On Mon, Nov 14, 2016 at 09:21:10AM -0800, Josh Triplett wrote:
> On Mon, Nov 14, 2016 at 08:57:11AM -0800, Paul E. McKenney wrote:
> > Although rcutorture will occasionally do a 50-millisecond grace-period
> > delay, these delays are quite rare. And rightly so, because otherwise
> > the read rate would be quite low. Thie means that it can be important
> > to identify whether or not a given run contained a long-delay read.
> > This commit therefore inserts a trace_rcu_torture_read() event to flag
> > runs containing long delays.
> >
> > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
>
> A couple of apparent typos below. With those fixed:
> Reviewed-by: Josh Triplett <j...@joshtriplett.org>
>
> > include/trace/events/rcu.h | 5 ++++-
> > kernel/rcu/rcutorture.c | 11 ++++++++++-
> > 2 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
> > index d3e756539d44..b31e05bc8e26 100644
> > --- a/include/trace/events/rcu.h
> > +++ b/include/trace/events/rcu.h
> > @@ -698,7 +698,10 @@ TRACE_EVENT(rcu_batch_end,
> > /*
> > * Tracepoint for rcutorture readers. The first argument is the name
> > * of the RCU flavor from rcutorture's viewpoint and the second argument
> > - * is the callback address.
> > + * is the callback address. The third callback is the start time in
> > + * seconds, and the last two arguments are the grace period numbers
> > + * and the beginning and end of the read, respectively. Note that the
> > + * callback address can be NULL.
>
> s/third callback/third argument/?
Good catch, fixed!
> Also, s/and the beginning/of the beginning/?
Let's see... "the last two arguments are the grace period numbers and
the beginning and end of the read, respectively." -ENONSENSE for sure.
I believe that the "and" needs to become "at" as follows:
"the last two arguments are the grace period numbers at the beginning
and end of the read, respectively."
Does that help?
Thanx, Paul
> > TRACE_EVENT(rcu_torture_read,
> >
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index bf08fee53dc7..87c51225ceec 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -289,15 +289,24 @@ static int rcu_torture_read_lock(void) __acquires(RCU)
> >
> > static void rcu_read_delay(struct torture_random_state *rrsp)
> > {
> > + unsigned long started;
> > + unsigned long completed;
> > const unsigned long shortdelay_us = 200;
> > const unsigned long longdelay_ms = 50;
> > + unsigned long long ts;
> >
> > /* We want a short delay sometimes to make a reader delay the grace
> > * period, and we want a long delay occasionally to trigger
> > * force_quiescent_state. */
> >
> > - if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
> > + if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
> > + started = cur_ops->completed();
> > + ts = rcu_trace_clock_local();
> > mdelay(longdelay_ms);
> > + completed = cur_ops->completed();
> > + do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
> > + started, completed);
> > + }
> > if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
> > udelay(shortdelay_us);
> > #ifdef CONFIG_PREEMPT
> > --
> > 2.5.2
> >
>
