Re: [PATCH v2 1/4] notifier: Fix broken error handling pattern

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Monday, October 7, 2019 10:25:42 AM CEST Peter Zijlstra wrote:
> The current notifiers have the following error handling pattern all
> over the place:
> 
> 	int err, nr;
> 
> 	err = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr);
> 	if (err & NOTIFIER_STOP_MASK)
> 		__foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL)
> 
> And aside from the endless repetition thereof, it is broken. Consider
> blocking notifiers; both calls take and drop the rwsem, this means
> that the notifier list can change in between the two calls, making @nr
> meaningless.
> 
> Fix this by replacing all the __foo_notifier_call_chain() functions
> with foo_notifier_call_chain_robust() that embeds the above pattern,
> but ensures it is inside a single lock region.
> 
> Note: I switched atomic_notifier_call_chain_robust() to use
>       the spinlock, since RCU cannot provide the guarantee
>       required for the recovery.
> 
> Note: software_resume() error handling was broken afaict.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Alexios Zavras <alexios.zavras@intel.com>
> Cc: Allison Randal <allison@lohutok.net>
> Cc: Sam Protsenko <semen.protsenko@linaro.org>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Todd Brandt <todd.e.brandt@linux.intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Vasily Averin <vvs@virtuozzo.com>
> Cc: Len Brown <len.brown@intel.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

for the bits I care about.

> ---
>  include/linux/notifier.h           |   15 +--
>  kernel/cpu_pm.c                    |   46 ++++-------
>  kernel/notifier.c                  |  144 ++++++++++++++++++++++---------------
>  kernel/power/hibernate.c           |   26 +++---
>  kernel/power/main.c                |    8 +-
>  kernel/power/power.h               |    3 
>  kernel/power/suspend.c             |   14 +--
>  kernel/power/user.c                |   14 +--
>  tools/power/pm-graph/sleepgraph.py |    2 
>  9 files changed, 139 insertions(+), 133 deletions(-)
> 
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h
> @@ -165,20 +165,19 @@ extern int srcu_notifier_chain_unregiste
>  
>  extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
>  		unsigned long val, void *v);
> -extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> -	unsigned long val, void *v, int nr_to_call, int *nr_calls);
>  extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
>  		unsigned long val, void *v);
> -extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
> -	unsigned long val, void *v, int nr_to_call, int *nr_calls);
>  extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
>  		unsigned long val, void *v);
> -extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
> -	unsigned long val, void *v, int nr_to_call, int *nr_calls);
>  extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
>  		unsigned long val, void *v);
> -extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> -	unsigned long val, void *v, int nr_to_call, int *nr_calls);
> +
> +extern int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh,
> +		unsigned long val_up, unsigned long val_down, void *v);
> +extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
> +		unsigned long val_up, unsigned long val_down, void *v);
> +extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
> +		unsigned long val_up, unsigned long val_down, void *v);
>  
>  #define NOTIFY_DONE		0x0000		/* Don't care */
>  #define NOTIFY_OK		0x0001		/* Suits me */
> --- a/kernel/cpu_pm.c
> +++ b/kernel/cpu_pm.c
> @@ -15,23 +15,31 @@
>  
>  static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
>  
> -static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
> +static int cpu_pm_notify(enum cpu_pm_event event)
>  {
>  	int ret;
>  
>  	/*
> -	 * __atomic_notifier_call_chain has a RCU read critical section, which
> +	 * atomic_notifier_call_chain has a RCU read critical section, which
>  	 * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
>  	 * RCU know this.
>  	 */
>  	rcu_irq_enter_irqson();
> -	ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
> -		nr_to_call, nr_calls);
> +	ret = atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL);
>  	rcu_irq_exit_irqson();
>  
>  	return notifier_to_errno(ret);
>  }
>  
> +static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
> +{
> +	int ret;
> +
> +	ret = atomic_notifier_call_chain_robust(&cpu_pm_notifier_chain, event_up, event_down, NULL);
> +
> +	return notifier_to_errno(ret);
> +}
> +
>  /**
>   * cpu_pm_register_notifier - register a driver with cpu_pm
>   * @nb: notifier block to register
> @@ -80,18 +88,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_unregister_noti
>   */
>  int cpu_pm_enter(void)
>  {
> -	int nr_calls;
> -	int ret = 0;
> -
> -	ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
> -	if (ret)
> -		/*
> -		 * Inform listeners (nr_calls - 1) about failure of CPU PM
> -		 * PM entry who are notified earlier to prepare for it.
