- refrigerator(0);
+ if (try_to_freeze)
goto no_signal;
- }

if (!oldset)
oldset = &current->blocked;
Index: linux-2.6.12/fs/lockd/clntproc.c
===================================================================
--- linux-2.6.12.orig/fs/lockd/clntproc.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/lockd/clntproc.c 2005-06-25 05:01:28.000000000 +0000
@@ -313,7 +313,7 @@ static int nlm_wait_on_grace(wait_queue_
prepare_to_wait(queue, &wait, TASK_INTERRUPTIBLE);
if (!signalled ()) {
schedule_timeout(NLMCLNT_GRACE_WAIT);
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
if (!signalled ())
status = 0;
}
Index: linux-2.6.12/fs/xfs/linux-2.6/xfs_buf.c
===================================================================
--- linux-2.6.12.orig/fs/xfs/linux-2.6/xfs_buf.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/xfs/linux-2.6/xfs_buf.c 2005-06-25 05:01:28.000000000 +0000
@@ -1771,9 +1771,9 @@ xfsbufd(

INIT_LIST_HEAD(&tmp);
do {
- if (unlikely(current->flags & PF_FREEZE)) {
+ if (unlikely(freezing(current))) {
xfsbufd_force_sleep = 1;
- refrigerator(PF_FREEZE);
+ refrigerator();
} else {
xfsbufd_force_sleep = 0;
}
Index: linux-2.6.12/arch/x86_64/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/arch/x86_64/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/x86_64/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -425,7 +425,7 @@ int do_signal(struct pt_regs *regs, sigs
if (!user_mode(regs))
return 1;

- if (try_to_freeze(0))
+ if (try_to_freeze())
goto no_signal;

if (!oldset)
Index: linux-2.6.12/fs/xfs/linux-2.6/xfs_super.c
===================================================================
--- linux-2.6.12.orig/fs/xfs/linux-2.6/xfs_super.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/xfs/linux-2.6/xfs_super.c 2005-06-25 05:01:28.000000000 +0000
@@ -483,7 +483,7 @@ xfssyncd(
set_current_state(TASK_INTERRUPTIBLE);
timeleft = schedule_timeout(timeleft);
/* swsusp */
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
if (vfsp->vfs_flag & VFS_UMOUNT)
break;

Index: linux-2.6.12/arch/ppc/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/arch/ppc/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/ppc/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -705,8 +705,7 @@ int do_signal(sigset_t *oldset, struct p
unsigned long frame, newsp;
int signr, ret;

- if (current->flags & PF_FREEZE) {
- refrigerator(PF_FREEZE);
+ if (try_to_freeze()) {
signr = 0;
if (!signal_pending(current))
goto no_signal;
Index: linux-2.6.12/Documentation/power/kernel_threads.txt
===================================================================
--- linux-2.6.12.orig/Documentation/power/kernel_threads.txt 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/Documentation/power/kernel_threads.txt 2005-06-25 05:01:28.000000000 +0000
@@ -12,8 +12,7 @@ refrigerator. Code to do this looks like
do {
hub_events();
wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list));
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
} while (!signal_pending(current));

from drivers/usb/core/hub.c::hub_thread()
Index: linux-2.6.12/arch/h8300/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/arch/h8300/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/h8300/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -517,10 +517,8 @@ asmlinkage int do_signal(struct pt_regs
if ((regs->ccr & 0x10))
return 1;

- if (current->flags & PF_FREEZE) {
- refrigerator(0);
+ if (try_to_freeze())
goto no_signal;
- }

current->thread.esp0 = (unsigned long) regs;

Index: linux-2.6.12/arch/m32r/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/arch/m32r/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/m32r/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -371,10 +371,8 @@ int do_signal(struct pt_regs *regs, sigs
if (!user_mode(regs))
return 1;

