freezer,sched: Rewrite core freezer logic

Message ID YMMijNqaLDbS3sIv@hirez.programming.kicks-ass.net
State New
Headers show
Series
  • freezer,sched: Rewrite core freezer logic
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Commit Message

Peter Zijlstra June 11, 2021, 8:45 a.m.
Rewrite the core freezer to behave better wrt thawing. By replacing
PF_FROZEN with TASK_FROZEN, a special block state, it is ensured frozen
tasks stay frozen until explicitly thawed and don't randomly wake up
early, as is currently possible.

As such, it does away with PF_FROZEN and PF_FREEZER_SKIP, freeing up
two PF_flags (yay).

The freezing was tested, and found good, using:

  echo freezer > /sys/power/pm_test
  echo mem > /sys/power/state

Even while having a GDB session active.

Another notable bit is in init/do_mounts_initrd.c; afaict that has been
'broken' for quite a while and is simply removed.

Requested-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 drivers/android/binder.c       |    4 
 drivers/media/pci/pt3/pt3.c    |    4 
 fs/cifs/inode.c                |    4 
 fs/cifs/transport.c            |    5 
 fs/coredump.c                  |    4 
 fs/nfs/file.c                  |    3 
 fs/nfs/inode.c                 |   12 --
 fs/nfs/nfs3proc.c              |    3 
 fs/nfs/nfs4proc.c              |   14 +-
 fs/nfs/nfs4state.c             |    3 
 fs/nfs/pnfs.c                  |    4 
 fs/xfs/xfs_trans_ail.c         |    8 -
 include/linux/completion.h     |    2 
 include/linux/freezer.h        |  244 +----------------------------------------
 include/linux/sched.h          |   16 ++
 include/linux/sunrpc/sched.h   |    7 -
 include/linux/wait.h           |   40 +++++-
 init/do_mounts_initrd.c        |    7 -
 kernel/cgroup/legacy_freezer.c |   23 +--
 kernel/exit.c                  |    4 
 kernel/fork.c                  |    4 
 kernel/freezer.c               |  116 +++++++++++++------
 kernel/futex.c                 |    4 
 kernel/hung_task.c             |    4 
 kernel/power/main.c            |    5 
 kernel/power/process.c         |   10 -
 kernel/sched/completion.c      |   16 ++
 kernel/sched/core.c            |    2 
 kernel/signal.c                |   14 +-
 kernel/time/hrtimer.c          |    4 
 mm/khugepaged.c                |    4 
 net/sunrpc/sched.c             |   12 --
 net/unix/af_unix.c             |    8 -
 33 files changed, 232 insertions(+), 382 deletions(-)

Comments

Oleg Nesterov June 14, 2021, 3:42 p.m. | #1
Hi Peter, sorry for delay,

On 06/11, Peter Zijlstra wrote:
>

> +/* Recursion relies on tail-call optimization to not blow away the stack */

> +static bool __frozen(struct task_struct *p)

> +{

> +	if (p->state == TASK_FROZEN)

> +		return true;

> +

> +	/*

> +	 * If stuck in TRACED, and the ptracer is FROZEN, we're frozen too.

> +	 */

> +	if (task_is_traced(p))

> +		return frozen(rcu_dereference(p->parent));


Why does it use frozen(), not __frozen() ?

This looks racy, p->parent can resume this task and then enter
__refrigerator().

Plus this task can be SIGKILL'ed even if it is traced.


> +	/*

> +	 * If stuck in STOPPED and the parent is FROZEN, we're frozen too.

> +	 */

> +	if (task_is_stopped(p))

> +		return frozen(rcu_dereference(p->real_parent));


(you could use ->parent in this case too and unify this check with the
"traced" case above)

I don't understand. How this connects to ->parent or ->real_parent?
SIGCONT can come from anywhere and wake this stopped task up?


I guess you do this to avoid freezable_schedule() in ptrace/signal_stop,
and we can't use TASK_STOPPED|TASK_FREEZABLE, it should not run after
thaw()... But see above, we can't rely on __frozen(parent).

Oleg.
Peter Zijlstra June 14, 2021, 4:12 p.m. | #2
On Mon, Jun 14, 2021 at 05:42:47PM +0200, Oleg Nesterov wrote:
> Hi Peter, sorry for delay,

> 

> On 06/11, Peter Zijlstra wrote:

> >

> > +/* Recursion relies on tail-call optimization to not blow away the stack */

> > +static bool __frozen(struct task_struct *p)

> > +{

> > +	if (p->state == TASK_FROZEN)

> > +		return true;

> > +

> > +	/*

> > +	 * If stuck in TRACED, and the ptracer is FROZEN, we're frozen too.

> > +	 */

> > +	if (task_is_traced(p))

> > +		return frozen(rcu_dereference(p->parent));

> 

> Why does it use frozen(), not __frozen() ?


(because I'm an idiot :/)

> This looks racy, p->parent can resume this task and then enter

> __refrigerator().


But this is about the child, we won't report it frozen, unless the
parent is also frozen. If the parent is frozen, it cannot resume the
task.

The other way around, if the parent resumes the task and then gets
frozen, then we'll wait until the task gets frozen.

That is, I don't see the race. Maybe it's been too warm, but could you
spell it out?

> Plus this task can be SIGKILL'ed even if it is traced.


Hurmm.. *that* is a problem.

> > +	/*

> > +	 * If stuck in STOPPED and the parent is FROZEN, we're frozen too.

> > +	 */

> > +	if (task_is_stopped(p))

> > +		return frozen(rcu_dereference(p->real_parent));

> 

> (you could use ->parent in this case too and unify this check with the

> "traced" case above)


Are you sure? The way I read the code ptrace_attach() will change
->parent, but STOPPED is controlled by the jobctl.

> I don't understand. How this connects to ->parent or ->real_parent?

> SIGCONT can come from anywhere and wake this stopped task up?


Could be me who's not understanding, I thought only the real parent
could do that.

> I guess you do this to avoid freezable_schedule() in ptrace/signal_stop,

> and we can't use TASK_STOPPED|TASK_FREEZABLE, it should not run after

> thaw()... But see above, we can't rely on __frozen(parent).


I do this because freezing puts a task in TASK_FROZEN, and that cannot
preserve TAKS_STOPPED or TASK_TRACED without being subject to wakups
from those bits. I suppose I can add TASK_FROZEN_STOPPED and
TASK_FROZEN_TRACED bits. Let me try that... (tomorrow, brain is cooked).
Oleg Nesterov June 14, 2021, 4:54 p.m. | #3
On 06/14, Peter Zijlstra wrote:
>

> On Mon, Jun 14, 2021 at 05:42:47PM +0200, Oleg Nesterov wrote:

> >

> > > +	/*

> > > +	 * If stuck in TRACED, and the ptracer is FROZEN, we're frozen too.

> > > +	 */

> > > +	if (task_is_traced(p))

> > > +		return frozen(rcu_dereference(p->parent));

> >

> > This looks racy, p->parent can resume this task and then enter

> > __refrigerator().

>

> But this is about the child, we won't report it frozen, unless the

> parent is also frozen. If the parent is frozen, it cannot resume the

> task.


Yes, but...

> The other way around, if the parent resumes the task and then gets

> frozen,


Yes ...

> then we'll wait until the task gets frozen.


how/where will we wait until the tracee gets frozen ?

Again, suppose that p->parent resumes p and gets frozen after the
task_is_traced(p) check and before the frozen(p->parent) check.

Then try_to_freeze_tasks() can succeed with todo == 0 and miss the
running "p" ?

> > > +	 * If stuck in STOPPED and the parent is FROZEN, we're frozen too.

> > > +	 */

> > > +	if (task_is_stopped(p))

> > > +		return frozen(rcu_dereference(p->real_parent));

> >

> > (you could use ->parent in this case too and unify this check with the

> > "traced" case above)

>

> Are you sure? The way I read the code ptrace_attach() will change

> ->parent, but STOPPED is controlled by the jobctl.


Yes, sorry I was not clear. let me add more details.

task_is_stopped() is only possible if task is not ptraced, see the
"if (!current->ptrace)" check before set_special_state(TASK_STOPPED)
in do_signal_stop(). And if the task is not traced, then
task->parent == task->real_parent.

> > I don't understand. How this connects to ->parent or ->real_parent?

> > SIGCONT can come from anywhere and wake this stopped task up?

