From: Matthew Wilcox <willy@infradead.org>
To: Qian Cai <cai@lca.pw>
Cc: akpm@linux-foundation.org, elver@google.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/vmscan: fix data races at kswapd_classzone_idx
Date: Tue, 25 Feb 2020 20:06:12 -0800 [thread overview]
Message-ID: <20200226040612.GW24185@bombadil.infradead.org> (raw)
In-Reply-To: <20200226035827.1285-1-cai@lca.pw>
On Tue, Feb 25, 2020 at 10:58:27PM -0500, Qian Cai wrote:
> pgdat->kswapd_classzone_idx could be accessed concurrently in
> wakeup_kswapd(). Plain writes and reads without any lock protection
> result in data races. Fix them by adding a pair of READ|WRITE_ONCE() as
> well as saving a branch (compilers might well optimize the original code
> in an unintentional way anyway). While at it, also take care of
> pgdat->kswapd_order and non-kswapd threads in allow_direct_reclaim().
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.
next prev parent reply other threads:[~2020-02-26 4:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 3:58 [PATCH v2] mm/vmscan: fix data races at kswapd_classzone_idx Qian Cai
2020-02-26 4:06 ` Matthew Wilcox [this message]
2020-02-26 11:50 ` Qian Cai
2020-02-26 13:49 ` Qian Cai
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