… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
442 | |
442 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
443 | This behaviour is useful when you want to do your own signal handling, or |
444 | want to handle signals only in specific threads and want to avoid libev |
444 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
445 | unblocking the signals. |
446 | |
446 | |
|
|
447 | It's also required by POSIX in a threaded program, as libev calls |
|
|
448 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
449 | |
447 | This flag's behaviour will become the default in future versions of libev. |
450 | This flag's behaviour will become the default in future versions of libev. |
448 | |
451 | |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
452 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
450 | |
453 | |
451 | This is your standard select(2) backend. Not I<completely> standard, as |
454 | This is your standard select(2) backend. Not I<completely> standard, as |
… | |
… | |
480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
483 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
481 | |
484 | |
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
485 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
483 | kernels). |
486 | kernels). |
484 | |
487 | |
485 | For few fds, this backend is a bit little slower than poll and select, |
488 | For few fds, this backend is a bit little slower than poll and select, but |
486 | but it scales phenomenally better. While poll and select usually scale |
489 | it scales phenomenally better. While poll and select usually scale like |
487 | like O(total_fds) where n is the total number of fds (or the highest fd), |
490 | O(total_fds) where total_fds is the total number of fds (or the highest |
488 | epoll scales either O(1) or O(active_fds). |
491 | fd), epoll scales either O(1) or O(active_fds). |
489 | |
492 | |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
493 | The epoll mechanism deserves honorable mention as the most misdesigned |
491 | of the more advanced event mechanisms: mere annoyances include silently |
494 | of the more advanced event mechanisms: mere annoyances include silently |
492 | dropping file descriptors, requiring a system call per change per file |
495 | dropping file descriptors, requiring a system call per change per file |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
497 | forks then I<both> parent and child process have to recreate the epoll |
500 | forks then I<both> parent and child process have to recreate the epoll |
498 | set, which can take considerable time (one syscall per file descriptor) |
501 | set, which can take considerable time (one syscall per file descriptor) |
499 | and is of course hard to detect. |
502 | and is of course hard to detect. |
500 | |
503 | |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
505 | but of course I<doesn't>, and epoll just loves to report events for |
503 | I<different> file descriptors (even already closed ones, so one cannot |
506 | totally I<different> file descriptors (even already closed ones, so |
504 | even remove them from the set) than registered in the set (especially |
507 | one cannot even remove them from the set) than registered in the set |
505 | on SMP systems). Libev tries to counter these spurious notifications by |
508 | (especially on SMP systems). Libev tries to counter these spurious |
506 | employing an additional generation counter and comparing that against the |
509 | notifications by employing an additional generation counter and comparing |
507 | events to filter out spurious ones, recreating the set when required. Last |
510 | that against the events to filter out spurious ones, recreating the set |
|
|
511 | when required. Epoll also errornously rounds down timeouts, but gives you |
|
|
512 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
513 | because epoll returns immediately despite a nonzero timeout. And last |
508 | not least, it also refuses to work with some file descriptors which work |
514 | not least, it also refuses to work with some file descriptors which work |
509 | perfectly fine with C<select> (files, many character devices...). |
515 | perfectly fine with C<select> (files, many character devices...). |
510 | |
516 | |
511 | Epoll is truly the train wreck analog among event poll mechanisms, |
517 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
512 | a frankenpoll, cobbled together in a hurry, no thought to design or |
518 | cobbled together in a hurry, no thought to design or interaction with |
513 | interaction with others. |
519 | others. Oh, the pain, will it ever stop... |
514 | |
520 | |
515 | While stopping, setting and starting an I/O watcher in the same iteration |
521 | While stopping, setting and starting an I/O watcher in the same iteration |
516 | will result in some caching, there is still a system call per such |
522 | will result in some caching, there is still a system call per such |
517 | incident (because the same I<file descriptor> could point to a different |
523 | incident (because the same I<file descriptor> could point to a different |
518 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
