Re: [RFC][PATCH RT 6/6] vtime: Convert vtime_seqlock into raw_spinlock_t and seqcount combo

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 2013-07-10 at 13:12 -0400, Paul Gortmaker wrote:
> [[RFC][PATCH RT 6/6] vtime: Convert vtime_seqlock into raw_spinlock_t and seqcount combo] On 26/06/2013 (Wed 15:28) Steven Rostedt wrote:
> 
> > The vtime seqlock needs to be taken in true interrupt context on -rt.
> > The normal seqlocks are converted to mutexes when PREEMPT_RT_FULL is
> > enabled, which will break the vtime code as the calls are done from
> > interrupt context.
> > 
> > Convert the vtime seqlock into the raw_spinlock_t and seqcount combo
> > that can be done in interrupt context.
> 
> Alternatively, we could revive the raw seqlock patch from Thomas?
> 
> https://lkml.org/lkml/2010/2/17/238
> 
> Below is a version updating it to 3.8.x-RT.  One downside is that
> current mainline kernels have raw_seqcount_begin() function, which has
> nothing to do with preempt-rt, so the seqcount function namespace can
> get confusing unless we rename raw_seqcount_begin to something that
> doesn't sound RT-ish.

There's a reason that Thomas didn't bring that patch forward, but I
don't recall what it was.

Thomas?

-- Steve