Re: [9fans] installs which hang

[Ramakrishnan Muthukrishnan <vu3rdd@gmail.com>]

On Sat, Jun 7, 2014 at 9:15 PM, erik quanstrom <quanstro@quanstro.net> wrote:
> i don't think this has been mentioned in a while, so i wanted
> to quickly jot down a few tricks for looking at a "hung" machine.
>
> there are three main things that can hang things up on initial boot
> that aren't related to the kernel misbehaving
> - unclean shutdown forcing a fs check.  this can take 15-20 minutes on a
> big drive, or slow vm disk.
> - dhcp (should be limited to 5-10 minutes on sources, and ~30s on atom)
> - timesync.  i saw this issue one in 2008, so i don't remember much about it.
> - interrupts incorrectly mapped.  (even acpi can get it wrong.)
>
> if you can hit enter on the console, and have it recognized, you can
> have some confidence that interrupts are working.
>
> if you can type ^T^Tp and get a process listing, that's even better.
> you may (especially if you have a serial console) be able to figure out who
> is misbehaving.
>
> if you can type ^T^Tq and get the scheduler dump that might tell you
> if you have a lot of runnable processes.
>
> if you can type ^T^Ti and get the interrupt dump, that might tell you
> if a some hardware isn't interrupting.
>
> if your machine isn't making it this far, there isn't too much that can be
> easily done, unless you can pxe boot.  i usually put prints in the boot to
> see where things are going wrong.  i had the pleasure of doing that yesterday
> putting new locks in the pae kernel.  (i really need to use charles' GS:
> extern register trick to avoid this MACHP nonsense.)

Thank you. This is very useful.

With the 9atom install on virtualbox which hangs at init: starting
/bin/rc, I can see the process listing with ^T^Tp. The scheduler
listing just show "nrdy 0". ^T^Ti does not show anything. Keyboard is
active.

--
  Ramakrishnan