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[146.241.68.231]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-39c0b7a4351sm13751264f8f.98.2025.04.01.01.52.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Apr 2025 01:52:18 -0700 (PDT) Message-ID: <38b9af46-0d03-424d-8ecc-461b7daf216c@redhat.com> Date: Tue, 1 Apr 2025 10:52:17 +0200 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v5 2/2] page_pool: Track DMA-mapped pages and unmap them when destroying the pool To: =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Andrew Lunn , Eric Dumazet , Ilias Apalodimas , Simon Horman , Andrew Morton , Mina Almasry , Yonglong Liu , Yunsheng Lin , Pavel Begunkov , Matthew Wilcox Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Qiuling Ren , Yuying Ma References: <20250328-page-pool-track-dma-v5-0-55002af683ad@redhat.com> <20250328-page-pool-track-dma-v5-2-55002af683ad@redhat.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20250328-page-pool-track-dma-v5-2-55002af683ad@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 3/28/25 1:19 PM, Toke Høiland-Jørgensen wrote: > @@ -463,13 +462,21 @@ page_pool_dma_sync_for_device(const struct page_pool *pool, > netmem_ref netmem, > u32 dma_sync_size) > { > - if (pool->dma_sync && dma_dev_need_sync(pool->p.dev)) > - __page_pool_dma_sync_for_device(pool, netmem, dma_sync_size); > + if (pool->dma_sync && dma_dev_need_sync(pool->p.dev)) { Lacking a READ_ONCE() here, I think it's within compiler's right do some unexpected optimization between this read and the next one. Also it will make the double read more explicit. Thanks, Paolo