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Diffstat (limited to 'ev.pod')
| -rw-r--r-- | ev.pod | 22 |
1 files changed, 22 insertions, 0 deletions
@@ -913,6 +913,28 @@ whether a file descriptor is really ready with a known-to-be good interface such as poll (fortunately in our Xlib example, Xlib already does this on its own, so its quite safe to use). +=head3 The special problem of disappearing file descriptors + +Some backends (e.g kqueue, epoll) need to be told about closing a file +descriptor (either by calling C<close> explicitly or by any other means, +such as C<dup>). The reason is that you register interest in some file +descriptor, but when it goes away, the operating system will silently drop +this interest. If another file descriptor with the same number then is +registered with libev, there is no efficient way to see that this is, in +fact, a different file descriptor. + +To avoid having to explicitly tell libev about such cases, libev follows +the following policy: Each time C<ev_io_set> is being called, libev +will assume that this is potentially a new file descriptor, otherwise +it is assumed that the file descriptor stays the same. That means that +you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the +descriptor even if the file descriptor number itself did not change. + +This is how one would do it normally anyway, the important point is that +the libev application should not optimise around libev but should leave +optimisations to libev. + + =over 4 =item ev_io_init (ev_io *, callback, int fd, int events) |