>

> Could be me who's not understanding, I thought only the real parent

> could do that.


No, any task can do this, as long as check_kill_permission() succeeds.
Even the kernel can send SIGCONT, say, you can use F_SETSIG(SIGCONT).

> > I guess you do this to avoid freezable_schedule() in ptrace/signal_stop,

> > and we can't use TASK_STOPPED|TASK_FREEZABLE, it should not run after

> > thaw()... But see above, we can't rely on __frozen(parent).

>

> I do this because freezing puts a task in TASK_FROZEN, and that cannot

> preserve TAKS_STOPPED or TASK_TRACED without being subject to wakups


Yes, yes, this is what I tried to say.

Oleg.
Peter Zijlstra June 14, 2021, 6:38 p.m. | #4
On Mon, Jun 14, 2021 at 06:54:23PM +0200, Oleg Nesterov wrote:
> On 06/14, Peter Zijlstra wrote:


> > > I guess you do this to avoid freezable_schedule() in ptrace/signal_stop,

> > > and we can't use TASK_STOPPED|TASK_FREEZABLE, it should not run after

> > > thaw()... But see above, we can't rely on __frozen(parent).

> >

> > I do this because freezing puts a task in TASK_FROZEN, and that cannot

> > preserve TAKS_STOPPED or TASK_TRACED without being subject to wakups

> 

> Yes, yes, this is what I tried to say.


OK, thanks for all that. Clearly I need to stare at this code longer and
harder.

One more thing; if I add additional state bits to preserve
__TASK_{TRACED,STOPPED}, then I need to figure out at thaw time if we've
missed a wakeup or not.

Do we have sufficient state for that? If so, don't we then also not have
sufficient state to tell if a task should've been TRACED/STOPPED in the
first place?

If not, I probably should add this... I'll go dig.
Oleg Nesterov June 15, 2021, 3:45 p.m. | #5
On 06/14, Peter Zijlstra wrote:
>

> One more thing; if I add additional state bits to preserve

> __TASK_{TRACED,STOPPED}, then I need to figure out at thaw time if we've

> missed a wakeup or not.

>

> Do we have sufficient state for that? If so, don't we then also not have

> sufficient state to tell if a task should've been TRACED/STOPPED in the

> first place?


Not sure I understand you, probably not, but I think the answer is "no" ;)

But this reminds me... can't we implement selective wakeups? So that if a
task T sleeps in state = STOPPED | FROZEN, then ttwu(T, FROZEN) won't wake
it up, it will only clear FROZEN from T->state. Similarly, ttwu(T, STOPPED)
will leave this task with state == FROZEN.

See also

	https://lore.kernel.org/lkml/20131112162136.GA29065@redhat.com/
	https://lore.kernel.org/lkml/20131113170724.GA17739@redhat.com/

just to remind you that we already discussed TASK_FROZEN a little bit almost
10 years ago ;)

What has been shall be, and what has been done is what will be done, and
there is nothing new under the sun.

Oleg.
Peter Zijlstra June 15, 2021, 9:35 p.m. | #6
On Tue, Jun 15, 2021 at 05:45:39PM +0200, Oleg Nesterov wrote:

> But this reminds me... can't we implement selective wakeups? So that if a

> task T sleeps in state = STOPPED | FROZEN, then ttwu(T, FROZEN) won't wake

> it up, it will only clear FROZEN from T->state. Similarly, ttwu(T, STOPPED)

> will leave this task with state == FROZEN.


All this started because I didn't want to touch the wakeup path for
freezing :/

> See also

> 

> 	https://lore.kernel.org/lkml/20131112162136.GA29065@redhat.com/

> 	https://lore.kernel.org/lkml/20131113170724.GA17739@redhat.com/

> 

> just to remind you that we already discussed TASK_FROZEN a little bit almost

> 10 years ago ;)

> 

> What has been shall be, and what has been done is what will be done, and

> there is nothing new under the sun.


Ha!, I had completely forgotten.
Peter Zijlstra June 15, 2021, 9:50 p.m. | #7
On Tue, Jun 15, 2021 at 05:45:39PM +0200, Oleg Nesterov wrote:
> On 06/14, Peter Zijlstra wrote:

> >

> > One more thing; if I add additional state bits to preserve

> > __TASK_{TRACED,STOPPED}, then I need to figure out at thaw time if we've

> > missed a wakeup or not.

> >

> > Do we have sufficient state for that? If so, don't we then also not have

> > sufficient state to tell if a task should've been TRACED/STOPPED in the

> > first place?

> 

> Not sure I understand you, probably not, but I think the answer is "no" ;)


I was thinking something like the below, such that we can then write
something like:

void __thaw_special(struct task_struct *p)
{
	spin_lock(&t->sighand->siglock);

	if (p->ptrace) {
		unsigned int state = __TASK_TRACED;

		if (!(p->ptrace & PT_STOPPED))
			goto unlock;

		if (p->ptrace & PT_STOPPED_FATAL) {
			state |= TASK_WAKEKILL;
			if (__fatal_signal_pending(p))
				goto unlock;
		}

		set_special_state(state);

	} else if ((p->jobctl & JOBCTL_STOP_PENDING) &&
		   !__fatal_signal_pending(p)) {

		set_special_state(TASK_STOPPED);
	}

unlock:
	spin_unlock(&t->sighand->siglock);
}



---
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index b5ebf6c01292..2123d6543125 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -28,30 +28,36 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
  * flags.  When the a task is stopped the ptracer owns task->ptrace.
  */
 
-#define PT_SEIZED	0x00010000	/* SEIZE used, enable new behavior */
-#define PT_PTRACED	0x00000001
-#define PT_DTRACE	0x00000002	/* delayed trace (used on m68k, i386) */
+#define PT_PTRACED	0x00000001						// 0x00000001
+#define PT_DTRACE	0x00000002 /* delayed trace (used on m68k, i386) */	// 0x00000002
 
 #define PT_OPT_FLAG_SHIFT	3
 /* PT_TRACE_* event enable flags */
 #define PT_EVENT_FLAG(event)	(1 << (PT_OPT_FLAG_SHIFT + (event)))
-#define PT_TRACESYSGOOD		PT_EVENT_FLAG(0)
-#define PT_TRACE_FORK		PT_EVENT_FLAG(PTRACE_EVENT_FORK)
-#define PT_TRACE_VFORK		PT_EVENT_FLAG(PTRACE_EVENT_VFORK)
-#define PT_TRACE_CLONE		PT_EVENT_FLAG(PTRACE_EVENT_CLONE)
-#define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
-#define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
-#define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
-#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)
-
-#define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)
-#define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT)
+
+#define PT_TRACESYSGOOD		PT_EVENT_FLAG(0)			        // 0x00000008
+#define PT_TRACE_FORK		PT_EVENT_FLAG(PTRACE_EVENT_FORK)	        // 0x00000010
+#define PT_TRACE_VFORK		PT_EVENT_FLAG(PTRACE_EVENT_VFORK)	        // 0x00000020
+#define PT_TRACE_CLONE		PT_EVENT_FLAG(PTRACE_EVENT_CLONE)	        // 0x00000040
+#define PT_TRACE_EXEC		PT_EVENT_FLAG(PTRACE_EVENT_EXEC)	        // 0x00000080
+#define PT_TRACE_VFORK_DONE	PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)	        // 0x00000100
+#define PT_TRACE_EXIT		PT_EVENT_FLAG(PTRACE_EVENT_EXIT)	        // 0x00000200
+#define PT_TRACE_SECCOMP	PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP)	        // 0x00000400
+
+#define PT_SEIZED		0x00010000 /* SEIZE used, enable new behavior */// 0x00010000
+#define PT_STOPPED		0x00020000					// 0x00020000
+#define PT_STOPPED_FATAL	0x00040000					// 0x00040000
+
+#define PT_STOPPED_MASK		(PT_STOPPED|PT_STOPPED_FATAL)
+
+#define PT_EXITKILL		(PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT)	// 0x00800000
+#define PT_SUSPEND_SECCOMP	(PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT) // 0x01000000
 
