Re: No freezing of kernel threads (was: Re: [GIT PULL] libata fixes for v3.13-rc5)

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > Well, it looks like we don't really know why things are done the way they
> > are done at least in some cases, so in my personal view it would be good to
> > go through all of the kernel freezer users just for this reason alone.  We
> > can't really say which of them are legitimate without that and how difficult
> > it would be for them to switch over to using something more fine grained than
> > the freezer.
> 
> I'm a bit worried about things which may not be explicit.
> ie. something which is broken but sorta working because things like
> writeback and jbd are frozen.  I think I worry about that because I
> remember one argument for kernel freezer from way way back, that it's
> too hard to implement proper suspend/resume for all drivers and by
> freezing most kthreads things should mostly work, which sounded pretty
> crazy to me even back then.  Hopefully, we don't have much left
> depending on such magic.

Careful there. Hibernation depends on data on disk not changing after
freeze.

So you definitely do _not_ want writeback/jbd running while uswsusp
does its image writing.

(I wonder what happens if uswsusp needs to trigger writeback to free
memory. But I'm too scared to check :-).
									Pavel
-- 
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