Re: [PATCH tip/core/rcu 16/86] rcu: make rcutorture version numbers available through debugfs

Josh Triplett
2011-05-02T17:40:13Z

On Mon, May 02, 2011 at 01:30:24AM -0700, Paul E. McKenney wrote:
> On Sun, May 01, 2011 at 08:29:03AM -0700, Josh Triplett wrote:
> > On Sun, May 01, 2011 at 06:20:56AM -0700, Paul E. McKenney wrote:
> > > From: Paul E. McKenney <paul.mckenney@linaro.org>
> > >
> > > It is not possible to accurately correlate rcutorture output with that
> > > of debugfs. This patch therefore adds a debugfs file that prints out
> > > the rcutorture version number, permitting easy correlation.
> >
> > You can't accurately correlate debugfs values with each
> > other, either, right? The rcutorture version number can change between
> > accesses to different debugfs files.
>
> True, but this is OK given the use case.
>
> The problem that I used to have was that an automated test run would get
> a grace-period hang somewhere in the middle of a long run. Now, in a
> grace-period hang, most of the interesting debugfs output is static,
> so it is not necessary to line them up exactly. All that is needed is
> for the corellation to be good enough for me to ignore the debugfs
> output that came a long time before the hang started.
>
> Also, if there is an RCU grace-period hang, the rcutorture version number
> will stop changing once it has the entire array waiting for a grace period,
> which normally happens in a few seconds.
>
> Make sense, or am I missing your point?

Makes sense.

- Josh Triplett