… | |
… | |
75 | While this document tries to be as complete as possible in documenting |
75 | While this document tries to be as complete as possible in documenting |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
82 | |
82 | |
83 | =head1 ABOUT LIBEV |
83 | =head1 ABOUT LIBEV |
84 | |
84 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
… | |
… | |
98 | =head2 FEATURES |
98 | =head2 FEATURES |
99 | |
99 | |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
103 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
104 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
105 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
106 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
107 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
108 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
109 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
110 | |
111 | |
111 | It also is quite fast (see this |
112 | It also is quite fast (see this |
112 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | for example). |
114 | for example). |
114 | |
115 | |
… | |
… | |
117 | Libev is very configurable. In this manual the default (and most common) |
118 | Libev is very configurable. In this manual the default (and most common) |
118 | configuration will be described, which supports multiple event loops. For |
119 | configuration will be described, which supports multiple event loops. For |
119 | more info about various configuration options please have a look at |
120 | more info about various configuration options please have a look at |
120 | B<EMBED> section in this manual. If libev was configured without support |
121 | B<EMBED> section in this manual. If libev was configured without support |
121 | for multiple event loops, then all functions taking an initial argument of |
122 | for multiple event loops, then all functions taking an initial argument of |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | this argument. |
124 | this argument. |
124 | |
125 | |
125 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
126 | |
127 | |
127 | Libev represents time as a single floating point number, representing |
128 | Libev represents time as a single floating point number, representing |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practise |
129 | near the beginning of 1970, details are complicated, don't ask). This |
130 | somewhere near the beginning of 1970, details are complicated, don't |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
131 | aliases to the C<double> type in C. When you need to do any calculations |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
132 | on it, you should treat it as some floating point value. Unlike the name |
133 | any calculations on it, you should treat it as some floating point value. |
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134 | |
133 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
134 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
135 | |
137 | |
136 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
137 | |
139 | |
138 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
139 | and internal errors (bugs). |
141 | and internal errors (bugs). |
… | |
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190 | as this indicates an incompatible change. Minor versions are usually |
192 | as this indicates an incompatible change. Minor versions are usually |
191 | compatible to older versions, so a larger minor version alone is usually |
193 | compatible to older versions, so a larger minor version alone is usually |
192 | not a problem. |
194 | not a problem. |
193 | |
195 | |
194 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
195 | version. |
197 | version (note, however, that this will not detect ABI mismatches :). |
196 | |
198 | |
197 | assert (("libev version mismatch", |
199 | assert (("libev version mismatch", |
198 | ev_version_major () == EV_VERSION_MAJOR |
200 | ev_version_major () == EV_VERSION_MAJOR |
199 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
200 | |
202 | |
… | |
… | |
344 | useful to try out specific backends to test their performance, or to work |
346 | useful to try out specific backends to test their performance, or to work |
345 | around bugs. |
347 | around bugs. |
346 | |
348 | |
347 | =item C<EVFLAG_FORKCHECK> |
349 | =item C<EVFLAG_FORKCHECK> |
348 | |
350 | |
349 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
351 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
350 | a fork, you can also make libev check for a fork in each iteration by |
352 | make libev check for a fork in each iteration by enabling this flag. |
351 | enabling this flag. |
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352 | |
353 | |
353 | This works by calling C<getpid ()> on every iteration of the loop, |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
354 | and thus this might slow down your event loop if you do a lot of loop |
355 | and thus this might slow down your event loop if you do a lot of loop |
355 | iterations and little real work, but is usually not noticeable (on my |
356 | iterations and little real work, but is usually not noticeable (on my |
356 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
362 | flag. |
363 | flag. |
363 | |
364 | |
364 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | environment variable. |
366 | environment variable. |
366 | |
367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
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369 | |
|
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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374 | |
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375 | =item C<EVFLAG_SIGNALFD> |
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376 | |
|
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377 | When this flag is specified, then libev will attempt to use the |
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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379 | delivers signals synchronously, which makes it both faster and might make |
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380 | it possible to get the queued signal data. It can also simplify signal |
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381 | handling with threads, as long as you properly block signals in your |
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382 | threads that are not interested in handling them. |
|
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383 | |
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384 | Signalfd will not be used by default as this changes your signal mask, and |
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385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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386 | example) that can't properly initialise their signal masks. |
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387 | |
367 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
368 | |
389 | |
369 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
370 | libev tries to roll its own fd_set with no limits on the number of fds, |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
371 | but if that fails, expect a fairly low limit on the number of fds when |
392 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
394 | |
415 | |
395 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
396 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
397 | |
418 | |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
|
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420 | |
|
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421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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422 | kernels). |
399 | |
423 | |
400 | For few fds, this backend is a bit little slower than poll and select, |
424 | For few fds, this backend is a bit little slower than poll and select, |
401 | but it scales phenomenally better. While poll and select usually scale |
425 | but it scales phenomenally better. While poll and select usually scale |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
403 | epoll scales either O(1) or O(active_fds). |
427 | epoll scales either O(1) or O(active_fds). |
… | |
… | |
415 | of course I<doesn't>, and epoll just loves to report events for totally |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
416 | I<different> file descriptors (even already closed ones, so one cannot |
440 | I<different> file descriptors (even already closed ones, so one cannot |
417 | even remove them from the set) than registered in the set (especially |
441 | even remove them from the set) than registered in the set (especially |
418 | on SMP systems). Libev tries to counter these spurious notifications by |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
419 | employing an additional generation counter and comparing that against the |
443 | employing an additional generation counter and comparing that against the |
420 | events to filter out spurious ones, recreating the set when required. |
444 | events to filter out spurious ones, recreating the set when required. Last |
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445 | not least, it also refuses to work with some file descriptors which work |
|
|
446 | perfectly fine with C<select> (files, many character devices...). |
421 | |
447 | |
422 | While stopping, setting and starting an I/O watcher in the same iteration |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
423 | will result in some caching, there is still a system call per such |
449 | will result in some caching, there is still a system call per such |
424 | incident (because the same I<file descriptor> could point to a different |
450 | incident (because the same I<file descriptor> could point to a different |
425 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
518 | |
544 | |
519 | It is definitely not recommended to use this flag. |
545 | It is definitely not recommended to use this flag. |
520 | |
546 | |
521 | =back |
547 | =back |
522 | |
548 | |
523 | If one or more of these are or'ed into the flags value, then only these |
549 | If one or more of the backend flags are or'ed into the flags value, |
524 | backends will be tried (in the reverse order as listed here). If none are |
550 | then only these backends will be tried (in the reverse order as listed |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
551 | here). If none are specified, all backends in C<ev_recommended_backends |
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552 | ()> will be tried. |
526 | |
553 | |
527 | Example: This is the most typical usage. |
554 | Example: This is the most typical usage. |
528 | |
555 | |
529 | if (!ev_default_loop (0)) |
556 | if (!ev_default_loop (0)) |
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
557 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
542 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
569 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
543 | |
570 | |
544 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
571 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
545 | |
572 | |
546 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
573 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
547 | always distinct from the default loop. Unlike the default loop, it cannot |
574 | always distinct from the default loop. |
548 | handle signal and child watchers, and attempts to do so will be greeted by |
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549 | undefined behaviour (or a failed assertion if assertions are enabled). |
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550 | |
575 | |
551 | Note that this function I<is> thread-safe, and the recommended way to use |
576 | Note that this function I<is> thread-safe, and one common way to use |
552 | libev with threads is indeed to create one loop per thread, and using the |
577 | libev with threads is indeed to create one loop per thread, and using the |
553 | default loop in the "main" or "initial" thread. |
578 | default loop in the "main" or "initial" thread. |
554 | |
579 | |
555 | Example: Try to create a event loop that uses epoll and nothing else. |
580 | Example: Try to create a event loop that uses epoll and nothing else. |
556 | |
581 | |
… | |
… | |
558 | if (!epoller) |
583 | if (!epoller) |
559 | fatal ("no epoll found here, maybe it hides under your chair"); |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
560 | |
585 | |
561 | =item ev_default_destroy () |
586 | =item ev_default_destroy () |
562 | |
587 | |
563 | Destroys the default loop again (frees all memory and kernel state |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
564 | etc.). None of the active event watchers will be stopped in the normal |
589 | of the active event watchers will be stopped in the normal sense, so |
565 | sense, so e.g. C<ev_is_active> might still return true. It is your |
590 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
591 | either stop all watchers cleanly yourself I<before> calling this function, |
567 | calling this function, or cope with the fact afterwards (which is usually |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
568 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
593 | can just ignore the watchers and/or C<free ()> them for example). |
569 | for example). |
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570 | |
594 | |
571 | Note that certain global state, such as signal state (and installed signal |
595 | Note that certain global state, such as signal state (and installed signal |
572 | handlers), will not be freed by this function, and related watchers (such |
596 | handlers), will not be freed by this function, and related watchers (such |
573 | as signal and child watchers) would need to be stopped manually. |
597 | as signal and child watchers) would need to be stopped manually. |
574 | |
598 | |
575 | In general it is not advisable to call this function except in the |
599 | In general it is not advisable to call this function except in the |
576 | rare occasion where you really need to free e.g. the signal handling |
600 | rare occasion where you really need to free e.g. the signal handling |
577 | pipe fds. If you need dynamically allocated loops it is better to use |
601 | pipe fds. If you need dynamically allocated loops it is better to use |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
602 | C<ev_loop_new> and C<ev_loop_destroy>. |
579 | |
603 | |
580 | =item ev_loop_destroy (loop) |
604 | =item ev_loop_destroy (loop) |
581 | |
605 | |
582 | Like C<ev_default_destroy>, but destroys an event loop created by an |
606 | Like C<ev_default_destroy>, but destroys an event loop created by an |
583 | earlier call to C<ev_loop_new>. |
607 | earlier call to C<ev_loop_new>. |
… | |
… | |
589 | name, you can call it anytime, but it makes most sense after forking, in |
613 | name, you can call it anytime, but it makes most sense after forking, in |
590 | the child process (or both child and parent, but that again makes little |
614 | the child process (or both child and parent, but that again makes little |
591 | sense). You I<must> call it in the child before using any of the libev |
615 | sense). You I<must> call it in the child before using any of the libev |
592 | functions, and it will only take effect at the next C<ev_loop> iteration. |
616 | functions, and it will only take effect at the next C<ev_loop> iteration. |
593 | |
617 | |
|
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618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
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619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
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620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
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621 | during fork. |
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622 | |
594 | On the other hand, you only need to call this function in the child |
623 | On the other hand, you only need to call this function in the child |
595 | process if and only if you want to use the event library in the child. If |
624 | process if and only if you want to use the event loop in the child. If you |
596 | you just fork+exec, you don't have to call it at all. |
625 | just fork+exec or create a new loop in the child, you don't have to call |
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626 | it at all. |
597 | |
627 | |
598 | The function itself is quite fast and it's usually not a problem to call |
628 | The function itself is quite fast and it's usually not a problem to call |
599 | it just in case after a fork. To make this easy, the function will fit in |
629 | it just in case after a fork. To make this easy, the function will fit in |
600 | quite nicely into a call to C<pthread_atfork>: |
630 | quite nicely into a call to C<pthread_atfork>: |
601 | |
631 | |
… | |
… | |
603 | |
633 | |
604 | =item ev_loop_fork (loop) |
634 | =item ev_loop_fork (loop) |
605 | |
635 | |
606 | Like C<ev_default_fork>, but acts on an event loop created by |
636 | Like C<ev_default_fork>, but acts on an event loop created by |
607 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
637 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
608 | after fork that you want to re-use in the child, and how you do this is |
638 | after fork that you want to re-use in the child, and how you keep track of |
609 | entirely your own problem. |
639 | them is entirely your own problem. |
610 | |
640 | |
611 | =item int ev_is_default_loop (loop) |
641 | =item int ev_is_default_loop (loop) |
612 | |
642 | |
613 | Returns true when the given loop is, in fact, the default loop, and false |
643 | Returns true when the given loop is, in fact, the default loop, and false |
614 | otherwise. |
644 | otherwise. |
615 | |
645 | |
616 | =item unsigned int ev_loop_count (loop) |
646 | =item unsigned int ev_iteration (loop) |
617 | |
647 | |
618 | Returns the count of loop iterations for the loop, which is identical to |
648 | Returns the current iteration count for the loop, which is identical to |
619 | the number of times libev did poll for new events. It starts at C<0> and |
649 | the number of times libev did poll for new events. It starts at C<0> and |
620 | happily wraps around with enough iterations. |
650 | happily wraps around with enough iterations. |
621 | |
651 | |
622 | This value can sometimes be useful as a generation counter of sorts (it |
652 | This value can sometimes be useful as a generation counter of sorts (it |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
653 | "ticks" the number of loop iterations), as it roughly corresponds with |
624 | C<ev_prepare> and C<ev_check> calls. |
654 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
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655 | prepare and check phases. |
|
|
656 | |
|
|
657 | =item unsigned int ev_depth (loop) |
|
|
658 | |
|
|
659 | Returns the number of times C<ev_loop> was entered minus the number of |
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|
660 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
661 | |
|
|
662 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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663 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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664 | in which case it is higher. |
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665 | |
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666 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
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667 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
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668 | ungentleman behaviour unless it's really convenient. |
625 | |
669 | |
626 | =item unsigned int ev_backend (loop) |
670 | =item unsigned int ev_backend (loop) |
627 | |
671 | |
628 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
672 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
629 | use. |
673 | use. |
… | |
… | |
644 | |
688 | |
645 | This function is rarely useful, but when some event callback runs for a |
689 | This function is rarely useful, but when some event callback runs for a |
646 | very long time without entering the event loop, updating libev's idea of |
690 | very long time without entering the event loop, updating libev's idea of |
647 | the current time is a good idea. |
691 | the current time is a good idea. |
648 | |
692 | |
649 | See also "The special problem of time updates" in the C<ev_timer> section. |
693 | See also L<The special problem of time updates> in the C<ev_timer> section. |
650 | |
694 | |
651 | =item ev_suspend (loop) |
695 | =item ev_suspend (loop) |
652 | |
696 | |
653 | =item ev_resume (loop) |
697 | =item ev_resume (loop) |
654 | |
698 | |
… | |
… | |
663 | C<ev_resume> directly afterwards to resume timer processing. |
707 | C<ev_resume> directly afterwards to resume timer processing. |
664 | |
708 | |
665 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
709 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
666 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
710 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
667 | will be rescheduled (that is, they will lose any events that would have |
711 | will be rescheduled (that is, they will lose any events that would have |
668 | occured while suspended). |
712 | occurred while suspended). |
669 | |
713 | |
670 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
714 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
671 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
715 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
672 | without a previous call to C<ev_suspend>. |
716 | without a previous call to C<ev_suspend>. |
673 | |
717 | |
… | |
… | |
675 | event loop time (see C<ev_now_update>). |
719 | event loop time (see C<ev_now_update>). |
676 | |
720 | |
677 | =item ev_loop (loop, int flags) |
721 | =item ev_loop (loop, int flags) |
678 | |
722 | |
679 | Finally, this is it, the event handler. This function usually is called |
723 | Finally, this is it, the event handler. This function usually is called |
680 | after you initialised all your watchers and you want to start handling |
724 | after you have initialised all your watchers and you want to start |
681 | events. |
725 | handling events. |
682 | |
726 | |
683 | If the flags argument is specified as C<0>, it will not return until |
727 | If the flags argument is specified as C<0>, it will not return until |
684 | either no event watchers are active anymore or C<ev_unloop> was called. |
728 | either no event watchers are active anymore or C<ev_unloop> was called. |
685 | |
729 | |
686 | Please note that an explicit C<ev_unloop> is usually better than |
730 | Please note that an explicit C<ev_unloop> is usually better than |
… | |
… | |
750 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
794 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
751 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
795 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
752 | |
796 | |
753 | This "unloop state" will be cleared when entering C<ev_loop> again. |
797 | This "unloop state" will be cleared when entering C<ev_loop> again. |
754 | |
798 | |
755 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
799 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
756 | |
800 | |
757 | =item ev_ref (loop) |
801 | =item ev_ref (loop) |
758 | |
802 | |
759 | =item ev_unref (loop) |
803 | =item ev_unref (loop) |
760 | |
804 | |
761 | Ref/unref can be used to add or remove a reference count on the event |
805 | Ref/unref can be used to add or remove a reference count on the event |
762 | loop: Every watcher keeps one reference, and as long as the reference |
806 | loop: Every watcher keeps one reference, and as long as the reference |
763 | count is nonzero, C<ev_loop> will not return on its own. |
807 | count is nonzero, C<ev_loop> will not return on its own. |
764 | |
808 | |
765 | If you have a watcher you never unregister that should not keep C<ev_loop> |
809 | This is useful when you have a watcher that you never intend to |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
810 | unregister, but that nevertheless should not keep C<ev_loop> from |
|
|
811 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
767 | stopping it. |
812 | before stopping it. |
768 | |
813 | |
769 | As an example, libev itself uses this for its internal signal pipe: It |
814 | As an example, libev itself uses this for its internal signal pipe: It |
770 | is not visible to the libev user and should not keep C<ev_loop> from |
815 | is not visible to the libev user and should not keep C<ev_loop> from |
771 | exiting if no event watchers registered by it are active. It is also an |
816 | exiting if no event watchers registered by it are active. It is also an |
772 | excellent way to do this for generic recurring timers or from within |
817 | excellent way to do this for generic recurring timers or from within |
… | |
… | |
811 | |
856 | |
812 | By setting a higher I<io collect interval> you allow libev to spend more |
857 | By setting a higher I<io collect interval> you allow libev to spend more |
813 | time collecting I/O events, so you can handle more events per iteration, |
858 | time collecting I/O events, so you can handle more events per iteration, |
814 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
859 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
815 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
860 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
816 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
861 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
862 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
863 | once per this interval, on average. |
817 | |
864 | |
818 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
865 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
819 | to spend more time collecting timeouts, at the expense of increased |
866 | to spend more time collecting timeouts, at the expense of increased |
820 | latency/jitter/inexactness (the watcher callback will be called |
867 | latency/jitter/inexactness (the watcher callback will be called |
821 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
868 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
823 | |
870 | |
824 | Many (busy) programs can usually benefit by setting the I/O collect |
871 | Many (busy) programs can usually benefit by setting the I/O collect |
825 | interval to a value near C<0.1> or so, which is often enough for |
872 | interval to a value near C<0.1> or so, which is often enough for |
826 | interactive servers (of course not for games), likewise for timeouts. It |
873 | interactive servers (of course not for games), likewise for timeouts. It |
827 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
874 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
828 | as this approaches the timing granularity of most systems. |
875 | as this approaches the timing granularity of most systems. Note that if |
|
|
876 | you do transactions with the outside world and you can't increase the |
|
|
877 | parallelity, then this setting will limit your transaction rate (if you |
|
|
878 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
879 | then you can't do more than 100 transactions per second). |
829 | |
880 | |
830 | Setting the I<timeout collect interval> can improve the opportunity for |
881 | Setting the I<timeout collect interval> can improve the opportunity for |
831 | saving power, as the program will "bundle" timer callback invocations that |
882 | saving power, as the program will "bundle" timer callback invocations that |
832 | are "near" in time together, by delaying some, thus reducing the number of |
883 | are "near" in time together, by delaying some, thus reducing the number of |
833 | times the process sleeps and wakes up again. Another useful technique to |
884 | times the process sleeps and wakes up again. Another useful technique to |
834 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
885 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
835 | they fire on, say, one-second boundaries only. |
886 | they fire on, say, one-second boundaries only. |
836 | |
887 | |
|
|
888 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
889 | more often than 100 times per second: |
|
|
890 | |
|
|
891 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
892 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
893 | |
|
|
894 | =item ev_invoke_pending (loop) |
|
|
895 | |
|
|
896 | This call will simply invoke all pending watchers while resetting their |
|
|
897 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
898 | but when overriding the invoke callback this call comes handy. |
|
|
899 | |
|
|
900 | =item int ev_pending_count (loop) |
|
|
901 | |
|
|
902 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
903 | are pending. |
|
|
904 | |
|
|
905 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
906 | |
|
|
907 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
908 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
909 | this callback instead. This is useful, for example, when you want to |
|
|
910 | invoke the actual watchers inside another context (another thread etc.). |
|
|
911 | |
|
|
912 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
913 | callback. |
|
|
914 | |
|
|
915 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
916 | |
|
|
917 | Sometimes you want to share the same loop between multiple threads. This |
|
|
918 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
919 | each call to a libev function. |
|
|
920 | |
|
|
921 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
