Re: frequent lockups in 3.18rc4

From: Dave Jones
Date: Wed Nov 19 2014 - 10:39:13 EST

On Wed, Nov 19, 2014 at 10:03:33AM -0500, Vivek Goyal wrote:

> Not being able to capture the dump I can understand but having wedged
> the machine so that it does not reboot after dump failure sounds bad.
> So you could not get machine to boot even after a power cycle? Would
> you remember what was failing. I am curious to know what did kdump do
> to make machine unbootable.

Power cycling was fine, because then it booted into the non-kdump kernel.
The issue was when I caused that kernel to panic, it would just sit there
wedged, with no indication it even tried to switch to the kdump kernel.

> > > Unless there's some magic step missing from the documentation at
> > >
> > > then I'm not optimistic it'll be useful.
> I had a quick look at it and it basically looks fine. In fedora ideally
> it is just two steps process.
> - Reserve memory using crashkernel. Say crashkernel=160M
> - systemctl start kdump
> - Crash the system or wait for it to crash.
> So despite your bad experience in the past, I would encourage you to
> give it a try.

'the past' here, is two weeks ago, on Fedora 21.

But, since then, I've reinstalled that box with Fedora 20 because I didn't
trust gcc 4.9, and on f20 things are actually even worse.

Right now it doesn't even create the image correctly:

dracut: *** Stripping files done ***
dracut: *** Store current command line parameters ***
dracut: *** Creating image file ***
dracut: *** Creating image file done ***
kdumpctl: cat: write error: Broken pipe
kdumpctl: kexec: failed to load kdump kernel
kdumpctl: Starting kdump: [FAILED]

It works if I run a Fedora kernel, but not with a self-built one.
And there's zero information as to what I'm doing wrong.

I saw something similar on F21, got past it somehow a few weeks ago,
but I can't remember what I had to do. Unfortunatly that was still
fruitless as it didn't actually dump anything, leading to my frustration
with the state of kdump.

I'll try again when I put F21 back on that machine, but I'm
not particularly optimistic tbh.


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