savecore: first and last dump headers disagree

[Dan Nelson]

In the last episode (May 23), Palle Girgensohn said:
> We have an amd64 system that still experiences crashes after
> installing 5.4, mostly during high loads. (It's been unstable all the
> time, really; see previous posts.)
> 
> I've added dumpdev="/dev/amrd0s2b", and some time ago I did get coredumps, 
> but with latest versions of the kernel, savecore does not give me a dump, 
> instead it says:
> 
> savecore: first and last dump headers disagree on /dev/amrd0s2b
> savecore: unsaved dumps found but not saved

"savecore -vv" should print enough of both headers to let you see
what's different.

> Fatal trap 12: page fault while in kernel mode
> cpuid = 0: apic id = 00
> fault virtual address    = 0x00
> ...
> trap number              = 12
> panic: page fault
> cpuid = 0
> boot() called on cpu#0
> Uptime: 1d23h50m36s
> Dumping 2047 MB
> 16 32
> --------
> The cursor sits at the position after "32".

That's probably why your headers disagree :)  If you put "options
KDB_TRACE" in your kernel config file, it will print a small stack
trace before trying to dump, which might be enough to track down the
cause of the panic even without a dump.


-- 
	Dan Nelson
	dnelson at allantgroup.com