922 | wait for it to return. One way around this is to wake up the loop via |
|
|
923 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
924 | and I<acquire> callbacks on the loop. |
|
|
925 | |
|
|
926 | When set, then C<release> will be called just before the thread is |
|
|
927 | suspended waiting for new events, and C<acquire> is called just |
|
|
928 | afterwards. |
|
|
929 | |
|
|
930 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
931 | C<acquire> will just call the mutex_lock function again. |
|
|
932 | |
|
|
933 | While event loop modifications are allowed between invocations of |
|
|
934 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
935 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
936 | have no effect on the set of file descriptors being watched, or the time |
|
|
937 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
938 | to take note of any changes you made. |
|
|
939 | |
|
|
940 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
941 | invocations of C<release> and C<acquire>. |
|
|
942 | |
|
|
943 | See also the locking example in the C<THREADS> section later in this |
|
|
944 | document. |
|
|
945 | |
|
|
946 | =item ev_set_userdata (loop, void *data) |
|
|
947 | |
|
|
948 | =item ev_userdata (loop) |
|
|
949 | |
|
|
950 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
951 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
952 | C<0.> |
|
|
953 | |
|
|
954 | These two functions can be used to associate arbitrary data with a loop, |
|
|
955 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
956 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
957 | any other purpose as well. |
|
|
958 | |
837 | =item ev_loop_verify (loop) |
959 | =item ev_loop_verify (loop) |
838 | |
960 | |
839 | This function only does something when C<EV_VERIFY> support has been |
961 | This function only does something when C<EV_VERIFY> support has been |
840 | compiled in, which is the default for non-minimal builds. It tries to go |
962 | compiled in, which is the default for non-minimal builds. It tries to go |
841 | through all internal structures and checks them for validity. If anything |
963 | through all internal structures and checks them for validity. If anything |
… | |
… | |
917 | =item C<EV_WRITE> |
1039 | =item C<EV_WRITE> |
918 | |
1040 | |
919 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1041 | The file descriptor in the C<ev_io> watcher has become readable and/or |
920 | writable. |
1042 | writable. |
921 | |
1043 | |
922 | =item C<EV_TIMEOUT> |
1044 | =item C<EV_TIMER> |
923 | |
1045 | |
924 | The C<ev_timer> watcher has timed out. |
1046 | The C<ev_timer> watcher has timed out. |
925 | |
1047 | |
926 | =item C<EV_PERIODIC> |
1048 | =item C<EV_PERIODIC> |
927 | |
1049 | |
… | |
… | |
1017 | |
1139 | |
1018 | ev_io w; |
1140 | ev_io w; |
1019 | ev_init (&w, my_cb); |
1141 | ev_init (&w, my_cb); |
1020 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1142 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1021 | |
1143 | |
1022 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1144 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
1023 | |
1145 | |
1024 | This macro initialises the type-specific parts of a watcher. You need to |
1146 | This macro initialises the type-specific parts of a watcher. You need to |
1025 | call C<ev_init> at least once before you call this macro, but you can |
1147 | call C<ev_init> at least once before you call this macro, but you can |
1026 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1148 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1027 | macro on a watcher that is active (it can be pending, however, which is a |
1149 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
1040 | |
1162 | |
1041 | Example: Initialise and set an C<ev_io> watcher in one step. |
1163 | Example: Initialise and set an C<ev_io> watcher in one step. |
1042 | |
1164 | |
1043 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1165 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1044 | |
1166 | |
1045 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1167 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
1046 | |
1168 | |
1047 | Starts (activates) the given watcher. Only active watchers will receive |
1169 | Starts (activates) the given watcher. Only active watchers will receive |
1048 | events. If the watcher is already active nothing will happen. |
1170 | events. If the watcher is already active nothing will happen. |
1049 | |
1171 | |
1050 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1172 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1051 | whole section. |
1173 | whole section. |
1052 | |
1174 | |
1053 | ev_io_start (EV_DEFAULT_UC, &w); |
1175 | ev_io_start (EV_DEFAULT_UC, &w); |
1054 | |
1176 | |
1055 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1177 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1056 | |
1178 | |
1057 | Stops the given watcher if active, and clears the pending status (whether |
1179 | Stops the given watcher if active, and clears the pending status (whether |
1058 | the watcher was active or not). |
1180 | the watcher was active or not). |
1059 | |
1181 | |
1060 | It is possible that stopped watchers are pending - for example, |
1182 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1085 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1207 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1086 | |
1208 | |
1087 | Change the callback. You can change the callback at virtually any time |
1209 | Change the callback. You can change the callback at virtually any time |
1088 | (modulo threads). |
1210 | (modulo threads). |
1089 | |
1211 | |
1090 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1212 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1091 | |
1213 | |
1092 | =item int ev_priority (ev_TYPE *watcher) |
1214 | =item int ev_priority (ev_TYPE *watcher) |
1093 | |
1215 | |
1094 | Set and query the priority of the watcher. The priority is a small |
1216 | Set and query the priority of the watcher. The priority is a small |
1095 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1217 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
… | |
… | |
1126 | returns its C<revents> bitset (as if its callback was invoked). If the |
1248 | returns its C<revents> bitset (as if its callback was invoked). If the |
1127 | watcher isn't pending it does nothing and returns C<0>. |
1249 | watcher isn't pending it does nothing and returns C<0>. |
1128 | |
1250 | |
1129 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1251 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1130 | callback to be invoked, which can be accomplished with this function. |
1252 | callback to be invoked, which can be accomplished with this function. |
|
|
1253 | |
|
|
1254 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1255 | |
|
|
1256 | Feeds the given event set into the event loop, as if the specified event |
|
|
1257 | had happened for the specified watcher (which must be a pointer to an |
|
|
1258 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1259 | not free the watcher as long as it has pending events. |
|
|
1260 | |
|
|
1261 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1262 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1263 | not started in the first place. |
|
|
1264 | |
|
|
1265 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1266 | functions that do not need a watcher. |
1131 | |
1267 | |
1132 | =back |
1268 | =back |
1133 | |
1269 | |
1134 | |
1270 | |
1135 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1271 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
1184 | #include <stddef.h> |
1320 | #include <stddef.h> |
1185 | |
1321 | |
1186 | static void |
1322 | static void |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1323 | t1_cb (EV_P_ ev_timer *w, int revents) |
1188 | { |
1324 | { |
1189 | struct my_biggy big = (struct my_biggy * |
1325 | struct my_biggy big = (struct my_biggy *) |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1326 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1191 | } |
1327 | } |
1192 | |
1328 | |
1193 | static void |
1329 | static void |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1330 | t2_cb (EV_P_ ev_timer *w, int revents) |
1195 | { |
1331 | { |
1196 | struct my_biggy big = (struct my_biggy * |
1332 | struct my_biggy big = (struct my_biggy *) |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1333 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1198 | } |
1334 | } |
1199 | |
1335 | |
1200 | =head2 WATCHER PRIORITY MODELS |
1336 | =head2 WATCHER PRIORITY MODELS |
1201 | |
1337 | |
… | |
… | |
1246 | |
1382 | |
1247 | For example, to emulate how many other event libraries handle priorities, |
1383 | For example, to emulate how many other event libraries handle priorities, |
1248 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1384 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1249 | the normal watcher callback, you just start the idle watcher. The real |
1385 | the normal watcher callback, you just start the idle watcher. The real |
1250 | processing is done in the idle watcher callback. This causes libev to |
1386 | processing is done in the idle watcher callback. This causes libev to |
1251 | continously poll and process kernel event data for the watcher, but when |
1387 | continuously poll and process kernel event data for the watcher, but when |
1252 | the lock-out case is known to be rare (which in turn is rare :), this is |
1388 | the lock-out case is known to be rare (which in turn is rare :), this is |
1253 | workable. |
1389 | workable. |
1254 | |
1390 | |
1255 | Usually, however, the lock-out model implemented that way will perform |
1391 | Usually, however, the lock-out model implemented that way will perform |
1256 | miserably under the type of load it was designed to handle. In that case, |
1392 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1270 | { |
1406 | { |
1271 | // stop the I/O watcher, we received the event, but |
1407 | // stop the I/O watcher, we received the event, but |
1272 | // are not yet ready to handle it. |
1408 | // are not yet ready to handle it. |
1273 | ev_io_stop (EV_A_ w); |
1409 | ev_io_stop (EV_A_ w); |
1274 | |
1410 | |
1275 | // start the idle watcher to ahndle the actual event. |
1411 | // start the idle watcher to handle the actual event. |
1276 | // it will not be executed as long as other watchers |
1412 | // it will not be executed as long as other watchers |
1277 | // with the default priority are receiving events. |
1413 | // with the default priority are receiving events. |
1278 | ev_idle_start (EV_A_ &idle); |
1414 | ev_idle_start (EV_A_ &idle); |
1279 | } |
1415 | } |
1280 | |
1416 | |
1281 | static void |
1417 | static void |
1282 | idle-cb (EV_P_ ev_idle *w, int revents) |
1418 | idle_cb (EV_P_ ev_idle *w, int revents) |
1283 | { |
1419 | { |
1284 | // actual processing |
1420 | // actual processing |
1285 | read (STDIN_FILENO, ...); |
1421 | read (STDIN_FILENO, ...); |
1286 | |
1422 | |
1287 | // have to start the I/O watcher again, as |
1423 | // have to start the I/O watcher again, as |
… | |
… | |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
1468 | descriptors to non-blocking mode is also usually a good idea (but not |
1333 | required if you know what you are doing). |
1469 | required if you know what you are doing). |
1334 | |
1470 | |
1335 | If you cannot use non-blocking mode, then force the use of a |
1471 | If you cannot use non-blocking mode, then force the use of a |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
1472 | known-to-be-good backend (at the time of this writing, this includes only |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1473 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1474 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1475 | files) - libev doesn't guarantee any specific behaviour in that case. |
1338 | |
1476 | |
1339 | Another thing you have to watch out for is that it is quite easy to |
1477 | Another thing you have to watch out for is that it is quite easy to |
1340 | receive "spurious" readiness notifications, that is your callback might |
1478 | receive "spurious" readiness notifications, that is your callback might |
1341 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1479 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1342 | because there is no data. Not only are some backends known to create a |
1480 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1407 | |
1545 | |
1408 | So when you encounter spurious, unexplained daemon exits, make sure you |
1546 | So when you encounter spurious, unexplained daemon exits, make sure you |
1409 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1547 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1410 | somewhere, as that would have given you a big clue). |
1548 | somewhere, as that would have given you a big clue). |
1411 | |
1549 | |
|
|
1550 | =head3 The special problem of accept()ing when you can't |
|
|
1551 | |
|
|
1552 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1553 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1554 | connection from the pending queue in all error cases. |
|
|
1555 | |
|
|
1556 | For example, larger servers often run out of file descriptors (because |
|
|
1557 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1558 | rejecting the connection, leading to libev signalling readiness on |
|
|
1559 | the next iteration again (the connection still exists after all), and |
|
|
1560 | typically causing the program to loop at 100% CPU usage. |
|
|
1561 | |
|
|
1562 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1563 | operating systems, there is usually little the app can do to remedy the |
|
|
1564 | situation, and no known thread-safe method of removing the connection to |
|
|
1565 | cope with overload is known (to me). |
|
|
1566 | |
|
|
1567 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1568 | - when the program encounters an overload, it will just loop until the |
|
|
1569 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1570 | event-based way to handle this situation, so it's the best one can do. |
|
|
1571 | |
|
|
1572 | A better way to handle the situation is to log any errors other than |
|
|
1573 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1574 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1575 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1576 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1577 | usage. |
|
|
1578 | |
|
|
1579 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1580 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1581 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1582 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1583 | clients under typical overload conditions. |
|
|
1584 | |
|
|
1585 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1586 | is often done with C<malloc> failures, but this results in an easy |
