From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Hui Zhu <hui.zhu@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Hui Zhu <zhuhui@kylinos.cn>
Subject: Re: [PATCH v2] mm: avoid KCSAN false positive in memdesc_nid()
Date: Tue, 23 Jun 2026 13:48:17 +0200 [thread overview]
Message-ID: <b7527f33-c0ef-41ec-9eb5-1b9a4d547689@kernel.org> (raw)
In-Reply-To: <20260623084432.701120-1-hui.zhu@linux.dev>
On 6/23/26 10:44, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
>
> KCSAN reports a data race between page_to_nid()/folio_nid() reading
> page->flags and folio_trylock()/folio_lock() concurrently doing
> test_and_set_bit_lock(PG_locked, ...) on the same word, e.g.:
>
> BUG: KCSAN: data-race in __lruvec_stat_mod_folio / shmem_get_folio_gfp
>
> The node id occupies a fixed bit-range of page->flags that is set
> once at page init and never modified afterwards, so it can never
> overlap with the low PG_locked/PG_waiters bits touched by the folio
> lock path.
>
> Use ASSERT_EXCLUSIVE_BITS() in memdesc_nid() to scope the exemption
> to just the node-id bits, consistent with how memdesc_zonenum()
> already handles the same class of race for the zone-id bits.
>
> Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
> ---
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
prev parent reply other threads:[~2026-06-23 11:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-23 8:44 [PATCH v2] mm: avoid KCSAN false positive in memdesc_nid() Hui Zhu
2026-06-23 11:48 ` David Hildenbrand (Arm) [this message]
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