Re: [PATCH v3] rcuscale: Console output claims too few grace periods

[Han, Jiangong]

Hi,  Paul,

I think your words are much clear than mine, no missings, thanks for 
your help.  :)
Thanks for your quickly response again.

Br,

Jiangong


在 2021/6/25 上午12:40, Paul E. McKenney 写道:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On Thu, Jun 24, 2021 at 10:34:24PM +0800, Jiangong.Han wrote:
> > The rcuscale console output claims N grace periods, numbered from zero
> > to N, which means that there were really N+1 grace periods.  The root
> > cause of this bug is that rcu_scale_writer() stores the number of the
> > last grace period (numbered from zero) into writer_n_durations[me]
> > instead of the number of grace periods. This commit therefore assigns
> > the actual number of grace periods to writer_n_durations[me], and also
> > makes the corresponding adjustment to the loop outputting per-grace-period
> > measurements.
> >
> > Sample of old console output:
> >        rcu-scale: writer 0 gps: 133
> >        ......
> >        rcu-scale:    0 writer-duration:     0 44003961
> >        rcu-scale:    0 writer-duration:     1 32003582
> >        ......
> >        rcu-scale:    0 writer-duration:   132 28004391
> >        rcu-scale:    0 writer-duration:   133 27996410
> >
> > Sample of new console output:
> >        rcu-scale: writer 0 gps: 134
> >        ......
> >        rcu-scale:    0 writer-duration:     0 44003961
> >        rcu-scale:    0 writer-duration:     1 32003582
> >        ......
> >        rcu-scale:    0 writer-duration:   132 28004391
> >        rcu-scale:    0 writer-duration:   133 27996410
> >
> > Signed-off-by: Jiangong.Han <jiangong.han@xxxxxxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> I already have it queued in -rcu here:
>
> 4c154a910344 ("rcuscale: Console output claims too few grace periods")
>
> Or did you find an error in my wordsmithed version of your commit log?
> If so, please point out the error explicitly.  (It looks identical to me,
> but I could easily be missing something.)
>
>                                                          Thanx, Paul
>
> > ---
> >   kernel/rcu/rcuscale.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> > index dca51fe9c73f..2cc34a22a506 100644
> > --- a/kernel/rcu/rcuscale.c
> > +++ b/kernel/rcu/rcuscale.c
> > @@ -487,7 +487,7 @@ rcu_scale_writer(void *arg)
> >        if (gp_async) {
> >                cur_ops->gp_barrier();
> >        }
> > -     writer_n_durations[me] = i_max;
> > +     writer_n_durations[me] = i_max + 1;
> >        torture_kthread_stopping("rcu_scale_writer");
> >        return 0;
> >   }
> > @@ -561,7 +561,7 @@ rcu_scale_cleanup(void)
> >                        wdpp = writer_durations[i];
> >                        if (!wdpp)
> >                                continue;
> > -                     for (j = 0; j <= writer_n_durations[i]; j++) {
> > +                     for (j = 0; j < writer_n_durations[i]; j++) {
> >                                wdp = &wdpp[j];
> >                                pr_alert("%s%s %4d writer-duration: %5d %llu\n",
> >                                        scale_type, SCALE_FLAG,
> > --
> > 2.17.1