|
|
1587 | opportunity for a DoS attack. |
1412 | |
1588 | |
1413 | =head3 Watcher-Specific Functions |
1589 | =head3 Watcher-Specific Functions |
1414 | |
1590 | |
1415 | =over 4 |
1591 | =over 4 |
1416 | |
1592 | |
… | |
… | |
1463 | year, it will still time out after (roughly) one hour. "Roughly" because |
1639 | year, it will still time out after (roughly) one hour. "Roughly" because |
1464 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1640 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1465 | monotonic clock option helps a lot here). |
1641 | monotonic clock option helps a lot here). |
1466 | |
1642 | |
1467 | The callback is guaranteed to be invoked only I<after> its timeout has |
1643 | The callback is guaranteed to be invoked only I<after> its timeout has |
1468 | passed. If multiple timers become ready during the same loop iteration |
1644 | passed (not I<at>, so on systems with very low-resolution clocks this |
1469 | then the ones with earlier time-out values are invoked before ones with |
1645 | might introduce a small delay). If multiple timers become ready during the |
1470 | later time-out values (but this is no longer true when a callback calls |
1646 | same loop iteration then the ones with earlier time-out values are invoked |
1471 | C<ev_loop> recursively). |
1647 | before ones of the same priority with later time-out values (but this is |
|
|
1648 | no longer true when a callback calls C<ev_loop> recursively). |
1472 | |
1649 | |
1473 | =head3 Be smart about timeouts |
1650 | =head3 Be smart about timeouts |
1474 | |
1651 | |
1475 | Many real-world problems involve some kind of timeout, usually for error |
1652 | Many real-world problems involve some kind of timeout, usually for error |
1476 | recovery. A typical example is an HTTP request - if the other side hangs, |
1653 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1520 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1697 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1521 | member and C<ev_timer_again>. |
1698 | member and C<ev_timer_again>. |
1522 | |
1699 | |
1523 | At start: |
1700 | At start: |
1524 | |
1701 | |
1525 | ev_timer_init (timer, callback); |
1702 | ev_init (timer, callback); |
1526 | timer->repeat = 60.; |
1703 | timer->repeat = 60.; |
1527 | ev_timer_again (loop, timer); |
1704 | ev_timer_again (loop, timer); |
1528 | |
1705 | |
1529 | Each time there is some activity: |
1706 | Each time there is some activity: |
1530 | |
1707 | |
… | |
… | |
1562 | ev_tstamp timeout = last_activity + 60.; |
1739 | ev_tstamp timeout = last_activity + 60.; |
1563 | |
1740 | |
1564 | // if last_activity + 60. is older than now, we did time out |
1741 | // if last_activity + 60. is older than now, we did time out |
1565 | if (timeout < now) |
1742 | if (timeout < now) |
1566 | { |
1743 | { |
1567 | // timeout occured, take action |
1744 | // timeout occurred, take action |
1568 | } |
1745 | } |
1569 | else |
1746 | else |
1570 | { |
1747 | { |
1571 | // callback was invoked, but there was some activity, re-arm |
1748 | // callback was invoked, but there was some activity, re-arm |
1572 | // the watcher to fire in last_activity + 60, which is |
1749 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1592 | |
1769 | |
1593 | To start the timer, simply initialise the watcher and set C<last_activity> |
1770 | To start the timer, simply initialise the watcher and set C<last_activity> |
1594 | to the current time (meaning we just have some activity :), then call the |
1771 | to the current time (meaning we just have some activity :), then call the |
1595 | callback, which will "do the right thing" and start the timer: |
1772 | callback, which will "do the right thing" and start the timer: |
1596 | |
1773 | |
1597 | ev_timer_init (timer, callback); |
1774 | ev_init (timer, callback); |
1598 | last_activity = ev_now (loop); |
1775 | last_activity = ev_now (loop); |
1599 | callback (loop, timer, EV_TIMEOUT); |
1776 | callback (loop, timer, EV_TIMER); |
1600 | |
1777 | |
1601 | And when there is some activity, simply store the current time in |
1778 | And when there is some activity, simply store the current time in |
1602 | C<last_activity>, no libev calls at all: |
1779 | C<last_activity>, no libev calls at all: |
1603 | |
1780 | |
1604 | last_actiivty = ev_now (loop); |
1781 | last_activity = ev_now (loop); |
1605 | |
1782 | |
1606 | This technique is slightly more complex, but in most cases where the |
1783 | This technique is slightly more complex, but in most cases where the |
1607 | time-out is unlikely to be triggered, much more efficient. |
1784 | time-out is unlikely to be triggered, much more efficient. |
1608 | |
1785 | |
1609 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1786 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
… | |
… | |
1663 | |
1840 | |
1664 | If the event loop is suspended for a long time, you can also force an |
1841 | If the event loop is suspended for a long time, you can also force an |
1665 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1842 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1666 | ()>. |
1843 | ()>. |
1667 | |
1844 | |
|
|
1845 | =head3 The special problems of suspended animation |
|
|
1846 | |
|
|
1847 | When you leave the server world it is quite customary to hit machines that |
|
|
1848 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1849 | |
|
|
1850 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1851 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1852 | to run until the system is suspended, but they will not advance while the |
|
|
1853 | system is suspended. That means, on resume, it will be as if the program |
|
|
1854 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1855 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1856 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1857 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1858 | be adjusted accordingly. |
|
|
1859 | |
|
|
1860 | I would not be surprised to see different behaviour in different between |
|
|
1861 | operating systems, OS versions or even different hardware. |
|
|
1862 | |
|
|
1863 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1864 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1865 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1866 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1867 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1868 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1869 | |
|
|
1870 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1871 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1872 | deterministic behaviour in this case (you can do nothing against |
|
|
1873 | C<SIGSTOP>). |
|
|
1874 | |
1668 | =head3 Watcher-Specific Functions and Data Members |
1875 | =head3 Watcher-Specific Functions and Data Members |
1669 | |
1876 | |
1670 | =over 4 |
1877 | =over 4 |
1671 | |
1878 | |
1672 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1879 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1697 | If the timer is repeating, either start it if necessary (with the |
1904 | If the timer is repeating, either start it if necessary (with the |
1698 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1905 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1699 | |
1906 | |
1700 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1907 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1701 | usage example. |
1908 | usage example. |
|
|
1909 | |
|
|
1910 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
1911 | |
|
|
1912 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1913 | then this time is relative to the current event loop time, otherwise it's |
|
|
1914 | the timeout value currently configured. |
|
|
1915 | |
|
|
1916 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1917 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1918 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1919 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1920 | too), and so on. |
1702 | |
1921 | |
1703 | =item ev_tstamp repeat [read-write] |
1922 | =item ev_tstamp repeat [read-write] |
1704 | |
1923 | |
1705 | The current C<repeat> value. Will be used each time the watcher times out |
1924 | The current C<repeat> value. Will be used each time the watcher times out |
1706 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1925 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1906 | Example: Call a callback every hour, or, more precisely, whenever the |
2125 | Example: Call a callback every hour, or, more precisely, whenever the |
1907 | system time is divisible by 3600. The callback invocation times have |
2126 | system time is divisible by 3600. The callback invocation times have |
1908 | potentially a lot of jitter, but good long-term stability. |
2127 | potentially a lot of jitter, but good long-term stability. |
1909 | |
2128 | |
1910 | static void |
2129 | static void |
1911 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2130 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1912 | { |
2131 | { |
1913 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2132 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1914 | } |
2133 | } |
1915 | |
2134 | |
1916 | ev_periodic hourly_tick; |
2135 | ev_periodic hourly_tick; |
… | |
… | |
1942 | Signal watchers will trigger an event when the process receives a specific |
2161 | Signal watchers will trigger an event when the process receives a specific |
1943 | signal one or more times. Even though signals are very asynchronous, libev |
2162 | signal one or more times. Even though signals are very asynchronous, libev |
1944 | will try it's best to deliver signals synchronously, i.e. as part of the |
2163 | will try it's best to deliver signals synchronously, i.e. as part of the |
1945 | normal event processing, like any other event. |
2164 | normal event processing, like any other event. |
1946 | |
2165 | |
1947 | If you want signals asynchronously, just use C<sigaction> as you would |
2166 | If you want signals to be delivered truly asynchronously, just use |
1948 | do without libev and forget about sharing the signal. You can even use |
2167 | C<sigaction> as you would do without libev and forget about sharing |
1949 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2168 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2169 | synchronously wake up an event loop. |
1950 | |
2170 | |
1951 | You can configure as many watchers as you like per signal. Only when the |
2171 | You can configure as many watchers as you like for the same signal, but |
|
|
2172 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2173 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2174 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2175 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2176 | |
1952 | first watcher gets started will libev actually register a signal handler |
2177 | When the first watcher gets started will libev actually register something |
1953 | with the kernel (thus it coexists with your own signal handlers as long as |
2178 | with the kernel (thus it coexists with your own signal handlers as long as |
1954 | you don't register any with libev for the same signal). Similarly, when |
2179 | you don't register any with libev for the same signal). |
1955 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1956 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1957 | |
2180 | |
1958 | If possible and supported, libev will install its handlers with |
2181 | If possible and supported, libev will install its handlers with |
1959 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2182 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1960 | interrupted. If you have a problem with system calls getting interrupted by |
2183 | not be unduly interrupted. If you have a problem with system calls getting |
1961 | signals you can block all signals in an C<ev_check> watcher and unblock |
2184 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1962 | them in an C<ev_prepare> watcher. |
2185 | and unblock them in an C<ev_prepare> watcher. |
|
|
2186 | |
|
|
2187 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2188 | |
|
|
2189 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2190 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2191 | stopping it again), that is, libev might or might not block the signal, |
|
|
2192 | and might or might not set or restore the installed signal handler. |
|
|
2193 | |
|
|
2194 | While this does not matter for the signal disposition (libev never |
|
|
2195 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2196 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2197 | certain signals to be blocked. |
|
|
2198 | |
|
|
2199 | This means that before calling C<exec> (from the child) you should reset |
|
|
2200 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2201 | choice usually). |
|
|
2202 | |
|
|
2203 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2204 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2205 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2206 | |
|
|
2207 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2208 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2209 | the window of opportunity for problems, it will not go away, as libev |
|
|
2210 | I<has> to modify the signal mask, at least temporarily. |
|
|
2211 | |
|
|
2212 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2213 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2214 | is not a libev-specific thing, this is true for most event libraries. |
1963 | |
2215 | |
1964 | =head3 Watcher-Specific Functions and Data Members |
2216 | =head3 Watcher-Specific Functions and Data Members |
1965 | |
2217 | |
1966 | =over 4 |
2218 | =over 4 |
1967 | |
2219 | |
… | |
… | |
1999 | some child status changes (most typically when a child of yours dies or |
2251 | some child status changes (most typically when a child of yours dies or |
2000 | exits). It is permissible to install a child watcher I<after> the child |
2252 | exits). It is permissible to install a child watcher I<after> the child |
2001 | has been forked (which implies it might have already exited), as long |
2253 | has been forked (which implies it might have already exited), as long |
2002 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2254 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2003 | forking and then immediately registering a watcher for the child is fine, |
2255 | forking and then immediately registering a watcher for the child is fine, |
2004 | but forking and registering a watcher a few event loop iterations later is |
2256 | but forking and registering a watcher a few event loop iterations later or |
2005 | not. |
2257 | in the next callback invocation is not. |
2006 | |
2258 | |
2007 | Only the default event loop is capable of handling signals, and therefore |
2259 | Only the default event loop is capable of handling signals, and therefore |
