Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@kernel.org>,
	Karol Herbst <karolherbst@gmail.com>,
	Pekka Paalanen <ppaalanen@gmail.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	nouveau@lists.freedesktop.org,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Sedat Dilek <sedat.dilek@gmail.com>
Subject: Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables
Date: Mon, 18 May 2020 11:52:47 -0700	[thread overview]
Message-ID: <CAKwvOdmXgYThHRDpt5dFZy5T1zS6MYQhcBNcq6-rsuc5fjiE6Q@mail.gmail.com> (raw)
In-Reply-To: <20200518093117.GA719849@ubuntu-s3-xlarge-x86>

On Mon, May 18, 2020 at 2:31 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Wed, Apr 08, 2020 at 01:53:23PM -0700, Nathan Chancellor 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@gmail.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Thanks for the patch, sorry I'm falling behind on code review!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> > ---
> >  arch/x86/mm/mmio-mod.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
> > index 109325d77b3e..43fd19b3f118 100644
> > --- a/arch/x86/mm/mmio-mod.c
> > +++ b/arch/x86/mm/mmio-mod.c
> > @@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
> >       int cpu;
> >       int err;
> >
> > -     if (downed_cpus == NULL &&
> > +     if (!cpumask_available(downed_cpus) &&
> >           !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
> >               pr_notice("Failed to allocate mask\n");
> >               goto out;
> > @@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
> >       int cpu;
> >       int err;
> >
> > -     if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> > +     if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
> >               return;
> >       pr_notice("Re-enabling CPUs...\n");
> >       for_each_cpu(cpu, downed_cpus) {
> >
> > base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
> > --
> > 2.26.0
> >
>
> Gentle ping for acceptance, I am not sure who should take this.

Looks like Steven or Ingo are the listed maintainers for MMIOTRACE?

-- 
Thanks,
~Nick Desaulniers