2012/5/14 Shuah Khan shuahkhan@gmail.com:
On Mon, 2012-05-14 at 08:58 -0700, Greg Kroah-Hartman wrote:
On Fri, May 11, 2012 at 05:15:06PM -0700, Anton Vorontsov wrote:
Hi all,
There are currently two competing debug facilities to store kernel messages in a persistent storage: a generic pstore and Google's persistent_ram. Not so long ago (https://lkml.org/lkml/2012/3/8/252), it was decided that we should fix this situation.
Recently ramoops has switched to pstore, which basically means that it became a RAM backend for the pstore framework.
persistent_ram+ram_console and ramoops+pstore have almost the same features, except:
- Ramoops doesn't support ECC. Having ECC is useful when a hardware
reset was used to bring the machine back to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat corrupt, but usually it is restorable.
- Pstore doesn't support logging kernel messages in run-time, it only
dumps dmesg when kernel oopses/panics. This makes pstore useless for debugging hangs caused by HW issues or improper use of HW (e.g. weird device inserted -> driver tried to write a reserved bits -> SoC hanged. In that case we don't get any messages in the pstore.
These patches solve the first issue, plus move things to their proper places. Patches that will fix the second issue are pending.
I've applied the first 7 patches, as they were localized to the drivers/staging/android/ directory, but in order for me to apply the rest, I need acks from the respective subsystem maintainers.
pstore developers, what do you say about these changes, are you ok with them?
Good to see this work get done. Anton beat me to it. :) I have been talking to pstore developers (Tony Luck) and ramoops maintainers (Kees Cook) about this re-architecture work since I first floated this idea on ce-android mailing list. I have been working on this rec-architecture focusing on the second feature "Pstore doesn't support logging kernel messages in run-time" and didn't get to ECC even though it is on my feature list to do bring ramconsole features into ramoops.
Anton! Is it safe to assume you are planning to cover the second feature as well, in which case I can drop my plans to get this work done.
-- Shuah
thanks,
greg k-h
My ack for ramoops patches. You can add my acked-by.
Marco