On Fri, Jun 22, 2007 at 04:58:37PM +0200, Edgar Fuß wrote:
> > gdb netbsd.gdb
> > (gdb) info line *(dqget+0x118)
> > Line 729 of "/var/tmp/src-4.0beta2/sys/ufs/ufs/ufs_quota.c"
> >    starts at address 0xffffffff8028e4df <dqget+255>
> >    and ends at 0xffffffff8028e4fb <dqget+283>.
> 
> After spending several hours trying to find out what might go wrong in that
> TAILQ_REMOVE, I disassembled dqget and it looks like gdb lied about the
> line number.
> 
> The problem seems in fact to be the
> *dqp = dq;
> two lines below but how can dqp be NULL?
> 

Just built GENERIC.MP from my NetBSD4 tree and it looks like Line 729
is right and the error comes from TAILQ_REMOVE when it assigns
*(elm)->field.tqe_prev = (elm)->field.tqe_next.

? rdx = (elm)->field.tqe_next
? (elm)->field.tqe_next->field.tqe_prev = (elm)->field.tqe_prev;

  dqget+0x10c 8037bc2c   48 8b 43 18             mov    0x18(%rbx),%rax
  dqget+0x110 8037bc30   48 89 42 18             mov    %rax,0x18(%rdx)

? *(elm)->field.tqe_prev = (elm)->field.tqe_next;

  dqget+0x114 8037bc34   48 8b 43 18             mov    0x18(%rbx),%rax
  dqget+0x118 8037bc38   48 89 10                mov    %rdx,(%rax)

  dqget+0x11b 8037bc3b   48 89 df                mov    %rbx,%rdi
  dqget+0x11e 8037bc3e   e8 2d fc ff ff          callq  8037b870 <dqref>

It could help to enable queue debugging with `options QUEUEDEBUG'.

-- 
Juergen Hannken-Illjes - hannken@eis.cs.tu-bs.de - TU Braunschweig (Germany)