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[2603:800c:1a02:1bae:e24f:43ff:fee6:449f]) by smtp.gmail.com with ESMTPSA id q2sm39651861pfj.94.2022.02.14.11.43.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Feb 2022 11:43:53 -0800 (PST) Date: Mon, 14 Feb 2022 09:43:52 -1000 From: Tejun Heo To: Padmanabha Srinivasaiah Cc: jiangshanlai@gmail.com, linux-kernel@vger.kernel.org, paulmck@kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] workqueue: Fix race in schedule and flush work Message-ID: References: <20220210184319.25009-1-treasure4paddy@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220210184319.25009-1-treasure4paddy@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220214_114357_957985_77A2245A X-CRM114-Status: GOOD ( 14.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello, > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 33f1106b4f99..a3f53f859e9d 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -3326,28 +3326,38 @@ EXPORT_SYMBOL(cancel_delayed_work_sync); > */ > int schedule_on_each_cpu(work_func_t func) > { > - int cpu; > struct work_struct __percpu *works; > + cpumask_var_t sched_cpumask; > + int cpu, ret = 0; > > - works = alloc_percpu(struct work_struct); > - if (!works) > + if (!alloc_cpumask_var(&sched_cpumask, GFP_KERNEL)) > return -ENOMEM; > > + works = alloc_percpu(struct work_struct); > + if (!works) { > + ret = -ENOMEM; > + goto free_cpumask; > + } > + > cpus_read_lock(); > > - for_each_online_cpu(cpu) { > + cpumask_copy(sched_cpumask, cpu_online_mask); > + for_each_cpu_and(cpu, sched_cpumask, cpu_online_mask) { This definitely would need a comment explaining what's going on cuz it looks weird to be copying the cpumask which is supposed to stay stable due to the cpus_read_lock(). Given that it can only happen during early boot and the online cpus can only be expanding, maybe just add sth like: if (early_during_boot) { for_each_possible_cpu(cpu) INIT_WORK(per_cpu_ptr(works, cpu), func); } BTW, who's calling schedule_on_each_cpu() that early during boot. It makes no sense to do this while the cpumasks can't be stabilized. Thanks. -- tejun _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel