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Tue, 17 Aug 2021 07:57:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id HyfCDP1rG2GcNAAAMHmgww (envelope-from ); Tue, 17 Aug 2021 07:57:49 +0000 Subject: Re: [PATCH] mm, slub: add cpus_read_lock/unlock() for slab_mem_going_offline_callback() To: David Hildenbrand , qiang.zhang@windriver.com, akpm@linux-foundation.org, sfr@canb.auug.org.au Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210816074605.30336-1-qiang.zhang@windriver.com> From: Vlastimil Babka Message-ID: Date: Tue, 17 Aug 2021 09:57:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 18BE6501901B Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=egDfmTWg; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=g9+tvvJp; dmarc=none; spf=pass (imf01.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Rspamd-Server: rspam04 X-Stat-Signature: sscgw6pgsinfju63kqwrabyygrfnupkb X-HE-Tag: 1629187071-228870 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 8/16/21 10:04 AM, David Hildenbrand wrote: > On 16.08.21 09:46, qiang.zhang@windriver.com wrote: >> From: "Qiang.Zhang" >> >> The flush_all_cpus_locked() should be called with cpus_read_lock/unlock(), >> ensure flush_cpu_slab() can be executed on schedule_on CPU. >> >> Fixes: 1c84f3c91640 ("mm, slub: fix memory and cpu hotplug related lock ordering issues") > Memory notifiers are getting called from online_pages()/offline_pages(), > where we call memory_notify(MEM_GOING_OFFLINE, &arg) under > mem_hotplug_begin(). > > mem_hotplug_begin() does a cpus_read_lock(). Exactly. Also flush_all_cpus_locked() has a lockdep assert for cpus_read_lock() which doesn't trigger in testing. > How does this even work or against which branch is this? >