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Revision 1.419 by root, Sun Jun 24 14:30:40 2012 UTC vs.
Revision 1.424 by root, Sun Nov 25 01:38:51 2012 UTC

569kernel is more efficient (which says nothing about its actual speed, of 569kernel is more efficient (which says nothing about its actual speed, of
570course). While stopping, setting and starting an I/O watcher does never 570course). While stopping, setting and starting an I/O watcher does never
571cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to 571cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
572two event changes per incident. Support for C<fork ()> is very bad (you 572two event changes per incident. Support for C<fork ()> is very bad (you
573might have to leak fd's on fork, but it's more sane than epoll) and it 573might have to leak fd's on fork, but it's more sane than epoll) and it
574drops fds silently in similarly hard-to-detect cases 574drops fds silently in similarly hard-to-detect cases.
575 575
576This backend usually performs well under most conditions. 576This backend usually performs well under most conditions.
577 577
578While nominally embeddable in other event loops, this doesn't work 578While nominally embeddable in other event loops, this doesn't work
579everywhere, so you might need to test for this. And since it is broken 579everywhere, so you might need to test for this. And since it is broken
1393transition between them will be described in more detail - and while these 1393transition between them will be described in more detail - and while these
1394rules might look complicated, they usually do "the right thing". 1394rules might look complicated, they usually do "the right thing".
1395 1395
1396=over 4 1396=over 4
1397 1397
1398=item initialiased 1398=item initialised
1399 1399
1400Before a watcher can be registered with the event loop it has to be 1400Before a watcher can be registered with the event loop it has to be
1401initialised. This can be done with a call to C<ev_TYPE_init>, or calls to 1401initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1402C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. 1402C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1403 1403
2962 2962
2963Using an C<ev_check> watcher is almost enough: it will be called on the 2963Using an C<ev_check> watcher is almost enough: it will be called on the
2964next event loop iteration. However, that isn't as soon as possible - 2964next event loop iteration. However, that isn't as soon as possible -
2965without external events, your C<ev_check> watcher will not be invoked. 2965without external events, your C<ev_check> watcher will not be invoked.
2966 2966
2967
2968This is where C<ev_idle> watchers come in handy - all you need is a 2967This is where C<ev_idle> watchers come in handy - all you need is a
2969single global idle watcher that is active as long as you have one active 2968single global idle watcher that is active as long as you have one active
2970C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop 2969C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
2971will not sleep, and the C<ev_check> watcher makes sure a callback gets 2970will not sleep, and the C<ev_check> watcher makes sure a callback gets
2972invoked. Neither watcher alone can do that. 2971invoked. Neither watcher alone can do that.
3178 3177
3179=over 4 3178=over 4
3180 3179
3181=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 3180=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
3182 3181
3183=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 3182=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
3184 3183
3185Configures the watcher to embed the given loop, which must be 3184Configures the watcher to embed the given loop, which must be
3186embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be 3185embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
3187invoked automatically, otherwise it is the responsibility of the callback 3186invoked automatically, otherwise it is the responsibility of the callback
3188to invoke it (it will continue to be called until the sweep has been done, 3187to invoke it (it will continue to be called until the sweep has been done,
3251 3250
3252=head2 C<ev_fork> - the audacity to resume the event loop after a fork 3251=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3253 3252
3254Fork watchers are called when a C<fork ()> was detected (usually because 3253Fork watchers are called when a C<fork ()> was detected (usually because
3255whoever is a good citizen cared to tell libev about it by calling 3254whoever is a good citizen cared to tell libev about it by calling
3256C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the 3255C<ev_loop_fork>). The invocation is done before the event loop blocks next
3257event loop blocks next and before C<ev_check> watchers are being called, 3256and before C<ev_check> watchers are being called, and only in the child
3258and only in the child after the fork. If whoever good citizen calling 3257after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3259C<ev_default_fork> cheats and calls it in the wrong process, the fork 3258and calls it in the wrong process, the fork handlers will be invoked, too,
3260handlers will be invoked, too, of course. 3259of course.
3261 3260
3262=head3 The special problem of life after fork - how is it possible? 3261=head3 The special problem of life after fork - how is it possible?
3263 3262
3264Most uses of C<fork()> consist of forking, then some simple calls to set 3263Most uses of C<fork()> consist of forking, then some simple calls to set
3265up/change the process environment, followed by a call to C<exec()>. This 3264up/change the process environment, followed by a call to C<exec()>. This
3659already been invoked. 3658already been invoked.
