linux-kernel - Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var

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Message-ID: <20200415095125.5efc372e@gandalf.local.home>
Date:   Wed, 15 Apr 2020 09:51:25 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Karol Herbst <karolherbst@...il.com>,
        Pekka Paalanen <ppaalanen@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, nouveau@...ts.freedesktop.org,
        clang-built-linux@...glegroups.com,
        Sedat Dilek <sedat.dilek@...il.com>
Subject: Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t
 variables

On Wed,  8 Apr 2020 13:53:23 -0700
Nathan Chancellor <natechancellor@...il.com> wrote:

> When building with Clang + -Wtautological-compare and
> CONFIG_CPUMASK_OFFSTACK unset:
> 
> arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL &&
>             ^~~~~~~~~~~    ~~~~
> arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
>             ^~~~~~~~~~~    ~~~~
> 2 warnings generated.
> 
> Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> cpumask_available to fix warnings of this nature. Use that here so that
> clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/982
> Reported-by: Sedat Dilek <sedat.dilek@...il.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
> 

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve