On Thu, 2015-10-22 at 08:15 +0200, casper....@oracle.com wrote: > >It's been said that the current mechanisms in Linux & some BSD variants > >can be subject to races, and the behaviour exhibited doesn't conform to > >POSIX, for example requiring the use of shutdown() on unconnected > >sockets because close() doesn't kick off other threads accept()ing on > >the same fd. I'd be interested to hear if there's a better and more > >performant way of handling the situation that doesn't involve doing the > >sort of bookkeeping Casper described,. > > Of course, the implementation is now around 18 years old; clearly a lot of > things have changed since then. > > In the particular case of Linux close() on a socket, surely it must be > possible to detect at close that it is a listening socket and that you are > about to close the last reference; the kernel could then do the shutdown() > all by itself.
We absolutely do not _want_ to do this just so that linux becomes slower to the point Solaris can compete, or you guys can avoid some work. close(fd) is very far from knowing a file is a 'listener' or even a 'socket' without extra cache line misses. To force a close of an accept() or whatever blocking socket related system call a shutdown() makes a lot of sense. This would have zero additional overhead for the fast path. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
