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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fac1535cbdsm106932925ad.134.2024.07.03.11.28.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jul 2024 11:28:13 -0700 (PDT) Sender: Tejun Heo Date: Wed, 3 Jul 2024 08:28:12 -1000 From: Tejun Heo To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, Lai Jiangshan , Waiman Long Subject: Re: [PATCH 2/6] workqueue: Protect wq_unbound_cpumask with wq_pool_attach_mutex in init_rescuer() Message-ID: References: <20240703033855.3373-1-jiangshanlai@gmail.com> <20240703033855.3373-3-jiangshanlai@gmail.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: <20240703033855.3373-3-jiangshanlai@gmail.com> Hello, Lai. On Wed, Jul 03, 2024 at 11:38:51AM +0800, Lai Jiangshan wrote: > @@ -5533,6 +5533,9 @@ static int init_rescuer(struct workqueue_struct *wq) > return ret; > } > > + /* lock wq_pool_attach_mutex for wq_unbound_cpumask */ > + mutex_lock(&wq_pool_attach_mutex); > + > wq->rescuer = rescuer; > if (wq->flags & WQ_UNBOUND) > kthread_bind_mask(rescuer->task, wq_unbound_cpumask); > @@ -5540,6 +5543,8 @@ static int init_rescuer(struct workqueue_struct *wq) > kthread_bind_mask(rescuer->task, cpu_possible_mask); > wake_up_process(rescuer->task); > > + mutex_unlock(&wq_pool_attach_mutex); > + Isn't that just protecting the reads on wq_unbound_cpumask? I don't understand what this protects against. Shouldn't the interlocking be something like "either new rescuer reads the updated cpumask or the workqueue is already on the workqueue list"? Thanks. -- tejun