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Mon, 04 May 2020 14:25:13 -0700 (PDT) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id gl12sm372771pjb.27.2020.05.04.14.25.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2020 14:25:13 -0700 (PDT) Date: Mon, 4 May 2020 14:25:12 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Kevin Hao cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , Joonsoo Kim , Andrew Morton , Sebastian Andrzej Siewior , Thomas Gleixner , Steven Rostedt Subject: Re: [PATCH v5.6-rt] mm: slub: Always flush the delayed empty slubs in flush_all() In-Reply-To: <20200504033407.2385-1-haokexin@gmail.com> Message-ID: References: <20200504033407.2385-1-haokexin@gmail.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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, 4 May 2020, Kevin Hao wrote: > After commit f0b231101c94 ("mm/SLUB: delay giving back empty slubs to > IRQ enabled regions"), when the free_slab() is invoked with the IRQ > disabled, the empty slubs are moved to a per-CPU list and will be > freed after IRQ enabled later. But in the current codes, there is > a check to see if there really has the cpu slub on a specific cpu > before flushing the delayed empty slubs, this may cause a reference > of already released kmem_cache in a scenario like below: > cpu 0 cpu 1 > kmem_cache_destroy() > flush_all() > --->IPI flush_cpu_slab() > flush_slab() > deactivate_slab() > discard_slab() > free_slab() > c->page = NULL; > for_each_online_cpu(cpu) > if (!has_cpu_slab(1, s)) > continue > this skip to flush the delayed > empty slub released by cpu1 > kmem_cache_free(kmem_cache, s) > > kmalloc() > __slab_alloc() > free_delayed() > __free_slab() > reference to released kmem_cache > > Fixes: f0b231101c94 ("mm/SLUB: delay giving back empty slubs to IRQ enabled regions") > Signed-off-by: Kevin Hao Acked-by: David Rientjes