On Thu, 22 Oct 2015 13:57:25 +0700 Robert Elz <k...@munnari.oz.au> wrote:
> Date: Thu, 22 Oct 2015 07:52:06 +0200 > From: "Ian D. Leroux" <idler...@fastmail.fm> > Message-ID: <20151022075206.995f2caa63b153174b7f7...@fastmail.fm> > | How are tmpfs filesystems special in this regard? > > Well.... > > The problem is that it is permitted to swap onto files. If we did > away with that, there would be no problems to solve. > > [detailed and patient explanation of the interaction between tmpfs > filesystems and file-backed swap] Thanks! That helped a lot. > | That sounds to me like there are several possibly-unrelated > | shutdown hangs, > > Could be ... or it is also possible that the /dev problem and no space > message you're seeing are co-incidental. and while annoying, not > actually related to the hang you're seeing. Ok, so let's separate the issues. 1- With tmpfs-mounted /dev, /etc/rc.d/swap1 attempts to umount -f /dev before userland is finished at shutdown time. Whether or not this causes the hang and error message I see, this is clearly not a desirable outcome. I think we understand what the problem is, and there are workarounds for my case and most others I can think of, although it's not clear what the right general fix is. I'll file a PR for this, and further discussion can go there or in another thread. 2- The system will sometimes hang after printing a kernel error message of the general form "on /var: file system full", despite the fact that /var is not full and that the immediate trigger for the hang, at least in my case and apparently also in the case of Robert Swindells, is unmounting a tmpfs filesystem that has nothing to do with /var. To investigate the second issue we need a way of triggering the hang that is not as manifestly crazy as removing /dev, which seems to be the only way I've ever triggered it (Robert Swindells seems to have found another way, though it's not clear what). I'll try populating an on-disk /dev and then seeing if I still get a hang at shutdown. -- IDL