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

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Message-Id: <200703092107.23820.rjw@sisk.pl>
Date:	Fri, 9 Mar 2007 21:07:22 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Pavel Machek <pavel@....cz>
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,

On Friday, 9 March 2007 09:54, Pavel Machek wrote:
> 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?

Rafael


---
 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();
 			}
 			break;
 
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