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Old 01-05-2009, 11:55 PM   #1
rakuenso
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Registered: Jan 2009
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kexec crash kernel oddity/insanity


I've been getting this horribly annoying kernel panic in X recently, so I decided to use kdump/kexec to try and get at my vmcore.

I've set up kexec as per the instructions in /Documentation/kdump/kdump.txt

I've enabled sysrq in both the kernel, AND, in the /etc/sysctl.conf

The system responds to sysrq-C when I'm in the console and before startx, which properly loads the dump kernel and I can get access to my /proc/vmcore

However, when I'm in X (after startx), sysrq-c does NOT load up the crash kernel, and INSTEAD responds by hanging my system (NO blinking capslock though).

I'm on a Intel Core 2 Duo, 64-bit, 2GB of memory, NVIDIA QUADRO FX 570M, and note that my CONFIG_PHYSICAL_START is 0x200000, NOT 0x100000, (I wasn't sure if this should be changed as the default was 0x200000). But this shouldn't matter because the kernel is RELOCATABLE(=y)

I've attached my:

.config : http://dpaste.com/105844/
lspci : http://dpaste.com/105846/
lsmod : http://dpaste.com/105848/
dmesg : http://dpaste.com/105849/
grub.conf : http://dpaste.com/105850/

my kexec command is "sudo kexec -p /usr/src/linux-2.6.28-gentoo/arch/x86/boot/bzImage --append=root=/dev/sda3 1 irqpoll maxcpus=1 reset_devices"


Please help.
 
Old 08-10-2009, 10:42 AM   #2
chandan_raka
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Registered: Apr 2005
Location: BC
Distribution: Centos
Posts: 34

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kexec vmcore

Hi,

Are you still facing the same issue? I also faced similar issue but working around with the values of crashkernel=x@y solved my issue.

Now I am facing issues in reading the /proc/vmcore ... /dev/oldmem.
Can you please share how to read the memory using /proc/vmcore interface?

or any application program?

Like if I want to read a perticual page fram number etc.

Moreover, if you have any idea regarding reading data to 32 bit user space from 64 bit kernel space.
 
Old 08-12-2009, 11:35 AM   #3
investmentbnker75
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Registered: Oct 2007
Location: Eastern Seaboard
Distribution: CentOS
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Chandan,

How did you resolve the issues with the crashkernel setting? I am currently having an issue with that myself but havent been able to resolve them. I have set crashkernel=128M@64M in my grub.conf file but kdump still complains it hasnt been set when restarting kdump.
 
Old 08-12-2009, 11:53 AM   #4
chandan_raka
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Registered: Apr 2005
Location: BC
Distribution: Centos
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hi,

Please make sure that you have set kexec in your .config file.

CONFIG_KEXEC=y
CONFIG_CRASH_DUMP=y
CONFIG_PHYSICAL_START=0x200000
CONFIG_RELOCATABLE=y
CONFIG_PHYSICAL_ALIGN=0x200000

and then remember to pass crashkernl=Y@X into your primary kernel. Moreover, please check the .config file of the kdum in /etc.

Currently I am facing issues with generating the /proc/vmcore file. Its getting generated but of zero size. and working on it.

Hope it helps.

Dhanyawad
 
  


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