Re: [PATCH 1/3] PM suspend/hibernate: Call notifier after freezing processes

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

On Sunday, April 05, 2015 07:20:17 PM Pali Rohár wrote:
> To prevent race conditions on userspace processes with I/O some taks must be
> called after processes are freezed. This patch adds new events which are
> delivered by pm_notifier_call_chain() after freezing processes when doing
> suspend or hibernate action.
> 
> Signed-off-by: Pali Rohár <pali.rohar@gmail.com>

Please don't add more notifiers.  Just call whatever you need directly from
where you need to call that.

If that is device-related, try to use device PM suspend/hibernate callbacks
instead.

> ---
>  include/linux/suspend.h  |    2 ++
>  kernel/power/hibernate.c |    2 ++
>  kernel/power/suspend.c   |    4 +++-
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> index 5efe743..bc743c8 100644
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -368,6 +368,8 @@ static inline bool hibernation_available(void) { return false; }
>  #define PM_POST_SUSPEND		0x0004 /* Suspend finished */
>  #define PM_RESTORE_PREPARE	0x0005 /* Going to restore a saved image */
>  #define PM_POST_RESTORE		0x0006 /* Restore failed */
> +#define PM_HIBERNATION_AFTER_FREEZE	0x0007 /* After hibernation freeze */
> +#define PM_SUSPEND_AFTER_FREEZE		0x0008 /* After suspend freeze */
>  
>  extern struct mutex pm_mutex;
>  
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 2329daa..184f7ee 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -671,6 +671,8 @@ int hibernate(void)
>  	if (error)
>  		goto Exit;
>  
> +	pm_notifier_call_chain(PM_HIBERNATION_AFTER_FREEZE);
> +
>  	lock_device_hotplug();
>  	/* Allocate memory management structures */
>  	error = create_basic_memory_bitmaps();
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index b7d6b3a..1776938 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -268,8 +268,10 @@ static int suspend_prepare(suspend_state_t state)
>  	trace_suspend_resume(TPS("freeze_processes"), 0, true);
>  	error = suspend_freeze_processes();
>  	trace_suspend_resume(TPS("freeze_processes"), 0, false);
> -	if (!error)
> +	if (!error) {
> +		pm_notifier_call_chain(PM_SUSPEND_AFTER_FREEZE);
>  		return 0;
> +	}
>  
>  	suspend_stats.failed_freeze++;
>  	dpm_save_failed_step(SUSPEND_FREEZE);
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.