linux-kernel - Re: [PATCH] asm-generic: bug: add unlikely() to BUG

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Date:   Fri, 7 Sep 2018 22:41:00 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Igor Stoppa <igor.stoppa@...il.com>
Cc:     igor.stoppa@...wei.com, linux-arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] asm-generic: bug: add unlikely() to BUG_ON()

On Fri, Sep 7, 2018 at 9:21 PM Igor Stoppa <igor.stoppa@...il.com> wrote:
>
> Add a hint to the compiler.
> If BUG_ON() is used instead of BUG(), it means that probably the
> preferred outcome is to not BUG().
>
> The optimization is disabled, in case CONFIG_PROFILE_ANNOTATED_BRANCHES
> is turned on.

This sounds like a good idea, as this is one of the more likely causes
of false-positive -Wmaybe-uninitialized warnings with
CONFIG_PROFILE_ANNOTATED_BRANCHES

Could you add a comment about -Wmaybe-uninitialized next to the definition?
Otherwise that is easily lost.

Also, I see that the file has two separate definitions of BUG_ON(), and the
other one does have an unlikely() in it already. Can you change both
to do the same thing with unlikely() or not unlikely()?

       Arnd