> -		 */
> -		cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
> -
> -	return ret;
> +	return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
>  }
>  EXPORT_SYMBOL_GPL(cpu_pm_enter);
>  
> @@ -109,7 +106,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter);
>   */
>  int cpu_pm_exit(void)
>  {
> -	return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
> +	return cpu_pm_notify(CPU_PM_EXIT);
>  }
>  EXPORT_SYMBOL_GPL(cpu_pm_exit);
>  
> @@ -131,18 +128,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_exit);
>   */
>  int cpu_cluster_pm_enter(void)
>  {
> -	int nr_calls;
> -	int ret = 0;
> -
> -	ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
> -	if (ret)
> -		/*
> -		 * Inform listeners (nr_calls - 1) about failure of CPU cluster
> -		 * PM entry who are notified earlier to prepare for it.
> -		 */
> -		cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
> -
> -	return ret;
> +	return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
>  }
>  EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
>  
> @@ -163,7 +149,7 @@ EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
>   */
>  int cpu_cluster_pm_exit(void)
>  {
> -	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
> +	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
>  }
>  EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
>  
> --- a/kernel/notifier.c
> +++ b/kernel/notifier.c
> @@ -106,6 +106,34 @@ static int notifier_call_chain(struct no
>  }
>  NOKPROBE_SYMBOL(notifier_call_chain);
>  
> +/**
> + * notifier_call_chain_robust - Inform the registered notifiers about an event
> + *                              and rollback on error.
> + * @nl:		Pointer to head of the blocking notifier chain
> + * @val_up:	Value passed unmodified to the notifier function
> + * @val_down:	Value passed unmodified to the notifier function when recovering
> + *              from an error on @val_up
> + * @v		Pointer passed unmodified to the notifier function
> + *
> + * NOTE:	It is important the @nl chain doesn't change between the two
> + *		invocations of notifier_call_chain() such that we visit the
> + *		exact same notifier callbacks; this rules out any RCU usage.
> + *
> + * Returns:	the return value of the @val_up call.
> + */
> +static int notifier_call_chain_robust(struct notifier_block **nl,
> +				     unsigned long val_up, unsigned long val_down,
> +				     void *v)
> +{
> +	int ret, nr = 0;
> +
> +	ret = notifier_call_chain(nl, val_up, v, -1, &nr);
> +	if (ret & NOTIFY_STOP_MASK)
> +		notifier_call_chain(nl, val_down, v, nr-1, NULL);
> +
> +	return ret;
> +}
> +
>  /*
>   *	Atomic notifier chain routines.  Registration and unregistration
>   *	use a spinlock, and call_chain is synchronized by RCU (no locks).
> @@ -156,13 +184,30 @@ int atomic_notifier_chain_unregister(str
>  }
>  EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
>  
> +int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh,
> +		unsigned long val_up, unsigned long val_down, void *v)
> +{
> +	unsigned long flags;
> +	int ret;
> +
> +	/*
> +	 * Musn't use RCU; because then the notifier list can
> +	 * change between the up and down traversal.
> +	 */
> +	spin_lock_irqsave(&nh->lock, flags);
> +	ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
> +	spin_unlock_irqrestore(&nh->lock, flags);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(atomic_notifier_call_chain_robust);
> +NOKPROBE_SYMBOL(atomic_notifier_call_chain_robust);
> +
>  /**
> - *	__atomic_notifier_call_chain - Call functions in an atomic notifier chain
> + *	atomic_notifier_call_chain - Call functions in an atomic notifier chain
>   *	@nh: Pointer to head of the atomic notifier chain
>   *	@val: Value passed unmodified to notifier function
>   *	@v: Pointer passed unmodified to notifier function
> - *	@nr_to_call: See the comment for notifier_call_chain.
> - *	@nr_calls: See the comment for notifier_call_chain.
>   *
>   *	Calls each function in a notifier chain in turn.  The functions
>   *	run in an atomic context, so they must not block.
> @@ -175,24 +220,16 @@ EXPORT_SYMBOL_GPL(atomic_notifier_chain_
>   *	Otherwise the return value is the return value
>   *	of the last notifier function called.
