From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Muchun Song <songmuchun@bytedance.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
Charan Teja Kalla <quic_charante@quicinc.com>
Cc: Muchun Song <muchun.song@linux.dev>,
Kairui Song <kasong@tencent.com>, Qi Zheng <qi.zheng@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Barry Song <baohua@kernel.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
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,
linux-cxl@vger.kernel.org
Subject: Re: [PATCH] mm/sparse: Fix race on mem_section->usage in pfn walkers
Date: Wed, 15 Apr 2026 10:04:38 +0200 [thread overview]
Message-ID: <09d1ef13-e02b-41e9-b431-4c3254e42011@kernel.org> (raw)
In-Reply-To: <20260415022326.53218-1-songmuchun@bytedance.com>
On 4/15/26 04:23, Muchun Song wrote:
> When memory is hot-removed, section_deactivate() can tear down
> mem_section->usage while concurrent pfn walkers still inspect the
> subsection map via pfn_section_valid() or pfn_section_first_valid().
I'll note that it's all racy either way: someone checking pfn_valid() /
pfn_to_online_page() can race with concurrent unplug.
We've known that for years; it's hard to fix; it never ever triggers :)
So is this really worth it, when we should in fact, work on protecting
the users of pfn_valid() / pfn_to_online_page() with rcu or similar?
--
Cheers,
David
next prev parent reply other threads:[~2026-04-15 8:04 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-15 2:23 Muchun Song
2026-04-15 5:44 ` Andrew Morton
2026-04-15 6:06 ` Muchun Song
2026-04-15 8:04 ` David Hildenbrand (Arm) [this message]
2026-04-15 9:20 ` Muchun Song
2026-04-15 8:37 ` Oscar Salvador
2026-04-15 9:45 ` Muchun Song
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