On Tue, 20 Jan 2026 21:44:09 -0800 Bobby Eshleman wrote: > 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.
My question was more why the system-wide policy exists, rather than binding-by-binding. Naively I'd think that a single socket must pick but system wide there could easily be multiple bindings not bothering each other, doing different things? > > > +- 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)? TBH I read the doc before reading the code, which I guess may actually be better since we don't expect users to read the code first either.. Now after reading the code I'm not sure the doc explains things properly. AFAIU there's no association of token <> socket within the same binding. User can close socket A and return the tokens via socket B. As written the doc made me think that there will be a leak if socket is closed without releasing tokens, or that there may be a race with data queued but not read. Neither is true, really?