 /* single stepping state bits (used on ARM and PA-RISC) */
 #define PT_SINGLESTEP_BIT	31
-#define PT_SINGLESTEP		(1<<PT_SINGLESTEP_BIT)
+#define PT_SINGLESTEP		(1<<PT_SINGLESTEP_BIT)				// 0x80000000
 #define PT_BLOCKSTEP_BIT	30
-#define PT_BLOCKSTEP		(1<<PT_BLOCKSTEP_BIT)
+#define PT_BLOCKSTEP		(1<<PT_BLOCKSTEP_BIT)				// 0x40000000
 
 extern long arch_ptrace(struct task_struct *child, long request,
 			unsigned long addr, unsigned long data);
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 0d7fec79d28f..0cf806030bfd 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -424,6 +424,8 @@ static inline void signal_wake_up(struct task_struct *t, bool resume)
 }
 static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
 {
+	if (resume)
+		t->ptrace &= ~PT_STOPPED_MASK;
 	signal_wake_up_state(t, resume ? __TASK_TRACED : 0);
 }
 
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 2997ca600d18..4fc4e1f91ecd 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -197,6 +197,8 @@ static bool ptrace_freeze_traced(struct task_struct *task)
 	spin_lock_irq(&task->sighand->siglock);
 	if (task_is_traced(task) && !looks_like_a_spurious_pid(task) &&
 	    !__fatal_signal_pending(task)) {
+		task->ptrace &= ~PT_STOPPED_MASK;
+		task->ptrace |= PT_STOPPED;
 		task->state = __TASK_TRACED;
 		ret = true;
 	}
@@ -218,10 +220,13 @@ static void ptrace_unfreeze_traced(struct task_struct *task)
 	 */
 	spin_lock_irq(&task->sighand->siglock);
 	if (task->state == __TASK_TRACED) {
-		if (__fatal_signal_pending(task))
+		if (__fatal_signal_pending(task)) {
+			task->ptrace &= ~PT_STOPPED_MASK;
 			wake_up_state(task, __TASK_TRACED);
-		else
+		} else {
+			task->ptrace |= PT_STOPPED_MASK;
 			task->state = TASK_TRACED;
+		}
 	}
 	spin_unlock_irq(&task->sighand->siglock);
 }
@@ -835,8 +840,6 @@ static long ptrace_get_rseq_configuration(struct task_struct *task,
 static int ptrace_resume(struct task_struct *child, long request,
 			 unsigned long data)
 {
-	bool need_siglock;
-
 	if (!valid_signal(data))
 		return -EIO;
 
@@ -877,13 +880,11 @@ static int ptrace_resume(struct task_struct *child, long request,
 	 * status and clears the code too; this can't race with the tracee, it
 	 * takes siglock after resume.
 	 */
-	need_siglock = data && !thread_group_empty(current);
-	if (need_siglock)
-		spin_lock_irq(&child->sighand->siglock);
+	spin_lock_irq(&child->sighand->siglock);
 	child->exit_code = data;
+	child->ptrace &= ~PT_STOPPED_MASK;
 	wake_up_state(child, __TASK_TRACED);
-	if (need_siglock)
-		spin_unlock_irq(&child->sighand->siglock);
+	spin_unlock_irq(&child->sighand->siglock);
 
 	return 0;
 }
diff --git a/kernel/signal.c b/kernel/signal.c
index f7c6ffcbd044..35cdb92b7f1d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2195,6 +2195,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 			return;
 	}
 
+	current->ptrace |= PT_STOPPED_MASK;
 	set_special_state(TASK_TRACED);
 
 	/*

Patch

--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -3712,10 +3712,9 @@  static int binder_wait_for_work(struct b
 	struct binder_proc *proc = thread->proc;
 	int ret = 0;
 
-	freezer_do_not_count();
 	binder_inner_proc_lock(proc);
 	for (;;) {
-		prepare_to_wait(&thread->wait, &wait, TASK_INTERRUPTIBLE);
+		prepare_to_wait(&thread->wait, &wait, TASK_INTERRUPTIBLE|TASK_FREEZABLE);
 		if (binder_has_work_ilocked(thread, do_proc_work))
 			break;
 		if (do_proc_work)
@@ -3732,7 +3731,6 @@  static int binder_wait_for_work(struct b
 	}
 	finish_wait(&thread->wait, &wait);
 	binder_inner_proc_unlock(proc);
-	freezer_count();
 
 	return ret;
 }
--- a/drivers/media/pci/pt3/pt3.c
+++ b/drivers/media/pci/pt3/pt3.c
@@ -445,8 +445,8 @@  static int pt3_fetch_thread(void *data)
 		pt3_proc_dma(adap);
 
 		delay = ktime_set(0, PT3_FETCH_DELAY * NSEC_PER_MSEC);
-		set_current_state(TASK_UNINTERRUPTIBLE);
-		freezable_schedule_hrtimeout_range(&delay,
+		set_current_state(TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
+		schedule_hrtimeout_range(&delay,
 					PT3_FETCH_DELAY_DELTA * NSEC_PER_MSEC,
 					HRTIMER_MODE_REL);
 	}
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2280,7 +2280,7 @@  cifs_invalidate_mapping(struct inode *in
 static int
 cifs_wait_bit_killable(struct wait_bit_key *key, int mode)
 {
-	freezable_schedule_unsafe();
+	schedule();
 	if (signal_pending_state(mode, current))
 		return -ERESTARTSYS;
 	return 0;
@@ -2297,7 +2297,7 @@  cifs_revalidate_mapping(struct inode *in
 		return 0;
 
 	rc = wait_on_bit_lock_action(flags, CIFS_INO_LOCK, cifs_wait_bit_killable,
-				     TASK_KILLABLE);
+				     TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 	if (rc)
 		return rc;
 
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -771,8 +771,9 @@  wait_for_response(struct TCP_Server_Info
 {
 	int error;
 
-	error = wait_event_freezekillable_unsafe(server->response_q,
-				    midQ->mid_state != MID_REQUEST_SUBMITTED);
+	error = wait_event_state(server->response_q,
+				 midQ->mid_state != MID_REQUEST_SUBMITTED,
+				 (TASK_KILLABLE|TASK_FREEZABLE_UNSAFE));
 	if (error < 0)
 		return -ERESTARTSYS;
 
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -465,9 +465,7 @@  static int coredump_wait(int exit_code,
 	if (core_waiters > 0) {
 		struct core_thread *ptr;
 
-		freezer_do_not_count();
-		wait_for_completion(&core_state->startup);
-		freezer_count();
+		wait_for_completion_freezable(&core_state->startup);
 		/*
 		 * Wait for all the threads to become inactive, so that
 		 * all the thread context (extended register state, like
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -558,7 +558,8 @@  static vm_fault_t nfs_vm_page_mkwrite(st
 	nfs_fscache_wait_on_page_write(NFS_I(inode), page);
 
 	wait_on_bit_action(&NFS_I(inode)->flags, NFS_INO_INVALIDATING,
-			nfs_wait_bit_killable, TASK_KILLABLE);
+			   nfs_wait_bit_killable,
+			   TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 
 	lock_page(page);
 	mapping = page_file_mapping(page);
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -72,18 +72,13 @@  nfs_fattr_to_ino_t(struct nfs_fattr *fat
 	return nfs_fileid_to_ino_t(fattr->fileid);
 }
 
-static int nfs_wait_killable(int mode)
+int nfs_wait_bit_killable(struct wait_bit_key *key, int mode)
 {
-	freezable_schedule_unsafe();
+	schedule();
 	if (signal_pending_state(mode, current))
 		return -ERESTARTSYS;
 	return 0;
 }
-
-int nfs_wait_bit_killable(struct wait_bit_key *key, int mode)
-{
-	return nfs_wait_killable(mode);
-}
 EXPORT_SYMBOL_GPL(nfs_wait_bit_killable);
 
 /**
@@ -1323,7 +1318,8 @@  int nfs_clear_invalid_mapping(struct add
 	 */
 	for (;;) {
 		ret = wait_on_bit_action(bitlock, NFS_INO_INVALIDATING,
-					 nfs_wait_bit_killable, TASK_KILLABLE);
+					 nfs_wait_bit_killable,
+					 TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 		if (ret)
 			goto out;
 		spin_lock(&inode->i_lock);
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -36,7 +36,8 @@  nfs3_rpc_wrapper(struct rpc_clnt *clnt,
 		res = rpc_call_sync(clnt, msg, flags);
 		if (res != -EJUKEBOX)
 			break;
-		freezable_schedule_timeout_killable_unsafe(NFS_JUKEBOX_RETRY_TIME);
+		__set_current_state(TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
+		schedule_timeout(NFS_JUKEBOX_RETRY_TIME);
 		res = -ERESTARTSYS;
 	} while (!fatal_signal_pending(current));
 	return res;
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -411,8 +411,8 @@  static int nfs4_delay_killable(long *tim
 {
 	might_sleep();
 
