rcutorture: Select from only online CPUs
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Message ID 20190323034619.15792-1-joel@joelfernandes.org
State New
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Series
  • rcutorture: Select from only online CPUs
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Commit Message

Joel Fernandes March 23, 2019, 3:46 a.m. UTC
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@joelfernandes.org>
---
 tools/testing/selftests/rcutorture/bin/jitter.sh | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Comments

Paul E. McKenney March 25, 2019, 3:01 p.m. UTC | #1
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@joelfernandes.org>

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 |

>  		sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
>  		grep -v '^0*$'`

Of course, now I have no idea why I excluded CPU 0...  :-/

> +
> +	for c in $cpus; do
> +		if [ "$(cat /sys/devices/system/cpu/cpu$c/online)" == "1" ];
> +		then
> +			cpus_tmp="$cpus_tmp $c"
> +		fi
> +	done
> +	cpus=$cpus_tmp
> +
>  	cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
>  		srand(n + me + systime());
>  		ncpus = split(cpus, ca);
> -- 
> 2.21.0.392.gf8f6787159e-goog
>
Joel Fernandes March 25, 2019, 4:33 p.m. UTC | #2
On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
>
> 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
Paul E. McKenney March 25, 2019, 4:42 p.m. UTC | #3
On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> >
> > 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 :-)

Please feel free to try including CPU 0 and running the set of single-CPU
rcutorture scenarios.  ;-)

							Thanx, Paul
Joel Fernandes March 25, 2019, 10:02 p.m. UTC | #4
On Mon, Mar 25, 2019 at 09:42:53AM -0700, Paul E. McKenney wrote:
> On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> > >
> > > 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 :-)
> 
> Please feel free to try including CPU 0 and running the set of single-CPU
> rcutorture scenarios.  ;-)

Sounds good, I will test that out on your latest dev branch. Thanks,

- Joel
Joel Fernandes March 25, 2019, 10:40 p.m. UTC | #5
On Mon, Mar 25, 2019 at 12:42 PM Paul E. McKenney <paulmck@linux.ibm.com> wrote:
>
> On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> > >
> > > 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 :-)
>
> Please feel free to try including CPU 0 and running the set of single-CPU
> rcutorture scenarios.  ;-)

Will do and then will update the patch by adding the CPU back, if all
is well. Thanks.
Paul E. McKenney March 26, 2019, 4:01 p.m. UTC | #6
On Mon, Mar 25, 2019 at 06:40:17PM -0400, Joel Fernandes wrote:
> On Mon, Mar 25, 2019 at 12:42 PM Paul E. McKenney <paulmck@linux.ibm.com> wrote:
> >
> > On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> > > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> > > >
> > > > 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 :-)
> >
> > Please feel free to try including CPU 0 and running the set of single-CPU
> > rcutorture scenarios.  ;-)
> 
> Will do and then will update the patch by adding the CPU back, if all
> is well. Thanks.

And rcutorture doesn't like the rcu_is_cpu_rrupt_from_idle() patch on
scenarios SRCU-P, TASKS01, and TREE05, which are the Tree RCU scenarios
that enable CONFIG_PROVE_RCU.  The compiler error is:

kernel/rcu/tree.c:391:2: error: implicit declaration of function ‘_this_cpu_read’ [-Werror=implicit-function-declaration]

My guess is that the initial underscore needs to go.  I will drop
these two patches in favor of an update from you.  ;-)