>   */
> -int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> -				 unsigned long val, void *v,
> -				 int nr_to_call, int *nr_calls)
> +int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> +			       unsigned long val, void *v)
>  {
>  	int ret;
>  
>  	rcu_read_lock();
> -	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
> +	ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
>  	rcu_read_unlock();
> -	return ret;
> -}
> -EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
> -NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
>  
> -int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> -			       unsigned long val, void *v)
> -{
> -	return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
>  NOKPROBE_SYMBOL(atomic_notifier_call_chain);
> @@ -285,13 +322,30 @@ int blocking_notifier_chain_unregister(s
>  }
>  EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
>  
> +int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
> +		unsigned long val_up, unsigned long val_down, void *v)
> +{
> +	int ret = NOTIFY_DONE;
> +
> +	/*
> +	 * We check the head outside the lock, but if this access is
> +	 * racy then it does not matter what the result of the test
> +	 * is, we re-check the list after having taken the lock anyway:
> +	 */
> +	if (rcu_access_pointer(nh->head)) {
> +		down_read(&nh->rwsem);
> +		ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
> +		up_read(&nh->rwsem);
> +	}
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_robust);
> +
>  /**
> - *	__blocking_notifier_call_chain - Call functions in a blocking notifier chain
> + *	blocking_notifier_call_chain - Call functions in a blocking notifier chain
>   *	@nh: Pointer to head of the blocking notifier chain
>   *	@val: Value passed unmodified to notifier function
>   *	@v: Pointer passed unmodified to notifier function
> - *	@nr_to_call: See comment for notifier_call_chain.
> - *	@nr_calls: See comment for notifier_call_chain.
>   *
>   *	Calls each function in a notifier chain in turn.  The functions
>   *	run in a process context, so they are allowed to block.
> @@ -303,9 +357,8 @@ EXPORT_SYMBOL_GPL(blocking_notifier_chai
>   *	Otherwise the return value is the return value
>   *	of the last notifier function called.
>   */
> -int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
> -				   unsigned long val, void *v,
> -				   int nr_to_call, int *nr_calls)
> +int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
> +		unsigned long val, void *v)
>  {
>  	int ret = NOTIFY_DONE;
>  
> @@ -316,19 +369,11 @@ int __blocking_notifier_call_chain(struc
>  	 */
>  	if (rcu_access_pointer(nh->head)) {
>  		down_read(&nh->rwsem);
> -		ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
> -					nr_calls);
> +		ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
>  		up_read(&nh->rwsem);
>  	}
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
> -
> -int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
> -		unsigned long val, void *v)
> -{
> -	return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
> -}
>  EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
>  
>  /*
> @@ -370,13 +415,18 @@ int raw_notifier_chain_unregister(struct
>  }
>  EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
>  
> +int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
> +		unsigned long val_up, unsigned long val_down, void *v)
> +{
> +	return notifier_call_chain_robust(&nh->head, val_up, val_down, v);
> +}
> +EXPORT_SYMBOL_GPL(raw_notifier_call_chain_robust);
> +
>  /**
> - *	__raw_notifier_call_chain - Call functions in a raw notifier chain
> + *	raw_notifier_call_chain - Call functions in a raw notifier chain
>   *	@nh: Pointer to head of the raw notifier chain
>   *	@val: Value passed unmodified to notifier function
>   *	@v: Pointer passed unmodified to notifier function
> - *	@nr_to_call: See comment for notifier_call_chain.
> - *	@nr_calls: See comment for notifier_call_chain
>   *
>   *	Calls each function in a notifier chain in turn.  The functions
>   *	run in an undefined context.
> @@ -389,18 +439,10 @@ EXPORT_SYMBOL_GPL(raw_notifier_chain_unr
>   *	Otherwise the return value is the return value
>   *	of the last notifier function called.
