From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B90B0C433ED for ; Wed, 14 Apr 2021 07:18:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 48963613A9 for ; Wed, 14 Apr 2021 07:18:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 48963613A9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C4A6B6B0070; Wed, 14 Apr 2021 03:18:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BF9EB6B0071; Wed, 14 Apr 2021 03:18:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A9B3C6B0072; Wed, 14 Apr 2021 03:18:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0002.hostedemail.com [216.40.44.2]) by kanga.kvack.org (Postfix) with ESMTP id 8A0B06B0070 for ; Wed, 14 Apr 2021 03:18:06 -0400 (EDT) Received: from smtpin36.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 3B20218017064 for ; Wed, 14 Apr 2021 07:18:06 +0000 (UTC) X-FDA: 78030118572.36.4573146 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf05.hostedemail.com (Postfix) with ESMTP id 2140AE000105 for ; Wed, 14 Apr 2021 07:18:05 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7E650AC87; Wed, 14 Apr 2021 07:18:04 +0000 (UTC) Date: Wed, 14 Apr 2021 09:18:02 +0200 From: Oscar Salvador To: Mel Gorman Cc: Andrew Morton , "Michael S. Tsirkin" , Vlastimil Babka , Alexander Duyck , Minchan Kim , Michal Hocko , David Hildenbrand , Linux-MM , LKML Subject: Re: [PATCH v2 resend] mm/memory_hotplug: Make unpopulated zones PCP structures unreachable during hot remove Message-ID: <20210414071756.GA20401@linux> References: <20210412120842.GY3697@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210412120842.GY3697@techsingularity.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-Stat-Signature: etmfgpemnghc7c91448a97sertouz5dk X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2140AE000105 Received-SPF: none (suse.de>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: none/none X-HE-Tag: 1618384685-473429 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 Mon, Apr 12, 2021 at 01:08:42PM +0100, Mel Gorman wrote: > zone_pcp_reset allegedly protects against a race with drain_pages > using local_irq_save but this is bogus. local_irq_save only operates > on the local CPU. If memory hotplug is running on CPU A and drain_pages > is running on CPU B, disabling IRQs on CPU A does not affect CPU B and > offers no protection. > > This patch deletes IRQ disable/enable on the grounds that IRQs protect > nothing and assumes the existing hotplug paths guarantees the PCP cannot be > used after zone_pcp_enable(). That should be the case already because all > the pages have been freed and there is no page to put on the PCP lists. > > Signed-off-by: Mel Gorman Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE L3