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From:   Qian Cai <cai@lca.pw>
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Subject: Re: [PATCH v2] mm/vmscan: fix data races at kswapd_classzone_idx
Date:   Wed, 26 Feb 2020 06:50:01 -0500
Message-Id: <8C6CE0C4-7B15-41D5-A1B2-F48F6241200F@lca.pw>
References: <20200226040612.GW24185@bombadil.infradead.org>
Cc:     akpm@linux-foundation.org, elver@google.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <20200226040612.GW24185@bombadil.infradead.org>
To:     Matthew Wilcox <willy@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Feb 25, 2020, at 11:06 PM, Matthew Wilcox <willy@infradead.org> wrote:
>=20
> I don't understand why the usages of kswapd_classzone_idx in kswapd() and
> kswapd_try_to_sleep() don't need changing too?  kswapd_classzone_idx()
> looks safe to me, but I'm prone to missing stupid things that compilers
> are allowed to do.

I am not sure. Although it looks possible on paper, I am wondering why KCSAN=
 did not trigger it yet which seems rather common. I did stress testing thos=
e areas with KCSAN for a few months now, but it might just be that I missed t=
he report at the first place.

I=E2=80=99ll keep running some testing to confirm it, but until that happens=
 or someone else could confirm it could happen, I=E2=80=99ll leave it out fo=
r this version. We can always submit an incremental patch later if necessary=
.=