-	freezable_schedule_timeout_killable_unsafe(
-		nfs4_update_delay(timeout));
+	__set_current_state(TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
+	schedule_timeout(nfs4_update_delay(timeout));
 	if (!__fatal_signal_pending(current))
 		return 0;
 	return -EINTR;
@@ -422,7 +422,8 @@  static int nfs4_delay_interruptible(long
 {
 	might_sleep();
 
-	freezable_schedule_timeout_interruptible_unsafe(nfs4_update_delay(timeout));
+	__set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE_UNSAFE);
+	schedule_timeout(nfs4_update_delay(timeout));
 	if (!signal_pending(current))
 		return 0;
 	return __fatal_signal_pending(current) ? -EINTR :-ERESTARTSYS;
@@ -7280,7 +7281,8 @@  nfs4_retry_setlk_simple(struct nfs4_stat
 		status = nfs4_proc_setlk(state, cmd, request);
 		if ((status != -EAGAIN) || IS_SETLK(cmd))
 			break;
-		freezable_schedule_timeout_interruptible(timeout);
+		__set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
+		schedule_timeout(timeout);
 		timeout *= 2;
 		timeout = min_t(unsigned long, NFS4_LOCK_MAXTIMEOUT, timeout);
 		status = -ERESTARTSYS;
@@ -7348,10 +7350,8 @@  nfs4_retry_setlk(struct nfs4_state *stat
 			break;
 
 		status = -ERESTARTSYS;
-		freezer_do_not_count();
-		wait_woken(&waiter.wait, TASK_INTERRUPTIBLE,
+		wait_woken(&waiter.wait, TASK_INTERRUPTIBLE|TASK_FREEZABLE,
 			   NFS4_LOCK_MAXTIMEOUT);
-		freezer_count();
 	} while (!signalled());
 
 	remove_wait_queue(q, &waiter.wait);
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1307,7 +1307,8 @@  int nfs4_wait_clnt_recover(struct nfs_cl
 
 	refcount_inc(&clp->cl_count);
 	res = wait_on_bit_action(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING,
-				 nfs_wait_bit_killable, TASK_KILLABLE);
+				 nfs_wait_bit_killable,
+				 TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 	if (res)
 		goto out;
 	if (clp->cl_cons_state < 0)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1897,7 +1897,7 @@  static int pnfs_prepare_to_retry_layoutg
 	pnfs_layoutcommit_inode(lo->plh_inode, false);
 	return wait_on_bit_action(&lo->plh_flags, NFS_LAYOUT_RETURN,
 				   nfs_wait_bit_killable,
-				   TASK_KILLABLE);
+				   TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 }
 
 static void nfs_layoutget_begin(struct pnfs_layout_hdr *lo)
@@ -3172,7 +3172,7 @@  pnfs_layoutcommit_inode(struct inode *in
 		status = wait_on_bit_lock_action(&nfsi->flags,
 				NFS_INO_LAYOUTCOMMITTING,
 				nfs_wait_bit_killable,
-				TASK_KILLABLE);
+				TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 		if (status)
 			goto out;
 	}
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -585,9 +585,9 @@  xfsaild(
 
 	while (1) {
 		if (tout && tout <= 20)
-			set_current_state(TASK_KILLABLE);
+			set_current_state(TASK_KILLABLE|TASK_FREEZABLE);
 		else
-			set_current_state(TASK_INTERRUPTIBLE);
+			set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
 
 		/*
 		 * Check kthread_should_stop() after we set the task state to
@@ -636,14 +636,14 @@  xfsaild(
 		    ailp->ail_target == ailp->ail_target_prev &&
 		    list_empty(&ailp->ail_buf_list)) {
 			spin_unlock(&ailp->ail_lock);
-			freezable_schedule();
+			schedule();
 			tout = 0;
 			continue;
 		}
 		spin_unlock(&ailp->ail_lock);
 
 		if (tout)
-			freezable_schedule_timeout(msecs_to_jiffies(tout));
+			schedule_timeout(msecs_to_jiffies(tout));
 
 		__set_current_state(TASK_RUNNING);
 
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -100,9 +100,11 @@  static inline void reinit_completion(str
 }
 
 extern void wait_for_completion(struct completion *);
+extern void wait_for_completion_freezable(struct completion *);
 extern void wait_for_completion_io(struct completion *);
 extern int wait_for_completion_interruptible(struct completion *x);
 extern int wait_for_completion_killable(struct completion *x);
+extern int wait_for_completion_killable_freezable(struct completion *x);
 extern unsigned long wait_for_completion_timeout(struct completion *x,
 						   unsigned long timeout);
 extern unsigned long wait_for_completion_io_timeout(struct completion *x,
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -8,9 +8,11 @@ 
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <linux/atomic.h>
+#include <linux/jump_label.h>
 
 #ifdef CONFIG_FREEZER
-extern atomic_t system_freezing_cnt;	/* nr of freezing conds in effect */
+DECLARE_STATIC_KEY_FALSE(freezer_active);
+
 extern bool pm_freezing;		/* PM freezing in effect */
 extern bool pm_nosig_freezing;		/* PM nosig freezing in effect */
 
@@ -22,10 +24,7 @@  extern unsigned int freeze_timeout_msecs
 /*
  * Check if a process has been frozen
  */
-static inline bool frozen(struct task_struct *p)
-{
-	return p->flags & PF_FROZEN;
-}
+extern bool frozen(struct task_struct *p);
 
 extern bool freezing_slow_path(struct task_struct *p);
 
@@ -34,9 +33,10 @@  extern bool freezing_slow_path(struct ta
  */
 static inline bool freezing(struct task_struct *p)
 {
-	if (likely(!atomic_read(&system_freezing_cnt)))
-		return false;
-	return freezing_slow_path(p);
+	if (static_branch_unlikely(&freezer_active))
+		return freezing_slow_path(p);
+
+	return false;
 }
 
 /* Takes and releases task alloc lock using task_lock() */
@@ -48,23 +48,14 @@  extern int freeze_kernel_threads(void);
 extern void thaw_processes(void);
 extern void thaw_kernel_threads(void);
 
-/*
- * DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION
- * If try_to_freeze causes a lockdep warning it means the caller may deadlock
- */
-static inline bool try_to_freeze_unsafe(void)
+static inline bool try_to_freeze(void)
 {
 	might_sleep();
 	if (likely(!freezing(current)))
 		return false;
-	return __refrigerator(false);
-}
-
-static inline bool try_to_freeze(void)
-{
 	if (!(current->flags & PF_NOFREEZE))
 		debug_check_no_locks_held();
-	return try_to_freeze_unsafe();
+	return __refrigerator(false);
 }
 