2008 | you can only register child watchers in the default event loop. |
2260 | you can only register child watchers in the default event loop. |
2009 | |
2261 | |
|
|
2262 | Due to some design glitches inside libev, child watchers will always be |
|
|
2263 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2264 | libev) |
|
|
2265 | |
2010 | =head3 Process Interaction |
2266 | =head3 Process Interaction |
2011 | |
2267 | |
2012 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2268 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2013 | initialised. This is necessary to guarantee proper behaviour even if |
2269 | initialised. This is necessary to guarantee proper behaviour even if the |
2014 | the first child watcher is started after the child exits. The occurrence |
2270 | first child watcher is started after the child exits. The occurrence |
2015 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2271 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2016 | synchronously as part of the event loop processing. Libev always reaps all |
2272 | synchronously as part of the event loop processing. Libev always reaps all |
2017 | children, even ones not watched. |
2273 | children, even ones not watched. |
2018 | |
2274 | |
2019 | =head3 Overriding the Built-In Processing |
2275 | =head3 Overriding the Built-In Processing |
… | |
… | |
2029 | =head3 Stopping the Child Watcher |
2285 | =head3 Stopping the Child Watcher |
2030 | |
2286 | |
2031 | Currently, the child watcher never gets stopped, even when the |
2287 | Currently, the child watcher never gets stopped, even when the |
2032 | child terminates, so normally one needs to stop the watcher in the |
2288 | child terminates, so normally one needs to stop the watcher in the |
2033 | callback. Future versions of libev might stop the watcher automatically |
2289 | callback. Future versions of libev might stop the watcher automatically |
2034 | when a child exit is detected. |
2290 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2291 | problem). |
2035 | |
2292 | |
2036 | =head3 Watcher-Specific Functions and Data Members |
2293 | =head3 Watcher-Specific Functions and Data Members |
2037 | |
2294 | |
2038 | =over 4 |
2295 | =over 4 |
2039 | |
2296 | |
… | |
… | |
2365 | // no longer anything immediate to do. |
2622 | // no longer anything immediate to do. |
2366 | } |
2623 | } |
2367 | |
2624 | |
2368 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2625 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2369 | ev_idle_init (idle_watcher, idle_cb); |
2626 | ev_idle_init (idle_watcher, idle_cb); |
2370 | ev_idle_start (loop, idle_cb); |
2627 | ev_idle_start (loop, idle_watcher); |
2371 | |
2628 | |
2372 | |
2629 | |
2373 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2630 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2374 | |
2631 | |
2375 | Prepare and check watchers are usually (but not always) used in pairs: |
2632 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2468 | struct pollfd fds [nfd]; |
2725 | struct pollfd fds [nfd]; |
2469 | // actual code will need to loop here and realloc etc. |
2726 | // actual code will need to loop here and realloc etc. |
2470 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2727 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2471 | |
2728 | |
2472 | /* the callback is illegal, but won't be called as we stop during check */ |
2729 | /* the callback is illegal, but won't be called as we stop during check */ |
2473 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2730 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2474 | ev_timer_start (loop, &tw); |
2731 | ev_timer_start (loop, &tw); |
2475 | |
2732 | |
2476 | // create one ev_io per pollfd |
2733 | // create one ev_io per pollfd |
2477 | for (int i = 0; i < nfd; ++i) |
2734 | for (int i = 0; i < nfd; ++i) |
2478 | { |
2735 | { |
… | |
… | |
2708 | event loop blocks next and before C<ev_check> watchers are being called, |
2965 | event loop blocks next and before C<ev_check> watchers are being called, |
2709 | and only in the child after the fork. If whoever good citizen calling |
2966 | and only in the child after the fork. If whoever good citizen calling |
2710 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2967 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2711 | handlers will be invoked, too, of course. |
2968 | handlers will be invoked, too, of course. |
2712 | |
2969 | |
|
|
2970 | =head3 The special problem of life after fork - how is it possible? |
|
|
2971 | |
|
|
2972 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
2973 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2974 | sequence should be handled by libev without any problems. |
|
|
2975 | |
|
|
2976 | This changes when the application actually wants to do event handling |
|
|
2977 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2978 | fork. |
|
|
2979 | |
|
|
2980 | The default mode of operation (for libev, with application help to detect |
|
|
2981 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2982 | when I<either> the parent I<or> the child process continues. |
|
|
2983 | |
|
|
2984 | When both processes want to continue using libev, then this is usually the |
|
|
2985 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2986 | supposed to continue with all watchers in place as before, while the other |
|
|
2987 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2988 | |
|
|
2989 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2990 | simply create a new event loop, which of course will be "empty", and |
|
|
2991 | use that for new watchers. This has the advantage of not touching more |
|
|
2992 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2993 | disadvantage of having to use multiple event loops (which do not support |
|
|
2994 | signal watchers). |
|
|
2995 | |
|
|
2996 | When this is not possible, or you want to use the default loop for |
|
|
2997 | other reasons, then in the process that wants to start "fresh", call |
|
|
2998 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2999 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
3000 | have to be careful not to execute code that modifies those watchers. Note |
|
|
3001 | also that in that case, you have to re-register any signal watchers. |
|
|
3002 | |
2713 | =head3 Watcher-Specific Functions and Data Members |
3003 | =head3 Watcher-Specific Functions and Data Members |
2714 | |
3004 | |
2715 | =over 4 |
3005 | =over 4 |
2716 | |
3006 | |
2717 | =item ev_fork_init (ev_signal *, callback) |
3007 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2721 | believe me. |
3011 | believe me. |
2722 | |
3012 | |
2723 | =back |
3013 | =back |
2724 | |
3014 | |
2725 | |
3015 | |
2726 | =head2 C<ev_async> - how to wake up another event loop |
3016 | =head2 C<ev_async> - how to wake up an event loop |
2727 | |
3017 | |
2728 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3018 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2729 | asynchronous sources such as signal handlers (as opposed to multiple event |
3019 | asynchronous sources such as signal handlers (as opposed to multiple event |
2730 | loops - those are of course safe to use in different threads). |
3020 | loops - those are of course safe to use in different threads). |
2731 | |
3021 | |
2732 | Sometimes, however, you need to wake up another event loop you do not |
3022 | Sometimes, however, you need to wake up an event loop you do not control, |
2733 | control, for example because it belongs to another thread. This is what |
3023 | for example because it belongs to another thread. This is what C<ev_async> |
2734 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3024 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2735 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3025 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2736 | safe. |
|
|
2737 | |
3026 | |
2738 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3027 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2739 | too, are asynchronous in nature, and signals, too, will be compressed |
3028 | too, are asynchronous in nature, and signals, too, will be compressed |
2740 | (i.e. the number of callback invocations may be less than the number of |
3029 | (i.e. the number of callback invocations may be less than the number of |
2741 | C<ev_async_sent> calls). |
3030 | C<ev_async_sent> calls). |
… | |
… | |
2746 | =head3 Queueing |
3035 | =head3 Queueing |
2747 | |
3036 | |
2748 | C<ev_async> does not support queueing of data in any way. The reason |
3037 | C<ev_async> does not support queueing of data in any way. The reason |
2749 | is that the author does not know of a simple (or any) algorithm for a |
3038 | is that the author does not know of a simple (or any) algorithm for a |
2750 | multiple-writer-single-reader queue that works in all cases and doesn't |
3039 | multiple-writer-single-reader queue that works in all cases and doesn't |
2751 | need elaborate support such as pthreads. |
3040 | need elaborate support such as pthreads or unportable memory access |
|
|
3041 | semantics. |
2752 | |
3042 | |
2753 | That means that if you want to queue data, you have to provide your own |
3043 | That means that if you want to queue data, you have to provide your own |
2754 | queue. But at least I can tell you how to implement locking around your |
3044 | queue. But at least I can tell you how to implement locking around your |
2755 | queue: |
3045 | queue: |
2756 | |
3046 | |
… | |
… | |
2895 | |
3185 | |
2896 | If C<timeout> is less than 0, then no timeout watcher will be |
3186 | If C<timeout> is less than 0, then no timeout watcher will be |
2897 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3187 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2898 | repeat = 0) will be started. C<0> is a valid timeout. |
3188 | repeat = 0) will be started. C<0> is a valid timeout. |
2899 | |
3189 | |
2900 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3190 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2901 | passed an C<revents> set like normal event callbacks (a combination of |
3191 | passed an C<revents> set like normal event callbacks (a combination of |
2902 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3192 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2903 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3193 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2904 | a timeout and an io event at the same time - you probably should give io |
3194 | a timeout and an io event at the same time - you probably should give io |
2905 | events precedence. |
3195 | events precedence. |
2906 | |
3196 | |
2907 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3197 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2908 | |
3198 | |
2909 | static void stdin_ready (int revents, void *arg) |
3199 | static void stdin_ready (int revents, void *arg) |
2910 | { |
3200 | { |
2911 | if (revents & EV_READ) |
3201 | if (revents & EV_READ) |
2912 | /* stdin might have data for us, joy! */; |
3202 | /* stdin might have data for us, joy! */; |
2913 | else if (revents & EV_TIMEOUT) |
3203 | else if (revents & EV_TIMER) |
2914 | /* doh, nothing entered */; |
3204 | /* doh, nothing entered */; |
2915 | } |
3205 | } |
2916 | |
3206 | |
2917 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3207 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2918 | |
3208 | |
2919 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2920 | |
|
|
2921 | Feeds the given event set into the event loop, as if the specified event |
|
|
2922 | had happened for the specified watcher (which must be a pointer to an |
|
|
2923 | initialised but not necessarily started event watcher). |
|
|
2924 | |
|
|
2925 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3209 | =item ev_feed_fd_event (loop, int fd, int revents) |
2926 | |
3210 | |
2927 | Feed an event on the given fd, as if a file descriptor backend detected |
3211 | Feed an event on the given fd, as if a file descriptor backend detected |
2928 | the given events it. |
3212 | the given events it. |
2929 | |
3213 | |
2930 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3214 | =item ev_feed_signal_event (loop, int signum) |
2931 | |
3215 | |
2932 | Feed an event as if the given signal occurred (C<loop> must be the default |
3216 | Feed an event as if the given signal occurred (C<loop> must be the default |
2933 | loop!). |
3217 | loop!). |
2934 | |
3218 | |
2935 | =back |
3219 | =back |
… | |
… | |
3015 | |
3299 | |
3016 | =over 4 |
3300 | =over 4 |
3017 | |
3301 | |
3018 | =item ev::TYPE::TYPE () |
3302 | =item ev::TYPE::TYPE () |
3019 | |
3303 | |
3020 | =item ev::TYPE::TYPE (struct ev_loop *) |
3304 | =item ev::TYPE::TYPE (loop) |
3021 | |
3305 | |
3022 | =item ev::TYPE::~TYPE |
3306 | =item ev::TYPE::~TYPE |
3023 | |
3307 | |
3024 | The constructor (optionally) takes an event loop to associate the watcher |
3308 | The constructor (optionally) takes an event loop to associate the watcher |
3025 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3309 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
3058 | myclass obj; |
3342 | myclass obj; |
3059 | ev::io iow; |
3343 | ev::io iow; |
3060 | iow.set <myclass, &myclass::io_cb> (&obj); |
3344 | iow.set <myclass, &myclass::io_cb> (&obj); |
3061 | |
3345 | |
3062 | =item w->set (object *) |
3346 | =item w->set (object *) |
3063 | |
|
|
3064 | This is an B<experimental> feature that might go away in a future version. |
|
|
3065 | |
3347 | |
3066 | This is a variation of a method callback - leaving out the method to call |
3348 | This is a variation of a method callback - leaving out the method to call |
3067 | will default the method to C<operator ()>, which makes it possible to use |
3349 | will default the method to C<operator ()>, which makes it possible to use |
3068 | functor objects without having to manually specify the C<operator ()> all |
3350 | functor objects without having to manually specify the C<operator ()> all |
3069 | the time. Incidentally, you can then also leave out the template argument |
3351 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3102 | Example: Use a plain function as callback. |
3384 | Example: Use a plain function as callback. |
3103 | |
3385 | |
3104 | static void io_cb (ev::io &w, int revents) { } |
3386 | static void io_cb (ev::io &w, int revents) { } |
3105 | iow.set <io_cb> (); |
3387 | iow.set <io_cb> (); |
3106 | |
3388 | |
3107 | =item w->set (struct ev_loop *) |
3389 | =item w->set (loop) |
3108 | |
3390 | |
3109 | Associates a different C<struct ev_loop> with this watcher. You can only |
3391 | Associates a different C<struct ev_loop> with this watcher. You can only |
3110 | do this when the watcher is inactive (and not pending either). |
3392 | do this when the watcher is inactive (and not pending either). |
3111 | |
3393 | |
3112 | =item w->set ([arguments]) |
3394 | =item w->set ([arguments]) |
… | |
… | |
