Hello, Herbert. On Sun, Sep 27, 2015 at 03:41:10AM +0800, Herbert Xu wrote: > Thread 1 Thread 2 > sendmsg getsockname > netlink_autobind netlink_getname > > Thread 2 should not have to do anything special to guarantee that > getsockname does not return garbage. It must either be the bound > portid if the autobind completed in thread 1 and is visible or it > should return zero. > > As it stands thread 2 may see a portid belonging to somebody else > if it catches the autobind in thread 1 trying different portids > while roving.
If the fact that thread 1 finished autobind isn't visible to thread 2, it's valid for getsockname to return zero. No ordering between the two operations is defined. If the fact that thread 1 finished autobind is visible to thread 2, ordering is defined and because ordering is transitive, by that very ordering, the port number is visible to thread 2 too as long as thread 1 does proper barriering. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
