linux-kernel - Re: [PATCH v2] scripts: coccinelle: check for !(un)?likely usage

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Message-ID: <3c0f82d5-369a-1493-799e-b201a28aa671@web.de>
Date:   Fri, 30 Aug 2019 09:55:41 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Denis Efremov <efremov@...ux.com>, cocci@...teme.lip6.fr,
        kernel-janitors@...r.kernel.org,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Julia Lawall <Julia.Lawall@...6.fr>,
        Joe Perches <joe@...ches.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] scripts: coccinelle: check for !(un)?likely usage

> +/// Notations !unlikely(x) and !likely(x) are confusing.

I am curious if more software developers will share their views around
these likeliness annotations.

* How much does the scope matter for expressions?

* Are different coding style preferences involved?


> +//----------------------------------------------------------
> +//  For context mode
> +//----------------------------------------------------------
> +
> +@...ends on context disable unlikely@

I wonder about the need for such a comment when the specification
of SmPL rule dependencies should be sufficient.


> +@...ends on patch disable unlikely@
> +expression E;
> +@@
> +
> +(
> +-!likely(!E)
> ++unlikely(E)
> +|
> +-!likely(E)
> ++unlikely(!E)
> +|
> +-!unlikely(!E)
> ++likely(E)
> +|
> +-!unlikely(E)
> ++likely(!E)
> +)

Will another variant for the change specification with the semantic
patch language influence corresponding readability concerns?

+@...lacement depends on patch disable unlikely@
+expression x;
+@@
+-!
+(
+(
+-unlikely
++likely
+|
+-likely
++unlikely
+)
+       (
+-       !
+        x
+       )
+|
+(
+-unlikely
++likely
+|
+-likely
++unlikely
+)
+       (
++       !
+        x
+       )
+)


Can the use of nested SmPL disjunctions help here together with
an other SmPL code formatting?

Regards,
Markus