- if (current->flags & PF_FREEZE) {
- refrigerator(0);
+ if (try_to_freeze())
goto no_signal;
- }

if (!oldset)
oldset = &current->blocked;
Index: linux-2.6.12/fs/afs/kafsasyncd.c
===================================================================
--- linux-2.6.12.orig/fs/afs/kafsasyncd.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/afs/kafsasyncd.c 2005-06-25 05:01:28.000000000 +0000
@@ -116,7 +116,7 @@ static int kafsasyncd(void *arg)
remove_wait_queue(&kafsasyncd_sleepq, &myself);
set_current_state(TASK_RUNNING);

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

/* discard pending signals */
afs_discard_my_signals();
Index: linux-2.6.12/fs/afs/kafstimod.c
===================================================================
--- linux-2.6.12.orig/fs/afs/kafstimod.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/fs/afs/kafstimod.c 2005-06-25 05:01:28.000000000 +0000
@@ -91,7 +91,7 @@ static int kafstimod(void *arg)
complete_and_exit(&kafstimod_dead, 0);
}

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

/* discard pending signals */
afs_discard_my_signals();
Index: linux-2.6.12/Documentation/power/swsusp.txt
===================================================================
--- linux-2.6.12.orig/Documentation/power/swsusp.txt 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/Documentation/power/swsusp.txt 2005-06-25 05:01:28.000000000 +0000
@@ -164,8 +164,7 @@ place where the thread is safe to be fro
should be held at that point and it must be safe to sleep there), and
add:

- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

If the thread is needed for writing the image to storage, you should
instead set the PF_NOFREEZE process flag when creating the thread.
Index: linux-2.6.12/arch/frv/kernel/signal.c
===================================================================
--- linux-2.6.12.orig/arch/frv/kernel/signal.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/arch/frv/kernel/signal.c 2005-06-25 05:01:28.000000000 +0000
@@ -536,10 +536,8 @@ int do_signal(struct pt_regs *regs, sigs
if (!user_mode(regs))
return 1;

- if (current->flags & PF_FREEZE) {
- refrigerator(0);
+ if (try_to_freeze())
goto no_signal;
- }

if (!oldset)
oldset = &current->blocked;
Index: linux-2.6.12/net/rxrpc/krxtimod.c
===================================================================
--- linux-2.6.12.orig/net/rxrpc/krxtimod.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/net/rxrpc/krxtimod.c 2005-06-25 05:01:28.000000000 +0000
@@ -90,7 +90,7 @@ static int krxtimod(void *arg)
complete_and_exit(&krxtimod_dead, 0);
}

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

/* discard pending signals */
rxrpc_discard_my_signals();
Index: linux-2.6.12/net/rxrpc/krxiod.c
===================================================================
--- linux-2.6.12.orig/net/rxrpc/krxiod.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/net/rxrpc/krxiod.c 2005-06-25 05:01:28.000000000 +0000
@@ -138,7 +138,7 @@ static int rxrpc_krxiod(void *arg)

_debug("### End Work");

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

/* discard pending signals */
rxrpc_discard_my_signals();
Index: linux-2.6.12/net/rxrpc/krxsecd.c
===================================================================
--- linux-2.6.12.orig/net/rxrpc/krxsecd.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/net/rxrpc/krxsecd.c 2005-06-25 05:01:28.000000000 +0000
@@ -107,7 +107,7 @@ static int rxrpc_krxsecd(void *arg)

_debug("### End Inbound Calls");

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

/* discard pending signals */
rxrpc_discard_my_signals();
Index: linux-2.6.12/drivers/media/dvb/dvb-core/dvb_frontend.c
===================================================================
--- linux-2.6.12.orig/drivers/media/dvb/dvb-core/dvb_frontend.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/media/dvb/dvb-core/dvb_frontend.c 2005-06-25 05:01:28.000000000 +0000
@@ -391,8 +391,7 @@ static int dvb_frontend_thread(void *dat
break;
}

- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

if (down_interruptible(&fepriv->sem))
break;
Index: linux-2.6.12/drivers/media/video/msp3400.c
===================================================================
--- linux-2.6.12.orig/drivers/media/video/msp3400.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/media/video/msp3400.c 2005-06-25 05:01:28.000000000 +0000
@@ -750,8 +750,7 @@ static int msp34xx_sleep(struct msp3400c
#endif
}
}
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
remove_wait_queue(&msp->wq, &wait);
return msp->restart;
}
Index: linux-2.6.12/drivers/net/irda/stir4200.c
===================================================================
--- linux-2.6.12.orig/drivers/net/irda/stir4200.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/net/irda/stir4200.c 2005-06-25 05:01:28.000000000 +0000
@@ -763,7 +763,7 @@ static int stir_transmit_thread(void *ar
{
#ifdef CONFIG_PM
/* if suspending, then power off and wait */
- if (unlikely(current->flags & PF_FREEZE)) {
+ if (unlikely(freezing(current))) {
if (stir->receiving)
receive_stop(stir);
else
@@ -771,7 +771,7 @@ static int stir_transmit_thread(void *ar

write_reg(stir, REG_CTRL1, CTRL1_TXPWD|CTRL1_RXPWD);

- refrigerator(PF_FREEZE);
+ refrigerator();

if (change_speed(stir, stir->speed))
break;
Index: linux-2.6.12/drivers/input/gameport/gameport.c
===================================================================
--- linux-2.6.12.orig/drivers/input/gameport/gameport.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/input/gameport/gameport.c 2005-06-25 05:01:28.000000000 +0000
@@ -439,7 +439,7 @@ static int gameport_thread(void *nothing
do {
gameport_handle_events();
wait_event_interruptible(gameport_wait, !list_empty(&gameport_event_list));
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
} while (!signal_pending(current));

printk(KERN_DEBUG "gameport: kgameportd exiting\n");
Index: linux-2.6.12/drivers/usb/gadget/file_storage.c
===================================================================
--- linux-2.6.12.orig/drivers/usb/gadget/file_storage.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/usb/gadget/file_storage.c 2005-06-25 05:01:28.000000000 +0000
@@ -1554,8 +1554,7 @@ static int sleep_thread(struct fsg_dev *
rc = wait_event_interruptible(fsg->thread_wqh,
fsg->thread_wakeup_needed);
fsg->thread_wakeup_needed = 0;
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
return (rc ? -EINTR : 0);
}

Index: linux-2.6.12/drivers/pnp/pnpbios/core.c
===================================================================
--- linux-2.6.12.orig/drivers/pnp/pnpbios/core.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/pnp/pnpbios/core.c 2005-06-25 05:01:28.000000000 +0000
@@ -182,7 +182,7 @@ static int pnp_dock_thread(void * unused
msleep_interruptible(2000);

if(signal_pending(current)) {
- if (try_to_freeze(PF_FREEZE))
+ if (try_to_freeze())
continue;
break;
}
Index: linux-2.6.12/drivers/net/wireless/airo.c
===================================================================
--- linux-2.6.12.orig/drivers/net/wireless/airo.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/net/wireless/airo.c 2005-06-25 05:01:28.000000000 +0000
@@ -2918,7 +2918,7 @@ static int airo_thread(void *data) {
flush_signals(current);

/* make swsusp happy with our thread */
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();

if (test_bit(JOB_DIE, &ai->flags))
break;
Index: linux-2.6.12/drivers/macintosh/therm_adt746x.c
===================================================================
--- linux-2.6.12.orig/drivers/macintosh/therm_adt746x.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/macintosh/therm_adt746x.c 2005-06-25 05:01:28.000000000 +0000
@@ -328,9 +328,7 @@ static int monitor_task(void *arg)
struct thermostat* th = arg;

while(!kthread_should_stop()) {
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
-
+ try_to_freeze();
msleep_interruptible(2000);