>   */
> -int __raw_notifier_call_chain(struct raw_notifier_head *nh,
> -			      unsigned long val, void *v,
> -			      int nr_to_call, int *nr_calls)
> -{
> -	return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
> -}
> -EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
> -
>  int raw_notifier_call_chain(struct raw_notifier_head *nh,
>  		unsigned long val, void *v)
>  {
> -	return __raw_notifier_call_chain(nh, val, v, -1, NULL);
> +	return notifier_call_chain(&nh->head, val, v, -1, NULL);
>  }
>  EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
>  
> @@ -472,12 +514,10 @@ int srcu_notifier_chain_unregister(struc
>  EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
>  
>  /**
> - *	__srcu_notifier_call_chain - Call functions in an SRCU notifier chain
> + *	srcu_notifier_call_chain - Call functions in an SRCU notifier chain
>   *	@nh: Pointer to head of the SRCU notifier chain
>   *	@val: Value passed unmodified to notifier function
>   *	@v: Pointer passed unmodified to notifier function
> - *	@nr_to_call: See comment for notifier_call_chain.
> - *	@nr_calls: See comment for notifier_call_chain
>   *
>   *	Calls each function in a notifier chain in turn.  The functions
>   *	run in a process context, so they are allowed to block.
> @@ -489,25 +529,17 @@ EXPORT_SYMBOL_GPL(srcu_notifier_chain_un
>   *	Otherwise the return value is the return value
>   *	of the last notifier function called.
>   */
> -int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> -			       unsigned long val, void *v,
> -			       int nr_to_call, int *nr_calls)
> +int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> +		unsigned long val, void *v)
>  {
>  	int ret;
>  	int idx;
>  
>  	idx = srcu_read_lock(&nh->srcu);
> -	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
> +	ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
>  	srcu_read_unlock(&nh->srcu, idx);
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
> -
> -int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
> -		unsigned long val, void *v)
> -{
> -	return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
> -}
>  EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
>  
>  /**
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -693,8 +693,8 @@ static int load_image_and_restore(void)
>   */
>  int hibernate(void)
>  {
> -	int error, nr_calls = 0;
>  	bool snapshot_test = false;
> +	int error;
>  
>  	if (!hibernation_available()) {
>  		pm_pr_dbg("Hibernation not available.\n");
> @@ -710,11 +710,9 @@ int hibernate(void)
>  
>  	pr_info("hibernation entry\n");
>  	pm_prepare_console();
> -	error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
> -	if (error) {
> -		nr_calls--;
> -		goto Exit;
> -	}
> +	error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
> +	if (error)
> +		goto Restore;
>  
>  	ksys_sync_helper();
>  
> @@ -772,7 +770,8 @@ int hibernate(void)
>  	/* Don't bother checking whether freezer_test_done is true */
>  	freezer_test_done = false;
>   Exit:
> -	__pm_notifier_call_chain(PM_POST_HIBERNATION, nr_calls, NULL);
> +	pm_notifier_call_chain(PM_POST_HIBERNATION);
> + Restore:
>  	pm_restore_console();
>  	atomic_inc(&snapshot_device_available);
>   Unlock:
> @@ -800,7 +799,7 @@ int hibernate(void)
>   */
>  static int software_resume(void)
>  {
> -	int error, nr_calls = 0;
> +	int error;
>  
>  	/*
>  	 * If the user said "noresume".. bail out early.
> @@ -887,11 +886,9 @@ static int software_resume(void)
>  
>  	pr_info("resume from hibernation\n");
>  	pm_prepare_console();
> -	error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
> -	if (error) {
> -		nr_calls--;
> -		goto Close_Finish;
> -	}
> +	error = pm_notifier_call_chain_robust(PM_RESTORE_PREPARE, PM_POST_RESTORE);
> +	if (error)
> +		goto Restore;
>  
>  	pm_pr_dbg("Preparing processes for restore.\n");
>  	error = freeze_processes();
> @@ -900,7 +897,8 @@ static int software_resume(void)
>  	error = load_image_and_restore();
>  	thaw_processes();
>   Finish:
> -	__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
> +	pm_notifier_call_chain(PM_POST_RESTORE);
