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bh=vdW463lMrSIv6E0tgsiWW1gHVmKWpAD6pFZXhTowmDg=; b=Qx6ain5zpkrw9c0mIzTsdZJ2CziF6CqWWukuvArgsC4szGXpIxgHH/QINUH69+TsLjxssH ZtxAQFYwuObC448FwupWmc7cUrlmNSCsooOlcluSRtZZY6pYhdU1BzpiCRzn6PbD3KizpC 4L7T1dbr7DA9xUiX9gIYM06Sfvfta2AfHmq2q35mD6ZAtj2jcPQDNrmZzdvmzJ8GMApr5/ iGlCfU6kuA3lVF3/mkvgmYEof908j9ue1JEDCXtEoce6c8IjDMHZkEJXk6Xcu/CUbBu0+W UGBgV1oE9MTEaT3pNQ3m6Qwa6IBMyht89rhKb2igK55qXqX/QkuQS/OYHXhnqQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1681157522; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vdW463lMrSIv6E0tgsiWW1gHVmKWpAD6pFZXhTowmDg=; b=qCqxFj5jAYh3BVZhm6uZMnl5peEQBRM5008KIMURBjiOGz05/O+U/0Y2t9lJJYalfATkJu tJYspYOL2pZ2mQAA== To: Ye Bin , dennis@kernel.org, tj@kernel.org, cl@linux.com, linux-mm@kvack.org, yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk Cc: linux-kernel@vger.kernel.org, dchinner@redhat.com, yebin10@huawei.com, yebin@huaweicloud.com Subject: Re: [PATCH v2 1/2] cpu/hotplug: introduce 'num_dying_cpus' to get dying CPUs count In-Reply-To: <20230406015629.1804722-2-yebin@huaweicloud.com> References: <20230406015629.1804722-1-yebin@huaweicloud.com> <20230406015629.1804722-2-yebin@huaweicloud.com> Date: Mon, 10 Apr 2023 22:12:02 +0200 Message-ID: <87bkjv1oq5.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 7B0A6A0023 X-Stat-Signature: xewig563aeb5ojh7hxnq7js6p8i7xnuh X-Rspam-User: X-HE-Tag: 1681157528-294254 X-HE-Meta: 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 WtbbgT+i 0Yh0hqG8C3X9wlBzEMJCGGzHKEJd7Bxd/F8X7c1s+wdIM4uANMjxftEY03LH8D75Po2R/6SL3c591fOD6BEOaaHccXud/dF6kbUQUATPXNe9K/pGc+ChY/H9K/5fBvKMkLeQ+KTJZf4P54eSyDLpn0c2cKpYaj+Y+JG89fXPdiAfNuOIOCNZOEh1877tPnhuIJYo0eEX1p3qKt3Wl2/97qC6mlc9V7zRrUXkU 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: On Thu, Apr 06 2023 at 09:56, Ye Bin wrote: > From: Ye Bin > > Introduce '__num_dying_cpus' variable to cache the number of dying CPUs > in the core and just return the cached variable. Why? That atomic counter is racy too if read and acted upon w/o having CPUs read locked. All it does is making the race window smaller vs. the cpumask_weight() based implementation. It's still racy and incorrect. So no, this is not going to happen. Thanks, tglx