 extern bool freeze_task(struct task_struct *p);
@@ -79,195 +70,6 @@  static inline bool cgroup_freezing(struc
 }
 #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
- * function.  Next, the parent should call try_to_freeze() to freeze itself
- * appropriately in case the child has exited before the freezing of tasks is
- * complete.  However, we don't want kernel threads to be frozen in unexpected
- * places, so we allow them to block freeze_processes() instead or to set
- * PF_NOFREEZE if needed. Fortunately, in the ____call_usermodehelper() case the
- * parent won't really block freeze_processes(), since ____call_usermodehelper()
- * (the child) does a little before exec/exit and it can't be frozen before
- * waking up the parent.
- */
-
-
-/**
- * freezer_do_not_count - tell freezer to ignore %current
- *
- * Tell freezers to ignore the current task when determining whether the
- * target frozen state is reached.  IOW, the current task will be
- * considered frozen enough by freezers.
- *
- * The caller shouldn't do anything which isn't allowed for a frozen task
- * until freezer_cont() is called.  Usually, freezer[_do_not]_count() pair
- * wrap a scheduling operation and nothing much else.
- */
-static inline void freezer_do_not_count(void)
-{
-	current->flags |= PF_FREEZER_SKIP;
-}
-
-/**
- * freezer_count - tell freezer to stop ignoring %current
- *
- * Undo freezer_do_not_count().  It tells freezers that %current should be
- * considered again and tries to freeze if freezing condition is already in
- * effect.
- */
-static inline void freezer_count(void)
-{
-	current->flags &= ~PF_FREEZER_SKIP;
-	/*
-	 * If freezing is in progress, the following paired with smp_mb()
-	 * in freezer_should_skip() ensures that either we see %true
-	 * freezing() or freezer_should_skip() sees !PF_FREEZER_SKIP.
-	 */
-	smp_mb();
-	try_to_freeze();
-}
-
-/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
-static inline void freezer_count_unsafe(void)
-{
-	current->flags &= ~PF_FREEZER_SKIP;
-	smp_mb();
-	try_to_freeze_unsafe();
-}
-
-/**
- * freezer_should_skip - whether to skip a task when determining frozen
- *			 state is reached
- * @p: task in quesion
- *
- * This function is used by freezers after establishing %true freezing() to
- * test whether a task should be skipped when determining the target frozen
- * state is reached.  IOW, if this function returns %true, @p is considered
- * frozen enough.
- */
-static inline bool freezer_should_skip(struct task_struct *p)
-{
-	/*
-	 * The following smp_mb() paired with the one in freezer_count()
-	 * ensures that either freezer_count() sees %true freezing() or we
-	 * see cleared %PF_FREEZER_SKIP and return %false.  This makes it
-	 * impossible for a task to slip frozen state testing after
-	 * clearing %PF_FREEZER_SKIP.
-	 */
-	smp_mb();
-	return p->flags & PF_FREEZER_SKIP;
-}
-
-/*
- * These functions are intended to be used whenever you want allow a sleeping
- * task to be frozen. Note that neither return any clear indication of
- * whether a freeze event happened while in this function.
- */
-
-/* Like schedule(), but should not block the freezer. */
-static inline void freezable_schedule(void)
-{
-	freezer_do_not_count();
-	schedule();
-	freezer_count();
-}
-
-/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
-static inline void freezable_schedule_unsafe(void)
-{
-	freezer_do_not_count();
-	schedule();
-	freezer_count_unsafe();
-}
-
-/*
- * Like schedule_timeout(), but should not block the freezer.  Do not
- * call this with locks held.
- */
-static inline long freezable_schedule_timeout(long timeout)
-{
-	long __retval;
-	freezer_do_not_count();
-	__retval = schedule_timeout(timeout);
-	freezer_count();
-	return __retval;
-}
-
-/*
- * Like schedule_timeout_interruptible(), but should not block the freezer.  Do not
- * call this with locks held.
- */
-static inline long freezable_schedule_timeout_interruptible(long timeout)
-{
-	long __retval;
-	freezer_do_not_count();
-	__retval = schedule_timeout_interruptible(timeout);
-	freezer_count();
-	return __retval;
-}
-
-/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
-static inline long freezable_schedule_timeout_interruptible_unsafe(long timeout)
-{
-	long __retval;
-
-	freezer_do_not_count();
-	__retval = schedule_timeout_interruptible(timeout);
-	freezer_count_unsafe();
-	return __retval;
-}
-
-/* Like schedule_timeout_killable(), but should not block the freezer. */
-static inline long freezable_schedule_timeout_killable(long timeout)
-{
-	long __retval;
-	freezer_do_not_count();
-	__retval = schedule_timeout_killable(timeout);
-	freezer_count();
-	return __retval;
-}
-
-/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
-static inline long freezable_schedule_timeout_killable_unsafe(long timeout)
-{
-	long __retval;
-	freezer_do_not_count();
-	__retval = schedule_timeout_killable(timeout);
-	freezer_count_unsafe();
-	return __retval;
-}
-
-/*
- * Like schedule_hrtimeout_range(), but should not block the freezer.  Do not
- * call this with locks held.
- */
-static inline int freezable_schedule_hrtimeout_range(ktime_t *expires,
-		u64 delta, const enum hrtimer_mode mode)
-{
-	int __retval;
-	freezer_do_not_count();
-	__retval = schedule_hrtimeout_range(expires, delta, mode);
-	freezer_count();
-	return __retval;
-}
-
-/*
- * Freezer-friendly wrappers around wait_event_interruptible(),
- * wait_event_killable() and wait_event_interruptible_timeout(), originally
- * defined in <linux/wait.h>
- */
-
-/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
-#define wait_event_freezekillable_unsafe(wq, condition)			\
-({									\
-	int __retval;							\
-	freezer_do_not_count();						\
-	__retval = wait_event_killable(wq, (condition));		\
-	freezer_count_unsafe();						\
-	__retval;							\
-})
-
 #else /* !CONFIG_FREEZER */
 static inline bool frozen(struct task_struct *p) { return false; }
 static inline bool freezing(struct task_struct *p) { return false; }
@@ -281,35 +83,9 @@  static inline void thaw_kernel_threads(v
 
 static inline bool try_to_freeze(void) { return false; }
 
-static inline void freezer_do_not_count(void) {}
 static inline void freezer_count(void) {}
-static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 static inline void set_freezable(void) {}
 
-#define freezable_schedule()  schedule()
-
-#define freezable_schedule_unsafe()  schedule()
-
-#define freezable_schedule_timeout(timeout)  schedule_timeout(timeout)
-
-#define freezable_schedule_timeout_interruptible(timeout)		\
-	schedule_timeout_interruptible(timeout)
-
-#define freezable_schedule_timeout_interruptible_unsafe(timeout)	\
-	schedule_timeout_interruptible(timeout)
-
-#define freezable_schedule_timeout_killable(timeout)			\
-	schedule_timeout_killable(timeout)
-
-#define freezable_schedule_timeout_killable_unsafe(timeout)		\
-	schedule_timeout_killable(timeout)
-
-#define freezable_schedule_hrtimeout_range(expires, delta, mode)	\
-	schedule_hrtimeout_range(expires, delta, mode)
-
-#define wait_event_freezekillable_unsafe(wq, condition)			\
-		wait_event_killable(wq, condition)
-
 #endif /* !CONFIG_FREEZER */
 
 #endif	/* FREEZER_H_INCLUDED */
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -95,7 +95,15 @@  struct task_group;
 #define TASK_WAKING			0x0200
 #define TASK_NOLOAD			0x0400
 #define TASK_NEW			0x0800
-#define TASK_STATE_MAX			0x1000
+#define TASK_FREEZABLE			0x1000
+#define __TASK_FREEZABLE_UNSAFE		(0x2000 * IS_ENABLED(CONFIG_LOCKDEP))
+#define TASK_FROZEN			0x4000
+#define TASK_STATE_MAX			0x8000
+
+/*
+ * DO NOT ADD ANY NEW USERS !
+ */
+#define TASK_FREEZABLE_UNSAFE		(TASK_FREEZABLE | __TASK_FREEZABLE_UNSAFE)
 
 /* Convenience macros for the sake of set_current_state: */
 #define TASK_KILLABLE			(TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
@@ -126,7 +134,8 @@  struct task_group;
  * the comment with set_special_state().
  */
 #define is_special_task_state(state)				\
-	((state) & (__TASK_STOPPED | __TASK_TRACED | TASK_PARKED | TASK_DEAD))
+	((state) & (__TASK_STOPPED | __TASK_TRACED |		\
+		    TASK_PARKED | TASK_DEAD | TASK_FROZEN))
 
 #define __set_current_state(state_value)			\
 	do {							\
@@ -146,6 +155,7 @@  struct task_group;
 	do {								\
 		unsigned long flags; /* may shadow */			\
 		WARN_ON_ONCE(!is_special_task_state(state_value));	\
+		WARN_ON_ONCE(state_value == TASK_FROZEN);		\
 		raw_spin_lock_irqsave(&current->pi_lock, flags);	\
 		current->task_state_change = _THIS_IP_;			\
 		current->state = (state_value);				\
@@ -1579,7 +1589,6 @@  extern struct pid *cad_pid;
 #define PF_USED_MATH		0x00002000	/* If unset the fpu must be initialized before use */
 #define PF_USED_ASYNC		0x00004000	/* Used async_schedule*(), used by module init */
 #define PF_NOFREEZE		0x00008000	/* This thread should not be frozen */
-#define PF_FROZEN		0x00010000	/* Frozen for system suspend */
 #define PF_KSWAPD		0x00020000	/* I am kswapd */
 #define PF_MEMALLOC_NOFS	0x00040000	/* All allocation requests will inherit GFP_NOFS */
 #define PF_MEMALLOC_NOIO	0x00080000	/* All allocation requests will inherit GFP_NOIO */
@@ -1591,7 +1600,6 @@  extern struct pid *cad_pid;
 #define PF_NO_SETAFFINITY	0x04000000	/* Userland is not allowed to meddle with cpus_mask */
 #define PF_MCE_EARLY		0x08000000      /* Early kill for mce process policy */
 #define PF_MEMALLOC_PIN		0x10000000	/* Allocation context constrained to zones which allow long term pinning. */
-#define PF_FREEZER_SKIP		0x40000000	/* Freezer should not count it as freezable */
 #define PF_SUSPEND_TASK		0x80000000      /* This thread called freeze_processes() and should not be frozen */
 
