linux-kernel - Re: [RFC][PATCH] PM: Make PM core handle device registrations concurrent with suspend/hibernation

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Message-ID: <Pine.LNX.4.44L0.0803051658290.4318-100000@iolanthe.rowland.org>
Date:	Wed, 5 Mar 2008 17:00:07 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	Pavel Machek <pavel@....cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] PM: Make PM core handle device registrations
 concurrent with suspend/hibernation

On Wed, 5 Mar 2008, Rafael J. Wysocki wrote:

> On Wednesday, 5 of March 2008, Alan Stern wrote:
> > On Wed, 5 Mar 2008, Rafael J. Wysocki wrote:
> > 
> > > -void device_pm_add(struct device *dev)
> > > +int device_pm_add(struct device *dev)
> > >  {
> > > +	int error = 0;
> > > +
> > >  	pr_debug("PM: Adding info for %s:%s\n",
> > >  		 dev->bus ? dev->bus->name : "No Bus",
> > >  		 kobject_name(&dev->kobj));
> > >  	mutex_lock(&dpm_list_mtx);
> > > -	list_add_tail(&dev->power.entry, &dpm_active);
> > > +	if (dev->parent && dev->parent->power.sleeping) {
> > > +		WARN_ON(true);
> > 
> > I would prefer to put a dev_warn() line here, so that people reading
> > the kernel log can easily tell which device caused the problem and what
> > sort of problem it is.  Something like this:
> > 
> > 		dev_warn(dev, "device added while parent %s is asleep\n",
> > 				dev->parent->bus_id);
> > 		WARN_ON(true);
> 
> Added.
> 
> > > @@ -426,6 +406,12 @@ static int dpm_suspend(pm_message_t stat
> > >  		struct list_head *entry = dpm_active.prev;
> > >  		struct device *dev = to_device(entry);
> > >  
> > > +		if (dev->parent && dev->parent->power.sleeping) {
> > > +			WARN_ON(true);
> > > +			error = -EAGAIN;
> > > +			break;
> > 
> > Again, a dev_warn() would be appropriate.
> 
> I chose just "WARN_ON(dev->parent && dev->parent->power.sleeping)",
> which is shorter. :-)
> 
> I don't really expect it to appear and if it's reported, it'll be easy to
> figure out everything from the stack trace.

Okay.

> Revised patch below.

It looks good.  Let's hope it doesn't mess up ACPI too badly...  :-)

Acked-by: Alan Stern <stern@...land.harvard.edu>

Alan Stern

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