linux-kernel - Re: [PATCH net-next v10 4/5] net: devmem: document NETDEV_A_DMABUF

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Message-ID: <20260120163650.5a962648@kernel.org>
Date: Tue, 20 Jan 2026 16:36:50 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Bobby Eshleman <bobbyeshleman@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, Willem de Bruijn
 <willemb@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, David Ahern
 <dsahern@...nel.org>, Mina Almasry <almasrymina@...gle.com>, Arnd Bergmann
 <arnd@...db.de>, Jonathan Corbet <corbet@....net>, Andrew Lunn
 <andrew+netdev@...n.ch>, Shuah Khan <shuah@...nel.org>, Donald Hunter
 <donald.hunter@...il.com>, Stanislav Fomichev <sdf@...ichev.me>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kselftest@...r.kernel.org, asml.silence@...il.com,
 matttbe@...nel.org, skhawaja@...gle.com, Bobby Eshleman
 <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v10 4/5] net: devmem: document
 NETDEV_A_DMABUF_AUTORELEASE netlink attribute

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?

> +- 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()?