> + Restore:
>  	pm_restore_console();
>  	pr_info("resume from hibernation failed (%d)\n", error);
>  	atomic_inc(&snapshot_device_available);
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -79,18 +79,18 @@ int unregister_pm_notifier(struct notifi
>  }
>  EXPORT_SYMBOL_GPL(unregister_pm_notifier);
>  
> -int __pm_notifier_call_chain(unsigned long val, int nr_to_call, int *nr_calls)
> +int pm_notifier_call_chain_robust(unsigned long val_up, unsigned long val_down)
>  {
>  	int ret;
>  
> -	ret = __blocking_notifier_call_chain(&pm_chain_head, val, NULL,
> -						nr_to_call, nr_calls);
> +	ret = blocking_notifier_call_chain_robust(&pm_chain_head, val_up, val_down, NULL);
>  
>  	return notifier_to_errno(ret);
>  }
> +
>  int pm_notifier_call_chain(unsigned long val)
>  {
> -	return __pm_notifier_call_chain(val, -1, NULL);
> +	return blocking_notifier_call_chain(&pm_chain_head, val, NULL);
>  }
>  
>  /* If set, devices may be suspended and resumed asynchronously. */
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -210,8 +210,7 @@ static inline void suspend_test_finish(c
>  
>  #ifdef CONFIG_PM_SLEEP
>  /* kernel/power/main.c */
> -extern int __pm_notifier_call_chain(unsigned long val, int nr_to_call,
> -				    int *nr_calls);
> +extern int pm_notifier_call_chain_robust(unsigned long val_up, unsigned long val_down);
>  extern int pm_notifier_call_chain(unsigned long val);
>  #endif
>  
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -352,18 +352,16 @@ static int suspend_test(int level)
>   */
>  static int suspend_prepare(suspend_state_t state)
>  {
> -	int error, nr_calls = 0;
> +	int error;
>  
>  	if (!sleep_state_supported(state))
>  		return -EPERM;
>  
>  	pm_prepare_console();
>  
> -	error = __pm_notifier_call_chain(PM_SUSPEND_PREPARE, -1, &nr_calls);
> -	if (error) {
> -		nr_calls--;
> -		goto Finish;
> -	}
> +	error = pm_notifier_call_chain_robust(PM_SUSPEND_PREPARE, PM_POST_SUSPEND);
> +	if (error)
> +		goto Restore;
>  
>  	trace_suspend_resume(TPS("freeze_processes"), 0, true);
>  	error = suspend_freeze_processes();
> @@ -373,8 +371,8 @@ static int suspend_prepare(suspend_state
>  
>  	suspend_stats.failed_freeze++;
>  	dpm_save_failed_step(SUSPEND_FREEZE);
> - Finish:
> -	__pm_notifier_call_chain(PM_POST_SUSPEND, nr_calls, NULL);
> +	pm_notifier_call_chain(PM_POST_SUSPEND);
> + Restore:
>  	pm_restore_console();
>  	return error;
>  }
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -44,7 +44,7 @@ atomic_t snapshot_device_available = ATO
>  static int snapshot_open(struct inode *inode, struct file *filp)
>  {
>  	struct snapshot_data *data;
> -	int error, nr_calls = 0;
> +	int error;
>  
>  	if (!hibernation_available())
>  		return -EPERM;
> @@ -71,9 +71,7 @@ static int snapshot_open(struct inode *i
>  			swap_type_of(swsusp_resume_device, 0, NULL) : -1;
>  		data->mode = O_RDONLY;
>  		data->free_bitmaps = false;
> -		error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
> -		if (error)
> -			__pm_notifier_call_chain(PM_POST_HIBERNATION, --nr_calls, NULL);
> +		error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
>  	} else {
>  		/*
>  		 * Resuming.  We may need to wait for the image device to
> @@ -83,15 +81,11 @@ static int snapshot_open(struct inode *i
>  
>  		data->swap = -1;
>  		data->mode = O_WRONLY;
> -		error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
> +		error = pm_notifier_call_chain_robust(PM_RESTORE_PREPARE, PM_POST_RESTORE);
>  		if (!error) {
>  			error = create_basic_memory_bitmaps();
>  			data->free_bitmaps = !error;
> -		} else
> -			nr_calls--;
> -
> -		if (error)
> -			__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
> +		}
>  	}
>  	if (error)
>  		atomic_inc(&snapshot_device_available);
> --- a/tools/power/pm-graph/sleepgraph.py
> +++ b/tools/power/pm-graph/sleepgraph.py
> @@ -153,7 +153,7 @@ import base64
>  	tracefuncs = {
>  		'sys_sync': {},
>  		'ksys_sync': {},
> -		'__pm_notifier_call_chain': {},
> +		'pm_notifier_call_chain_robust': {},
>  		'pm_prepare_console': {},
>  		'pm_notifier_call_chain': {},
>  		'freeze_processes': {},
> 
> 
>