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Fri, 08 May 2026 01:22:06 -0700 (PDT) Received: from lima-ubuntu.hz.ali.com ([47.246.98.218]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e643f891asm21071455e9.4.2026.05.08.01.21.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2026 01:22:05 -0700 (PDT) From: Qing Wang To: Vlastimil Babka , Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qing Wang Subject: [PATCH] mm/slub: hold cpus_read_lock around flush_rcu_sheaves_on_cache() Date: Fri, 8 May 2026 16:21:49 +0800 Message-Id: <20260508082149.182139-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7C03640002 X-Stat-Signature: 6brfudgqhgawxnon5kjj14sxeq46brp4 X-Rspam-User: X-HE-Tag: 1778228528-43347 X-HE-Meta: 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 TBy4Wi+b 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: flush_rcu_sheaves_on_cache() calls queue_work_on() in a for_each_online_cpu() loop, which requires the cpu to stay online. But cpus_read_lock() is not held in kvfree_rcu_barrier_on_cache(). There are two paths that call flush_rcu_sheaves_on_cache(): // has cpus_read_lock() flush_all_rcu_sheaves() -> flush_rcu_sheaves_on_cache() // no cpus_read_lock() kvfree_rcu_barrier_on_cache() -> flush_rcu_sheaves_on_cache() Fix this by holding cpus_read_lock() in kvfree_rcu_barrier_on_cache(). Why not move cpus_read_lock() from flush_all_rcu_sheaves() into flush_rcu_sheaves_on_cache()? The reason is it would introduce a new l ock order (slab_mutex -> cpu_hotplug_lock). The reverse order (cpu_hotplug_lock -> slab_mutex) is established by - cpuhp_setup_state_nocalls(..., slub_cpu_setup, ...) - kmem_cache_destroy() The two orders together would form an AB-BA deadlock. Finally, add lockdep_assert_cpus_held() in flush_rcu_sheaves_on_cache() to catch the same problem in the future. Signed-off-by: Qing Wang --- mm/slab_common.c | 6 ++++++ mm/slub.c | 1 + 2 files changed, 7 insertions(+) diff --git a/mm/slab_common.c b/mm/slab_common.c index d5a70a831a2a..0ee5a4189453 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -2110,7 +2110,13 @@ EXPORT_SYMBOL_GPL(kvfree_rcu_barrier); void kvfree_rcu_barrier_on_cache(struct kmem_cache *s) { if (cache_has_sheaves(s)) { + /* + * flush_rcu_sheaves_on_cache() use queue_work_on() and queue_work_on() + * must be called with the CPU hotplug read lock. + */ + cpus_read_lock(); flush_rcu_sheaves_on_cache(s); + cpus_read_unlock(); rcu_barrier(); } diff --git a/mm/slub.c b/mm/slub.c index 161079ac5ba1..2a005d1e3a74 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4024,6 +4024,7 @@ void flush_rcu_sheaves_on_cache(struct kmem_cache *s) struct slub_flush_work *sfw; unsigned int cpu; + lockdep_assert_cpus_held(); mutex_lock(&flush_lock); for_each_online_cpu(cpu) { -- 2.34.1