 /*
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -263,7 +263,7 @@  int		rpc_malloc(struct rpc_task *);
 void		rpc_free(struct rpc_task *);
 int		rpciod_up(void);
 void		rpciod_down(void);
-int		__rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *);
+int		rpc_wait_for_completion_task(struct rpc_task *task);
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 struct net;
 void		rpc_show_tasks(struct net *);
@@ -274,11 +274,6 @@  extern struct workqueue_struct *rpciod_w
 extern struct workqueue_struct *xprtiod_workqueue;
 void		rpc_prepare_task(struct rpc_task *task);
 
-static inline int rpc_wait_for_completion_task(struct rpc_task *task)
-{
-	return __rpc_wait_for_completion_task(task, NULL);
-}
-
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
 static inline const char * rpc_qname(const struct rpc_wait_queue *q)
 {
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -335,8 +335,8 @@  do {										\
 } while (0)
 
 #define __wait_event_freezable(wq_head, condition)				\
-	___wait_event(wq_head, condition, TASK_INTERRUPTIBLE, 0, 0,		\
-			    freezable_schedule())
+	___wait_event(wq_head, condition, (TASK_INTERRUPTIBLE|TASK_FREEZABLE),	\
+			0, 0, schedule())
 
 /**
  * wait_event_freezable - sleep (or freeze) until a condition gets true
@@ -394,8 +394,8 @@  do {										\
 
 #define __wait_event_freezable_timeout(wq_head, condition, timeout)		\
 	___wait_event(wq_head, ___wait_cond_timeout(condition),			\
-		      TASK_INTERRUPTIBLE, 0, timeout,				\
-		      __ret = freezable_schedule_timeout(__ret))
+		      (TASK_INTERRUPTIBLE|TASK_FREEZABLE), 0, timeout,		\
+		      __ret = schedule_timeout(__ret))
 
 /*
  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
@@ -615,8 +615,8 @@  do {										\
 
 
 #define __wait_event_freezable_exclusive(wq, condition)				\
-	___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0,			\
-			freezable_schedule())
+	___wait_event(wq, condition, (TASK_INTERRUPTIBLE|TASK_FREEZABLE), 1, 0,\
+			schedule())
 
 #define wait_event_freezable_exclusive(wq, condition)				\
 ({										\
@@ -905,6 +905,34 @@  extern int do_wait_intr_irq(wait_queue_h
 	__ret;									\
 })
 
+#define __wait_event_state(wq, condition, state)				\
+	___wait_event(wq, condition, state, 0, 0, schedule())
+
+/**
+ * wait_event_state - sleep until a condition gets true
+ * @wq_head: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ * @state: state to sleep in
+ *
+ * The process is put to sleep (@state) until the @condition evaluates to true
+ * or a signal is received.  The @condition is checked each time the waitqueue
+ * @wq_head is woken up.
+ *
+ * wake_up() has to be called after changing any variable that could
+ * change the result of the wait condition.
+ *
+ * The function will return -ERESTARTSYS if it was interrupted by a
+ * signal and 0 if @condition evaluated to true.
+ */
+#define wait_event_state(wq_head, condition, state)				\
+({										\
+	int __ret = 0;								\
+	might_sleep();								\
+	if (!(condition))							\
+		__ret = __wait_event_state(wq_head, condition, state);		\
+	__ret;									\
+})
+
 #define __wait_event_killable_timeout(wq_head, condition, timeout)		\
 	___wait_event(wq_head, ___wait_cond_timeout(condition),			\
 		      TASK_KILLABLE, 0, timeout,				\
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -80,10 +80,9 @@  static void __init handle_initrd(void)
 	init_chdir("/old");
 
 	/*
-	 * In case that a resume from disk is carried out by linuxrc or one of
-	 * its children, we need to tell the freezer not to wait for us.
+	 * PF_FREEZER_SKIP is pointless because UMH is laundered through a
+	 * workqueue and that doesn't have the current context.
 	 */
-	current->flags |= PF_FREEZER_SKIP;
 
 	info = call_usermodehelper_setup("/linuxrc", argv, envp_init,
 					 GFP_KERNEL, init_linuxrc, NULL, NULL);
@@ -91,8 +90,6 @@  static void __init handle_initrd(void)
 		return;
 	call_usermodehelper_exec(info, UMH_WAIT_PROC);
 
-	current->flags &= ~PF_FREEZER_SKIP;
-
 	/* move initrd to rootfs' /old */
 	init_mount("..", ".", NULL, MS_MOVE, NULL);
 	/* switch root and cwd back to / of rootfs */
--- a/kernel/cgroup/legacy_freezer.c
+++ b/kernel/cgroup/legacy_freezer.c
@@ -113,7 +113,7 @@  static int freezer_css_online(struct cgr
 
 	if (parent && (parent->state & CGROUP_FREEZING)) {
 		freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN;
-		atomic_inc(&system_freezing_cnt);
+		static_branch_inc(&freezer_active);
 	}
 
 	mutex_unlock(&freezer_mutex);
@@ -134,7 +134,7 @@  static void freezer_css_offline(struct c
 	mutex_lock(&freezer_mutex);
 
 	if (freezer->state & CGROUP_FREEZING)
-		atomic_dec(&system_freezing_cnt);
+		static_branch_dec(&freezer_active);
 
 	freezer->state = 0;
 
@@ -179,6 +179,7 @@  static void freezer_attach(struct cgroup
 			__thaw_task(task);
 		} else {
 			freeze_task(task);
+
 			/* clear FROZEN and propagate upwards */
 			while (freezer && (freezer->state & CGROUP_FROZEN)) {
 				freezer->state &= ~CGROUP_FROZEN;
@@ -271,16 +272,8 @@  static void update_if_frozen(struct cgro
 	css_task_iter_start(css, 0, &it);
 
 	while ((task = css_task_iter_next(&it))) {
-		if (freezing(task)) {
-			/*
-			 * freezer_should_skip() indicates that the task
-			 * should be skipped when determining freezing
-			 * completion.  Consider it frozen in addition to
-			 * the usual frozen condition.
-			 */
-			if (!frozen(task) && !freezer_should_skip(task))
-				goto out_iter_end;
-		}
+		if (freezing(task) && !frozen(task))
+			goto out_iter_end;
 	}
 
 	freezer->state |= CGROUP_FROZEN;
@@ -357,7 +350,7 @@  static void freezer_apply_state(struct f
 
 	if (freeze) {
 		if (!(freezer->state & CGROUP_FREEZING))
-			atomic_inc(&system_freezing_cnt);
+			static_branch_inc(&freezer_active);
 		freezer->state |= state;
 		freeze_cgroup(freezer);
 	} else {
@@ -366,9 +359,9 @@  static void freezer_apply_state(struct f
 		freezer->state &= ~state;
 
 		if (!(freezer->state & CGROUP_FREEZING)) {
-			if (was_freezing)
-				atomic_dec(&system_freezing_cnt);
 			freezer->state &= ~CGROUP_FROZEN;
+			if (was_freezing)
+				static_branch_dec(&freezer_active);
 			unfreeze_cgroup(freezer);
 		}
 	}
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -468,10 +468,10 @@  static void exit_mm(void)
 			complete(&core_state->startup);
 
 		for (;;) {
-			set_current_state(TASK_UNINTERRUPTIBLE);
+			set_current_state(TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
 			if (!self.task) /* see coredump_finish() */
 				break;
-			freezable_schedule();
+			schedule();
 		}
 		__set_current_state(TASK_RUNNING);
 		mmap_read_lock(mm);
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1272,11 +1272,9 @@  static int wait_for_vfork_done(struct ta
 {
 	int killed;
 
