linux-kernel - Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

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Date:	Tue, 3 Jul 2007 22:45:43 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Miklos Szeredi <miklos@...redi.hu>, mjg59@...f.ucam.org,
	linux-kernel@...r.kernel.org, pavel@....cz,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

Am Dienstag, 3. Juli 2007 schrieben Sie:
> On Tue, 3 Jul 2007, Oliver Neukum wrote:
> 
> > Well, but you did remove sys_sync() from the freezer, which is
> > and must be called in the hibernate path.
> 
> That's not really true.  We _want_ to call sys_sync() in both the 
> hibernate and suspend paths (in case the batteries run down), to help 
> avoid filesystem problems if something goes wrong with the resume.  But 
> it isn't a hard requirement.

But the ability to launder pages is needed. During hibernation we need
to shrink memory. I don't see how this would be fundamentally different
from calling sync.

> > > I'm not sure why this can't be made atomic, but assuming, that it
> > > can't, fuse should still not need to be implicated.  If it is, that's
> > > an indication about something wrong in the suspend procedure.
> > 
> > Nope, something's wrong in fuse. You must be able to deal with sync
> > until every task is frozen.
> 
> That's ridiculous.  FUSE itself runs partially as a user task.  How can
> you expect it to carry out a sync or anything else when it is frozen?

I don't and it might point to a fundamental problem.
But I cannot help but notice that syscalls may happen while the system
is partially frozen. It must be dealt with.

> I suppose you could "deal" with it by having the kernel portion return
> an error if the userspace part is frozen.  If the hibernate/suspend 
> code bothered to check the return value, it would immediately abort 
> the suspend.

Where exactly would that code notice the errors?

	Regards
		Oliver

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