linux-kernel - Re: [PATCH v2 1/3] PM suspend/hibernate: Call notifier after freezing processes

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Message-ID: <3729395.1oJCgMXcLU@vostro.rjw.lan>
Date:	Thu, 16 Jul 2015 03:02:03 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Alasdair Kergon <agk@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>, Neil Brown <neilb@...e.de>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	dm-devel@...hat.com, linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/3] PM suspend/hibernate: Call notifier after freezing processes

On Sunday, June 21, 2015 01:20:32 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@...il.com>
> ---
>  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);

Don't we need to check errors from these?

Also, if you're adding AFTER_FREEZE, it would be good to add BEFORE_THAW too
for symmetry.

> +
>  	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 8d7a1ef..ba2a945 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -277,8 +277,10 @@ 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.
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