							Thanx, Paul
Joel Fernandes March 26, 2019, 6:35 p.m. UTC | #7
On Tue, Mar 26, 2019 at 09:01:40AM -0700, Paul E. McKenney wrote:
> On Mon, Mar 25, 2019 at 06:40:17PM -0400, Joel Fernandes wrote:
> > On Mon, Mar 25, 2019 at 12:42 PM Paul E. McKenney <paulmck@linux.ibm.com> wrote:
> > >
> > > On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> > > > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> > > > >
> > > > > 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 :-)
> > >
> > > Please feel free to try including CPU 0 and running the set of single-CPU
> > > rcutorture scenarios.  ;-)
> > 
> > Will do and then will update the patch by adding the CPU back, if all
> > is well. Thanks.
> 
> And rcutorture doesn't like the rcu_is_cpu_rrupt_from_idle() patch on
> scenarios SRCU-P, TASKS01, and TREE05, which are the Tree RCU scenarios
> that enable CONFIG_PROVE_RCU.  The compiler error is:
> 
> kernel/rcu/tree.c:391:2: error: implicit declaration of function ‘_this_cpu_read’ [-Werror=implicit-function-declaration]
> 
> My guess is that the initial underscore needs to go.  I will drop
> these two patches in favor of an update from you.  ;-)

Sorry, I fixed that up and running tests now.

By the way, may be you decided to not run the jitter on CPU0 just because on
some systems, CPU0 does not have an 'online' file? In this case, the grep may
throw errors I guess which troubles the script.

From the old cpu hotplug docs, I found that if CONFIG_BOOTPARAM_HOTPLUG_CPU0
or cpu0_hotplug boot command line option is not passed, then cpu0 cannot be
offlined in which case, presumably the 'online' file will be missing, like
some systems I am testing on.

thanks,

 - Joel
Joel Fernandes March 26, 2019, 6:40 p.m. UTC | #8
On Tue, Mar 26, 2019 at 02:35:49PM -0400, Joel Fernandes wrote:
> On Tue, Mar 26, 2019 at 09:01:40AM -0700, Paul E. McKenney wrote:
> > On Mon, Mar 25, 2019 at 06:40:17PM -0400, Joel Fernandes wrote:
> > > On Mon, Mar 25, 2019 at 12:42 PM Paul E. McKenney <paulmck@linux.ibm.com> wrote:
> > > >
> > > > On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> > > > > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> > > > > >
> > > > > > 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 :-)
> > > >
> > > > Please feel free to try including CPU 0 and running the set of single-CPU
> > > > rcutorture scenarios.  ;-)
> > > 
> > > Will do and then will update the patch by adding the CPU back, if all
> > > is well. Thanks.
> > 
> > And rcutorture doesn't like the rcu_is_cpu_rrupt_from_idle() patch on
> > scenarios SRCU-P, TASKS01, and TREE05, which are the Tree RCU scenarios
> > that enable CONFIG_PROVE_RCU.  The compiler error is:
> > 
> > kernel/rcu/tree.c:391:2: error: implicit declaration of function ‘_this_cpu_read’ [-Werror=implicit-function-declaration]
> > 
> > My guess is that the initial underscore needs to go.  I will drop
> > these two patches in favor of an update from you.  ;-)
> 
> Sorry, I fixed that up and running tests now.
> 
> By the way, may be you decided to not run the jitter on CPU0 just because on
> some systems, CPU0 does not have an 'online' file? In this case, the grep may
> throw errors I guess which troubles the script.
> 
> From the old cpu hotplug docs, I found that if CONFIG_BOOTPARAM_HOTPLUG_CPU0
> or cpu0_hotplug boot command line option is not passed, then cpu0 cannot be
> offlined in which case, presumably the 'online' file will be missing, like
> some systems I am testing on.

Never mind, the "*" in your path search would take care of not erroring out :-)

The other reason you may have done it is for making the jitter be
consistent across systems that can offline CPU0, and the others that can't :-).
I am just guessing.

