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Revision 1.145 by root, Wed Apr 9 22:07:50 2008 UTC vs.
Revision 1.148 by root, Thu Apr 24 01:42:11 2008 UTC

1634When C<inotify (7)> support has been compiled into libev (generally only 1634When C<inotify (7)> support has been compiled into libev (generally only
1635available on Linux) and present at runtime, it will be used to speed up 1635available on Linux) and present at runtime, it will be used to speed up
1636change detection where possible. The inotify descriptor will be created lazily 1636change detection where possible. The inotify descriptor will be created lazily
1637when the first C<ev_stat> watcher is being started. 1637when the first C<ev_stat> watcher is being started.
1638 1638
1639Inotify presense does not change the semantics of C<ev_stat> watchers 1639Inotify presence does not change the semantics of C<ev_stat> watchers
1640except that changes might be detected earlier, and in some cases, to avoid 1640except that changes might be detected earlier, and in some cases, to avoid
1641making regular C<stat> calls. Even in the presense of inotify support 1641making regular C<stat> calls. Even in the presence of inotify support
1642there are many cases where libev has to resort to regular C<stat> polling. 1642there are many cases where libev has to resort to regular C<stat> polling.
1643 1643
1644(There is no support for kqueue, as apparently it cannot be used to 1644(There is no support for kqueue, as apparently it cannot be used to
1645implement this functionality, due to the requirement of having a file 1645implement this functionality, due to the requirement of having a file
1646descriptor open on the object at all times). 1646descriptor open on the object at all times).
2378 2378
2379=item * Priorities are not currently supported. Initialising priorities 2379=item * Priorities are not currently supported. Initialising priorities
2380will fail and all watchers will have the same priority, even though there 2380will fail and all watchers will have the same priority, even though there
2381is an ev_pri field. 2381is an ev_pri field.
2382 2382
2383=item * In libevent, the last base created gets the signals, in libev, the
2384first base created (== the default loop) gets the signals.
2385
2383=item * Other members are not supported. 2386=item * Other members are not supported.
2384 2387
2385=item * The libev emulation is I<not> ABI compatible to libevent, you need 2388=item * The libev emulation is I<not> ABI compatible to libevent, you need
2386to use the libev header file and library. 2389to use the libev header file and library.
2387 2390
3257calling select (O(n²)) will likely make this unworkable. 3260calling select (O(n²)) will likely make this unworkable.
3258 3261
3259=back 3262=back
3260 3263
3261 3264
3265=head1 PORTABILITY REQUIREMENTS
3266
3267In addition to a working ISO-C implementation, libev relies on a few
3268additional extensions:
3269
3270=over 4
3271
3272=item C<sig_atomic_t volatile> must be thread-atomic as well
3273
3274The type C<sig_atomic_t volatile> (or whatever is defined as
3275C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
3276threads. This is not part of the specification for C<sig_atomic_t>, but is
3277believed to be sufficiently portable.
3278
3279=item C<sigprocmask> must work in a threaded environment
3280
3281Libev uses C<sigprocmask> to temporarily block signals. This is not
3282allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
3283pthread implementations will either allow C<sigprocmask> in the "main
3284thread" or will block signals process-wide, both behaviours would
3285be compatible with libev. Interaction between C<sigprocmask> and
3286C<pthread_sigmask> could complicate things, however.
3287
3288The most portable way to handle signals is to block signals in all threads
3289except the initial one, and run the default loop in the initial thread as
3290well.
3291
3292=back
3293
3294If you know of other additional requirements drop me a note.
3295
3296
3262=head1 AUTHOR 3297=head1 AUTHOR
3263 3298
3264Marc Lehmann <libev@schmorp.de>. 3299Marc Lehmann <libev@schmorp.de>.
3265 3300

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