From: Aleksa Sarai > Sent: 19 April 2020 11:44 > > On 2020-04-13, Josh Triplett <josh@xxxxxxxxxxxxxxxx> wrote: > > Inspired by the X protocol's handling of XIDs, allow userspace to select > > the file descriptor opened by openat2, so that it can use the resulting > > file descriptor in subsequent system calls without waiting for the > > response to openat2. > > > > In io_uring, this allows sequences like openat2/read/close without > > waiting for the openat2 to complete. Multiple such sequences can > > overlap, as long as each uses a distinct file descriptor. > > I'm not sure I understand this explanation -- how can you trigger a > syscall with an fd that hasn't yet been registered (unless you're just > hoping the race goes in your favour)? I suspect (there are no comments in the io_uring code to say what it does) that the io_uring code uses a thread of the user process to sequentially execute IO requests that the main application has added to a queue. So it might make sense to queue up open/read/close. But that ought to be within the io_uring code. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
