On Thu, Aug 24, 2023 at 5:15 AM Paul E. McKenney [off-list ref] wrote:

On Tue, May 02, 2023 at 11:06:02PM +0800, zhouzhouyi@gmail.com wrote:

quoted

From: Zhouyi Zhou <redacted>

Currently, default time between rcu torture forward-progress tests is 60HZ,
Under this configuration, false positive caused by __stack_chk_fail [1] is
difficult to reproduce (needs average 5*420 seconds for SRCU-P),
which means one has to invoke [2] 5 times in average to make [1] appear.

With time between rcu torture forward-progress tests be 1 HZ, above
phenomenon will be reproduced within 3 minutes, which means we can
reproduce [1] everytime we invoke [2].

Although [1] is a false positive, this change will make possible future
true bugs easier to be discovered.

[1] Link: https://lore.kernel.org/lkml/CAABZP2yS5=ZUwEZQ7iHkV0wDm_HgO8K-TeAhyJrZhavzKDa44Q@mail.gmail.com/T/ (local)
[2] tools/testing/selftests/rcutorture/bin/torture.sh

Tested in PPC VM of Opensource Lab of Oregon State Univerisity.

Signed-off-by: Zhouyi Zhou <redacted>

Please accept my apologies for being ridiculously slow to reply!

Never mind. I have made a lot of self improvement during the study of
RCU and RCU torture and your book ;-)

In recent -rcu, module parameters such as this one that simply set a
value can be overridden on the command line.  So you could get the effect
(again, in recent kernels) in your testing by adding:

        --bootargs "rcutorture.fwd_progress_holdoff=1"

The reason that I am reluctant to accept this patch is that we sometimes
have trouble with this forward-progress testing exhausting memory, and
making in happen could therefore cause trouble with generic rcutorture
testing.

Agree, false positives can disrupt our judgement in many cases.

Thanx Zhouyi

Or am I missing the point of this change?

                                                        Thanx, Paul

quoted

---
 tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot  | 1 +
 tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot  | 1 +
 tools/testing/selftests/rcutorture/configs/rcu/TRACE02.boot | 1 +
 tools/testing/selftests/rcutorture/configs/rcu/TREE02.boot  | 1 +
 tools/testing/selftests/rcutorture/configs/rcu/TREE10.boot  | 1 +
 5 files changed, 5 insertions(+)

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot
index ce0694fd9b92..982582bff041 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot

@@ -1,2 +1,3 @@
 rcutorture.torture_type=srcu
 rcutorture.fwd_progress=3
+rcutorture.fwd_progress_holdoff=1

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot
index 2db39f298d18..18f5d7361d8a 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot

@@ -1,4 +1,5 @@
 rcutorture.torture_type=srcud
 rcupdate.rcu_self_test=1
 rcutorture.fwd_progress=3
+rcutorture.fwd_progress_holdoff=1
 srcutree.big_cpu_lim=5

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRACE02.boot b/tools/testing/selftests/rcutorture/configs/rcu/TRACE02.boot
index c70b5db6c2ae..b86bc7df7603 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TRACE02.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TRACE02.boot

@@ -1,2 +1,3 @@
 rcutorture.torture_type=tasks-tracing
 rcutorture.fwd_progress=2
+rcutorture.fwd_progress_holdoff=1

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE02.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE02.boot
index dd914fa8f690..933302f885df 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE02.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE02.boot

@@ -1 +1,2 @@
 rcutorture.fwd_progress=2
+rcutorture.fwd_progress_holdoff=1

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE10.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE10.boot
index dd914fa8f690..933302f885df 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE10.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE10.boot

@@ -1 +1,2 @@
 rcutorture.fwd_progress=2
+rcutorture.fwd_progress_holdoff=1
--

2.34.1