linux-kernel - Re: [PATCH v2 1/3] PM / Sleep: Make [un]lock_system

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Message-Id: <201112062335.53670.rjw@sisk.pl>
Date:	Tue, 6 Dec 2011 23:35:53 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	pavel@....cz, len.brown@...el.com, ebiederm@...ssion.com,
	tj@...nel.org, rdunlap@...otime.net, linux-doc@...r.kernel.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, oleg@...hat.com
Subject: Re: [PATCH v2 1/3] PM / Sleep: Make [un]lock_system_sleep() generic

On Tuesday, December 06, 2011, Srivatsa S. Bhat wrote:
> The [un]lock_system_sleep() APIs were originally introduced to mutually
> exclude memory hotplug and hibernation.
> 
> Directly using mutex_lock(&pm_mutex) to achieve mutual exclusion with
> suspend or hibernation code can lead to freezing failures. However, the
> APIs [un]lock_system_sleep() can be safely used to achieve the same,
> without causing freezing failures.
> 
> So, since it would be beneficial to modify all the existing users of
> mutex_lock(&pm_mutex) (in all parts of the kernel), so that they use these
> safe APIs intead, make these APIs generic by removing the restriction that
> they work only when CONFIG_HIBERNATE_CALLBACKS is set. Moreover, that
> restriction didn't buy us anything anyway.
> 
> v2: Rebased on top of the patchset posted at:
>     https://lkml.org/lkml/2011/12/6/334
> 
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

All patches in this series applied to linux-pm/linux-next.

Thanks,
Rafael


> ---
> 
>  include/linux/suspend.h |   36 ++++++++++++++++--------------------
>  1 files changed, 16 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> index 906d62c..95040cc 100644
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -332,6 +332,8 @@ static inline bool system_entering_hibernation(void) { return false; }
>  #define PM_RESTORE_PREPARE	0x0005 /* Going to restore a saved image */
>  #define PM_POST_RESTORE		0x0006 /* Restore failed */
>  
> +extern struct mutex pm_mutex;
> +
>  #ifdef CONFIG_PM_SLEEP
>  void save_processor_state(void);
>  void restore_processor_state(void);
> @@ -352,6 +354,19 @@ extern bool events_check_enabled;
>  extern bool pm_wakeup_pending(void);
>  extern bool pm_get_wakeup_count(unsigned int *count);
>  extern bool pm_save_wakeup_count(unsigned int count);
> +
> +static inline void lock_system_sleep(void)
> +{
> +	freezer_do_not_count();
> +	mutex_lock(&pm_mutex);
> +}
> +
> +static inline void unlock_system_sleep(void)
> +{
> +	mutex_unlock(&pm_mutex);
> +	freezer_count();
> +}
> +
>  #else /* !CONFIG_PM_SLEEP */
>  
>  static inline int register_pm_notifier(struct notifier_block *nb)
> @@ -367,30 +382,11 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
>  #define pm_notifier(fn, pri)	do { (void)(fn); } while (0)
>  
>  static inline bool pm_wakeup_pending(void) { return false; }
> -#endif /* !CONFIG_PM_SLEEP */
> -
> -extern struct mutex pm_mutex;
>  
> -#ifndef CONFIG_HIBERNATE_CALLBACKS
>  static inline void lock_system_sleep(void) {}
>  static inline void unlock_system_sleep(void) {}
>  
> -#else
> -
> -/* Let some subsystems like memory hotadd exclude hibernation */
> -
> -static inline void lock_system_sleep(void)
> -{
> -	freezer_do_not_count();
> -	mutex_lock(&pm_mutex);
> -}
> -
> -static inline void unlock_system_sleep(void)
> -{
> -	mutex_unlock(&pm_mutex);
> -	freezer_count();
> -}
> -#endif
> +#endif /* !CONFIG_PM_SLEEP */
>  
>  #ifdef CONFIG_ARCH_SAVE_PAGE_KEYS
>  /*
> 
> --
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> 

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