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([2601:188:ca00:a00:f844:fad5:7984:7bd7]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-46a3e653f52sm199069491cf.16.2025.01.08.12.04.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jan 2025 12:04:41 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <6fb6d82f-a321-4b29-9fd6-60f7a8758233@redhat.com> Date: Wed, 8 Jan 2025 15:04:39 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] cgroup/cpuset: remove kernfs active break To: Tejun Heo , Waiman Long Cc: Chen Ridong , hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250106081904.721655-1-chenridong@huaweicloud.com> <625d03cd-302f-41b1-9502-dfd25eb677e1@redhat.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/8/25 3:00 PM, Tejun Heo wrote: > Hello, > > On Wed, Jan 08, 2025 at 02:50:19PM -0500, Waiman Long wrote: > ... >> It is not the strict ordering that I am worrying about. It is all about the >> possibility of hitting some race conditions. >> >> I am thinking of a scenario where a cpuset loses all its CPUs in hotunplug >> and then restored by adding other CPUs. There is chance that the css will be >> operated on concurrently by the auto-transfer task and another task moving >> new task to the css. I am not sure if that will be a problem or not. Anyway, >> it is very rare that we will be in such a situation. > Hmm... I might be missing something but cgroup_transfer_tasks() is fully > synchronized against migrations. I don't see anything dangerous there. > > Thanks. I probably misread some of the code. Then it is not an issue anymore. Thanks, Longman