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

[Oliver Neukum <oliver@neukum.org>]

Am Dienstag, 3. Juli 2007 schrieb Miklos Szeredi:
> > > > > So to summarize, the plan that makes things work with fuse is:
> > > > > 
> > > > >  - For STR, don't do the freezer thing.
> > > > > 
> > > > >  - For STD, don't sys_sync() after you froze
> > > > > 
> > > > > There might be -other- issues, but that should get you through some of
> > > > 
> > > > At the risk of repeating myself. Character device drivers are written
> > > > with the assumption that normal io and suspend/resume do not race
> > > > with each other due to the freezer.
> > > > What do you intend to do about that?
> > > 
> > > Oliver, can you please explain your worries in a bit more detail?
> > > 
> > > I don't claim to know anything about how STR or hibernate works, but
> > > neither seem to have any problem with I/O on the fuse device "racing"
> > > with them.
> > 
> > The problem is not with fuse. The problem is generic in nature.
> > 
> > If you remove the freezer, user space remains active until the last CPU
> > goes into suspend. It can do syscalls. Or do you know a clean way to exempt
> > only the tasks fuse might use?
> 
> You are talking about hibernate, right?  Suspending (to ram) is
> instantaneous, in that _after_ suspend no CPU is active obviously.

If that is so, why do you care? If it is really atomic, fuse has no chance
to call out to its component in user space either. Removing the freezer
cannot make a difference.

Something is fishy here.

	Regards
		Oliver