524 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
822 | This is useful if you are waiting for some external event in conjunction |
828 | This is useful if you are waiting for some external event in conjunction |
823 | with something not expressible using other libev watchers (i.e. "roll your |
829 | with something not expressible using other libev watchers (i.e. "roll your |
824 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
830 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
825 | usually a better approach for this kind of thing. |
831 | usually a better approach for this kind of thing. |
826 | |
832 | |
827 | Here are the gory details of what C<ev_run> does: |
833 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
834 | understanding, not a guarantee that things will work exactly like this in |
|
|
835 | future versions): |
828 | |
836 | |
829 | - Increment loop depth. |
837 | - Increment loop depth. |
830 | - Reset the ev_break status. |
838 | - Reset the ev_break status. |
831 | - Before the first iteration, call any pending watchers. |
839 | - Before the first iteration, call any pending watchers. |
832 | LOOP: |
840 | LOOP: |
… | |
… | |
865 | anymore. |
873 | anymore. |
866 | |
874 | |
867 | ... queue jobs here, make sure they register event watchers as long |
875 | ... queue jobs here, make sure they register event watchers as long |
868 | ... as they still have work to do (even an idle watcher will do..) |
876 | ... as they still have work to do (even an idle watcher will do..) |
869 | ev_run (my_loop, 0); |
877 | ev_run (my_loop, 0); |
870 | ... jobs done or somebody called unloop. yeah! |
878 | ... jobs done or somebody called break. yeah! |
871 | |
879 | |
872 | =item ev_break (loop, how) |
880 | =item ev_break (loop, how) |
873 | |
881 | |
874 | Can be used to make a call to C<ev_run> return early (but only after it |
882 | Can be used to make a call to C<ev_run> return early (but only after it |
875 | has processed all outstanding events). The C<how> argument must be either |
883 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
1375 | |
1383 | |
1376 | Before a watcher can be registered with the event looop it has to be |
1384 | Before a watcher can be registered with the event looop it has to be |
1377 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1385 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1378 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1386 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1379 | |
1387 | |
1380 | In this state it is simply some block of memory that is suitable for use |
1388 | In this state it is simply some block of memory that is suitable for |
1381 | in an event loop. It can be moved around, freed, reused etc. at will. |
1389 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1390 | will - as long as you either keep the memory contents intact, or call |
|
|
1391 | C<ev_TYPE_init> again. |
1382 | |
1392 | |
1383 | =item started/running/active |
1393 | =item started/running/active |
1384 | |
1394 | |
1385 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1395 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1386 | property of the event loop, and is actively waiting for events. While in |
1396 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1414 | latter will clear any pending state the watcher might be in, regardless |
1424 | latter will clear any pending state the watcher might be in, regardless |
1415 | of whether it was active or not, so stopping a watcher explicitly before |
1425 | of whether it was active or not, so stopping a watcher explicitly before |
1416 | freeing it is often a good idea. |
1426 | freeing it is often a good idea. |
1417 | |
1427 | |
1418 | While stopped (and not pending) the watcher is essentially in the |
1428 | While stopped (and not pending) the watcher is essentially in the |
1419 | initialised state, that is it can be reused, moved, modified in any way |
1429 | initialised state, that is, it can be reused, moved, modified in any way |
1420 | you wish. |
1430 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1431 | it again). |
1421 | |
1432 | |
1422 | =back |
1433 | =back |
1423 | |
1434 | |
1424 | =head2 WATCHER PRIORITY MODELS |
1435 | =head2 WATCHER PRIORITY MODELS |
1425 | |
1436 | |
… | |
… | |
1618 | always get a readiness notification instantly, and your read (or possibly |
1629 | always get a readiness notification instantly, and your read (or possibly |
1619 | write) will still block on the disk I/O. |
1630 | write) will still block on the disk I/O. |
1620 | |
1631 | |
1621 | Another way to view it is that in the case of sockets, pipes, character |
1632 | Another way to view it is that in the case of sockets, pipes, character |
1622 | devices and so on, there is another party (the sender) that delivers data |
1633 | devices and so on, there is another party (the sender) that delivers data |
1623 | on it's own, but in the case of files, there is no such thing: the disk |
1634 | on its own, but in the case of files, there is no such thing: the disk |
1624 | will not send data on it's own, simply because it doesn't know what you |
