[LITMUS^RT] Extracting TRACE logs from crashed system

[Joshua Bakita]

Hello all,

I've been implementing the EDF-SC scheduler (Hobbs, Tong, Anderson RTNS
2019) in LITMUS^RT, and occasionally run into kernel panics that prevent
pending I/O from being flushed to the serial console. The system under test
is in a QEMU VM, so gdb can easily be attached and the lx-dmesg command can
be used to get the kernel log messages. However, this obviously doesn't
include pending TRACE messages.

Is anyone aware of a way to get at the pending TRACE message buffer from
gdb? It seems like you could read the trace buffer off the ftdev_minor
struct easily enough in gdb, but I can't figure out a way to get a handle
to that without trying to parse through the VFS state in gdb.

If anyone can help me figure this out, I'd be happy to contribute the
result back up to LITMUS^RT as a new helper script for gdb. I can also
provide the core dump if someone else would like to take a look at it.

Best,

Joshua Bakita
PhD Student - UNC Chapel Hill
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