On 2/9/20 2:25 AM, Jonas Bonn wrote: > Hi Jens, > > I've been trying to use io_uring to flood a network link with UDP > packets. Essentially, the program just pushes a series of sendmsg() > calls through the SQE ring and keeps topping it up with new calls as > soon as the completions come in. > > When the sendmsg() calls complete immediately then everything works > fine; however, when the calls 'block' and get queued up in the kernel > then the calls return either errno 97 or 22 when they're retried through > the workqueue (effectively, bad address or invalid iovec length). > > My gut-feeling is that there's some issue copying the msghdr struct so > that the call that's retried isn't exactly the same one that was > requested. I looked into the kernel code a bit, but couldn't really > make heads or tails of it so I though I'd ask for some input while I > keep investigating. > > I noticed that liburing has a simple test for sendmsg that sends a > single message; the 'punted' case doesn't seem to be tested. Is this > something you've tried? > > Tested on kernels 5.3 to 5.6-pre and the behaviour's pretty much the > same with regards to the above. You could try and pull: git://git.kernel.dk/linux-block io_uring-5.6 into the current 5.6-pre tree and see if it works for you. In any case, do you have a test case for this? -- Jens Axboe