1635 | will not send data on its own, simply because it doesn't know what you |
1625 | wish to read - you would first have to request some data. |
1636 | wish to read - you would first have to request some data. |
1626 | |
1637 | |
1627 | Since files are typically not-so-well supported by advanced notification |
1638 | Since files are typically not-so-well supported by advanced notification |
1628 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1639 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1629 | to files, even though you should not use it. The reason for this is |
1640 | to files, even though you should not use it. The reason for this is |
… | |
… | |
2145 | |
2156 | |
2146 | Another way to think about it (for the mathematically inclined) is that |
2157 | Another way to think about it (for the mathematically inclined) is that |
2147 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2158 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2148 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2159 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2149 | |
2160 | |
2150 | For numerical stability it is preferable that the C<offset> value is near |
2161 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2151 | C<ev_now ()> (the current time), but there is no range requirement for |
2162 | interval value should be higher than C<1/8192> (which is around 100 |
2152 | this value, and in fact is often specified as zero. |
2163 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2164 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2165 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2166 | C<0> and C<interval>, which is also the recommended range. |
2153 | |
2167 | |
2154 | Note also that there is an upper limit to how often a timer can fire (CPU |
2168 | Note also that there is an upper limit to how often a timer can fire (CPU |
2155 | speed for example), so if C<interval> is very small then timing stability |
2169 | speed for example), so if C<interval> is very small then timing stability |
2156 | will of course deteriorate. Libev itself tries to be exact to be about one |
2170 | will of course deteriorate. Libev itself tries to be exact to be about one |
2157 | millisecond (if the OS supports it and the machine is fast enough). |
2171 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2300 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2314 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2301 | |
2315 | |
2302 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2316 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2303 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2317 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2304 | stopping it again), that is, libev might or might not block the signal, |
2318 | stopping it again), that is, libev might or might not block the signal, |
2305 | and might or might not set or restore the installed signal handler. |
2319 | and might or might not set or restore the installed signal handler (but |
|
|
2320 | see C<EVFLAG_NOSIGMASK>). |
2306 | |
2321 | |
2307 | While this does not matter for the signal disposition (libev never |
2322 | While this does not matter for the signal disposition (libev never |
2308 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2323 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2309 | C<execve>), this matters for the signal mask: many programs do not expect |
2324 | C<execve>), this matters for the signal mask: many programs do not expect |
2310 | certain signals to be blocked. |
2325 | certain signals to be blocked. |
… | |
… | |
3181 | atexit (program_exits); |
3196 | atexit (program_exits); |
3182 | |
3197 | |
3183 | |
3198 | |
3184 | =head2 C<ev_async> - how to wake up an event loop |
3199 | =head2 C<ev_async> - how to wake up an event loop |
3185 | |
3200 | |
3186 | In general, you cannot use an C<ev_run> from multiple threads or other |
3201 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3187 | asynchronous sources such as signal handlers (as opposed to multiple event |
3202 | asynchronous sources such as signal handlers (as opposed to multiple event |
3188 | loops - those are of course safe to use in different threads). |
3203 | loops - those are of course safe to use in different threads). |
3189 | |
3204 | |
3190 | Sometimes, however, you need to wake up an event loop you do not control, |
3205 | Sometimes, however, you need to wake up an event loop you do not control, |
3191 | for example because it belongs to another thread. This is what C<ev_async> |
3206 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3301 | trust me. |
3316 | trust me. |
3302 | |
3317 | |
3303 | =item ev_async_send (loop, ev_async *) |
3318 | =item ev_async_send (loop, ev_async *) |
3304 | |
3319 | |
3305 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3320 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3306 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3321 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3322 | returns. |
|
|
3323 | |
3307 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3324 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3308 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3325 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3309 | section below on what exactly this means). |
