From: Matthew Wilcox <willy@infradead.org>
To: "Liam R. Howlett (Google)" <liam@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Thomas Graf <tgraf@suug.ch>,
Herbert Xu <herbert@gondor.apana.org.au>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
maple-tree@lists.infradead.org, Lorenzo Stoakes <ljs@kernel.org>,
Chris Mason <mason@kernel.org>, Alice Ryhl <aliceryhl@google.com>,
Andrew Ballance <andrewjballance@gmail.com>,
stable@vger.kernel.org,
"David Hildenbrand (Arm)" <david@kernel.org>
Subject: Re: [PATCH 4/4] rhashtable: fix vmalloc() deadlock in atomic rehash
Date: Thu, 29 Oct 2026 20:02:32 +0000 [thread overview]
Message-ID: <auOmWM5uiQC9LPwx@casper.infradead.org> (raw)
In-Reply-To: <20261028154218.1668182-5-liam@infradead.org>
On Wed, Oct 28, 2026 at 11:42:18AM -0400, Liam R. Howlett (Google) wrote:
> Below, one CPU adds an FDB entry for an RTM_NEWNEIGH netlink request,
> while another CPU is inside vmalloc() or vfree():
>
> RTM_NEWNEIGH vmalloc() or vfree()
> ============ ====================
> spin_lock_bh(&br->hash_lock)
> spin_lock(&vn->busy.lock)
> rhashtable_insert_rehash()
> kvmalloc(GFP_ATOMIC)
> vmalloc()
> spin_lock(&vn->busy.lock)
> waits for the other CPU
> softirq: a frame for the bridge
> spin_lock(&br->hash_lock)
> waits for RTM_NEWNEIGH
This seems like the kind of deadlock that lockdep can catch. Why
hasn't it? Do we need to add a fake lock for RTM_NEWNEIGH?
prev parent reply other threads:[~2026-10-29 20:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-28 15:42 [PATCH 0/4] Lib fixes for 7.3 Liam R. Howlett (Google)
2026-10-28 15:42 ` [PATCH 1/4] maple_tree: Fix rcu reader NULL dereference after the tree is emptied Liam R. Howlett (Google)
2026-10-28 15:42 ` [PATCH 2/4] maple_tree: Test emptying tree while RCU reading Liam R. Howlett (Google)
2026-10-28 15:42 ` [PATCH 3/4] maple_tree: Update internal warning and bug_on code Liam R. Howlett (Google)
2026-10-28 17:54 ` Lorenzo Stoakes (ARM)
2026-10-28 18:37 ` Liam R. Howlett (Google)
2026-10-28 15:42 ` [PATCH 4/4] rhashtable: fix vmalloc() deadlock in atomic rehash Liam R. Howlett (Google)
2026-10-29 2:16 ` Herbert Xu
2026-10-29 10:08 ` Uladzislau Rezki
2026-10-29 14:53 ` Liam R. Howlett (Google)
2026-10-29 16:23 ` Michal Hocko
2026-10-29 20:02 ` Matthew Wilcox [this message]
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