Re: [ANNOUNCE] 3.12.6-rt9

From: Nicholas Mc Guire
Date: Fri Dec 27 2013 - 15:00:31 EST

On Mon, 23 Dec 2013, Sebastian Andrzej Siewior wrote:

> Dear RT folks!
> I'm pleased to announce the v3.12.6-rt9 patch set.
> Changes since v3.12.6-rt8
> - A patch from Thomas Gleixner not to raise the timer softirq
> unconditionally (only if a timer is pending)

This one seems to deadlock early in the boot sequence on x86
(i3/i7/Phenom-4x here and Carsten Emde also had boot failures)

after droping this patch with:
patch -p1 -R < ../paches/timers-do-not-raise-softirq-unconditionally.patch
3.12.6-rt9 boots up fine. cyclictest seems to be back to what it was before
(only ran for a few minutes idle and 1h with load on an i3).

The main problem with this patch though are proceduaral isues
the commit note - which is a mail exchange - actually does not explain what
the rational for the changes is (...well I don't understand the logic of
run_local_timers - if someone can explain - pleas do) and notably:

from timers-do-not-raise-softirq-unconditionally.patch
well, that very same problem is in mainline if you add "threadirqs" to
the command line. But we can be smart about this. The untested patch
below should address that issue. If that works on mainline we can
adapt it for RT (needs a trylock(&base->lock) there).

does make me wonder why this went into -rt9 ?
It also build fails with CONFIG_PREEMPT_RT_FULL not set.

as with this patch, systems that booted just fine with 3.12.5-rt7 don't
even boot (atleast my 3 x86 test boxes here did not) this raises some
questions regarding the process of getting patches into -rtX - are
we going to fast here ?

I would prefere if such patches would go out with a request for testing
or atleast a "might blow up your system" note in them...

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