3326 | embedding section below on what exactly this means). |
3310 | |
3327 | |
3311 | Note that, as with other watchers in libev, multiple events might get |
3328 | Note that, as with other watchers in libev, multiple events might get |
3312 | compressed into a single callback invocation (another way to look at this |
3329 | compressed into a single callback invocation (another way to look at this |
3313 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3330 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3314 | reset when the event loop detects that). |
3331 | reset when the event loop detects that). |
… | |
… | |
3504 | exit_main_loop = exit_nested_loop = 1; |
3521 | exit_main_loop = exit_nested_loop = 1; |
3505 | |
3522 | |
3506 | =head2 THREAD LOCKING EXAMPLE |
3523 | =head2 THREAD LOCKING EXAMPLE |
3507 | |
3524 | |
3508 | Here is a fictitious example of how to run an event loop in a different |
3525 | Here is a fictitious example of how to run an event loop in a different |
3509 | thread than where callbacks are being invoked and watchers are |
3526 | thread from where callbacks are being invoked and watchers are |
3510 | created/added/removed. |
3527 | created/added/removed. |
3511 | |
3528 | |
3512 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3529 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3513 | which uses exactly this technique (which is suited for many high-level |
3530 | which uses exactly this technique (which is suited for many high-level |
3514 | languages). |
3531 | languages). |
… | |
… | |
3540 | // now associate this with the loop |
3557 | // now associate this with the loop |
3541 | ev_set_userdata (EV_A_ u); |
3558 | ev_set_userdata (EV_A_ u); |
3542 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3559 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3543 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3560 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3544 | |
3561 | |
3545 | // then create the thread running ev_loop |
3562 | // then create the thread running ev_run |
3546 | pthread_create (&u->tid, 0, l_run, EV_A); |
3563 | pthread_create (&u->tid, 0, l_run, EV_A); |
3547 | } |
3564 | } |
3548 | |
3565 | |
3549 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3566 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3550 | solely to wake up the event loop so it takes notice of any new watchers |
3567 | solely to wake up the event loop so it takes notice of any new watchers |
… | |
… | |
4195 | F<event.h> that are not directly supported by the libev core alone. |
4212 | F<event.h> that are not directly supported by the libev core alone. |
4196 | |
4213 | |
4197 | In standalone mode, libev will still try to automatically deduce the |
4214 | In standalone mode, libev will still try to automatically deduce the |
4198 | configuration, but has to be more conservative. |
4215 | configuration, but has to be more conservative. |
4199 | |
4216 | |
|
|
4217 | =item EV_USE_FLOOR |
|
|
4218 | |
|
|
4219 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4220 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4221 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4222 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4223 | function is not available will fail, so the safe default is to not enable |
|
|
4224 | this. |
|
|
4225 | |
4200 | =item EV_USE_MONOTONIC |
4226 | =item EV_USE_MONOTONIC |
4201 | |
4227 | |
4202 | If defined to be C<1>, libev will try to detect the availability of the |
4228 | If defined to be C<1>, libev will try to detect the availability of the |
4203 | monotonic clock option at both compile time and runtime. Otherwise no |
4229 | monotonic clock option at both compile time and runtime. Otherwise no |
4204 | use of the monotonic clock option will be attempted. If you enable this, |
4230 | use of the monotonic clock option will be attempted. If you enable this, |
… | |
… | |
5215 | The physical time that is observed. It is apparently strictly monotonic :) |
5241 | The physical time that is observed. It is apparently strictly monotonic :) |
5216 | |
5242 | |
5217 | =item wall-clock time |
5243 | =item wall-clock time |
5218 | |
5244 | |
5219 | The time and date as shown on clocks. Unlike real time, it can actually |
5245 | The time and date as shown on clocks. Unlike real time, it can actually |
5220 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5246 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5221 | clock. |
5247 | clock. |
5222 | |
5248 | |
5223 | =item watcher |
5249 | =item watcher |
5224 | |
5250 | |
5225 | A data structure that describes interest in certain events. Watchers need |
5251 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5228 | =back |
5254 | =back |
5229 | |
5255 | |
5230 | =head1 AUTHOR |
5256 | =head1 AUTHOR |
5231 | |
5257 | |
5232 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5258 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5233 | Magnusson and Emanuele Giaquinta. |
5259 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5234 | |
5260 | |