[Ce-android-mainline] [PATCH 04/10] android: ram_console: split out persistent ram
john stultz
johnstul at us.ibm.com
Tue Feb 21 00:47:01 UTC 2012
On Mon, 2012-02-20 at 14:45 -0800, Colin Cross wrote:
> On Mon, Feb 20, 2012 at 2:24 PM, john stultz <johnstul at us.ibm.com> wrote:
> > On Sun, 2012-02-19 at 16:44 -0800, Colin Cross wrote:
> >> Split ram_console into two halves.
> >>
> >> persistent_ram is a set of apis that handle a block of memory
> >> that does not get erased across a reboot. It provides functions
> >> to fill it as a single buffer or a ring buffer, and to extract
> >> the old data after a reboot. It handles ecc on the data to
> >> correct bit errors introduced during reboot.
> >>
> >> ram_console is now a small wrapper around persistent_ram that
> >> feeds console data into the ringbuffer, and exports the old
> >> data to /proc/last_kmsg after a reboot.
> >
> > This looks very cool (esp the ftrace bit), although have you looked at
> > all into the pstore work to see how it might be able to be integrated?
> >
> > Kees (cc'ed) has apparently been working to get the ramoops driver
> > (which writes oops and panic messages to a similar in-ram circular
> > buffer) working with pstore and there seems like there is some overlap
> > here.
> >
> > I'm not saying this should block this code going into staging, but just
> > wanted to know if you had looked into the similar works and if so, could
> > articulate why they couldn't be reused (so others can try to help
> > integrate things if necessary).
> >
> > thanks
> > -john
> >
> >
>
> pstore is just an interface to write to a persistent storage, with a
> tiny driver on it to dump console messages after a panic. With the
> number of crashes we see on ARM cpus that are not panics (mostly
> watchdog resets), logging only after a panic is not appropriate, so it
> can't replace ramconsole. persistent_ram could easily be a pstore
> driver, but that would not give any new useful functionality, since
> ramconsole is better for us than pstore_dump.
>
> Looking at ramoops, it is exactly the same as pstore on ioremapped
> ram, but was originally implemented separately. I see patches now
> that convert it to a pstore backend, which leaves us in the same state
> as above - only logging panics.
Thanks for filling me in here, of course, looking at the
cd-android-mainline list from Jan, I see this was already discussed in
detail, so my apologies for re-asking.
That said, it might be good to provide a similar summary with the
patchset when sending to lkml.
thanks
-john
More information about the Ce-android-mainline
mailing list