3209 | =item Ocaml |
3491 | =item Ocaml |
3210 | |
3492 | |
3211 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3493 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3212 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3494 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3213 | |
3495 | |
|
|
3496 | =item Lua |
|
|
3497 | |
|
|
3498 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3499 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3500 | L<http://github.com/brimworks/lua-ev>. |
|
|
3501 | |
3214 | =back |
3502 | =back |
3215 | |
3503 | |
3216 | |
3504 | |
3217 | =head1 MACRO MAGIC |
3505 | =head1 MACRO MAGIC |
3218 | |
3506 | |
… | |
… | |
3371 | libev.m4 |
3659 | libev.m4 |
3372 | |
3660 | |
3373 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3661 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3374 | |
3662 | |
3375 | Libev can be configured via a variety of preprocessor symbols you have to |
3663 | Libev can be configured via a variety of preprocessor symbols you have to |
3376 | define before including any of its files. The default in the absence of |
3664 | define before including (or compiling) any of its files. The default in |
3377 | autoconf is documented for every option. |
3665 | the absence of autoconf is documented for every option. |
|
|
3666 | |
|
|
3667 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3668 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3669 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3670 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3671 | users of libev and the libev code itself must be compiled with compatible |
|
|
3672 | settings. |
3378 | |
3673 | |
3379 | =over 4 |
3674 | =over 4 |
3380 | |
3675 | |
3381 | =item EV_STANDALONE |
3676 | =item EV_STANDALONE (h) |
3382 | |
3677 | |
3383 | Must always be C<1> if you do not use autoconf configuration, which |
3678 | Must always be C<1> if you do not use autoconf configuration, which |
3384 | keeps libev from including F<config.h>, and it also defines dummy |
3679 | keeps libev from including F<config.h>, and it also defines dummy |
3385 | implementations for some libevent functions (such as logging, which is not |
3680 | implementations for some libevent functions (such as logging, which is not |
3386 | supported). It will also not define any of the structs usually found in |
3681 | supported). It will also not define any of the structs usually found in |
3387 | F<event.h> that are not directly supported by the libev core alone. |
3682 | F<event.h> that are not directly supported by the libev core alone. |
3388 | |
3683 | |
3389 | In stanbdalone mode, libev will still try to automatically deduce the |
3684 | In standalone mode, libev will still try to automatically deduce the |
3390 | configuration, but has to be more conservative. |
3685 | configuration, but has to be more conservative. |
3391 | |
3686 | |
3392 | =item EV_USE_MONOTONIC |
3687 | =item EV_USE_MONOTONIC |
3393 | |
3688 | |
3394 | If defined to be C<1>, libev will try to detect the availability of the |
3689 | If defined to be C<1>, libev will try to detect the availability of the |
… | |
… | |
3459 | be used is the winsock select). This means that it will call |
3754 | be used is the winsock select). This means that it will call |
3460 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3755 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3461 | it is assumed that all these functions actually work on fds, even |
3756 | it is assumed that all these functions actually work on fds, even |
3462 | on win32. Should not be defined on non-win32 platforms. |
3757 | on win32. Should not be defined on non-win32 platforms. |
3463 | |
3758 | |
3464 | =item EV_FD_TO_WIN32_HANDLE |
3759 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3465 | |
3760 | |
3466 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3761 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3467 | file descriptors to socket handles. When not defining this symbol (the |
3762 | file descriptors to socket handles. When not defining this symbol (the |
3468 | default), then libev will call C<_get_osfhandle>, which is usually |
3763 | default), then libev will call C<_get_osfhandle>, which is usually |
3469 | correct. In some cases, programs use their own file descriptor management, |
3764 | correct. In some cases, programs use their own file descriptor management, |
3470 | in which case they can provide this function to map fds to socket handles. |
3765 | in which case they can provide this function to map fds to socket handles. |
|
|
3766 | |
|
|
3767 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3768 | |
|
|
3769 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3770 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3771 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3772 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3773 | |
|
|
3774 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3775 | |
|
|
3776 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3777 | macro can be used to override the C<close> function, useful to unregister |
|
|
3778 | file descriptors again. Note that the replacement function has to close |
|
|
3779 | the underlying OS handle. |
3471 | |
3780 | |
3472 | =item EV_USE_POLL |
3781 | =item EV_USE_POLL |
3473 | |
3782 | |
3474 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3783 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3475 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3784 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3522 | as well as for signal and thread safety in C<ev_async> watchers. |
3831 | as well as for signal and thread safety in C<ev_async> watchers. |
3523 | |
3832 | |
3524 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3833 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3525 | (from F<signal.h>), which is usually good enough on most platforms. |
3834 | (from F<signal.h>), which is usually good enough on most platforms. |
3526 | |
3835 | |
3527 | =item EV_H |
3836 | =item EV_H (h) |
3528 | |
3837 | |
3529 | The name of the F<ev.h> header file used to include it. The default if |
3838 | The name of the F<ev.h> header file used to include it. The default if |
3530 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3839 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3531 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3840 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3532 | |
3841 | |
3533 | =item EV_CONFIG_H |
3842 | =item EV_CONFIG_H (h) |
3534 | |
3843 | |
3535 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3844 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3536 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3845 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3537 | C<EV_H>, above. |
3846 | C<EV_H>, above. |
3538 | |
3847 | |
3539 | =item EV_EVENT_H |
3848 | =item EV_EVENT_H (h) |
3540 | |
3849 | |
3541 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3850 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3542 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3851 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3543 | |
3852 | |
3544 | =item EV_PROTOTYPES |
3853 | =item EV_PROTOTYPES (h) |
3545 | |
3854 | |
3546 | If defined to be C<0>, then F<ev.h> will not define any function |
3855 | If defined to be C<0>, then F<ev.h> will not define any function |
3547 | prototypes, but still define all the structs and other symbols. This is |
3856 | prototypes, but still define all the structs and other symbols. This is |
3548 | occasionally useful if you want to provide your own wrapper functions |
3857 | occasionally useful if you want to provide your own wrapper functions |
3549 | around libev functions. |
3858 | around libev functions. |
… | |
… | |
3571 | fine. |
3880 | fine. |
3572 | |
3881 | |
3573 | If your embedding application does not need any priorities, defining these |
3882 | If your embedding application does not need any priorities, defining these |
3574 | both to C<0> will save some memory and CPU. |
3883 | both to C<0> will save some memory and CPU. |
3575 | |
3884 | |
3576 | =item EV_PERIODIC_ENABLE |
3885 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3886 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3887 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3577 | |
3888 | |
3578 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3889 | If undefined or defined to be C<1> (and the platform supports it), then |
3579 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3890 | the respective watcher type is supported. If defined to be C<0>, then it |
3580 | code. |
3891 | is not. Disabling watcher types mainly saves code size. |
3581 | |
3892 | |
3582 | =item EV_IDLE_ENABLE |
3893 | =item EV_FEATURES |
3583 | |
|
|
3584 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3585 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3586 | code. |
|
|
3587 | |
|
|
3588 | =item EV_EMBED_ENABLE |
|
|
3589 | |
|
|
3590 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3591 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3592 | watcher types, which therefore must not be disabled. |
|
|
3593 | |
|
|
3594 | =item EV_STAT_ENABLE |
|
|
3595 | |
|
|
3596 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3597 | defined to be C<0>, then they are not. |
|
|
3598 | |
|
|
3599 | =item EV_FORK_ENABLE |
|
|
3600 | |
|
|
3601 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3602 | defined to be C<0>, then they are not. |
|
|
3603 | |
|
|
3604 | =item EV_ASYNC_ENABLE |
|
|
3605 | |
|
|
3606 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3607 | defined to be C<0>, then they are not. |
|
|
3608 | |
|
|
3609 | =item EV_MINIMAL |
|
|
3610 | |
3894 | |
3611 | If you need to shave off some kilobytes of code at the expense of some |
3895 | If you need to shave off some kilobytes of code at the expense of some |
3612 | speed, define this symbol to C<1>. Currently this is used to override some |
3896 | speed (but with the full API), you can define this symbol to request |
3613 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3897 | certain subsets of functionality. The default is to enable all features |
3614 | much smaller 2-heap for timer management over the default 4-heap. |
3898 | that can be enabled on the platform. |
|
|
3899 | |
|
|
3900 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
3901 | with some broad features you want) and then selectively re-enable |
|
|
3902 | additional parts you want, for example if you want everything minimal, |
|
|
3903 | but multiple event loop support, async and child watchers and the poll |
|
|
3904 | backend, use this: |
|
|
3905 | |
|
|
3906 | #define EV_FEATURES 0 |
|
|
3907 | #define EV_MULTIPLICITY 1 |
|
|
3908 | #define EV_USE_POLL 1 |
|
|
3909 | #define EV_CHILD_ENABLE 1 |
|
|
3910 | #define EV_ASYNC_ENABLE 1 |
|
|
3911 | |
|
|
3912 | The actual value is a bitset, it can be a combination of the following |
|
|
3913 | values: |
|
|
3914 | |
|
|
3915 | =over 4 |
|
|
3916 | |
|
|
3917 | =item C<1> - faster/larger code |
|
|
3918 | |
|
|
3919 | Use larger code to speed up some operations. |
|
|
3920 | |
|
|
3921 | Currently this is used to override some inlining decisions (enlarging the |
|
|
3922 | code size by roughly 30% on amd64). |
|
|
3923 | |
|
|
3924 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3925 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3926 | assertions. |
|
|
3927 | |
|
|
3928 | =item C<2> - faster/larger data structures |
|
|
3929 | |
|
|
3930 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3931 | hash table sizes and so on. This will usually further increase code size |
|
|
3932 | and can additionally have an effect on the size of data structures at |
|
|
3933 | runtime. |
|
|
3934 | |
|
|
3935 | =item C<4> - full API configuration |
|
|
3936 | |
|
|
3937 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3938 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3939 | |
|
|
3940 | =item C<8> - full API |
|
|
3941 | |
|
|
3942 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3943 | details on which parts of the API are still available without this |
|
|
3944 | feature, and do not complain if this subset changes over time. |
|
|
3945 | |
|
|
3946 | =item C<16> - enable all optional watcher types |
|
|
3947 | |
|
|
3948 | Enables all optional watcher types. If you want to selectively enable |
|
|
3949 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3950 | embed, async, child...) you can enable them manually by defining |
|
|
3951 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3952 | |
|
|
3953 | =item C<32> - enable all backends |
|
|
3954 | |
|
|
3955 | This enables all backends - without this feature, you need to enable at |
|
|
3956 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3957 | |
|
|
3958 | =item C<64> - enable OS-specific "helper" APIs |
|
|
3959 | |
|
|
3960 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3961 | default. |
|
|
3962 | |
|
|
3963 | =back |
|
|
3964 | |
|
|
3965 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3966 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
3967 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
3968 | watchers, timers and monotonic clock support. |
|
|
3969 | |
|
|
3970 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3971 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3972 | your program might be left out as well - a binary starting a timer and an |
|
|
3973 | I/O watcher then might come out at only 5Kb. |
|
|
3974 | |
|
|
3975 | =item EV_AVOID_STDIO |
|
|
3976 | |
|
|
3977 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3978 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
3979 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3980 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3981 | big. |
|
|
3982 | |
|
|
3983 | Note that error messages might become less precise when this option is |
|
|
3984 | enabled. |
|
|
3985 | |
|
|
3986 | =item EV_NSIG |
|
|
3987 | |
|
|
3988 | The highest supported signal number, +1 (or, the number of |
|
|
3989 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3990 | automatically, but sometimes this fails, in which case it can be |
|
|
3991 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3992 | good for about any system in existence) can save some memory, as libev |
|
|
3993 | statically allocates some 12-24 bytes per signal number. |
3615 | |
3994 | |
3616 | =item EV_PID_HASHSIZE |
3995 | =item EV_PID_HASHSIZE |
3617 | |
3996 | |
3618 | C<ev_child> watchers use a small hash table to distribute workload by |
3997 | C<ev_child> watchers use a small hash table to distribute workload by |
3619 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3998 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3620 | than enough. If you need to manage thousands of children you might want to |
3999 | usually more than enough. If you need to manage thousands of children you |
