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Message-ID: <Pine.LNX.4.44L0.0707031529130.7671-100000@iolanthe.rowland.org>
Date: Tue, 3 Jul 2007 15:33:40 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: Matthew Garrett <mjg59@...f.ucam.org>
cc: linux-kernel@...r.kernel.org, <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH] Remove process freezer from suspend to RAM
pathway
On Tue, 3 Jul 2007, Matthew Garrett wrote:
> On Tue, Jul 03, 2007 at 12:57:17PM -0400, Alan Stern wrote:
> > On Tue, 3 Jul 2007, Matthew Garrett wrote:
> > > On Tue, Jul 03, 2007 at 12:03:33PM -0400, Alan Stern wrote:
> > > > Quite apart from the sync() matter, _any_ synchronous call to a FUSE
> > > > filesystem during STR will cause trouble. Even if the user task
> > > > implementing the filesystem isn't frozen, when it tries to carry out
> > > > some I/O to a suspended device it will either:
> > > >
> > > > block until the system wakes up, or
> > >
> > > For the suspend to RAM case, that sounds absolutely fine.
> >
> > It's not so good when your suspend process has to wait for the call to
> > complete!
>
> Why would it have to? Sorry, I suspect I'm missing something obvious
> here.
Well, the sys_sync() that caused your original problem did exactly
that. It's the reason you get deadlocks, right?
I agree that in general the suspend process should not have to wait for
a userspace callback to complete. Indeed, there's no particular
reason that anything running during STR should have to wait for
something in userspace to complete. Given that fact, I don't see
anything wrong with freezing userspace when doing STR.
Alan Stern
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