Re: [PATCH -rcu/kcsan 1/2] kcsan: Document static blacklisting options

Paul E. McKenney
2019-12-12T01:20:03Z

On Thu, Dec 12, 2019 at 01:07:08AM +0100, Marco Elver wrote:
> Updates the section on "Selective analysis", listing all available
> options to blacklist reporting data races for: specific accesses,
> functions, compilation units, and entire directories.
>
> These options should provide adequate control for maintainers to opt out
> of KCSAN analysis at varying levels of granularity. It is hoped to
> provide the required control to reflect preferences for handling data
> races across the kernel.
>
> Signed-off-by: Marco Elver <elver@google.com>

Both queued for testing and review, thank you!

Thanx, Paul

> ---
> Documentation/dev-tools/kcsan.rst | 24 +++++++++++++++++-------
> 1 file changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/dev-tools/kcsan.rst b/Documentation/dev-tools/kcsan.rst
> index a6f4f92df2fa..65a0be513b7d 100644
> --- a/Documentation/dev-tools/kcsan.rst
> +++ b/Documentation/dev-tools/kcsan.rst
> @@ -101,18 +101,28 @@ instrumentation or e.g. DMA accesses.
> Selective analysis
> ~~~~~~~~~~~~~~~~~~
>
> -To disable KCSAN data race detection for an entire subsystem, add to the
> -respective ``Makefile``::
> +It may be desirable to disable data race detection for specific accesses,
> +functions, compilation units, or entire subsystems. For static blacklisting,
> +the below options are available:
>
> - KCSAN_SANITIZE := n
> +* KCSAN understands the ``data_race(expr)`` annotation, which tells KCSAN that
> + any data races due to accesses in ``expr`` should be ignored and resulting
> + behaviour when encountering a data race is deemed safe.
> +
> +* Disabling data race detection for entire functions can be accomplished by
> + using the function attribute ``__no_kcsan`` (or ``__no_kcsan_or_inline`` for
> + ``__always_inline`` functions). To dynamically control for which functions
> + data races are reported, see the `debugfs`_ blacklist/whitelist feature.
>
> -To disable KCSAN on a per-file basis, add to the ``Makefile``::
> +* To disable data race detection for a particular compilation unit, add to the
> + ``Makefile``::
>
> KCSAN_SANITIZE_file.o := n
>
> -KCSAN also understands the ``data_race(expr)`` annotation, which tells KCSAN
> -that any data races due to accesses in ``expr`` should be ignored and resulting
> -behaviour when encountering a data race is deemed safe.
> +* To disable data race detection for all compilation units listed in a
> + ``Makefile``, add to the respective ``Makefile``::
> +
> + KCSAN_SANITIZE := n
>
> debugfs
> ~~~~~~~
> --
> 2.24.0.525.g8f36a354ae-goog
>