#ifndef DEBUG
Index: linux-2.6.12/drivers/net/irda/sir_kthread.c
===================================================================
--- linux-2.6.12.orig/drivers/net/irda/sir_kthread.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/net/irda/sir_kthread.c 2005-06-25 05:01:28.000000000 +0000
@@ -135,8 +135,7 @@ static int irda_thread(void *startup)
remove_wait_queue(&irda_rq_queue.kick, &wait);

/* make swsusp happy with our thread */
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

run_irda_queue();
}
Index: linux-2.6.12/drivers/media/video/video-buf-dvb.c
===================================================================
--- linux-2.6.12.orig/drivers/media/video/video-buf-dvb.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/media/video/video-buf-dvb.c 2005-06-25 05:01:28.000000000 +0000
@@ -62,8 +62,7 @@ static int videobuf_dvb_thread(void *dat
break;
if (kthread_should_stop())
break;
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();

/* feed buffer data to demux */
if (buf->state == STATE_DONE)
Index: linux-2.6.12/drivers/net/8139too.c
===================================================================
--- linux-2.6.12.orig/drivers/net/8139too.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/net/8139too.c 2005-06-25 05:01:28.000000000 +0000
@@ -1606,7 +1606,7 @@ static int rtl8139_thread (void *data)
do {
timeout = interruptible_sleep_on_timeout (&tp->thr_wait, timeout);
/* make swsusp happy with our thread */
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
} while (!signal_pending (current) && (timeout > 0));

if (signal_pending (current)) {
Index: linux-2.6.12/drivers/w1/w1.c
===================================================================
--- linux-2.6.12.orig/drivers/w1/w1.c 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/drivers/w1/w1.c 2005-06-25 05:01:28.000000000 +0000
@@ -646,7 +646,7 @@ static int w1_control(void *data)
while (!control_needs_exit || have_to_wait) {
have_to_wait = 0;

- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
msleep_interruptible(w1_timeout * 1000);

if (signal_pending(current))
@@ -725,7 +725,7 @@ int w1_process(void *data)
allow_signal(SIGTERM);

while (!test_bit(W1_MASTER_NEED_EXIT, &dev->flags)) {
- try_to_freeze(PF_FREEZE);
+ try_to_freeze();
msleep_interruptible(w1_timeout * 1000);

if (signal_pending(current))
Index: linux-2.6.12/include/linux/sched.h
===================================================================
--- linux-2.6.12.orig/include/linux/sched.h 2005-06-25 05:01:26.000000000 +0000
+++ linux-2.6.12/include/linux/sched.h 2005-06-25 05:41:28.000000000 +0000
@@ -1245,33 +1245,78 @@ extern void normalize_rt_tasks(void);

#endif

-/* try_to_freeze
- *
- * Checks whether we need to enter the refrigerator
- * and returns 1 if we did so.
- */
#ifdef CONFIG_PM
-extern void refrigerator(unsigned long);
+/*
+ * 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;
+}
+
+/*
+ * 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;
+}
+
+/*
+ * freezing is complete, mark process as frozen
+ */
+static inline void frozen_process(struct task_struct *p)
+{
+ p->flags = (p->flags & ~PF_FREEZE) | PF_FROZEN;
+}
+
+extern void refrigerator(void);
extern int freeze_processes(void);
extern void thaw_processes(void);

-static inline int try_to_freeze(unsigned long refrigerator_flags)
+static inline int try_to_freeze(void)
{
- if (unlikely(current->flags & PF_FREEZE)) {
- refrigerator(refrigerator_flags);
+ if (freezing(current)) {
+ refrigerator();
return 1;
} else
return 0;
}
#else
-static inline void refrigerator(unsigned long flag) {}
+static inline int frozen(struct task_struct *p) { return 0; }
+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 void refrigerator(void) {}
static inline int freeze_processes(void) { BUG(); return 0; }
static inline void thaw_processes(void) {}

-static inline int try_to_freeze(unsigned long refrigerator_flags)
-{
- return 0;
-}
+static inline int try_to_freeze(void) { return 0; }
+
#endif /* CONFIG_PM */
#endif /* __KERNEL__ */