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Date: Fri, 11 Oct 2019 00:01:02 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, rostedt@...dmis.org,
mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
torvalds@...ux-foundation.org, tglx@...utronix.de,
mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
ard.biesheuvel@...aro.org, Pavel Machek <pavel@....cz>,
Alexios Zavras <alexios.zavras@...el.com>,
Allison Randal <allison@...utok.net>,
Sam Protsenko <semen.protsenko@...aro.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Todd Brandt <todd.e.brandt@...ux.intel.com>,
Vasily Averin <vvs@...tuozzo.com>,
Len Brown <len.brown@...el.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 1/4] notifier: Fix broken error handling pattern
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@...radead.org>
> Cc: Pavel Machek <pavel@....cz>
> Cc: Alexios Zavras <alexios.zavras@...el.com>
> Cc: Allison Randal <allison@...utok.net>
> Cc: Sam Protsenko <semen.protsenko@...aro.org>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Todd Brandt <todd.e.brandt@...ux.intel.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Vasily Averin <vvs@...tuozzo.com>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.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': {},
>
>
>
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