[Ksummit-2012-discuss] [ATTEND] kernel core dump and "dying breath"

Tim Bird tim.bird at am.sony.com
Thu Jun 21 17:20:42 UTC 2012

On 06/21/2012 08:05 AM, Jason Wessel wrote:
> What I'd really like to have is a generic kernel interface to
> write this to the persistent storage for reclaim on the next boot,
> then I could do a capture and save of the output of the commands with
> in the kdb shell.  Of course there is no reason you cannot also use
> kdump etc..

I think the persistent RAM stuff that is in the process of being
migrated from Android's ram_console feature into ramoops and pstore
might be just what you are looking for.  This reserves a area of RAM
that can be read by the kernel after rebooting, and optionally adds
some error correction for bits which might flip over the reboot.
I believe the goal is to generalize this for use with other items
besides the log buffer.

Something besides oops handling is definitely needed, to capture
information from silent hangs (ones which are undetected by the kernel).
Something that preserves the log across a reboot (like ram_console)
is very nice.

For embedded, where the kernel loads into identical memory locations
every time, I've wondered if there couldn't be some trivial way
to preserve the log buffer position across the boot, and have each
boot append it's messages starting where the last one left off.
So a dmesg would show messages from the current and last (and
possibly even previous) boots.  It wouldn't be difficult to
find the start positions (to determine which messages go with
which invocations).

Put me down as interested in discussing this general topic
in August as well.
 -- Tim

Tim Bird
Architecture Group Chair, CE Workgroup of the Linux Foundation
Senior Staff Engineer, Sony Network Entertainment

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