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b=udd7Vot1d91cmE9l1YiWBC4Dpwq9GRa3cyguds5yLksbeH+ka4qJiHtlZPcV7dxiz PTqsv4jKvTF24ekQUZuli8taGYj+db6x4dVwLr2JectjKgKm5IHXr7co+cVzpUzR0V U8uct76BUcBbAnEmI9p0CAYRJmya6upqIFP5rUQY= Date: Thu, 10 Apr 2025 22:06:18 -0700 From: Andrew Morton To: Shakeel Butt Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Yosry Ahmed , Waiman Long , Vlastimil Babka , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: decouple memcg_hotplug_cpu_dead from stock_lock Message-Id: <20250410220618.405d00875ca61043c4ffa6e1@linux-foundation.org> In-Reply-To: <20250410210623.1016767-1-shakeel.butt@linux.dev> References: <20250410210623.1016767-1-shakeel.butt@linux.dev> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E0F9E18000A X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: xphwz696qp9usdjez3547doxxqmkhrt1 X-HE-Tag: 1744347980-600632 X-HE-Meta: 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 9mA9Ah7J UTOIrO1do7l92vaWhx+sCUzvKtTSRsnWzC6vloT8G90e1rzhKXo6SA9g/yPa3maRM4/NmpZcrXTIesZcZdelEYdLGOx2nEL8iwDi/mAk8P2AK+3RcYXtEcuZNHFDeCx30KFjiFfi474VBDcUjJ4QtIQNg0+SNWzjBmkceT4OUW0REAxVxNHkh6sc9iV6Ik7RKZS0rQLrowzh1TsOus3Bi6v8uPXvF990RdSq+zzeQwumRWbgcsUmTac42UeyO8n4EMGKs 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 Thu, 10 Apr 2025 14:06:23 -0700 Shakeel Butt wrote: > The function memcg_hotplug_cpu_dead works on the stock of a remote dead > CPU and drain_obj_stock works on the given stock instead of local stock, > so there is no need to take local stock_lock anymore. > > @@ -1964,10 +1964,10 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu) > > stock = &per_cpu(memcg_stock, cpu); > > - /* drain_obj_stock requires stock_lock */ > - local_lock_irqsave(&memcg_stock.stock_lock, flags); > - drain_obj_stock(stock); > - local_unlock_irqrestore(&memcg_stock.stock_lock, flags); > + local_irq_save(flag); > + /* stock of a remote dead cpu, no need for stock_lock. */ > + __drain_obj_stock(stock); > + local_irq_restore(flag); > s/flag/flags/ Obviously what-i-got isn't what-you-tested. Please check what happened here,