netdev - random crashes, kdump and so on

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Message-ID: <1edc4c5c-2732-8afc-3d6c-961ae9503edb@thelounge.net>
Date:   Mon, 25 Mar 2019 12:48:37 +0100
From:   Reindl Harald <h.reindl@...lounge.net>
To:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: random crashes, kdump and so on

besides that i get tired about random crashes over the last months (yeah
the connlimit crashes are fixed in the meantime but there is still
something broken) which are pretty sure in the netedev/netfilter area
and "kernel.panic = 1" is not a persistent solution

what in the world makes kdump on a VM with 2.5 GB RAM dump out 5.4GB and
why do you need a handful reboots to get rid of "Can't find kernel text
map area from kcore" when try to start the kdump service?

why can't the kernel just write out what it normally prints on the
screen to a fixed device like /dev/sdc without that whole dance, no
filesystem needed, just write it out like d and reboot

sdc is stable on a VM and the terminal output has cutted every relevant
information when you wait for HA of the hypervisor make a screenshot
before hard reset instead the automatic reboot from the guest

can we please get Linux as stable as it was or better to debug in
production so that one can submit useful infos in bugreports?

[root@...alhost:/var/crash/127.0.0.1-2019-03-25-10:34:04]$  ls
total 5.4G
drwxr-xr-x 2 root root 4.0K 2019-03-25 10:35 .
drwxr-xr-x 3 root root 4.0K 2019-03-25 10:34 ..
-rw------- 1 root root    0 2019-03-25 10:35 vmcore-incomplete
-rw-r--r-- 1 root root 5.4G 2019-03-25 10:35 vmcore-dmesg-incomplete.txt

[root@...alhost:/var/crash/127.0.0.1-2019-03-25-10:34:04]$  df
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/sdb1      ext4  5.8G  5.8G     0 100% /
/dev/sda1      ext4  485M   51M  431M  11% /boot

this seems to be still an issue
http://lkml.iu.edu/hypermail/linux/kernel/1310.2/01470.html

[root@...alhost:~]$  systemctl status kdump
● kdump.service - Crash recovery kernel arming
   Loaded: loaded (/etc/systemd/system/kdump.service; disabled; vendor
preset: disabled)
   Active: failed (Result: exit-code) since Mon 2019-03-25 12:33:07 CET;
5s ago
  Process: 25021 ExecStart=/usr/bin/kdumpctl start (code=exited,
status=1/FAILURE)
 Main PID: 25021 (code=exited, status=1/FAILURE)

Mar 25 12:33:05 localhost dracut[26225]: No dracut internal kernel
commandline stored in the initramfs
Mar 25 12:33:05 localhost dracut[26225]: *** Creating image file
'/boot/initramfs-4.20.17-100.fc28.x86_64kdump.img' ***
Mar 25 12:33:07 localhost dracut[26225]: *** Creating initramfs image
file '/boot/initramfs-4.20.17-100.fc28.x86_64kdump.img' done ***
Mar 25 12:33:07 localhost kdumpctl[25021]: Can't find kernel text map
area from kcore
Mar 25 12:33:07 localhost kdumpctl[25021]: Cannot load
/boot/vmlinuz-4.20.17-100.fc28.x86_64
Mar 25 12:33:07 localhost kdumpctl[25021]: kexec: failed to load kdump
kernel
Mar 25 12:33:07 localhost kdumpctl[25021]: Starting kdump: [FAILED]
Mar 25 12:33:07 localhost systemd[1]: kdump.service: Main process
exited, code=exited, status=1/FAILURE
Mar 25 12:33:07 localhost systemd[1]: kdump.service: Failed with result
'exit-code'.
Mar 25 12:33:07 localhost systemd[1]: Failed to start Crash recovery
kernel arming.