Re: random lockups (now suspecting zfs)

[Simon Burge <simonb%NetBSD.org@localhost>]

Hi Greg,

Greg Troxel wrote:

>  Fri, Oct 20, 2023 at 01:11:15PM -0400, Greg Troxel wrote:
>> A different machine has locked up, running recent netbsd-10.  I was
>> doing pkgsrc rebuilds in zfs, in a dom0 with 4G of RAM, with 8G total
>> physical.  It has a private patch to reduce the amount of memory used
>> for ARC, which has been working well.

Are you still seeing the problem below even with limiting the amount of
memory ARC can use?

> >> All 3 tmux windows show something like
> >> 
> >>   [ 373598.5266510] load: 0.00  cmd: bash 21965 [flt_noram5] 0.37u 2.89s 0% 6396k
> >> 
> >> and I can switch among them and ^T, but trying to run top is stuck (in
> >> flt_noram5).  I'll give it an hour or so, and have a look at the
> >> console.

I've seen cc1plus processes wedged in either flt_noram or tstile after
doing multiple builds, and a reboot is the only way out.  I'm using ZFS
for everything except swap and some mostly-unused media files that live
on an FFS.

> So to me this feels like a locking botch in a rare path in zfs.

This appears to be the case.  Chuck Silvers has some understanding of
the problem and I'm helping test, but at this stage there isn't a fix
available. :/

Cheers,
Simon.