On Wed, Dec 14, 2016 at 02:10:48PM -0800, Mark Johnston wrote:
> On Wed, Dec 14, 2016 at 12:14:16PM -0800, Mark Johnston wrote:
> > On Wed, Dec 14, 2016 at 11:49:26AM -0800, Steven G. Kargl wrote:
> > > Well, after 3 days of bisection, I finally found the commit
> > > that renders my system unbootable. The system does not panic.
> > > It simply gets stuck in some state. Nonfunctional keyboard,
> > > so can't break into debugger. No serial console available.
> > > The verbose dmesg.boot for a working kernel from revision
> > > 309656 is at
> > >
> > > http://troutmask.apl.washington.edu/~kargl/freebsd/dmesg.309656.txt
> > >
> > > The kernel config file is at
> > >
> > > http://troutmask.apl.washington.edu/~kargl/freebsd/SPEW.txt
> > >
> > > In looking at /usr/src/UPDATING, there is no warning that one
> > > can create a boat anchor by upgrading to 309657. If compiling
> > > a kernel with 'options DDB' is no longer supported, this should
> > > be stated in UPDATING. Or, UPDATING should state that 'options
> > > DDB' requires 'options STACK'. Or, 'options DDB' should simply
> > > to the right thing and pull in whatever 'option STACK' does.
> > It is supported though - the point of that change was to fix a problem
> > that occurred when DDB is configured but STACK isn't. While testing I
> > tried every combination of the two options, and I just tried and
> > successfully booted a kernel with DDB and !STACK.
> > Does the kernel boot successfully if STACK is added to your
> > configuration?
> I tried your config (plus virtio drivers) and was able to reproduce the
> hang in bhyve. Adding STACK "fixed" the hang, as did reverting part of
> my change to re-add dead code into the kernel. My VM was always hanging
> after printing
> 000.000050 [ 426] vtnet_netmap_attach virtio attached txq=1, txd=1024
> rxq=1, rxd=1024
> Sure enough, removing "device netmap" from your config also fixes the
> hang. When the hang occurs, I can see with "bhyvectl --get-rip" that
> we're stuck in DELAY(), but I can't get a stack at that point. I think
> my change is an innocent bystander - it just happened to expose a latent
> issue elsewhere.
> I don't have much more time to look at this right now, but I'll look
> into it more tonight.
Yes, adding STACK got me to a booting kernel. I can't remember
why I added netmap to my config file. Re-adding dead code seems to
point to some memory corruption issue or a rogue pointer. :(
BTW, I think it would be prudent to add something like
At revision 309657, 'options STACK' was introduced into
sys/x86/x86/mstack_machdep.c. Old kernel configuration files
that included 'options DDB' are now required to include also
to UPDATING or some such wording. I was jumping from circ Oct 10th world
to top of tree, and got caught by ~3000 commits.
Oh, and thanks for the work you've done on FreeBSD.
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