Re: PROBLEM: 3.0-rc kernels unbootable since -rc3

Paul E. McKenney
2011-07-10T21:47:04Z

On Sun, Jul 10, 2011 at 09:30:58PM +0100, julie Sullivan wrote:
> > But maybe not that much thought.  My current guess is that your
> > configuration is somehow causing some RCU callbacks to be executed
> > during early boot, and that these callbacks are attempting to use kernel
> > features that are not yet initialized.  If my guess is correct, then
> > the reason that enabling RCU_BOOST makes things work is that it prevents
> > RCU callbacks from executing until after the scheduler is up and running.
> >
> > So I added another commit to the jms.2011.07.07a branch in the -rcu
> > git tree.  If my guesses are correct, this will allow your system to
> > boot, possibly emitting a warning on the way up.  When you get a chance
> > to try this out, please let me know how it goes.
> >
> >                                                        Thanx, Paul
>
> Fantastic, now we boot perfectly!
> I also tried the same treatment on v3.0-rc5 and -rc6 (i.e. revert
> f8b7fc6b514f34a51875 and a46e0899eec7a3069bcad then add those
> 8 commits from the jms.2011.07.07a branch) with the same success.
>
> Thanks for giving me back 3.0-rc4, -rc5 and -rc6!

Very cool! Thank you very much for the testing -- I will put together an
upstreamable commit with your Tested-by.

Thanx, Paul