On Sat, Jun 7, 2014 at 9:15 PM, erik quanstrom <[email protected]> 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
