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Date:   Sun, 3 Jul 2022 13:39:21 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Sander Vanheule <sander@svanheule.net>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        elver@google.com, gregkh@linuxfoundation.org,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, vschneid@redhat.com,
        Yury Norov <yury.norov@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H . Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v4 0/5] cpumask: Fix invalid uniprocessor assumptions
Message-Id: <20220703133921.6800bf1e7df3b00cb586a3c1@linux-foundation.org>
In-Reply-To: <6a4ea3d21bfb4c692d257d3f38ba28c83f242dfc.camel@svanheule.net>
References: <cover.1656777646.git.sander@svanheule.net>
        <20220702133840.943817a7694406a135bb48a9@linux-foundation.org>
        <6a4ea3d21bfb4c692d257d3f38ba28c83f242dfc.camel@svanheule.net>
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On Sun, 03 Jul 2022 09:50:51 +0200 Sander Vanheule <sander@svanheule.net> w=
rote:

> On Sat, 2022-07-02 at 13:38 -0700, Andrew Morton wrote:
> > On Sat,=A0 2 Jul 2022 18:08:23 +0200 Sander Vanheule <sander@svanheule.=
net> wrote:
> >=20
> > > On uniprocessor builds, it is currently assumed that any cpumask will
> > > contain the single CPU: cpu0. This assumption is used to provide
> > > optimised implementations.
> > >=20
> > > The current assumption also appears to be wrong, by ignoring the fact
> > > that users can provide empty cpumask-s. This can result in bugs as
> > > explained in [1].
> >=20
> > It's a little unkind to send people off to some link to explain the
> > very core issue which this patchset addresses!=A0 So I enhanced this
> > paragraph:
> >=20
> > : The current assumption also appears to be wrong, by ignoring the fact=
 that
> > : users can provide empty cpumasks.=A0 This can result in bugs as expla=
ined in
> > : [1] - for_each_cpu() will run one iteration of the loop even when pas=
sed
> > : an empty cpumask.
>=20
> Makes sense to add this, sorry for the inconvenience.
>=20
> Just to make sure, since I'm not familiar with the process for patches go=
ing through the mm tree,

Patches enter -mm in quilt form and are published in the (rebasing)
mm-unstable branch
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.  Once they have
stopped changing and have been stabilized, I move them into the
non-rebasing mm-stable branch.

> can I still send a v5 to move the last patch forward in the series, and t=
o include Yury's tags?

I already added Yury's ack.  Please tell me the specific patch ordering
and I'll take care of that.