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Tue, 26 Aug 2025 01:23:13 -0700 (PDT) Date: Tue, 26 Aug 2025 01:23:11 -0700 From: Breno Leitao To: Gu Bowen Cc: Catalin Marinas , Andrew Morton , Greg Kroah-Hartman , Waiman Long , stable@vger.kernel.org, linux-mm@kvack.org, John Ogness , Lu Jialin Subject: Re: [PATCH v5] mm: Fix possible deadlock in kmemleak Message-ID: References: <20250822073541.1886469-1-gubowen5@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250822073541.1886469-1-gubowen5@huawei.com> X-Stat-Signature: fchw6pby5oicj5rp3peu6zbwbqaw7hbt X-Rspam-User: X-Rspamd-Queue-Id: D580B140004 X-Rspamd-Server: rspam01 X-HE-Tag: 1756196595-764533 X-HE-Meta: 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 lEOYHwv+ 1/uOAi3y2pIanjhix7ZdardrBZpX2lA5cZF3fMk4gdGoiXjvBREFNC9ezXCMfJ1LtFYZygGrll/hcJvb5kD+eImK5x+nrjSVLi3oCh/biBjl0QSyPLzgRiXwYoVACU40p9+TD3R+7+SWYd+lLULtq1HxLcizWhvAG+TNuQp1jcITBvX+TknDar6FOD04Lavpz4nJ0ETqhNDPbkP01GDJUtAQSLSyFiTK0fGXE+4HYmvS5l16SVfoRxEpNM40pzo196krpxvb0ZEwotYNLE8sFEgH5s5cyLEkzuTsqSFETTQOifaGr3l+OKMhXsI+8AK0aTh7nTtd2tCBLzatyp+PH6yty4wwXmWynguiLikDE7GsWHMMpFwor+n/LSX32T3cU7iyGi8VhW/MFjuvuyCzhFc3oFeTrMuCGJk1nRe7QKOOHs5pPqyVb1gKd19wibmoAiKmRrnQe7HX0kuU9ZuUH4oygGw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 22, 2025 at 03:35:41PM +0800, Gu Bowen wrote: > There are some AA deadlock issues in kmemleak, similar to the situation > reported by Breno [1]. The deadlock path is as follows: > > mem_pool_alloc() > -> raw_spin_lock_irqsave(&kmemleak_lock, flags); > -> pr_warn() > -> netconsole subsystem > -> netpoll > -> __alloc_skb > -> __create_object > -> raw_spin_lock_irqsave(&kmemleak_lock, flags); > > To solve this problem, switch to printk_safe mode before printing warning > message, this will redirect all printk()-s to a special per-CPU buffer, > which will be flushed later from a safe context (irq work), and this > deadlock problem can be avoided. The proper API to use should be > printk_deferred_enter()/printk_deferred_exit() [2]. Another way is to > place the warn print after kmemleak is released. > > [1] > https://lore.kernel.org/all/20250731-kmemleak_lock-v1-1-728fd470198f@debian.org/#t > [2] > https://lore.kernel.org/all/5ca375cd-4a20-4807-b897-68b289626550@redhat.com/ > ==================== > > Signed-off-by: Gu Bowen Reviewed-by: Breno Leitao