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a="188374906" X-IronPort-AV: E=Sophos;i="5.81,236,1610438400"; d="scan'208";a="188374906" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Mar 2021 14:07:45 -0800 IronPort-SDR: a4pra8I11xMU1mirj04YcFkc18VLXLn3WhsLjs0aWtWUtXNMUKtv0DZW3EeAAJhQKS6UoRx4G9 0PNBCA+RHnzA== X-IronPort-AV: E=Sophos;i="5.81,236,1610438400"; d="scan'208";a="447662582" Received: from jcchan4-mobl.amr.corp.intel.com (HELO [10.212.217.30]) ([10.212.217.30]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Mar 2021 14:07:44 -0800 Subject: Re: [PATCH 03/10] mm/migrate: update node demotion order during on hotplug events To: Yang Shi , Dave Hansen Cc: Linux Kernel Mailing List , Linux MM , Yang Shi , David Rientjes , Huang Ying , Dan Williams , David Hildenbrand , Oscar Salvador References: <20210304235949.7922C1C3@viggo.jf.intel.com> <20210304235955.05514241@viggo.jf.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/8/21 4:03 PM, Yang Shi wrote: >> +static int __meminit migrate_on_reclaim_callback(struct notifier_block *self, >> + unsigned long action, void *arg) >> +{ >> + switch (action) { >> + case MEM_GOING_OFFLINE: >> + /* >> + * Make sure there are not transient states where >> + * an offline node is a migration target. This >> + * will leave migration disabled until the offline >> + * completes and the MEM_OFFLINE case below runs. >> + */ >> + disable_all_migrate_targets(); >> + >> + /* >> + * Ensure the disable operation is globally visible. >> + * This avoids readers ever being able to >> + * simultaneously observe the old (pre-hotplug) and >> + * new (post-hotplug) migration targets. >> + */ >> + synchronize_rcu(); > It seems disable_all_migrate_targets() already has synchronize_rcu() > called. We don't need to call it twice. Otherwise, it looks good to > me. Reviewed-by: Yang Shi Thanks for noticing that. I've fixed it up.