Re: kdump with /proc/oldproc

[WANG Cong <xiyou.wangcong@gmail.com>]

On Tue, 17 May 2011 12:30:58 -0500, Nathan D Miller wrote:

> Hello-
> 
> Has anyone tried reconstituting a portion of the old kernel's /proc
> while in the capture kernel?
> 
> I had the idea while digging through the kexec/kdump code and it seemed
> intriguing.
> 
> It might be a means by which user-space dump applications running under
> the capture kernel could interrogate the old system, and identify bad
> processes that instigated the panic.  In particular, I'm thinking of Out
> Of Memory scenarios.   We've modified our kernel to panic instead of
> invoking the kernel's OOM killer, but we still have the problem of
> identifying the "bad" process while running in the capture kernel.
> 
> Perhaps everything could be accomplished using some sort of FUSE
> file-system around /proc/oldmem and /proc/vmcore.  Not all the
> proc/<pid>/ files would need to be implemented, of course.  In addition,
> each old process could have its own 'vmcore' file for getting a core
> dump of the original process.
> 

Well, actually you don't need to bother the old /proc
to find which process is the killer. The old dmesg contains
the PID/comm of the killer process, and we have a tool named
vmcore-dmesg to read out the dmesg from the vmcore.

With the utility 'crash', you can query any info of any process
in the old kernel, so why do you need a per-process vmcore anyway?

Thanks.


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