Re: problem 1 (was Re: removing refrigerator does not help with s2ram vs. fuse deadlocks (was Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway))

Rafael J. Wysocki
2007-07-07T20:48:33Z

On Saturday, 7 July 2007 14:08, Pavel Machek wrote:
> Hi!
>
> > > Now, if kernel needs FUSE services for some reason (that's the problem
> > > we hit in s2ram case, right?), we have a deadlock.
> > >
> > > So main problem still seems to be "kernel should not depend on
> > > userland services during suspend", refrigerator or not.
> >
> > And also "Userland should not depend on userland services", which is
> > rather more of a problem.
>
> No, that's not a problem. Or rather, that's different problem, called
> "problem 2" (fuse causes freezer to fail to stop processes).
>
> But we still have "problem 1" here: after devices are suspended,
> kernel tries to use fuse's services. That is not going to work, one
> way or another, because devices are suspended and userland can't work
> reliably.
>
> (Aha, it _may_ be it is kernel tries to use fuse's services after
> freezing userland but before freezing devices. I don't think it is).
>
> To solve "problem 1", we need to know which part of kernel asks for
> fuse services. sysrq-t trace is likely to tell us. Can someone repeat
> the "problem 1" scenario (freezer succeeds but then it deadlocks), and
> produce sysrq-t trace? That way we can solve "problem 1".

Well, such a trace would be helpful in any case.

Greetings,
Rafael

--
"Premature optimization is the root of all evil." - Donald Knuth