From: Gregory Price <gourry@gourry.net>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Chris Down <chris@chrisdown.name>,
Meta kernel team <kernel-team@meta.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, Sashiko <sashiko-bot@kernel.org>
Subject: Re: [PATCH] mm/page_counter: use WRITE_ONCE() for emin/elow when parent is the root
Date: Wed, 21 Oct 2026 17:24:20 -0400 [thread overview]
Message-ID: <atktYGL3OP088D9P@gourry-fedora-PF4VCD3F> (raw)
In-Reply-To: <20261021204818.3431099-1-shakeel.butt@linux.dev>
On Wed, Oct 21, 2026 at 01:48:18PM -0700, Shakeel Butt wrote:
> page_counter_calculate_protection() runs without locks. Several
> reclaimers can update the same counter's emin and elow at the same
> time, and readers such as mem_cgroup_below_min(), mem_cgroup_protection()
> and the dmem eviction code load them with READ_ONCE().
>
...
>
> Use WRITE_ONCE() for these two stores as well.
>
> There is no functional change. Readers already accept stale values, and
> compilers emit a single word-sized store either way: with GCC 14 the
> x86-64 object code is the same before and after this change.
>
> Fixes: b3a7822e5e75 ("mm, memcg: prevent mem_cgroup_protected store tearing")
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>
next prev parent reply other threads:[~2026-10-21 21:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-21 20:48 [PATCH] mm/page_counter: use WRITE_ONCE() for emin/elow when parent is the root Shakeel Butt
2026-10-21 21:24 ` Gregory Price [this message]
2026-10-22 0:53 ` SJ Park
2026-10-22 2:18 ` Muchun Song
2026-10-22 4:52 ` Anshuman Khandual
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