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

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Date:   Wed, 11 Dec 2019 17:20:00 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Marco Elver <elver@...gle.com>
Cc:     torvalds@...ux-foundation.org, mingo@...nel.org,
        peterz@...radead.org, will@...nel.org, tglx@...utronix.de,
        akpm@...ux-foundation.org, stern@...land.harvard.edu,
        dvyukov@...gle.com, mark.rutland@....com, parri.andrea@...il.com,
        edumazet@...gle.com, linux-doc@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -rcu/kcsan 1/2] kcsan: Document static blacklisting
 options

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@...gle.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
>