On Mon, May 05, 2025 at 12:03:10PM -0700, Paul E. McKenney wrote:
> Hello!
>
> Following up on off-list discussions and requests for more information.
>
> These reproduce reasonably easily, and here is an example:
>
> ------------------------------------------------------------------------
> [ 426.022056] rcu: NOCB: Cannot CB-offload online CPU 25
> [ 460.867350] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
> [ 460.867980] rcu: 0-...!: (1 GPs behind) idle=8fe4/1/0x4000000000000000
> softirq=2124/2125 fqs=0
> [ 460.868726] rcu: 1-...!: (1 GPs behind) idle=e0ac/1/0x4000000000000000
> softirq=3547/3547 fqs=0
Early returns suggest that the following patch suppresses this issue.
My guess is that the changes to TREE01 suffice, but I will try later
excluding the TREE01.boot changes. Architecture-dependent rcutorture
scenario files, anyone? :-/
Thanx, Paul
------------------------------------------------------------------------
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE01
b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
index 8ae41d5f81a3..6281dbdc189f 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE01
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE01
@@ -8,8 +8,9 @@ CONFIG_NO_HZ_IDLE=y
CONFIG_NO_HZ_FULL=n
CONFIG_RCU_TRACE=y
CONFIG_HOTPLUG_CPU=y
-CONFIG_MAXSMP=y
-CONFIG_CPUMASK_OFFSTACK=y
+#CONFIG_MAXSMP=y
+CONFIG_NR_CPUS=8
+#CONFIG_CPUMASK_OFFSTACK=y
CONFIG_RCU_NOCB_CPU=y
CONFIG_DEBUG_LOCK_ALLOC=n
CONFIG_RCU_BOOST=n
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot
b/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot
index 40af3df0f397..45e3b33f12a3 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot
@@ -1,4 +1,4 @@
-maxcpus=8 nr_cpus=43
+maxcpus=8 nr_cpus=8
rcutree.gp_preinit_delay=3
rcutree.gp_init_delay=3
rcutree.gp_cleanup_delay=3
