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

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Message-Id: <201504090836.57365@pali>
Date:	Thu, 9 Apr 2015 08:36:57 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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 1/3] PM suspend/hibernate: Call notifier after freezing processes

On Thursday 09 April 2015 02:28:41 Rafael J. Wysocki wrote:
> 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@...il.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.
> 

Hi! It is not possible to use any exiting pm notifiers! This is 
reason why I added new ones. As I wrote wiping dm crypt keys must 
be done *after* userspace processes are freezed to prevent race 
conditions...

> > ---
> > 
> >  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);

-- 
Pali Rohár
pali.rohar@...il.com

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