Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write()

Steven Rostedt
2011-09-20T15:17:57Z

On Tue, 2011-09-20 at 09:58 -0500, Christoph Lameter wrote:
> On Tue, 20 Sep 2011, Thomas Gleixner wrote:
>
> > > What's the latency hit on those very few locations if we simply put our
> > > collective foot down and not support a preemptable version of this_cpu_*()?
> > > "Yes, you *could* preempt here, but for our collective sanity that's not
> > > supported"...
> >
> > Full ack.
>
> Latency hit could be very significant in various critical kernel paths.
> Especially network subsystem, vm event counters etc.

Latency hit is better than incorrect behavior. I tell people working on
-rt all the time. A bug/kernel crash is much worse than a hit in
latency, as a bug/kernel crash causes a much bigger latency hit than
anything else.

-- Steve