3621 | increase this value (I<must> be a power of two). |
4000 | might want to increase this value (I<must> be a power of two). |
3622 | |
4001 | |
3623 | =item EV_INOTIFY_HASHSIZE |
4002 | =item EV_INOTIFY_HASHSIZE |
3624 | |
4003 | |
3625 | C<ev_stat> watchers use a small hash table to distribute workload by |
4004 | C<ev_stat> watchers use a small hash table to distribute workload by |
3626 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4005 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3627 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4006 | disabled), usually more than enough. If you need to manage thousands of |
3628 | watchers you might want to increase this value (I<must> be a power of |
4007 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3629 | two). |
4008 | power of two). |
3630 | |
4009 | |
3631 | =item EV_USE_4HEAP |
4010 | =item EV_USE_4HEAP |
3632 | |
4011 | |
3633 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4012 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3634 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4013 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3635 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4014 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3636 | faster performance with many (thousands) of watchers. |
4015 | faster performance with many (thousands) of watchers. |
3637 | |
4016 | |
3638 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4017 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3639 | (disabled). |
4018 | will be C<0>. |
3640 | |
4019 | |
3641 | =item EV_HEAP_CACHE_AT |
4020 | =item EV_HEAP_CACHE_AT |
3642 | |
4021 | |
3643 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4022 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3644 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4023 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3645 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4024 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3646 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4025 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3647 | but avoids random read accesses on heap changes. This improves performance |
4026 | but avoids random read accesses on heap changes. This improves performance |
3648 | noticeably with many (hundreds) of watchers. |
4027 | noticeably with many (hundreds) of watchers. |
3649 | |
4028 | |
3650 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4029 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3651 | (disabled). |
4030 | will be C<0>. |
3652 | |
4031 | |
3653 | =item EV_VERIFY |
4032 | =item EV_VERIFY |
3654 | |
4033 | |
3655 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4034 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3656 | be done: If set to C<0>, no internal verification code will be compiled |
4035 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3658 | called. If set to C<2>, then the internal verification code will be |
4037 | called. If set to C<2>, then the internal verification code will be |
3659 | called once per loop, which can slow down libev. If set to C<3>, then the |
4038 | called once per loop, which can slow down libev. If set to C<3>, then the |
3660 | verification code will be called very frequently, which will slow down |
4039 | verification code will be called very frequently, which will slow down |
3661 | libev considerably. |
4040 | libev considerably. |
3662 | |
4041 | |
3663 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4042 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3664 | C<0>. |
4043 | will be C<0>. |
3665 | |
4044 | |
3666 | =item EV_COMMON |
4045 | =item EV_COMMON |
3667 | |
4046 | |
3668 | By default, all watchers have a C<void *data> member. By redefining |
4047 | By default, all watchers have a C<void *data> member. By redefining |
3669 | this macro to a something else you can include more and other types of |
4048 | this macro to something else you can include more and other types of |
3670 | members. You have to define it each time you include one of the files, |
4049 | members. You have to define it each time you include one of the files, |
3671 | though, and it must be identical each time. |
4050 | though, and it must be identical each time. |
3672 | |
4051 | |
3673 | For example, the perl EV module uses something like this: |
4052 | For example, the perl EV module uses something like this: |
3674 | |
4053 | |
… | |
… | |
3727 | file. |
4106 | file. |
3728 | |
4107 | |
3729 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4108 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3730 | that everybody includes and which overrides some configure choices: |
4109 | that everybody includes and which overrides some configure choices: |
3731 | |
4110 | |
3732 | #define EV_MINIMAL 1 |
4111 | #define EV_FEATURES 8 |
3733 | #define EV_USE_POLL 0 |
4112 | #define EV_USE_SELECT 1 |
3734 | #define EV_MULTIPLICITY 0 |
|
|
3735 | #define EV_PERIODIC_ENABLE 0 |
4113 | #define EV_PREPARE_ENABLE 1 |
|
|
4114 | #define EV_IDLE_ENABLE 1 |
3736 | #define EV_STAT_ENABLE 0 |
4115 | #define EV_SIGNAL_ENABLE 1 |
3737 | #define EV_FORK_ENABLE 0 |
4116 | #define EV_CHILD_ENABLE 1 |
|
|
4117 | #define EV_USE_STDEXCEPT 0 |
3738 | #define EV_CONFIG_H <config.h> |
4118 | #define EV_CONFIG_H <config.h> |
3739 | #define EV_MINPRI 0 |
|
|
3740 | #define EV_MAXPRI 0 |
|
|
3741 | |
4119 | |
3742 | #include "ev++.h" |
4120 | #include "ev++.h" |
3743 | |
4121 | |
3744 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4122 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3745 | |
4123 | |
… | |
… | |
3805 | default loop and triggering an C<ev_async> watcher from the default loop |
4183 | default loop and triggering an C<ev_async> watcher from the default loop |
3806 | watcher callback into the event loop interested in the signal. |
4184 | watcher callback into the event loop interested in the signal. |
3807 | |
4185 | |
3808 | =back |
4186 | =back |
3809 | |
4187 | |
|
|
4188 | =head4 THREAD LOCKING EXAMPLE |
|
|
4189 | |
|
|
4190 | Here is a fictitious example of how to run an event loop in a different |
|
|
4191 | thread than where callbacks are being invoked and watchers are |
|
|
4192 | created/added/removed. |
|
|
4193 | |
|
|
4194 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4195 | which uses exactly this technique (which is suited for many high-level |
|
|
4196 | languages). |
|
|
4197 | |
|
|
4198 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4199 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4200 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4201 | |
|
|
4202 | First, you need to associate some data with the event loop: |
|
|
4203 | |
|
|
4204 | typedef struct { |
|
|
4205 | mutex_t lock; /* global loop lock */ |
|
|
4206 | ev_async async_w; |
|
|
4207 | thread_t tid; |
|
|
4208 | cond_t invoke_cv; |
|
|
4209 | } userdata; |
|
|
4210 | |
|
|
4211 | void prepare_loop (EV_P) |
|
|
4212 | { |
|
|
4213 | // for simplicity, we use a static userdata struct. |
|
|
4214 | static userdata u; |
|
|
4215 | |
|
|
4216 | ev_async_init (&u->async_w, async_cb); |
|
|
4217 | ev_async_start (EV_A_ &u->async_w); |
|
|
4218 | |
|
|
4219 | pthread_mutex_init (&u->lock, 0); |
|
|
4220 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4221 | |
|
|
4222 | // now associate this with the loop |
|
|
4223 | ev_set_userdata (EV_A_ u); |
|
|
4224 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4225 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4226 | |
|
|
4227 | // then create the thread running ev_loop |
|
|
4228 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4229 | } |
|
|
4230 | |
|
|
4231 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4232 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4233 | that might have been added: |
|
|
4234 | |
|
|
4235 | static void |
|
|
4236 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4237 | { |
|
|
4238 | // just used for the side effects |
|
|
4239 | } |
|
|
4240 | |
|
|
4241 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4242 | protecting the loop data, respectively. |
|
|
4243 | |
|
|
4244 | static void |
|
|
4245 | l_release (EV_P) |
|
|
4246 | { |
|
|
4247 | userdata *u = ev_userdata (EV_A); |
|
|
4248 | pthread_mutex_unlock (&u->lock); |
|
|
4249 | } |
|
|
4250 | |
|
|
4251 | static void |
|
|
4252 | l_acquire (EV_P) |
|
|
4253 | { |
|
|
4254 | userdata *u = ev_userdata (EV_A); |
|
|
4255 | pthread_mutex_lock (&u->lock); |
|
|
4256 | } |
|
|
4257 | |
|
|
4258 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4259 | into C<ev_loop>: |
|
|
4260 | |
|
|
4261 | void * |
|
|
4262 | l_run (void *thr_arg) |
|
|
4263 | { |
|
|
4264 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4265 | |
|
|
4266 | l_acquire (EV_A); |
|
|
4267 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4268 | ev_loop (EV_A_ 0); |
|
|
4269 | l_release (EV_A); |
|
|
4270 | |
|
|
4271 | return 0; |
|
|
4272 | } |
|
|
4273 | |
|
|
4274 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4275 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4276 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4277 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4278 | and b) skipping inter-thread-communication when there are no pending |
|
|
4279 | watchers is very beneficial): |
|
|
4280 | |
|
|
4281 | static void |
|
|
4282 | l_invoke (EV_P) |
|
|
4283 | { |
|
|
4284 | userdata *u = ev_userdata (EV_A); |
|
|
4285 | |
|
|
4286 | while (ev_pending_count (EV_A)) |
|
|
4287 | { |
|
|
4288 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4289 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4290 | } |
|
|
4291 | } |
|
|
4292 | |
|
|
4293 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4294 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4295 | thread to continue: |
|
|
4296 | |
|
|
4297 | static void |
|
|
4298 | real_invoke_pending (EV_P) |
|
|
4299 | { |
|
|
4300 | userdata *u = ev_userdata (EV_A); |
|
|
4301 | |
|
|
4302 | pthread_mutex_lock (&u->lock); |
|
|
4303 | ev_invoke_pending (EV_A); |
|
|
4304 | pthread_cond_signal (&u->invoke_cv); |
|
|
4305 | pthread_mutex_unlock (&u->lock); |
|
|
4306 | } |
|
|
4307 | |
|
|
4308 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4309 | event loop, you will now have to lock: |
|
|
4310 | |
|
|
4311 | ev_timer timeout_watcher; |
|
|
4312 | userdata *u = ev_userdata (EV_A); |
|
|
4313 | |
|
|
4314 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4315 | |
|
|
4316 | pthread_mutex_lock (&u->lock); |
|
|
4317 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4318 | ev_async_send (EV_A_ &u->async_w); |
|
|
4319 | pthread_mutex_unlock (&u->lock); |
|
|
4320 | |
|
|
4321 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4322 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4323 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4324 | watchers in the next event loop iteration. |
|
|
4325 | |
3810 | =head3 COROUTINES |
4326 | =head3 COROUTINES |
3811 | |
4327 | |
3812 | Libev is very accommodating to coroutines ("cooperative threads"): |
4328 | Libev is very accommodating to coroutines ("cooperative threads"): |
3813 | libev fully supports nesting calls to its functions from different |
4329 | libev fully supports nesting calls to its functions from different |
3814 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4330 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3815 | different coroutines, and switch freely between both coroutines running the |
4331 | different coroutines, and switch freely between both coroutines running |
3816 | loop, as long as you don't confuse yourself). The only exception is that |
4332 | the loop, as long as you don't confuse yourself). The only exception is |
3817 | you must not do this from C<ev_periodic> reschedule callbacks. |
4333 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3818 | |
4334 | |
3819 | Care has been taken to ensure that libev does not keep local state inside |
4335 | Care has been taken to ensure that libev does not keep local state inside |
3820 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4336 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3821 | they do not call any callbacks. |
4337 | they do not call any callbacks. |
3822 | |
4338 | |
… | |
… | |
3836 | maintainable. |
4352 | maintainable. |
3837 | |
4353 | |
3838 | And of course, some compiler warnings are just plain stupid, or simply |
4354 | And of course, some compiler warnings are just plain stupid, or simply |
3839 | wrong (because they don't actually warn about the condition their message |
4355 | wrong (because they don't actually warn about the condition their message |
3840 | seems to warn about). For example, certain older gcc versions had some |
4356 | seems to warn about). For example, certain older gcc versions had some |
3841 | warnings that resulted an extreme number of false positives. These have |
4357 | warnings that resulted in an extreme number of false positives. These have |
3842 | been fixed, but some people still insist on making code warn-free with |
4358 | been fixed, but some people still insist on making code warn-free with |
3843 | such buggy versions. |
4359 | such buggy versions. |
3844 | |
4360 | |
3845 | While libev is written to generate as few warnings as possible, |
4361 | While libev is written to generate as few warnings as possible, |
3846 | "warn-free" code is not a goal, and it is recommended not to build libev |
4362 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3882 | I suggest using suppression lists. |
4398 | I suggest using suppression lists. |
3883 | |
4399 | |
3884 | |
4400 | |
3885 | =head1 PORTABILITY NOTES |
4401 | =head1 PORTABILITY NOTES |
3886 | |
4402 | |
|
|
4403 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4404 | |
|
|
4405 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4406 | interfaces but I<disables> them by default. |
|
|
4407 | |
|
|
4408 | That means that libev compiled in the default environment doesn't support |
|
|
4409 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4410 | |
|
|
4411 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4412 | by enabling the large file API, which makes them incompatible with the |
|
|
4413 | standard libev compiled for their system. |
|
|
4414 | |
|
|
4415 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4416 | suddenly make it incompatible to the default compile time environment, |
|
|
4417 | i.e. all programs not using special compile switches. |
|
|
4418 | |
|
|
4419 | =head2 OS/X AND DARWIN BUGS |
|
|
4420 | |
|
|
4421 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4422 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4423 | OpenGL drivers. |
|
|
4424 | |
|
|
4425 | =head3 C<kqueue> is buggy |
|
|
4426 | |
|
|
4427 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4428 | only sockets, many support pipes. |
|
|
4429 | |
|
|
4430 | Libev tries to work around this by not using C<kqueue> by default on |
|
|
