Re: kernel panics with uvideo, savecores and coredumps

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Christoph Egger wrote:
> Hi,
> 
> I can reproduce kernel panics when two
> programs (mplayer and ekiga) *simultanously*
> try to access my webcam.
> 
> 
> In ddb I do "call dumpsys" or "sync" and reboot
> blindly (I'm in X when the panic happens).
> 
> On reboot, savecore prints things like
> 
> panic: kmem_poison_check  x != y  (where x and y are numbers)
> 
> or
> 
> panic: extent_alloc_subregion: bad size
> 
> To debug a crash dump I following the instructions from:
> http://www.netbsd.org/docs/kernel/#debugging_a_kernel_crash_dump
> 
> But I always get backtraces from ddb instead the one from the panic.
> 
> Using ps ax -M netbsd.x.core results in a segfault
> in kvm_getproc2() in libkvm.

The crash happens in lib/libkvm/kvm_proc.c , line 566:

kp2p->p_forw = kl[0].l_forw;

The kl pointer is NULL. kvm_getlwps() in line 560
returns NULL and there's no NULL-pointer check.
nlwps passed to kvm_getlwps() is 1.


Christoph