From: "Lukas Bulwahn" <lukas.bulwahn@gmail.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
kernel-janitors@vger.kernel.org, linux-safety@lists.elisa.tech
Subject: Re: [PATCH] x86/mm: drop superfluous initialization
Date: Tue, 29 Sep 2020 10:42:15 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.2009291034160.17656@felia> (raw)
In-Reply-To: <1d376c1f-2f14-5c29-671e-ca59853fa4a4@intel.com>
On Mon, 28 Sep 2020, Dave Hansen wrote:
> On 9/28/20 3:00 AM, Lukas Bulwahn wrote:
> > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> > index c7a47603537f..5632f02146ca 100644
> > --- a/arch/x86/mm/init.c
> > +++ b/arch/x86/mm/init.c
> > @@ -609,7 +609,7 @@ static void __init memory_map_top_down(unsigned long map_start,
> > step_size = PMD_SIZE;
> > max_pfn_mapped = 0; /* will get exact value next */
> > min_pfn_mapped = real_end >> PAGE_SHIFT;
> > - last_start = start = real_end;
> > + last_start = real_end;
>
> Thanks for finding this.
>
> This becomes even more obviously correct if we just move the 'start'
> declaration into the while() loop. If we do that, it puts the three
> assignment locations right next to the definition, and its trivial to
> spot that the initialization was not missed:
>
> while (last_start > map_start) {
> unsigned long start;
>
> if (last_start > step_size) {
> start = round_down(last_start - 1, step_size);
> if (start < map_start)
> start = map_start;
> } else
> start = map_start;
> ...
>
Agree, this point is simply a question of style:
Shall local variables be defined as "local" as possible or simply
consistently at the beginning of each function?
If there are no strong opinions of style, I would just keep this patch
as-is.
> Either way, your patch looks correct to me:
>
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
>
Thanks for the Ack.
Lukas
prev parent reply other threads:[~2020-09-29 8:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-28 10:00 [PATCH] x86/mm: drop superfluous initialization Lukas Bulwahn
2020-09-28 17:59 ` Dave Hansen
2020-09-29 8:42 ` Lukas Bulwahn [this message]
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