Re: I can't generate a kernel crash core.

[Jose Luis Rodriguez Garcia <joseyluis%gmail.com@localhost>]

I have been debuging this problem with gdb and printfs in the source
for locate the path.

I have found it fails in:

arch/amd64/amd64/machdep.c:dodumpsys does: psize = bdev_size(dumpdev);
kern/subr_devsw.c:bdev_size calls rv = (*d->d_psize)(dev)
In my case the dev has major 0 and minor 1
(gdb) print bdevsw[0].d_psize
$1 = (int (*)(dev_t)) 0xffffffff80a0ad60 <wdsize>

then d->d_psize is the function wdsize

dev/ata/wd.c:wdsize does wd = device_lookup_private(&wd_cd, WDUNIT(dev));
kern/subr_autoconf.c:device_lookup_private does  return
device_private(device_lookup(cd, unit));
kern/subr_autoconf.c:device_lookup fails and returns NULL. This is in
the sentence:


else if ((dv = cd->cd_devs[unit]) != NULL && dv->dv_del_gen != 0)
 dv = NULL;

config_alldevs_unlock(s);

 return dv;

because cd->cd_devs[unit]) is null.

I have checked these values with printf in the function and these are
(executing a reboot -d):
unit: 0
cd->cd_ndevs: 4
dv is assigned NULL in the asignement: dv = cd->cd_devs[unit])

If I check these values when the system is running cd->cd_devs[unit] isn't NULL.
(gdb) print wd_cd->cd_devs[0]
$23 = (device_t) 0xfffffe8107cc6408
(gdb) print (*wd_cd->cd_devs[0]).dv_del_gen
$24 = 0

It seems that in the ordered shutdow process this structure
(cd->cd_devs[unit] is destroyed, and the dump fails.



This is the log from dmesg. It says "dump area unavailable"
(file src/sys/arch/amd64/amd64/machdep.c line 1156)
.....
wd0: detached
atabus0: detached

dumping to dev 0,1 (offset=8410383, size=1046094):
dump area unavailable
rebooting...

The swap device configuration seems ok:
pc2$ swapctl -z
dump device is wd0b


On Sun, Jan 24, 2016 at 11:00 PM, Jose Luis Rodriguez Garcia
<joseyluis%gmail.com@localhost> wrote:
> If the kernel hash a panic, the dump is captured, etc. and it works ok
> (kern.dump_on_panic=1).
>
> I can't generate a crash dump of a running system.
>
>
> On Sun, Jan 24, 2016 at 10:28 PM, Jose Luis Rodriguez Garcia
> <joseyluis%gmail.com@localhost> wrote:
>> It is NetBSD 7.0 amd64
>>
>> The swap size is 8 GB, and the memory of the PC is 4GB.
>>