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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 Subject: Re: [PATCH net-next v5 2/2] page_pool: Track DMA-mapped pages and unmap them when destroying the pool In-Reply-To: <38b9af46-0d03-424d-8ecc-461b7daf216c@redhat.com> References: <20250328-page-pool-track-dma-v5-0-55002af683ad@redhat.com> <20250328-page-pool-track-dma-v5-2-55002af683ad@redhat.com> <38b9af46-0d03-424d-8ecc-461b7daf216c@redhat.com> X-Clacks-Overhead: GNU Terry Pratchett Date: Tue, 01 Apr 2025 11:12:35 +0200 Message-ID: <87y0wkmeik.fsf@toke.dk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Paolo Abeni writes: > On 3/28/25 1:19 PM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> @@ -463,13 +462,21 @@ page_pool_dma_sync_for_device(const struct page_po= ol *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. Right, good point; will respin! -Toke