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SubjectDumping kernel log (dmesg) and backtraces after a panic
We're using Red Hat EL3 Linux (2.4.21 base kernel plus 300 or so Red 
Hat and/or community patches) and I'm dearly missing KDB already, since
we previously used 2.4.21 from and applied the appropriate
KDB patch(es). Now with EL3, I'm not even sure what the right patch for
KDB would be.

The problem is how to debug a hang or panic without KDB. Specifically,
I'd like to dump out real backtraces of all (or selected) processes
instead of the pseudo-backtraces that the panic or Alt-Sysrq-t
provides, and I'd like to dump out the kernel log buffer (dmesg) after
a hang or panic.

When I say "pseudo-backtraces", it seems that the oops/sysrq processing
picks everything that looks like a text address from the stack of each
thread (or the thread that caused the panic) and formats it, rather
than walking the stack back correctly like KDB's 'bt' command does. And
I don't know of any way of getting the 'dmesg' output after a
hang/panic other than by using KDB.

To put it simply, is there either an alternative to KDB that works with
RH EL3 and provides what I need (bt and dmesg, or just dmesg), or is
there a version of KDB that would work with EL3 already?


Chris Johns

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