diff options
Diffstat (limited to 'eio.pod')
| -rw-r--r-- | eio.pod | 36 |
1 files changed, 21 insertions, 15 deletions
@@ -47,21 +47,24 @@ time differences throughout libeio. =head2 FORK SUPPORT -Calling C<fork ()> is fully supported by this module - but you must not -rely on this. It is currently implemented in these steps: - - 1. wait till all requests in "execute" state have been handled - (basically requests that are already handed over to the kernel). - 2. fork - 3. in the parent, continue business as usual, done - 4. in the child, destroy all ready and pending requests and free the - memory used by the worker threads. This gives you a fully empty - libeio queue. - -Note, however, since libeio does use threads, the above guarantee doesn't -cover your libc, for example, malloc and other libc functions are not -fork-safe, so there is very little you can do after a fork, and in fact, -the above might crash, and thus change. +Usage of pthreads in a program changes the semantics of fork +considerably. Specifically, only async-safe functions can be called after +fork. Libeio uses pthreads, so this applies, and makes using fork hard for +anything but relatively fork + exec uses. + +This library only works in the process that initialised it: Forking is +fully supported, but using libeio in any other process than the one that +called C<eio_init> is not. + +You might get around by not I<using> libeio before (or after) forking in +the parent, and using it in the child afterwards. You could also try to +call the L<eio_init> function again in the child, which will brutally +reinitialise all data structures, which isn't POSIX conformant, but +typically works. + +Otherwise, the only recommendation you should follow is: treat fork code +the same way you treat signal handlers, and only ever call C<eio_init> in +the process that uses it, and only once ever. =head1 INITIALISATION/INTEGRATION @@ -81,6 +84,9 @@ failure it returns C<-1> and sets C<errno> appropriately. It accepts two function pointers specifying callbacks as argument, both of which can be C<0>, in which case the callback isn't called. +There is currently no way to change these callbacks later, or to +"uninitialise" the library again. + =item want_poll callback The C<want_poll> callback is invoked whenever libeio wants attention (i.e. |