Any way, I will just add back CPU0 forcefully to the cpus list in my testing,
without checking for the online file existence, and see what happens :-) If
there's no smoke, then I'll roll that into a patch and send it out.

thanks.
Paul E. McKenney March 26, 2019, 8:46 p.m. UTC | #9
On Tue, Mar 26, 2019 at 02:40:13PM -0400, Joel Fernandes wrote:
> On Tue, Mar 26, 2019 at 02:35:49PM -0400, Joel Fernandes wrote:
> > On Tue, Mar 26, 2019 at 09:01:40AM -0700, Paul E. McKenney wrote:
> > > On Mon, Mar 25, 2019 at 06:40:17PM -0400, Joel Fernandes wrote:
> > > > On Mon, Mar 25, 2019 at 12:42 PM Paul E. McKenney <paulmck@linux.ibm.com> wrote:
> > > > >
> > > > > On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote:
> > > > > > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney <paulmck@linux.ibm.com> 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@joelfernandes.org>
> > > > > > >
> > > > > > > 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 :-)
> > > > >
> > > > > Please feel free to try including CPU 0 and running the set of single-CPU
> > > > > rcutorture scenarios.  ;-)
> > > > 
> > > > Will do and then will update the patch by adding the CPU back, if all
> > > > is well. Thanks.
> > > 
> > > And rcutorture doesn't like the rcu_is_cpu_rrupt_from_idle() patch on
> > > scenarios SRCU-P, TASKS01, and TREE05, which are the Tree RCU scenarios
> > > that enable CONFIG_PROVE_RCU.  The compiler error is:
> > > 
> > > kernel/rcu/tree.c:391:2: error: implicit declaration of function ‘_this_cpu_read’ [-Werror=implicit-function-declaration]
> > > 
> > > My guess is that the initial underscore needs to go.  I will drop
> > > these two patches in favor of an update from you.  ;-)
> > 
> > Sorry, I fixed that up and running tests now.

Very good.  ;-)

> > By the way, may be you decided to not run the jitter on CPU0 just because on
> > some systems, CPU0 does not have an 'online' file? In this case, the grep may
> > throw errors I guess which troubles the script.
> > 
> > From the old cpu hotplug docs, I found that if CONFIG_BOOTPARAM_HOTPLUG_CPU0
> > or cpu0_hotplug boot command line option is not passed, then cpu0 cannot be
> > offlined in which case, presumably the 'online' file will be missing, like
> > some systems I am testing on.
> 
> Never mind, the "*" in your path search would take care of not erroring out :-)
> 
> The other reason you may have done it is for making the jitter be
> consistent across systems that can offline CPU0, and the others that can't :-).
> I am just guessing.

Or maybe I was just being stupid.  If I wasn't being stupid, it might have
been that in the uniprocessor case the jitter caused some failure.  But the
kernel is a lot better about handling preemption these days, so that might
well be an obsolete concern.  Who knows?  ;-)

> Any way, I will just add back CPU0 forcefully to the cpus list in my testing,
> without checking for the online file existence, and see what happens :-) If
> there's no smoke, then I'll roll that into a patch and send it out.

Sounds good, especially if you include a few of the uniprocessor tests.  ;-)

							Thanx, Paul
Joel Fernandes March 26, 2019, 11:48 p.m. UTC | #10
On Tue, Mar 26, 2019 at 01:46:13PM -0700, Paul E. McKenney wrote:
[snip]
> > Any way, I will just add back CPU0 forcefully to the cpus list in my testing,
> > without checking for the online file existence, and see what happens :-) If
> > there's no smoke, then I'll roll that into a patch and send it out.
> 
> Sounds good, especially if you include a few of the uniprocessor tests.  ;-)

Yes, I will do those as well. Thanks for the reminder :-). Let us wait on
merging until then, then. I will reply back here about the uni processor
testing tomorrow.

thanks,

 - Joel

Patch
diff mbox series

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 |
 		sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
 		grep -v '^0*$'`
+
+	for c in $cpus; do
+		if [ "$(cat /sys/devices/system/cpu/cpu$c/online)" == "1" ];
+		then
+			cpus_tmp="$cpus_tmp $c"
+		fi
+	done
+	cpus=$cpus_tmp
+
 	cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
 		srand(n + me + systime());
 		ncpus = split(cpus, ca);