Re: [RFC PATCH 0/6] RCU: Preemptible-RCU

From: Paul E. McKenney
Date: Thu Dec 13 2007 - 18:42:21 EST


On Thu, Dec 13, 2007 at 09:38:04PM +0100, Ingo Molnar wrote:
>
> * Gautham R Shenoy <ego@xxxxxxxxxx> wrote:
>
> > Hello everyone,
> >
> > This patchset is an updated version of the preemptible RCU patchset
> > that Paul McKenney had posted it in September earlier this year that
> > can be found here --> http://lkml.org/lkml/2007/9/10/213
> >
> > This patchset incorporates the review comments from Oleg Nesterov and
> > Steven Rostedt.
> >
> > The testing report of the patchset is as follows:
> > ====================================================================
> > Patch-stack: 2.6.23-rc3 + cpu-hotplug patches from
> > http://lkml.org/lkml/2007/11/15/239 + Preempt-RCU
> > patches.
> > Test: RCU-Torture running parallelly with CPU-Hotplug
> > operations.
> > Duration: 24 hours.
> > Architectures: x86,x86_64, ppc64.
> > ====================================================================
> >
> >
> > Currently it is based against the latest linux-2.6-sched-devel.git
> >
> > Awaiting your feedback!
>
> thanks Gautham, the patchset from you and Paul looks good to me and i've
> applied it to sched-devel.git to get it tested and reviewed some more.
>
> from the Nitpicking Police, there are a couple of minor style
> problems/warnings with the code, you can see it via:
>
> scripts/checkpatch.pl --file kernel/rcu*.c
>
> nothing serious - RCU is still one of the cleanest subsystems in the
> kernel:
>
> errors lines of code errors/KLOC
> kernel/rcuclassic.c 0 575 0
> kernel/rcupdate.c 1 138 7.2

This one is the exception to checkpatch.pl's rule against "volatile". ;-)

The volatile declaration is within the ACCESS_ONCE() macro that is used
within rcu_read_lock() and rcu_read_unlock() to force the compiler to
maintain ordering with respect to interrupt handler running only on that
same CPU.

> kernel/rcupreempt.c 0 953 0
> kernel/rcupreempt_trace.c 0 330 0
> kernel/rcutorture.c 8 995 8.0

Hmmm... Definitely some old whitespace issues here...

> the eventual goal would be to match:
>
> scripts/checkpatch.pl --file kernel/sched*.[ch]
>
> output ;-)

We should be able to make some progress in that direction. ;-)

Thanx, Paul
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