[systemd-devel] more verbose debug info than systemd.log_level=debug?

[Lennart Poettering]

On Mon, 10.04.17 19:30, Chris Murphy (lists at colorremedies.com) wrote:

> >> Remember, all of this is because there *is* software that does the wrong
> >> thing, and it *is* possible for software to hang and be unkillable. It would
> >> be good for systemd to do the right thing even in the presence of that kind
> >> of software.
> >
> > Yeah, we do what we can.
> >
> > But I seriously doubt FIFREEZE will make things better. It's just
> > going to make shutdowns hang every now and then.
> 
> My understanding is freeze isn't ignorable, it's expressly for the use
> case when the disk has active processing writing and the fs must be
> made completely consistent, e.g. prior to taking a snapshot. The thaw
> immediately following freeze would prevent any shutdown hang.
> 
> The point of freeze/thaw is it will cause the file system metadata
> that grub depends on to know where the new grub.cfg is located, to get
> committed to disk prior to reboot. If some process is still hanging
> around with an open write, it doesn't really matter.

As mentioned: if you prep a patch that adds FIFREEZE+FITHAW when we
remount stuff read-only, then I'd merge it, even though I think the
kernel APIs for this are really broken, and it would be much
preferably having a proper API for this, either exposed via the
well-understood sync() syscall, or through a new ioctl, if they must.

Lennart

-- 
Lennart Poettering, Red Hat