Hi Paul
During the research, I found a already existing tool to detect
undefined Kconfig macro:
scripts/checkkconfigsymbols.py. It is marvellous!

By invoking ./scripts/checkkconfigsymbols.py > /tmp/log, I found
following possibly undefined Kconfig macros
which may need our attention:

PREEMPT_LOCK
Referencing files: include/linux/lockdep_types.h

PREEMT_DYNAMIC
Referencing files: kernel/entry/common.c

TREE_PREEMPT_RCU
Referencing files: arch/sh/configs/sdk7786_defconfig

RCU_CPU_STALL_INFO
Referencing files: arch/xtensa/configs/nommu_kc705_defconfig

RCU_NOCB_CPU_ALL
Referencing files:
Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst

RCU_TORTURE_TESTS
Referencing files: kernel/rcu/rcutorture.c

and finally the macro which drive me to do this research

TASKS_RCU_TRACE
Referencing files: include/linux/rcupdate.h, kernel/rcu/tree_plugin.h

On Fri, Jul 16, 2021 at 2:09 AM Paul E. McKenney [off-list ref] wrote:

On Thu, Jul 15, 2021 at 04:45:04PM +0800, Zhouyi Zhou wrote:

quoted

On Thu, Jul 15, 2021 at 11:51 AM Paul E. McKenney [off-list ref] wrote:

quoted

On Wed, Jul 14, 2021 at 12:44:36PM +0800, Zhouyi Zhou wrote:

quoted

On Tue, Jul 13, 2021 at 11:19 PM Paul E. McKenney [off-list ref] wrote:

quoted

On Tue, Jul 13, 2021 at 06:18:12AM -0700, Paul E. McKenney wrote:

quoted

On Tue, Jul 13, 2021 at 09:09:04AM -0400, Mathieu Desnoyers wrote:

quoted

----- On Jul 13, 2021, at 12:16 AM, paulmck paulmck@kernel.org wrote:

quoted

On Tue, Jul 13, 2021 at 08:56:45AM +0800, zhouzhouyi@gmail.com wrote:

quoted

From: Zhouyi Zhou <redacted>

Hi Paul,

During my studying of RCU, I did a grep in the kernel source tree.
I found there are 3 places where the macro name CONFIG_TASKS_RCU_TRACE
should be CONFIG_TASKS_TRACE_RCU instead.

Without memory fencing, the idle/userspace task inspection may not
be so accurate.

Thanks for your constant encouragement for my studying.

Best Wishes
Zhouyi

Signed-off-by: Zhouyi Zhou <redacted>

Good eyes, and those could cause real bugs, so thank you!

Hi Paul,

This makes me wonder: what is missing testing-wise in rcutorture to
catch those issues with testing before they reach mainline ?

My guess:  Running on weakly ordered architectures.  ;-)

And another guess:  A tool that identifies use of Kconfig options
that are not defined in any Kconfig* file.

Based on Paul's second guess ;-),  I did a small research, and I think
the best answer is to modify scripts/checkpatch.pl. We modify checkpatch.pl
to identify use of Kconfig options that are not defined in any Kconfig* file.

As I am a C/C++ programmer, I would be glad to take some time to learn
perl (checkpatch is implented in perl) first if no other volunteer is
about to do it ;-)

I haven't heard anyone else volunteer.  ;-)

Others might have opinions on where best to implement these checks,
but I must confess that I have not given it much thought.

I recklessly cc the maintainers of checkpatch.pl without your
permission to see others' opion,
and I begin to study perl at the same time, after all, learning
something is always good ;-)

Works for me!

                                                        Thanx, Paul

Best Wishes
Zhouyi