3660 3659
3661A common way around all these issues is to make sure that 3660A common way around all these issues is to make sure that
3662C<start_new_request> I<always> returns before the callback is invoked. If 3661C<start_new_request> I<always> returns before the callback is invoked. If
3663C<start_new_request> immediately knows the result, it can artificially 3662C<start_new_request> immediately knows the result, it can artificially
3664delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher 3663delay invoking the callback by using a C<prepare> or C<idle> watcher for
3665for example, or more sneakily, by reusing an existing (stopped) watcher 3664example, or more sneakily, by reusing an existing (stopped) watcher and
3666and pushing it into the pending queue: 3665pushing it into the pending queue:
3667 3666
3668 ev_set_cb (watcher, callback); 3667 ev_set_cb (watcher, callback);
3669 ev_feed_event (EV_A_ watcher, 0); 3668 ev_feed_event (EV_A_ watcher, 0);
3670 3669
3671This way, C<start_new_request> can safely return before the callback is 3670This way, C<start_new_request> can safely return before the callback is
3679 3678
3680This brings the problem of exiting - a callback might want to finish the 3679This brings the problem of exiting - a callback might want to finish the
3681main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but 3680main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
3682a modal "Are you sure?" dialog is still waiting), or just the nested one 3681a modal "Are you sure?" dialog is still waiting), or just the nested one
3683and not the main one (e.g. user clocked "Ok" in a modal dialog), or some 3682and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
3684other combination: In these cases, C<ev_break> will not work alone. 3683other combination: In these cases, a simple C<ev_break> will not work.
3685 3684
3686The solution is to maintain "break this loop" variable for each C<ev_run> 3685The solution is to maintain "break this loop" variable for each C<ev_run>
3687invocation, and use a loop around C<ev_run> until the condition is 3686invocation, and use a loop around C<ev_run> until the condition is
3688triggered, using C<EVRUN_ONCE>: 3687triggered, using C<EVRUN_ONCE>:
3689 3688
4625above. This reduces dependencies and makes libev faster. 4624above. This reduces dependencies and makes libev faster.
4626 4625
4627=item EV_ATOMIC_T 4626=item EV_ATOMIC_T
4628 4627
4629Libev requires an integer type (suitable for storing C<0> or C<1>) whose 4628Libev requires an integer type (suitable for storing C<0> or C<1>) whose
4630access is atomic and serialised with respect to other threads or signal 4629access is atomic with respect to other threads or signal contexts. No
4631contexts. No such type is easily found in the C language, so you can 4630such type is easily found in the C language, so you can provide your own
4632provide your own type that you know is safe for your purposes. It is used 4631type that you know is safe for your purposes. It is used both for signal
4633both for signal handler "locking" as well as for signal and thread safety 4632handler "locking" as well as for signal and thread safety in C<ev_async>
4634in C<ev_async> watchers. 4633watchers.
4635 4634
4636In the absence of this define, libev will use C<sig_atomic_t volatile> 4635In the absence of this define, libev will use C<sig_atomic_t volatile>
4637(from F<signal.h>), which is usually good enough on most platforms, 4636(from F<signal.h>), which is usually good enough on most platforms.
4638although strictly speaking using a type that also implies a memory fence
4639is required.
4640 4637
4641=item EV_H (h) 4638=item EV_H (h)
4642 4639
4643The name of the F<ev.h> header file used to include it. The default if 4640The name of the F<ev.h> header file used to include it. The default if
4644undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be 4641undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
5313thread" or will block signals process-wide, both behaviours would 5310thread" or will block signals process-wide, both behaviours would
5314be compatible with libev. Interaction between C<sigprocmask> and 5311be compatible with libev. Interaction between C<sigprocmask> and
5315C<pthread_sigmask> could complicate things, however. 5312C<pthread_sigmask> could complicate things, however.
5316 5313
5317The most portable way to handle signals is to block signals in all threads 5314The most portable way to handle signals is to block signals in all threads
5318except the initial one, and run the default loop in the initial thread as 5315except the initial one, and run the signal handling loop in the initial
5319well. 5316thread as well.
5320 5317
5321=item C<long> must be large enough for common memory allocation sizes 5318=item C<long> must be large enough for common memory allocation sizes
5322 5319
5323To improve portability and simplify its API, libev uses C<long> internally 5320To improve portability and simplify its API, libev uses C<long> internally
5324instead of C<size_t> when allocating its data structures. On non-POSIX 5321instead of C<size_t> when allocating its data structures. On non-POSIX

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