… | |
… | |
569 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
574 | drops fds silently in similarly hard-to-detect cases |
574 | drops fds silently in similarly hard-to-detect cases. |
575 | |
575 | |
576 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
577 | |
577 | |
578 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
579 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
1393 | transition between them will be described in more detail - and while these |
1393 | transition between them will be described in more detail - and while these |
1394 | rules might look complicated, they usually do "the right thing". |
1394 | rules 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 | |
1400 | Before a watcher can be registered with the event loop it has to be |
1400 | Before a watcher can be registered with the event loop it has to be |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1403 | |
1403 | |
… | |
… | |
2962 | |
2962 | |
2963 | Using an C<ev_check> watcher is almost enough: it will be called on the |
2963 | Using an C<ev_check> watcher is almost enough: it will be called on the |
2964 | next event loop iteration. However, that isn't as soon as possible - |
2964 | next event loop iteration. However, that isn't as soon as possible - |
2965 | without external events, your C<ev_check> watcher will not be invoked. |
2965 | without external events, your C<ev_check> watcher will not be invoked. |
2966 | |
2966 | |
2967 | |
|
|
2968 | This is where C<ev_idle> watchers come in handy - all you need is a |
2967 | This is where C<ev_idle> watchers come in handy - all you need is a |
2969 | single global idle watcher that is active as long as you have one active |
2968 | single global idle watcher that is active as long as you have one active |
2970 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
2969 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
2971 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
2970 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
2972 | invoked. Neither watcher alone can do that. |
2971 | invoked. 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 | |
3185 | Configures the watcher to embed the given loop, which must be |
3184 | Configures the watcher to embed the given loop, which must be |
3186 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3185 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3187 | invoked automatically, otherwise it is the responsibility of the callback |
3186 | invoked automatically, otherwise it is the responsibility of the callback |
3188 | to invoke it (it will continue to be called until the sweep has been done, |
3187 | to 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 | |
3254 | Fork watchers are called when a C<fork ()> was detected (usually because |
3253 | Fork watchers are called when a C<fork ()> was detected (usually because |
3255 | whoever is a good citizen cared to tell libev about it by calling |
3254 | whoever is a good citizen cared to tell libev about it by calling |
3256 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3255 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3257 | event loop blocks next and before C<ev_check> watchers are being called, |
3256 | and before C<ev_check> watchers are being called, and only in the child |
3258 | and only in the child after the fork. If whoever good citizen calling |
3257 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3259 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3258 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3260 | handlers will be invoked, too, of course. |
3259 | of 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 | |
3264 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3263 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3265 | up/change the process environment, followed by a call to C<exec()>. This |
3264 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3659 | already been invoked. |
3658 | already been invoked. |
3660 | |
3659 | |
3661 | A common way around all these issues is to make sure that |
3660 | A common way around all these issues is to make sure that |
3662 | C<start_new_request> I<always> returns before the callback is invoked. If |
3661 | C<start_new_request> I<always> returns before the callback is invoked. If |
3663 | C<start_new_request> immediately knows the result, it can artificially |
3662 | C<start_new_request> immediately knows the result, it can artificially |
3664 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
3663 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
3665 | for example, or more sneakily, by reusing an existing (stopped) watcher |
3664 | example, or more sneakily, by reusing an existing (stopped) watcher and |
3666 | and pushing it into the pending queue: |
3665 | pushing 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 | |
3671 | This way, C<start_new_request> can safely return before the callback is |
3670 | This way, C<start_new_request> can safely return before the callback is |
… | |
… | |
3679 | |
3678 | |
3680 | This brings the problem of exiting - a callback might want to finish the |
3679 | This brings the problem of exiting - a callback might want to finish the |
3681 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3680 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3682 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3681 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3683 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3682 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3684 | other combination: In these cases, C<ev_break> will not work alone. |
3683 | other combination: In these cases, a simple C<ev_break> will not work. |
3685 | |
3684 | |
3686 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3685 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3687 | invocation, and use a loop around C<ev_run> until the condition is |
3686 | invocation, and use a loop around C<ev_run> until the condition is |
3688 | triggered, using C<EVRUN_ONCE>: |
3687 | triggered, using C<EVRUN_ONCE>: |
3689 | |
3688 | |
… | |
… | |
5311 | thread" or will block signals process-wide, both behaviours would |
5310 | thread" or will block signals process-wide, both behaviours would |
5312 | be compatible with libev. Interaction between C<sigprocmask> and |
5311 | be compatible with libev. Interaction between C<sigprocmask> and |
5313 | C<pthread_sigmask> could complicate things, however. |
5312 | C<pthread_sigmask> could complicate things, however. |
5314 | |
5313 | |
5315 | The most portable way to handle signals is to block signals in all threads |
5314 | The most portable way to handle signals is to block signals in all threads |
5316 | except the initial one, and run the default loop in the initial thread as |
5315 | except the initial one, and run the signal handling loop in the initial |
5317 | well. |
5316 | thread as well. |
5318 | |
5317 | |
5319 | =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 |
5320 | |
5319 | |
5321 | To improve portability and simplify its API, libev uses C<long> internally |
5320 | To improve portability and simplify its API, libev uses C<long> internally |
5322 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5321 | instead of C<size_t> when allocating its data structures. On non-POSIX |