linux-kernel - Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

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Date:	Thu, 26 Apr 2007 20:40:30 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Pavel Machek <pavel@....cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Nick Piggin <npiggin@...e.de>,
	suspend2-devel@...ts.suspend2.net, Mike Galbraith <efault@....de>,
	linux-kernel@...r.kernel.org, Con Kolivas <kernel@...ivas.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-pm <linux-pm@...ts.linux-foundation.org>
Subject: Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)

On Thursday, 26 April 2007 18:31, Johannes Berg wrote:
> On Thu, 2007-04-26 at 13:30 +0200, Pavel Machek wrote:
> 
> > > From looking at pm_ops which I was recently working with a lot, it seems
> > > that it was designed by somebody who was reading the ACPI documentation
> > > and was otherwise pretty clueless, even at that level std tries to look
> > > like suspend. IMHO that is one of the first things that should be ripped
> > > out, no pm_ops for STD, it's a pain to work with.
> > 
> > That code goes back to Patrick, AFAICT. (And yes, ACPI S3 and ACPI S4
> > low-level enter is pretty similar).
> > 
> > Patches would be welcome
> 
> That was easier than I thought. This applies on top of a patch that
> makes kernel/power/user.c optional since I had no idea how to fix it,
> problems I see:
>  * it surfaces kernel implementation details about pm_ops and thus makes
>    the whole thing very fragile

Can you elaborate?

>  * it has yet another interface (yuck) to determine whether to reboot,
>    shut down etc, doesn't use /sys/power/disk

Yes.  In fact it was meant as a replacement for /sys/power/disk at one point.

>  * I generally had no idea wtf it is doing in some places

I could have told you if you had asked. :-)

> Anyway, this patch is only compile tested, it
>  * introduces include/linux/hibernate.h with hibernate_ops and
>    a new hibernate() function to hibernate the system

Do we need hibernate_ops at all?  There's only one user anyway and I'm not
sure there will be more of them in the future.

>  * rips apart a lot of the suspend code and puts it back together using
>    the hibernate_ops
>  * switches ACPI to hibernate_ops (the only user of pm_ops.pm_disk_mode)
>  * might apply/compile against -mm, I have all my and some of Rafael's
>    suspend/hibernate work in my tree.
>  * breaks user suspend as I noted above
>  * is incomplete, somewhere pm_suspend_disk() is still defined iirc

I think I can fix it up, just give me some time.

The idea is good, I think we should do someting like this.

Greetings,
Rafael
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