linux-kernel - Re: [PATCH] swsusp: Disable nonboot CPUs before entering platform suspend

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Message-ID: <20070309210746.GA6374@ucw.cz>
Date:	Fri, 9 Mar 2007 21:07:46 +0000
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] swsusp: Disable nonboot CPUs before entering platform suspend

Hi!

> > > > > Index: linux-2.6.21-rc2-mm2/kernel/power/disk.c
> > > > > ===================================================================
> > > > > --- linux-2.6.21-rc2-mm2.orig/kernel/power/disk.c
> > > > > +++ linux-2.6.21-rc2-mm2/kernel/power/disk.c
> > > > > @@ -61,6 +61,7 @@ static void power_down(suspend_disk_meth
> > > > >  	switch(mode) {
> > > > >  	case PM_DISK_PLATFORM:
> > > > >  		if (pm_ops && pm_ops->enter) {
> > > > > +			disable_nonboot_cpus();
> > > > >  			kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
> > > > >  			pm_ops->enter(PM_SUSPEND_DISK);
> > > > >  			break;
> > > > 
> > > > ...so, if pm_ops is non-null, power_down does nonboot cpu disabling,
> > > > otherwise we proceed with cpus enabled?
> > > > 
> > > > That looks ugly.
> > > > 
> > > > Is the warning bogus?
> > > 
> > > Well, maybe.  I'm not sure.
> > > 
> > > > Or maybe we should *always* disable nonboot cpus in powerdown path?
> > > 
> > > I think we should do that.
> > 
> > That would be acceptable.
> > 
> > > > > Index: linux-2.6.21-rc2-mm2/kernel/power/user.c
> > > > > ===================================================================
> > > > > --- linux-2.6.21-rc2-mm2.orig/kernel/power/user.c
> > > > > +++ linux-2.6.21-rc2-mm2/kernel/power/user.c
> > > > > @@ -398,9 +398,9 @@ static int snapshot_ioctl(struct inode *
> > > > >  
> > > > >  		case PMOPS_ENTER:
> > > > >  			if (data->platform_suspend) {
> > > > > +				disable_nonboot_cpus();
> > > > >  				kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
> > > > >  				error = pm_ops->enter(PM_SUSPEND_DISK);
> > > > > -				error = 0;
> > > > >  			}
> > > > >  			break;
> > > > 
> > > > Foe an userland application, disabling cpus during pmops_enter is at
> > > > least surprising.......
> > > 
> > > Yes, but this is not a usual ioctl().  OTOH, we can call enable_nonboot_cpus()
> > > if pm_ops->enter(PM_SUSPEND_DISK) returns an error (otherwise it souldn't
> > > return at all, no?).
> > 
> > Ok.
> 
> Well, does the appended patch look better?

Yes.

> ---
>  kernel/power/disk.c |    1 +
>  kernel/power/user.c |    3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.21-rc3/kernel/power/disk.c
> ===================================================================
> --- linux-2.6.21-rc3.orig/kernel/power/disk.c
> +++ linux-2.6.21-rc3/kernel/power/disk.c
> @@ -58,6 +58,7 @@ static inline int platform_prepare(void)
>  
>  static void power_down(suspend_disk_method_t mode)
>  {
> +	disable_nonboot_cpus();
>  	switch(mode) {
>  	case PM_DISK_PLATFORM:
>  		if (pm_ops && pm_ops->enter) {
> Index: linux-2.6.21-rc3/kernel/power/user.c
> ===================================================================
> --- linux-2.6.21-rc3.orig/kernel/power/user.c
> +++ linux-2.6.21-rc3/kernel/power/user.c
> @@ -402,9 +402,10 @@ static int snapshot_ioctl(struct inode *
>  
>  		case PMOPS_ENTER:
>  			if (data->platform_suspend) {
> +				disable_nonboot_cpus();
>  				kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
>  				error = pm_ops->enter(PM_SUSPEND_DISK);
> -				error = 0;
> +				enable_nonboot_cpus();

Why did we discard return code in previous versions? Do we still want
to do that?

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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