linux-kernel - Re: [REGRESION] Suspend hangs with 3.6-rc1 on Lenovo T60 notebook

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Message-ID: <Pine.LNX.4.44L0.1208161106350.24305-100000@netrider.rowland.org>
Date:	Thu, 16 Aug 2012 11:13:33 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Hans de Goede <hdegoede@...hat.com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Miklos Szeredi <miklos@...redi.hu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-pm@...r.kernel.org>
Subject: Re: [REGRESION] Suspend hangs with 3.6-rc1 on Lenovo T60 notebook

On Thu, 16 Aug 2012, Hans de Goede wrote:

> Ah right, these are bus_driver operations. That explains some things, so I've
> done some more research asking myself: "Why does generic_ide_suspend(), which
> is a *bus* op, call dev_get_drvdata?", the answer to that seems to be that
> the ide subsystem is abusing (IMHO) drvdata to store per device bus_driver
> data. Which I believe is not how drvdata is intended to be used.
> 
> With that said, the above knowledge has allowed me to write an (ugly) fix for
> the regression Miklos is seeing. Miklos can you give the attached patch a
> try please?
> 
> > It clearly should check if drive is not NULL before using that pointer.
> 
> I assume you mean drive*r*, yes I agree that generic_ide_remove should
> check for that. So who is going to write a patch for that?

The existing code could certainly be improved.  Your patch does:

> +               /*
> +                * device_register() will have cleared drvdata on
> +                * device_attach failure, but we use drvdata to store per
> +                * device bus info, rather then for driver info, so restore it.
> +                */
> +               dev_set_drvdata(dev, drive);

But at this point, dev is defined by:

		struct device *dev = &drive->gendev;

So why bother setting anything?  It seems to me that 
generic_ide_suspend() and generic_ide_resume() could easily replace

	ide_drive_t *drive = dev_get_drvdata(dev);

with

	ide_drive_t *drive = dev_to_ide_drive(dev);

where dev_to_ide_drive is defined as "container_of(dev, ide_drive_t,
gendev)" (if this isn't defined already).

Alan Stern

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