-	freezer_do_not_count();
 	cgroup_enter_frozen();
-	killed = wait_for_completion_killable(vfork);
+	killed = wait_for_completion_killable_freezable(vfork);
 	cgroup_leave_frozen(false);
-	freezer_count();
 
 	if (killed) {
 		task_lock(child);
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -13,8 +13,8 @@ 
 #include <linux/kthread.h>
 
 /* total number of freezing conditions in effect */
-atomic_t system_freezing_cnt = ATOMIC_INIT(0);
-EXPORT_SYMBOL(system_freezing_cnt);
+DEFINE_STATIC_KEY_FALSE(freezer_active);
+EXPORT_SYMBOL(freezer_active);
 
 /* indicate whether PM freezing is in effect, protected by
  * system_transition_mutex
@@ -29,7 +29,7 @@  static DEFINE_SPINLOCK(freezer_lock);
  * freezing_slow_path - slow path for testing whether a task needs to be frozen
  * @p: task to be tested
  *
- * This function is called by freezing() if system_freezing_cnt isn't zero
+ * This function is called by freezing() if freezer_active isn't zero
  * and tests whether @p needs to enter and stay in frozen state.  Can be
  * called under any context.  The freezers are responsible for ensuring the
  * target tasks see the updated state.
@@ -52,41 +52,67 @@  bool freezing_slow_path(struct task_stru
 }
 EXPORT_SYMBOL(freezing_slow_path);
 
+/* Recursion relies on tail-call optimization to not blow away the stack */
+static bool __frozen(struct task_struct *p)
+{
+	if (p->state == TASK_FROZEN)
+		return true;
+
+	/*
+	 * If stuck in TRACED, and the ptracer is FROZEN, we're frozen too.
+	 */
+	if (task_is_traced(p))
+		return frozen(rcu_dereference(p->parent));
+
+	/*
+	 * If stuck in STOPPED and the parent is FROZEN, we're frozen too.
+	 */
+	if (task_is_stopped(p))
+		return frozen(rcu_dereference(p->real_parent));
+
+	return false;
+}
+
+bool frozen(struct task_struct *p)
+{
+	bool ret;
+
+	rcu_read_lock();
+	ret = __frozen(p);
+	rcu_read_unlock();
+
+	return ret;
+}
+
 /* Refrigerator is place where frozen processes are stored :-). */
 bool __refrigerator(bool check_kthr_stop)
 {
-	/* Hmm, should we be allowed to suspend when there are realtime
-	   processes around? */
+	unsigned int state = READ_ONCE(current->state);
 	bool was_frozen = false;
-	long save = current->state;
 
 	pr_debug("%s entered refrigerator\n", current->comm);
 
+	WARN_ON_ONCE(state && !(state & TASK_NORMAL));
+
 	for (;;) {
-		set_current_state(TASK_UNINTERRUPTIBLE);
+		bool freeze;
+
+		set_current_state(TASK_FROZEN);
 
 		spin_lock_irq(&freezer_lock);
-		current->flags |= PF_FROZEN;
-		if (!freezing(current) ||
-		    (check_kthr_stop && kthread_should_stop()))
-			current->flags &= ~PF_FROZEN;
+		freeze = freezing(current) && !(check_kthr_stop && kthread_should_stop());
 		spin_unlock_irq(&freezer_lock);
 
-		if (!(current->flags & PF_FROZEN))
+		if (!freeze)
 			break;
+
 		was_frozen = true;
 		schedule();
 	}
+	__set_current_state(TASK_RUNNING);
 
 	pr_debug("%s left refrigerator\n", current->comm);
 
-	/*
-	 * Restore saved task state before returning.  The mb'd version
-	 * needs to be used; otherwise, it might silently break
-	 * synchronization which depends on ordered task state change.
-	 */
-	set_current_state(save);
-
 	return was_frozen;
 }
 EXPORT_SYMBOL(__refrigerator);
@@ -101,6 +127,38 @@  static void fake_signal_wake_up(struct t
 	}
 }
 
+/* See set_special_state(); serializes against ttwu() */
+static bool __freeze_task(struct task_struct *p)
+{
+	unsigned long flags;
+	unsigned int state;
+	bool frozen = false;
+
+	raw_spin_lock_irqsave(&p->pi_lock, flags);
+	state = READ_ONCE(p->state);
+	if (state & TASK_FREEZABLE) {
+		/*
+		 * Only TASK_NORMAL can be augmented with TASK_FREEZABLE,
+		 * since they can suffer spurious wakeups.
+		 */
+		WARN_ON_ONCE(!(state & TASK_NORMAL));
+
+#ifdef CONFIG_LOCKDEP
+		/*
+		 * It's dangerous to freeze with locks held; there be dragons there.
+		 */
+		if (!(state & __TASK_FREEZABLE_UNSAFE))
+			WARN_ON_ONCE(debug_locks && p->lockdep_depth);
+#endif
+
+		p->state = TASK_FROZEN;
+		frozen = true;
+	}
+	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+
+	return frozen;
+}
+
 /**
  * freeze_task - send a freeze request to given task
  * @p: task to send the request to
@@ -116,20 +174,8 @@  bool freeze_task(struct task_struct *p)
 {
 	unsigned long flags;
 
-	/*
-	 * This check can race with freezer_do_not_count, but worst case that
-	 * will result in an extra wakeup being sent to the task.  It does not
-	 * race with freezer_count(), the barriers in freezer_count() and
-	 * freezer_should_skip() ensure that either freezer_count() sees
-	 * freezing == true in try_to_freeze() and freezes, or
-	 * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
-	 * normally.
-	 */
-	if (freezer_should_skip(p))
-		return false;
-
 	spin_lock_irqsave(&freezer_lock, flags);
-	if (!freezing(p) || frozen(p)) {
+	if (!freezing(p) || frozen(p) || __freeze_task(p)) {
 		spin_unlock_irqrestore(&freezer_lock, flags);
 		return false;
 	}
@@ -137,7 +183,7 @@  bool freeze_task(struct task_struct *p)
 	if (!(p->flags & PF_KTHREAD))
 		fake_signal_wake_up(p);
 	else
-		wake_up_state(p, TASK_INTERRUPTIBLE);
+		wake_up_state(p, TASK_INTERRUPTIBLE); // TASK_NORMAL ?!?
 
 	spin_unlock_irqrestore(&freezer_lock, flags);
 	return true;
@@ -148,8 +194,8 @@  void __thaw_task(struct task_struct *p)
 	unsigned long flags;
 
 	spin_lock_irqsave(&freezer_lock, flags);
-	if (frozen(p))
-		wake_up_process(p);
+	WARN_ON_ONCE(freezing(p));
+	wake_up_state(p, TASK_FROZEN);
 	spin_unlock_irqrestore(&freezer_lock, flags);
 }
 
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2582,7 +2582,7 @@  static void futex_wait_queue_me(struct f
 	 * queue_me() calls spin_unlock() upon completion, both serializing
 	 * access to the hash list and forcing another memory barrier.
 	 */
-	set_current_state(TASK_INTERRUPTIBLE);
+	set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
 	queue_me(q, hb);
 
 	/* Arm the timer */
@@ -2600,7 +2600,7 @@  static void futex_wait_queue_me(struct f
 		 * is no timeout, or if it has yet to expire.
 		 */
 		if (!timeout || timeout->task)
-			freezable_schedule();
+			schedule();
 	}
 	__set_current_state(TASK_RUNNING);
 }
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -92,8 +92,8 @@  static void check_hung_task(struct task_
 	 * Ensure the task is not frozen.
 	 * Also, skip vfork and any other user process that freezer should skip.
 	 */
-	if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP)))
-	    return;
+	if (unlikely(t->state & (TASK_FREEZABLE | TASK_FROZEN)))
+		return;
 
