debugging kernel threads

Richard Nyberg rnyberg at
Wed Jan 26 11:01:26 PST 2005

At Wed, 26 Jan 2005 10:04:41 -0800 (PST),
Matthew Dillon wrote:
> :At Wed, 26 Jan 2005 10:52:45 +0100,
> :Richard Nyberg wrote:
> :> 
> :> I often use gdb's proc command to switch between different processes
> :> when debugging kernel cores. Now I want to debug a kernel thread
> :> and it doesn't seem to work. Does anyone know how to switch to a
> :> kernel thread? Maybe proc could be tweaked to work for threads too.
> :>
> :Replying to myself...
> : 
> :I RTFS and it looked like proc should work with kernel threads.
> :The problem seems to be that the threads td_pcb is invalid.
> :
> :Example:
>     Theoretically you can give the 'proc' command a thread address (not a
>     proc address, a thread address) and it should switch to it.
>     But Joerg's recent upgrades of gdb seem to have broken some things
>     that had been working before.
>     Pure kernel threads do not have PCBs in the conventional sense.  The
>     thread state is pushed onto the stack for the switch/restore instead.
>     Most of the pcb structure will be unused for a kernel thread.
Well, from looking at the code, it seems to me that gdb tries to use
the pcb in both cases (threads or processes). I'd be very grateful
if this could be fixed. :)


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