Re: 7.0 CURRENT kernel's ath driver causes page fault, kernel panic (debugging kernel)

On Fri, Jul 18, 2008 at 6:36 AM, Garrett Cooper <yanefbsd@xxxxxxxxx> wrote:
Some notes:

1. *blinks*... I hope you mean 8-CURRENT, not 7-CURRENT. 7 hasn't been
CURRENT for some months now (~6 months IIRC).

Oh my, I am an idiot. I'm using 7-STABLE, making this the wrong list
to ask; sorry. I guess I could repost to freebsd-stable in addition
to filing a PR. Would that be wise?

2. pciconf -lv might help with the PCI ID info. Then someone might be
able to tie your card back to the appropriate chipset.

This gives me:
ath0@pci0:3:0:0: class=0x020000 card=0x058a1014 chip=0x1014168c
rev=0x01 hdr=0x00
vendor = 'Atheros Communications Inc.'
device = 'AR5212 Atheros AR5212 802.11abg wireless'
class = network
subclass = ethernet
class = base peripheral

I get 167 pages on google that contain ar5212 and 0x1014168c and
0x058a1014. I only get one with ar5006ex instead of ar5212. I'm
inclined to believe my Lenovo representative was wrong; she's just a
sales rep and asked around about the part...

3. KDB, DDB, WITNESS and INVARIANTS support compiled into the kernel
would be extremely helpful, if not required to debug your issue.

I'm currently recompiling the kernel with these debug options:

makeoptions DEBUG=-g # Build kernel with gdb(1) debug symbols
options KDB
options DDB
options INVARIANTS
options WITNESS

As soon as it's done compiling, I'll try reproducing the error. I've
added "set dumpdev="/var/crash" in /etc/rc.conf.

As for the actual debug process, there's a spot in the dev handbook
about it (http://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug.html),
but when I tried debugging my issue with NTFS and SMB I didn't really
find it helpful to be honest...

Once I have a core dump, how should I proceed? Use kdb, and execute
"list *[instruction pointer]" to find out what (NULL) pointer is being
dereferenced? Run backtrace? If I post a PR, is it likely that
someone can guide me through this? I'm fairly familiar with C, but my
experience using debuggers is very limited...

You may also have to compile without SMP and with the 4BSD scheduler
just to see whether or not it's an issue reproducible with the ULE
scheduler, the driver, or something else...

After I get the dump with the current options (+ debug options), I'll
try w/o SMP and ULE...

Hopefully this gets you started on the right path...
-Garrett

Thanks so much, Garrett!
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