 	/*
 	 * When a freshly created task is scheduled once, changes its state to
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -23,7 +23,8 @@ 
 
 void lock_system_sleep(void)
 {
-	current->flags |= PF_FREEZER_SKIP;
+	WARN_ON_ONCE(current->flags & PF_NOFREEZE);
+	current->flags |= PF_NOFREEZE;
 	mutex_lock(&system_transition_mutex);
 }
 EXPORT_SYMBOL_GPL(lock_system_sleep);
@@ -46,7 +47,7 @@  void unlock_system_sleep(void)
 	 * Which means, if we use try_to_freeze() here, it would make them
 	 * enter the refrigerator, thus causing hibernation to lockup.
 	 */
-	current->flags &= ~PF_FREEZER_SKIP;
+	current->flags &= ~PF_NOFREEZE;
 	mutex_unlock(&system_transition_mutex);
 }
 EXPORT_SYMBOL_GPL(unlock_system_sleep);
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -53,8 +53,7 @@  static int try_to_freeze_tasks(bool user
 			if (p == current || !freeze_task(p))
 				continue;
 
-			if (!freezer_should_skip(p))
-				todo++;
+			todo++;
 		}
 		read_unlock(&tasklist_lock);
 
@@ -99,8 +98,7 @@  static int try_to_freeze_tasks(bool user
 		if (!wakeup || pm_debug_messages_on) {
 			read_lock(&tasklist_lock);
 			for_each_process_thread(g, p) {
-				if (p != current && !freezer_should_skip(p)
-				    && freezing(p) && !frozen(p))
+				if (p != current && freezing(p) && !frozen(p))
 					sched_show_task(p);
 			}
 			read_unlock(&tasklist_lock);
@@ -132,7 +130,7 @@  int freeze_processes(void)
 	current->flags |= PF_SUSPEND_TASK;
 
 	if (!pm_freezing)
-		atomic_inc(&system_freezing_cnt);
+		static_branch_inc(&freezer_active);
 
 	pm_wakeup_clear(true);
 	pr_info("Freezing user space processes ... ");
@@ -193,7 +191,7 @@  void thaw_processes(void)
 
 	trace_suspend_resume(TPS("thaw_processes"), 0, true);
 	if (pm_freezing)
-		atomic_dec(&system_freezing_cnt);
+		static_branch_dec(&freezer_active);
 	pm_freezing = false;
 	pm_nosig_freezing = false;
 
--- a/kernel/sched/completion.c
+++ b/kernel/sched/completion.c
@@ -139,6 +139,12 @@  void __sched wait_for_completion(struct
 }
 EXPORT_SYMBOL(wait_for_completion);
 
+void __sched wait_for_completion_freezable(struct completion *x)
+{
+	wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
+}
+EXPORT_SYMBOL(wait_for_completion_freezable);
+
 /**
  * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
  * @x:  holds the state of this particular completion
@@ -247,6 +253,16 @@  int __sched wait_for_completion_killable
 }
 EXPORT_SYMBOL(wait_for_completion_killable);
 
+int __sched wait_for_completion_killable_freezable(struct completion *x)
+{
+	long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT,
+				 TASK_KILLABLE|TASK_FREEZABLE);
+	if (t == -ERESTARTSYS)
+		return t;
+	return 0;
+}
+EXPORT_SYMBOL(wait_for_completion_killable_freezable);
+
 /**
  * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
  * @x:  holds the state of this particular completion
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5897,7 +5897,7 @@  static void __sched notrace __schedule(b
 			prev->sched_contributes_to_load =
 				(prev_state & TASK_UNINTERRUPTIBLE) &&
 				!(prev_state & TASK_NOLOAD) &&
-				!(prev->flags & PF_FROZEN);
+				!(prev_state & TASK_FROZEN);
 
 			if (prev->sched_contributes_to_load)
 				rq->nr_uninterruptible++;
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2265,7 +2265,7 @@  static void ptrace_stop(int exit_code, i
 		read_unlock(&tasklist_lock);
 		cgroup_enter_frozen();
 		preempt_enable_no_resched();
-		freezable_schedule();
+		schedule();
 		cgroup_leave_frozen(true);
 	} else {
 		/*
@@ -2445,7 +2445,7 @@  static bool do_signal_stop(int signr)
 
 		/* Now we don't run again until woken by SIGCONT or SIGKILL */
 		cgroup_enter_frozen();
-		freezable_schedule();
+		schedule();
 		return true;
 	} else {
 		/*
@@ -2521,11 +2521,11 @@  static void do_freezer_trap(void)
 	 * immediately (if there is a non-fatal signal pending), and
 	 * put the task into sleep.
 	 */
-	__set_current_state(TASK_INTERRUPTIBLE);
+	__set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
 	clear_thread_flag(TIF_SIGPENDING);
 	spin_unlock_irq(&current->sighand->siglock);
 	cgroup_enter_frozen();
-	freezable_schedule();
+	schedule();
 }
 
 static int ptrace_signal(int signr, kernel_siginfo_t *info)
@@ -3569,9 +3569,9 @@  static int do_sigtimedwait(const sigset_
 		recalc_sigpending();
 		spin_unlock_irq(&tsk->sighand->siglock);
 
-		__set_current_state(TASK_INTERRUPTIBLE);
-		ret = freezable_schedule_hrtimeout_range(to, tsk->timer_slack_ns,
-							 HRTIMER_MODE_REL);
+		__set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
+		ret = schedule_hrtimeout_range(to, tsk->timer_slack_ns,
+					       HRTIMER_MODE_REL);
 		spin_lock_irq(&tsk->sighand->siglock);
 		__set_task_blocked(tsk, &tsk->real_blocked);
 		sigemptyset(&tsk->real_blocked);
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1889,11 +1889,11 @@  static int __sched do_nanosleep(struct h
 	struct restart_block *restart;
 
 	do {
-		set_current_state(TASK_INTERRUPTIBLE);
+		set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
 		hrtimer_sleeper_start_expires(t, mode);
 
 		if (likely(t->task))
-			freezable_schedule();
+			schedule();
 
 		hrtimer_cancel(&t->timer);
 		mode = HRTIMER_MODE_ABS;
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -794,8 +794,8 @@  static void khugepaged_alloc_sleep(void)
 	DEFINE_WAIT(wait);
 
 	add_wait_queue(&khugepaged_wait, &wait);
-	freezable_schedule_timeout_interruptible(
-		msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
+	__set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
+	schedule_timeout(msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
 	remove_wait_queue(&khugepaged_wait, &wait);
 }
 
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -268,7 +268,7 @@  EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue
 
 static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
 {
-	freezable_schedule_unsafe();
+	schedule();
 	if (signal_pending_state(mode, current))
 		return -ERESTARTSYS;
 	return 0;
@@ -324,14 +324,12 @@  static int rpc_complete_task(struct rpc_
  * to enforce taking of the wq->lock and hence avoid races with
  * rpc_complete_task().
  */
-int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *action)
+int rpc_wait_for_completion_task(struct rpc_task *task)
 {
-	if (action == NULL)
-		action = rpc_wait_bit_killable;
 	return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
-			action, TASK_KILLABLE);
+			rpc_wait_bit_killable, TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
 }
-EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task);
+EXPORT_SYMBOL_GPL(rpc_wait_for_completion_task);
 
 /*
  * Make an RPC task runnable.
@@ -928,7 +926,7 @@  static void __rpc_execute(struct rpc_tas
 		trace_rpc_task_sync_sleep(task, task->tk_action);
 		status = out_of_line_wait_on_bit(&task->tk_runstate,
 				RPC_TASK_QUEUED, rpc_wait_bit_killable,
-				TASK_KILLABLE);
+				TASK_KILLABLE|TASK_FREEZABLE);
 		if (status < 0) {
 			/*
 			 * When a sync task receives a signal, it exits with
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2190,13 +2190,14 @@  static long unix_stream_data_wait(struct
 				  struct sk_buff *last, unsigned int last_len,
 				  bool freezable)
 {
+	unsigned int state = TASK_INTERRUPTIBLE | freezable * TASK_FREEZABLE;
 	struct sk_buff *tail;
 	DEFINE_WAIT(wait);
 
 	unix_state_lock(sk);
 
 	for (;;) {
-		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+		prepare_to_wait(sk_sleep(sk), &wait, state);
 
 		tail = skb_peek_tail(&sk->sk_receive_queue);
 		if (tail != last ||
@@ -2209,10 +2210,7 @@  static long unix_stream_data_wait(struct
 
 		sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 		unix_state_unlock(sk);
-		if (freezable)
-			timeo = freezable_schedule_timeout(timeo);
-		else
-			timeo = schedule_timeout(timeo);
+		timeo = schedule_timeout(timeo);
 		unix_state_lock(sk);
 
 		if (sock_flag(sk, SOCK_DEAD))