Panic: "Fatal trap 12: page fault while in kernel mode"

[Francois Tigeot]

On Sun, Jul 04, 2010 at 10:03:38AM -0700, Matthew Dillon wrote:
> :I have just been bitten by this panic on a 4 cores Xeon server running
> :DragonFly 2.6.3/i386.
> :It is usually lightly loaded and mainly used for mail services.
> :..
> :fault virtual address   = 0
> : stopped
> :Stopped at      devfs_getattr+0x1b:    movl    0(%edi),%edx
> :Francois Tigeot
> 
>     This line of assembly corresponds to the (dev = node->d_dev)
>     inside node_sync_dev_get() in vfs/devfs/devfs_vnops.c.  node
>     is NULL.
> 
> 	0xc04853f9 <devfs_getattr+27>:  mov    (%edi),%edx  (dev = node->d_dev)
> 					(but 'node' is NULL so it faults)
> 	0xc04853fb <devfs_getattr+29>:  test   %edx,%edx    test dev for NULL
> 
> 
>     It looks like the devfs node is getting ripped out from
>     under the vnode but unfortunately there isn't enough information
>     to figure out why that happened.

I have been able to reproduce the problem on a test machine.
The keyboard was still functional, but I could'nt get a coredump either:
call dumpsys did just print "0xdf4637cc" and I was stuck in the debugguer.

-- 
Francois Tigeot