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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-77d682b3909sm129760a12.88.2024.07.08.11.16.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Jul 2024 11:16:18 -0700 (PDT) Sender: Tejun Heo Date: Mon, 8 Jul 2024 08:16:17 -1000 From: Tejun Heo To: kernel test robot Cc: Lai Jiangshan , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Lai Jiangshan Subject: Re: [PATCH V2 4/5] workqueue: Put PWQ allocation and WQ enlistment in the same lock C.S. Message-ID: References: <20240704034915.2164-5-jiangshanlai@gmail.com> <202407081521.83b627c1-lkp@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202407081521.83b627c1-lkp@intel.com> Hello, On Mon, Jul 08, 2024 at 03:54:19PM +0800, kernel test robot wrote: ... > [ 2.269463][ T1] cpus_read_lock (include/linux/percpu-rwsem.h:53 kernel/cpu.c:488) > [ 2.273463][ T1] alloc_workqueue (kernel/workqueue.c:5152 kernel/workqueue.c:5730) > [ 2.273463][ T1] padata_alloc (kernel/padata.c:1007 (discriminator 1)) > [ 2.273463][ T1] pcrypt_init_padata (crypto/pcrypt.c:327 (discriminator 1)) > [ 2.277463][ T1] pcrypt_init (crypto/pcrypt.c:353) > [ 2.277463][ T1] do_one_initcall (init/main.c:1267) > [ 2.281464][ T1] do_initcalls (init/main.c:1328 (discriminator 1) init/main.c:1345 (discriminator 1)) > [ 2.281464][ T1] kernel_init_freeable (init/main.c:1364) > [ 2.285464][ T1] kernel_init (init/main.c:1469) > [ 2.285464][ T1] ret_from_fork (arch/x86/kernel/process.c:153) > [ 2.289466][ T1] ret_from_fork_asm (arch/x86/entry/entry_32.S:737) > [ 2.289466][ T1] entry_INT80_32 (arch/x86/entry/entry_32.S:944) Ah, this is unfortunate, so pcrypt is allocating a workqueue while holding cpus_read_lock(), so workqueue code can't do it again as that can lead to deadlocks if down_write starts after the first down_read. Lai, it looks like we'd need to switch to workqueue specific locking so that we don't depend on cpus_read_lock from alloc path. Thanks. -- tejun