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Wed, 09 Jun 2021 15:29:18 -0700 (PDT) Received: from grain.localdomain ([5.18.171.94]) by smtp.gmail.com with ESMTPSA id r3sm111100ljc.20.2021.06.09.15.29.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 15:29:16 -0700 (PDT) Received: by grain.localdomain (Postfix, from userid 1000) id C25C85A0041; Thu, 10 Jun 2021 01:29:15 +0300 (MSK) Date: Thu, 10 Jun 2021 01:29:15 +0300 From: Cyrill Gorcunov To: Vlastimil Babka Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim , Sebastian Andrzej Siewior , Thomas Gleixner , Mel Gorman , Jesper Dangaard Brouer , Peter Zijlstra , Jann Horn Subject: Re: [RFC v2 29/34] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context Message-ID: References: <20210609113903.1421-1-vbabka@suse.cz> <20210609113903.1421-30-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210609113903.1421-30-vbabka@suse.cz> User-Agent: Mutt/2.0.7 (2021-05-04) X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 7C2D8C0042C0 Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=rdDQNK6m; spf=pass (imf06.hostedemail.com: domain of gorcunov@gmail.com designates 209.85.208.176 as permitted sender) smtp.mailfrom=gorcunov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: z6u5yyh3ebztt7jh5c9mhs4ke3bo1jy5 X-HE-Tag: 1623277755-942301 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 Wed, Jun 09, 2021 at 01:38:58PM +0200, Vlastimil Babka wrote: > +static DEFINE_MUTEX(flush_lock); > +static DEFINE_PER_CPU(struct slub_flush_work, slub_flush); > + > static void flush_all(struct kmem_cache *s) > { > - on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1); > + struct slub_flush_work *sfw; > + unsigned int cpu; > + > + cpus_read_lock(); > + mutex_lock(&flush_lock); > + Hi, Vlastimil! Could you please point why do you lock cpus first and mutex only after? Why not mutex_lock + cpus_read_lock instead?