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I'm developing a kernel module. My env is centos 7.1 and I can find crash dump under the /var/crash folder.

But not every crash will generate a crash dump under the /var/crash folder, which makes me miserable to debug.

I do not know why sometimes a crash dump is generated but sometimes not. I do not have any related settings in my .bashrc. Could someone help with this?

Van Yu
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  • have you read https://www.kernel.org/doc/Documentation/kdump/kdump.txt ? – Marcus Müller Feb 24 '16 at 08:27
  • my kdump service is on by default and my boot cmdline contains crashkernel=128M, so I expect crash dump generated everytime. So I do not know why sometimes crash report is not generated. Is it due to the preserved memory size 128M is not enough? – Van Yu Feb 24 '16 at 09:11
  • could be; it's not that large usually, though. – Marcus Müller Feb 24 '16 at 09:15
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    Some crash situations don't allow kernel to do **anything useful**. Such situations could occure, e,g, if something bad occures while atomic context, or scheduler data have been corrupted. The kernel is just dead, so it cannot generate crash dump. – Tsyvarev Feb 24 '16 at 09:54
  • @Tsyvarev thanks. I try to increase crashkernel to 512M and it still has no crash dump generated. I think I've broken some important data as you said. – Van Yu Feb 24 '16 at 10:06

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