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Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Kuniyuki Iwashima , Willem de Bruijn , Neal Cardwell , David Ahern , Mina Almasry , Arnd Bergmann , Jonathan Corbet , Andrew Lunn , Shuah Khan , Donald Hunter , Stanislav Fomichev , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, asml.silence@gmail.com, matttbe@kernel.org, skhawaja@google.com, Bobby Eshleman Subject: Re: [PATCH net-next v10 4/5] net: devmem: document NETDEV_A_DMABUF_AUTORELEASE netlink attribute Message-ID: References: <20260115-scratch-bobbyeshleman-devmem-tcp-token-upstream-v10-0-686d0af71978@meta.com> <20260115-scratch-bobbyeshleman-devmem-tcp-token-upstream-v10-4-686d0af71978@meta.com> <20260120163650.5a962648@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260120163650.5a962648@kernel.org> On Tue, Jan 20, 2026 at 04:36:50PM -0800, Jakub Kicinski wrote: > On Thu, 15 Jan 2026 21:02:15 -0800 Bobby Eshleman wrote: > > +- Once a system-wide autorelease mode is selected (via the first binding), > > + all subsequent bindings must use the same mode. Attempts to create bindings > > + with a different mode will be rejected with -EBUSY. > > Why? > Originally I was using EINVAL, but when writing the tests I noticed this might be a confusing case for users to interpret EINVAL (i.e., some binding possibly made by someone else is in a different mode). I thought EBUSY could capture the semantic "the system is locked up in a different mode, try again when it isn't". I'm not married to it though. Happy to go back to EINVAL or another errno. > > +- Applications using manual release mode (autorelease=0) must ensure all tokens > > + are returned via SO_DEVMEM_DONTNEED before socket close to avoid resource > > + leaks during the lifetime of the dmabuf binding. Tokens not released before > > + close() will only be freed when all RX queues are unbound AND all sockets > > + that called recvmsg() are closed. > > Could you add a short example on how? by calling shutdown()? Show an example of the three steps: returning the tokens, unbinding, and closing the sockets (TCP/NL)? Best, Bobby