linux-kernel - Re: [git patches] libata hibernation fixes

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Date:	Tue, 4 Nov 2008 17:53:52 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jeff Garzik <jeff@...zik.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ide@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [git patches] libata hibernation fixes

On Tuesday, 4 of November 2008, Linus Torvalds wrote:
> 
> On Tue, 4 Nov 2008, Jeff Garzik wrote:
> > 
> > This adds code at a late stage (heading towards -rc4), but does
> > eliminate a particular spin-up overcycling behavior associated with
> > hibernation.
> 
> What does this have to do with hibernation? 
> 
> If it's a hibernation-only issue, then there is something wrong. 

No, it is not.  On some machines it is a power-off issue, on the others it is
hibernation and power-off issue.

> Also, if it is an issue for normal power-off as well, then I wonder why 
> this isn't an issue on Windows. Does windows not spin down disks at all?

In fact, AFAICS, it is an issue on Windows as well, at least if
other-than-HP-preloaded version of Windows is used.

> IOW, I really don't think this is correct. 
> 
> I _do_ think that correct might be:
> 
>  - maybe we just do something odd and different, triggering some BIOS 
>    behavior that isn't there under Windows.
> 
>    So we should power down thigns differently so that the BIOS.
> 
>  - quite possibly: we just should not spin down disks at all, and just 
>    flush them and do the "park" command thing. If we're _really_ powering 
>    off, the disks will spin down on their own when power goes away. Maybe 
>    that's what Windows does?
> 
> So I really don't want to pull this, because I want to get more of an 
> explanation for why we need to do this at all. I also don't think this is 
> even appropriate at this stage in -rc.
> 
> Is it a regression? If so, that just strengthens the questions above - 
> what did _we_ start doing wrong that this is needed at all? Let's just 
> stop doing that, not add some idiotic black-list for somethign that _we_ 
> do wrong.

This is a regression, but from something like 2.6.25 or even earlier.
I think what happened is we started to power-off disks at one point and these
BIOS-es just don't like that.

[Note that the issue only appears in _some_ HP boxes, other vendors don't
seem to be affected at all.]

Thanks,
Rafael
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