linux-kernel - Re: [PATCH v6 2/2] ARM hibernation / suspend-to-disk

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Date:	Tue, 04 Mar 2014 01:55:31 -0800
From:	Sebastian Capella <sebastian.capella@...aro.org>
To:	Sebastian Capella <sebastian.capella@...aro.org>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Russ Dill" <Russ.Dill@...com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Russell King" <linux@....linux.org.uk>,
	"Len Brown" <len.brown@...el.com>,
	"Nicolas Pitre" <nico@...aro.org>,
	"Santosh Shilimkar" <santosh.shilimkar@...com>,
	"Will Deacon" <Will.Deacon@....com>,
	"Jonathan Austin" <Jonathan.Austin@....com>,
	"Catalin Marinas" <Catalin.Marinas@....com>,
	"Uwe Kleine-K?nig" <u.kleine-koenig@...gutronix.de>,
	"Stephen Boyd" <sboyd@...eaurora.org>
Subject: Re: [PATCH v6 2/2] ARM hibernation / suspend-to-disk

Quoting Sebastian Capella (2014-02-28 15:38:54)
> Quoting Lorenzo Pieralisi (2014-02-28 14:49:33)
> > On Fri, Feb 28, 2014 at 08:15:57PM +0000, Sebastian Capella wrote:
> > > > 
> > > > This does not guarantee your stack is 8-byte aligned, that's not AAPCS
> > > > compliant and might buy you trouble.
> > > > 
> > > > Either you align the stack or you align the pointer you are passing.
> > > > 
> > > > Please have a look at kernel/process.c
> > > 
> > > I've added this for now, do you see any issues?
> > > 
> > > -static u8 resume_stack[PAGE_SIZE/2] __nosavedata;
> > > +static u64 resume_stack[PAGE_SIZE/2/sizeof(u64)] __nosavedata;
> > > -               resume_stack + sizeof(resume_stack));
> > > +               resume_stack + ARRAY_SIZE(resume_stack));
> > 
> > I do not see why the stack depends on the PAGE_SIZE. I would be surprised
> > if you need more than a few bytes (given that soft_restart switches stack
> > again...), go through it with a debugger, it is easy to check the stack
> > usage and allow for some extra buffer (but half a page is not needed).
> 
> I assuming this is becase the no-save region is one page anyway (we skip
> restoring the no-save region physical page).  So maybe 1/2 is a way to
> leave some room for whatever else may need to be here, but in any case
> the 4k is used for nosave.  I think you're right that it can be much less.

Hi Lorenzo,

Are you ok with this just being half a page?  Or do you want me to try
to reduce the stack size?  I am at Connect without my debugger, so in
that case it would have to wait until next week.

The change for alignment is in as discussed.

Thanks!

Sebastian
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