On Friday, 20 July 2007 23:33, Jeremy Maitin-Shepard wrote:
> "Rafael J. Wysocki" <[email protected]> writes:
>
> [snip]
>
> >> Or add a small bit of infrastructure that errors writes at make_request
> >> if you don't have a magic "i am a direct block device write from
> >> userspace" flag on the bio.
> >>
> >> The hibernate may fail, but you don't corrupt the media.
> >>
> >> If you don't get the image out, resume back to the "this is resume"
> >> instead of the power-down path.
>
> > Well, I don't think that is much prettier than the freezer ...
>
> It seems that a better solution to the "how do we write to a file on an
> in-use partition" has been suggested, which also handles swap partitions
> and swap files, and does not require mounting filesystems, so it seems
> that the filesystem issue need not be considered.
>
> [snip]
>
> > No. I'm saying that when you go back from the image-saving kernel to the
> > hibernated kernel, you need to make sure that no task will cause any
> > filesystem's on-disk state to be actually updated. If you can't make such
> > a guarantee, you just can't do that.
>
> > With the current state of the drivers, it's not doable without the
> > freezer.
>
> It seems that it should be feasible to fix the drivers so that
>
> 1. they can be taken from normal state to quiesced state without
> requiring the freezer;
>
> 2. they can be taken from normal state to low power state without
> requiring the freezer;
Yes, that's correct.
> 3. they can be taken from quiesced state to low power state without
> requiring the freezer.
>
> In the particular, it seems that it should be possible to do (3) without
> needing to schedule tasks.
For that, you'd have to forbid the drivers to call schedule() from the relevant
callbacks, which means, eg. no timeouts in there.
> It seems likely that (2) may in fact be almost exactly the same as, or
> at least similar to, (1) followed by (3), at least for many drivers.
> (1) is required by the kexec hibernate approach even ignoring suspend to
> both or S4. (2) is required for suspend to ram without the freezer,
> which seems to be desired anyway.
Yes, (2) is needed anyway.
Greetings,
Rafael
--
"Premature optimization is the root of all evil." - Donald Knuth
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
