Re: [PATCH] rcutorture: Select from only online CPUs

[Joel Fernandes]

On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@xxxxxxxxxxxxx> wrote:
>
> On Fri, Mar 22, 2019 at 11:46:19PM -0400, Joel Fernandes (Google) wrote:
> > The rcutorture jitter.sh script selects a random CPU but does not check
> > if it is offline or online. This leads to taskset errors many times. On
> > my machine, hyper threading is disabled so half the cores are offline
> > causing taskset errors a lot of times. Let us fix this by checking from
> > only the online CPUs on the system.
> >
> > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
>
> Good catch!
>
> Please see below for one suggestion for simplification.
>
>                                                         Thanx, Paul
>
> > ---
> >  tools/testing/selftests/rcutorture/bin/jitter.sh | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
> > index 3633828375e3..53bf9d99b5cd 100755
> > --- a/tools/testing/selftests/rcutorture/bin/jitter.sh
> > +++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
> > @@ -47,10 +47,19 @@ do
> >               exit 0;
> >       fi
> >
> > -     # Set affinity to randomly selected CPU
> > +     # Set affinity to randomly selected online CPU
> >       cpus=`ls /sys/devices/system/cpu/*/online |
>
>         cpus=`grep 1 /sys/devices/system/cpu/*/online |
>

Yes, this is better. Lets do it this way :)

> >               sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
> >               grep -v '^0*$'`
>
> Of course, now I have no idea why I excluded CPU 0...  :-/

Yes, I was wondering as well about that :-)

thanks,

 - Joel