Re: What do you use for kernel debugging?

On Sep 28, 2014, at 0:34, José Pérez Arauzo <fbl_at_aoek.com> wrote:

> Hello,
> I am trying to track down a (deadlock?) issue in CURRENT via DDB. The kernel does
> not complete hw probes on my Acer V5.
> 
> I get stuck on apic_isr looping which leads nowhere.
> 
> So I thought maybe things improve if I debug from another machine.
> 
> 
> What do you use for kernel debugging? According to the handbook kgdb over serial
> is a good option, do you agree? I'm on a netbook with no ethernet and no option
> for firewire: can I have a USB / nullmodem setup to work?
> 
> I have no old-style uarts hardware anymore, as the handbook suggests...
> 
> Any idea is welcome before I buy extra hw. I have a USB to serial showing up as
> /dev/cuaU0, do I need to grab another one and a nullmodem cable or there are better
> alternatives? Thank you.

There was some discussion recently about this on an internal list. Unfortunately no, there isn’t a usable way, but there were some interesting viable methods that came up (which haven’t been implemented): ethernet/sound/xHCI.

Your best bet, as others have noted, is to use boot -d, use WITNESS to spot locking issues, dtrace to isolate which section of code there are problems, and finally use one of the DEBUG options noted in /sys/conf/NOTES and /sys/<your-architecture>/conf/NOTES .

Hope that helps!
-Garrett