Re: Anyone recall the dreaded tstile issue?

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Fri, 22 Jul 2022 11:24:46 +0100
    From:        Patrick Welche <prlw1%talktalk.net@localhost>
    Message-ID:  <Ytp67vtQNvMFk96i@quark>

  | Having not seen the dreaded turnstile issue in ages, a NetBSD-9.99.99/amd64
  | got stuck on shutdown last night with:

How long did you wait?

I have seen situations where it takes 10-15 mins to sync everything to
drives (I have plenty of RAM available) - which I think is another
problem - but not this one.

It isn't the case that every time we find something "stuck" on a tstile
wait that the system is broken - they're just locks, sometimes processes
are going to need to wait for one.

In the kind of scenario described, things like sync and halt will need
to wait for all the filesystems to be flushed - if that's going to take
a long time (which it really shouldn't, but that's a different issue)
then it is going to take a long time.

The other day I managed to crash my system (my fault, though really what
I did - yanking a USB drive mid write - shouldn't really cause a crash,
just mangled data) in the middle of the afternoon.   It rebooted easily
enough, wapbl replaying logs kept all the filesystems safe enough (I think
the drive I pulled needs a little more attention, but that's a different
problem) but then I discovered that files I had written about 02:00 in the
morning (more than 12 hours earlier) were all full of zeroes - the data
must have been sitting in RAM all that time, and nothing had bothered to
send it to the drive.   That's not good ...   We also seem to no longer
have the ancient update(8) which used to issue a sync every 30 secs, to
attempt to minimize this kind of problem.

kre