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Date:   Thu, 20 Jul 2023 21:00:58 -0700
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Valentin Schneider <vschneid@redhat.com>
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Subject: Re: [RFC PATCH v2 17/20] rcutorture: Add a test config to torture
 test low RCU_DYNTICKS width
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 <20230720163056.2564824-18-vschneid@redhat.com>
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On Thu, Jul 20, 2023 at 12:53:05PM -0700, Paul E. McKenney wrote:
> On Thu, Jul 20, 2023 at 05:30:53PM +0100, Valentin Schneider wrote:
> > We now have an RCU_EXPORT knob for configuring the size of the dynticks
> > counter: CONFIG_RCU_DYNTICKS_BITS.
> > 
> > Add a torture config for a ridiculously small counter (2 bits). This is ac
> > opy of TREE4 with the added counter size restriction.
> > 
> > Link: http://lore.kernel.org/r/4c2cb573-168f-4806-b1d9-164e8276e66a@paulmck-laptop
> > Suggested-by: Paul E. McKenney <paulmck@kernel.org>
> > Signed-off-by: Valentin Schneider <vschneid@redhat.com>
> > ---
> >  .../selftests/rcutorture/configs/rcu/TREE11   | 19 +++++++++++++++++++
> >  .../rcutorture/configs/rcu/TREE11.boot        |  1 +
> >  2 files changed, 20 insertions(+)
> >  create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE11
> >  create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot
> > 
> > diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE11 b/tools/testing/selftests/rcutorture/configs/rcu/TREE11
> > new file mode 100644
> > index 0000000000000..aa7274efd9819
> > --- /dev/null
> > +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE11
> > @@ -0,0 +1,19 @@
> > +CONFIG_SMP=y
> > +CONFIG_NR_CPUS=8
> > +CONFIG_PREEMPT_NONE=n
> > +CONFIG_PREEMPT_VOLUNTARY=y
> > +CONFIG_PREEMPT=n
> > +CONFIG_PREEMPT_DYNAMIC=n
> > +#CHECK#CONFIG_TREE_RCU=y
> > +CONFIG_HZ_PERIODIC=n
> > +CONFIG_NO_HZ_IDLE=n
> > +CONFIG_NO_HZ_FULL=y
> > +CONFIG_RCU_TRACE=y
> > +CONFIG_RCU_FANOUT=4
> > +CONFIG_RCU_FANOUT_LEAF=3
> > +CONFIG_DEBUG_LOCK_ALLOC=n
> > +CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
> > +CONFIG_RCU_EXPERT=y
> > +CONFIG_RCU_EQS_DEBUG=y
> > +CONFIG_RCU_LAZY=y
> > +CONFIG_RCU_DYNTICKS_BITS=2
> 
> Why not just add this last line to the existing TREE04 scenario?
> That would ensure that it gets tested regularly without extending the
> time required to run a full set of rcutorture tests.

Please see below for the version of this patch that I am running overnight
tests with.  Does this one work for you?

							Thanx, Paul

------------------------------------------------------------------------

commit 1aa13731e665193cd833edac5ebc86a9c3fea2b7
Author: Valentin Schneider <vschneid@redhat.com>
Date:   Thu Jul 20 20:58:41 2023 -0700

    rcutorture: Add a test config to torture test low RCU_DYNTICKS width
    
    We now have an RCU_EXPORT knob for configuring the size of the dynticks
    counter: CONFIG_RCU_DYNTICKS_BITS.
    
    Modify scenario TREE04 to exercise a a ridiculously small counter
    (2 bits).
    
    Link: http://lore.kernel.org/r/4c2cb573-168f-4806-b1d9-164e8276e66a@paulmck-laptop
    Suggested-by: Paul E. McKenney <paulmck@kernel.org>
    Signed-off-by: Valentin Schneider <vschneid@redhat.com>
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
index dc4985064b3a..aa7274efd981 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04
@@ -16,3 +16,4 @@ CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
 CONFIG_RCU_EQS_DEBUG=y
 CONFIG_RCU_LAZY=y
+CONFIG_RCU_DYNTICKS_BITS=2