linux-kernel - Re: [RFC][PATCH 0/7] PM: Asynchronous suspend and resume (updated)

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Message-Id: <1250840434.17853.176.camel@rzhang-dt>
Date:	Fri, 21 Aug 2009 15:40:34 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Greg KH <gregkh@...e.de>
Subject: Re: [RFC][PATCH 0/7] PM: Asynchronous suspend and resume (updated)

On Thu, 2009-08-20 at 05:02 +0800, Rafael J. Wysocki wrote:
> On Wednesday 19 August 2009, Zhang Rui wrote:
> > On Wed, 2009-08-19 at 07:58 +0800, Rafael J. Wysocki wrote:
> > > On Tuesday 18 August 2009, Rafael J. Wysocki wrote:
> > > > On Tuesday 18 August 2009, Zhang Rui wrote:
> > > > > On Mon, 2009-08-17 at 08:15 +0800, Rafael J. Wysocki wrote:
> > > > > > On Wednesday 12 August 2009, Rafael J. Wysocki wrote:
> > > > > > > Hi,
> > > > > > > 
> > > > > > > The following patches introduce a mechanism allowing us to execute device
> > > > > > > drivers' suspend and resume callbacks asynchronously during system sleep
> > > > > > > transitions, such as suspend to RAM.  The idea is explained in the [1/1] patch
> > > > > > > message.
> > > > > > 
> > > > > > Changes:
> > > > > > 
> > > > > > * Added [1/7] that fixes kerneldoc comments in drivers/base/power/main.c
> > > > > >   (this is a 2.6.32 candidate).
> > > > > > 
> > > > > > * Added [2/7] adding a framework for representing PM link (idea described
> > > > > >   in the patch message).
> > > > > > 
> > > > > > * [3/7] is the async resume patch (idea described in the patch message).
> > > > > > 
> > > > > > * [4/7] is the async suspend patch.
> > > > > > 
> > > > > > * [5/7] - [7/7] set async_suspend for devices in a few selected subsystems.
> > > > > > 
> > > > > > The patches have been tested on HP nx6325.
> > > > > > 
> > > > > I tried this patch set and it does work. :)
> > > > > But unfortunately it doesn't save too much time.
> > > > > 
> > > > > I still think that the child device should inherit its parent's
> > > > > async_suspend flag to do the asynchronous resume more efficiently.
> > > > > 
> > > > > or at least we should provide such an interface
> > > > > in drivers/base/power/common.c, so that device can tell the device core
> > > > > to inherit this flag if there is no off-tree dependency.
> > > > 
> > > > Well, I'd prefer to identify all of the off-tree dependencies that have to be
> > > > taken into account and handle all devices asynchronously.
> > > 
> > > Anyway, I have tested the appended patch on top of [1/7]-[7/7] and my test box
> > > appears to work fine with it, although it doesn't work in the "async for all"
> > > case.
> > > 
> > > I guess the next step will be to see which devices are not handled
> > > asynchronously with the patch below and try to figure out which of them
> > > break(s) things.
> > > 
> > > Thanks,
> > > Rafael
> > > 
> > > ---
> > >  drivers/base/power/common.c |    6 +++++-
> > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > Index: linux-2.6/drivers/base/power/common.c
> > > ===================================================================
> > > --- linux-2.6.orig/drivers/base/power/common.c
> > > +++ linux-2.6/drivers/base/power/common.c
> > > @@ -32,7 +32,11 @@ void device_pm_add(struct device *dev)
> > >  	pr_debug("PM: Adding info for %s:%s\n",
> > >  		 dev->bus ? dev->bus->name : "No Bus",
> > >  		 kobject_name(&dev->kobj));
> > > -	pm_link_add(dev, dev->parent);
> > > +	if (dev->parent) {
> > > +		pm_link_add(dev, dev->parent);
> > > +		if (dev->parent->power.async_suspend)
> > > +			dev->power.async_suspend = true;
> > > +	}
> > 
> > to use this, we must make sure that device_enable_async_suspend is
> > called before any of its child device being registered, right?
> > should we check this in device_enable_async_suspend?
> > or at least we should add the comments stating this issue.
> 
> That's correct in general, but I added the patch for testing purposes only.
> 
> The goal still is to identify all of the dependencies that need to be taken
> care of and to represent them appropriately, so that we can safely set
> async_suspend for all devices.
> 
> I wonder if you get any improvement with this patch applied?
> 
No, it doesn't work.
the system hangs during suspend.
I have not figured out the root cause.

thanks,
rui


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