problem with function_graph self-test?

[Jake Edge <jake@lwn.net>]

Hi Steve,

This has taken me a bit to track down ... I built a kernel from Linus's
git tree (as of this morning: commit
03347e2592078a90df818670fddf97a33eec70fb) and when i boot it, it locks
up hard giving me a cursor in the upper left (which seems to grow then
shrink once, if that tells anyone anything) and no other output ... i
started messing with kernel params (turning off quiet, rhgb, adding
boot_delay and, eventually figuring out i needed lpj as well) to try
and extract some info ... it seems to reliably fail in the
function_graph tracer self-test with a variety of messages (I
unfortunately don't have a serial console on the laptop that I am
using) ... two of the messages that I got (possibly from different
boots):

BUG: unable to handle kernel NULL pointer dereference at 00000048
BUG: Function graph tracer hang!

I can try and get more information, but I wanted to check first if you
already know about this ... somehow i'll either need to type faster :)
or reliably slow it down and take pictures, which I can do if you'd
like ...

obviously, for my purposes, i can turn off the selftests and/or the
function_graph tracer ...

jake

-- 
Jake Edge - LWN - jake@lwn.net - http://lwn.net