4431 | this rotten platform, but of course you can still ask for it when creating |
|
|
4432 | a loop. |
|
|
4433 | |
|
|
4434 | =head3 C<poll> is buggy |
|
|
4435 | |
|
|
4436 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4437 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4438 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4439 | |
|
|
4440 | Libev tries to work around this by not using C<poll> by default on |
|
|
4441 | this rotten platform, but of course you can still ask for it when creating |
|
|
4442 | a loop. |
|
|
4443 | |
|
|
4444 | =head3 C<select> is buggy |
|
|
4445 | |
|
|
4446 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4447 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4448 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4449 | you use more. |
|
|
4450 | |
|
|
4451 | There is an undocumented "workaround" for this - defining |
|
|
4452 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4453 | work on OS/X. |
|
|
4454 | |
|
|
4455 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4456 | |
|
|
4457 | =head3 C<errno> reentrancy |
|
|
4458 | |
|
|
4459 | The default compile environment on Solaris is unfortunately so |
|
|
4460 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4461 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
|
|
4462 | isn't defined by default. |
|
|
4463 | |
|
|
4464 | If you want to use libev in threaded environments you have to make sure |
|
|
4465 | it's compiled with C<_REENTRANT> defined. |
|
|
4466 | |
|
|
4467 | =head3 Event port backend |
|
|
4468 | |
|
|
4469 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
|
|
4470 | this mechanism is very buggy. If you run into high CPU usage, your program |
|
|
4471 | freezes or you get a large number of spurious wakeups, make sure you have |
|
|
4472 | all the relevant and latest kernel patches applied. No, I don't know which |
|
|
4473 | ones, but there are multiple ones. |
|
|
4474 | |
|
|
4475 | If you can't get it to work, you can try running the program by setting |
|
|
4476 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4477 | C<select> backends. |
|
|
4478 | |
|
|
4479 | =head2 AIX POLL BUG |
|
|
4480 | |
|
|
4481 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4482 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4483 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4484 | with large bitsets, and AIX is dead anyway. |
|
|
4485 | |
3887 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4486 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4487 | |
|
|
4488 | =head3 General issues |
3888 | |
4489 | |
3889 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4490 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3890 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4491 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3891 | model. Libev still offers limited functionality on this platform in |
4492 | model. Libev still offers limited functionality on this platform in |
3892 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4493 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3893 | descriptors. This only applies when using Win32 natively, not when using |
4494 | descriptors. This only applies when using Win32 natively, not when using |
3894 | e.g. cygwin. |
4495 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4496 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4497 | environment. |
3895 | |
4498 | |
3896 | Lifting these limitations would basically require the full |
4499 | Lifting these limitations would basically require the full |
3897 | re-implementation of the I/O system. If you are into these kinds of |
4500 | re-implementation of the I/O system. If you are into this kind of thing, |
3898 | things, then note that glib does exactly that for you in a very portable |
4501 | then note that glib does exactly that for you in a very portable way (note |
3899 | way (note also that glib is the slowest event library known to man). |
4502 | also that glib is the slowest event library known to man). |
3900 | |
4503 | |
3901 | There is no supported compilation method available on windows except |
4504 | There is no supported compilation method available on windows except |
3902 | embedding it into other applications. |
4505 | embedding it into other applications. |
|
|
4506 | |
|
|
4507 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4508 | tries its best, but under most conditions, signals will simply not work. |
3903 | |
4509 | |
3904 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4510 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3905 | accept large writes: instead of resulting in a partial write, windows will |
4511 | accept large writes: instead of resulting in a partial write, windows will |
3906 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4512 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3907 | so make sure you only write small amounts into your sockets (less than a |
4513 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3912 | the abysmal performance of winsockets, using a large number of sockets |
4518 | the abysmal performance of winsockets, using a large number of sockets |
3913 | is not recommended (and not reasonable). If your program needs to use |
4519 | is not recommended (and not reasonable). If your program needs to use |
3914 | more than a hundred or so sockets, then likely it needs to use a totally |
4520 | more than a hundred or so sockets, then likely it needs to use a totally |
3915 | different implementation for windows, as libev offers the POSIX readiness |
4521 | different implementation for windows, as libev offers the POSIX readiness |
3916 | notification model, which cannot be implemented efficiently on windows |
4522 | notification model, which cannot be implemented efficiently on windows |
3917 | (Microsoft monopoly games). |
4523 | (due to Microsoft monopoly games). |
3918 | |
4524 | |
3919 | A typical way to use libev under windows is to embed it (see the embedding |
4525 | A typical way to use libev under windows is to embed it (see the embedding |
3920 | section for details) and use the following F<evwrap.h> header file instead |
4526 | section for details) and use the following F<evwrap.h> header file instead |
3921 | of F<ev.h>: |
4527 | of F<ev.h>: |
3922 | |
4528 | |
… | |
… | |
3929 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4535 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3930 | |
4536 | |
3931 | #include "evwrap.h" |
4537 | #include "evwrap.h" |
3932 | #include "ev.c" |
4538 | #include "ev.c" |
3933 | |
4539 | |
3934 | =over 4 |
|
|
3935 | |
|
|
3936 | =item The winsocket select function |
4540 | =head3 The winsocket C<select> function |
3937 | |
4541 | |
3938 | The winsocket C<select> function doesn't follow POSIX in that it |
4542 | The winsocket C<select> function doesn't follow POSIX in that it |
3939 | requires socket I<handles> and not socket I<file descriptors> (it is |
4543 | requires socket I<handles> and not socket I<file descriptors> (it is |
3940 | also extremely buggy). This makes select very inefficient, and also |
4544 | also extremely buggy). This makes select very inefficient, and also |
3941 | requires a mapping from file descriptors to socket handles (the Microsoft |
4545 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3950 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4554 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3951 | |
4555 | |
3952 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4556 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3953 | complexity in the O(n²) range when using win32. |
4557 | complexity in the O(n²) range when using win32. |
3954 | |
4558 | |
3955 | =item Limited number of file descriptors |
4559 | =head3 Limited number of file descriptors |
3956 | |
4560 | |
3957 | Windows has numerous arbitrary (and low) limits on things. |
4561 | Windows has numerous arbitrary (and low) limits on things. |
3958 | |
4562 | |
3959 | Early versions of winsocket's select only supported waiting for a maximum |
4563 | Early versions of winsocket's select only supported waiting for a maximum |
3960 | of C<64> handles (probably owning to the fact that all windows kernels |
4564 | of C<64> handles (probably owning to the fact that all windows kernels |
3961 | can only wait for C<64> things at the same time internally; Microsoft |
4565 | can only wait for C<64> things at the same time internally; Microsoft |
3962 | recommends spawning a chain of threads and wait for 63 handles and the |
4566 | recommends spawning a chain of threads and wait for 63 handles and the |
3963 | previous thread in each. Great). |
4567 | previous thread in each. Sounds great!). |
3964 | |
4568 | |
3965 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4569 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3966 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4570 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3967 | call (which might be in libev or elsewhere, for example, perl does its own |
4571 | call (which might be in libev or elsewhere, for example, perl and many |
3968 | select emulation on windows). |
4572 | other interpreters do their own select emulation on windows). |
3969 | |
4573 | |
3970 | Another limit is the number of file descriptors in the Microsoft runtime |
4574 | Another limit is the number of file descriptors in the Microsoft runtime |
3971 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4575 | libraries, which by default is C<64> (there must be a hidden I<64> |
3972 | or something like this inside Microsoft). You can increase this by calling |
4576 | fetish or something like this inside Microsoft). You can increase this |
3973 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4577 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3974 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4578 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3975 | libraries. |
|
|
3976 | |
|
|
3977 | This might get you to about C<512> or C<2048> sockets (depending on |
4579 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3978 | windows version and/or the phase of the moon). To get more, you need to |
4580 | (depending on windows version and/or the phase of the moon). To get more, |
3979 | wrap all I/O functions and provide your own fd management, but the cost of |
4581 | you need to wrap all I/O functions and provide your own fd management, but |
3980 | calling select (O(n²)) will likely make this unworkable. |
4582 | the cost of calling select (O(n²)) will likely make this unworkable. |
3981 | |
|
|
3982 | =back |
|
|
3983 | |
4583 | |
3984 | =head2 PORTABILITY REQUIREMENTS |
4584 | =head2 PORTABILITY REQUIREMENTS |
3985 | |
4585 | |
3986 | In addition to a working ISO-C implementation and of course the |
4586 | In addition to a working ISO-C implementation and of course the |
3987 | backend-specific APIs, libev relies on a few additional extensions: |
4587 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
4028 | =item C<double> must hold a time value in seconds with enough accuracy |
4628 | =item C<double> must hold a time value in seconds with enough accuracy |
4029 | |
4629 | |
4030 | The type C<double> is used to represent timestamps. It is required to |
4630 | The type C<double> is used to represent timestamps. It is required to |
4031 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4631 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4032 | enough for at least into the year 4000. This requirement is fulfilled by |
4632 | enough for at least into the year 4000. This requirement is fulfilled by |
4033 | implementations implementing IEEE 754 (basically all existing ones). |
4633 | implementations implementing IEEE 754, which is basically all existing |
|
|
4634 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4635 | 2200. |
4034 | |
4636 | |
4035 | =back |
4637 | =back |
4036 | |
4638 | |
4037 | If you know of other additional requirements drop me a note. |
4639 | If you know of other additional requirements drop me a note. |
4038 | |
4640 | |
… | |
… | |
4106 | involves iterating over all running async watchers or all signal numbers. |
4708 | involves iterating over all running async watchers or all signal numbers. |
4107 | |
4709 | |
4108 | =back |
4710 | =back |
4109 | |
4711 | |
4110 | |
4712 | |
|
|
4713 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4714 | |
|
|
4715 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4716 | |
|
|
4717 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4718 | compatibility, so most programs should still compile. Those might be |
|
|
4719 | removed in later versions of libev, so better update early than late. |
|
|
4720 | |
|
|
4721 | =over 4 |
|
|
4722 | |
|
|
4723 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4724 | |
|
|
4725 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4726 | |
|
|
4727 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4728 | |
|
|
4729 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4730 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4731 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4732 | C<ev_fork> typedef. |
|
|
4733 | |
|
|
4734 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4735 | |
|
|
4736 | This is a simple rename - all other watcher types use their name |
|
|
4737 | as revents flag, and now C<ev_timer> does, too. |
|
|
4738 | |
|
|
4739 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4740 | and continue to be present for the foreseeable future, so this is mostly a |
|
|
4741 | documentation change. |
|
|
4742 | |
|
|
4743 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4744 | |
|
|
4745 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4746 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4747 | and work, but the library code will of course be larger. |
|
|
4748 | |
|
|
4749 | =back |
|
|
4750 | |
|
|
4751 | |
4111 | =head1 GLOSSARY |
4752 | =head1 GLOSSARY |
4112 | |
4753 | |
4113 | =over 4 |
4754 | =over 4 |
4114 | |
4755 | |
4115 | =item active |
4756 | =item active |
… | |
… | |
4136 | A change of state of some external event, such as data now being available |
4777 | A change of state of some external event, such as data now being available |
4137 | for reading on a file descriptor, time having passed or simply not having |
4778 | for reading on a file descriptor, time having passed or simply not having |
4138 | any other events happening anymore. |
4779 | any other events happening anymore. |
4139 | |
4780 | |
4140 | In libev, events are represented as single bits (such as C<EV_READ> or |
4781 | In libev, events are represented as single bits (such as C<EV_READ> or |
4141 | C<EV_TIMEOUT>). |
4782 | C<EV_TIMER>). |
4142 | |
4783 | |
4143 | =item event library |
4784 | =item event library |
4144 | |
4785 | |
4145 | A software package implementing an event model and loop. |
4786 | A software package implementing an event model and loop. |
4146 | |
4787 | |