… | |
… | |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
609 | hacks). |
609 | hacks). |
610 | |
610 | |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
612 | even sun itself gets it wrong in their code examples: The event polling |
612 | even sun itself gets it wrong in their code examples: The event polling |
613 | function sometimes returning events to the caller even though an error |
613 | function sometimes returns events to the caller even though an error |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
615 | even documented that way) - deadly for edge-triggered interfaces where |
615 | even documented that way) - deadly for edge-triggered interfaces where you |
616 | you absolutely have to know whether an event occurred or not because you |
616 | absolutely have to know whether an event occurred or not because you have |
617 | have to re-arm the watcher. |
617 | to re-arm the watcher. |
618 | |
618 | |
619 | Fortunately libev seems to be able to work around these idiocies. |
619 | Fortunately libev seems to be able to work around these idiocies. |
620 | |
620 | |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
622 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
… | |
… | |
2023 | keep up with the timer (because it takes longer than those 10 seconds to |
2023 | keep up with the timer (because it takes longer than those 10 seconds to |
2024 | do stuff) the timer will not fire more than once per event loop iteration. |
2024 | do stuff) the timer will not fire more than once per event loop iteration. |
2025 | |
2025 | |
2026 | =item ev_timer_again (loop, ev_timer *) |
2026 | =item ev_timer_again (loop, ev_timer *) |
2027 | |
2027 | |
2028 | This will act as if the timer timed out and restart it again if it is |
2028 | This will act as if the timer timed out and restarts it again if it is |
2029 | repeating. The exact semantics are: |
2029 | repeating. The exact semantics are: |
2030 | |
2030 | |
2031 | If the timer is pending, its pending status is cleared. |
2031 | If the timer is pending, its pending status is cleared. |
2032 | |
2032 | |
2033 | If the timer is started but non-repeating, stop it (as if it timed out). |
2033 | If the timer is started but non-repeating, stop it (as if it timed out). |
… | |
… | |
3220 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3220 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3221 | of "global async watchers" by using a watcher on an otherwise unused |
3221 | of "global async watchers" by using a watcher on an otherwise unused |
3222 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3222 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3223 | even without knowing which loop owns the signal. |
3223 | even without knowing which loop owns the signal. |
3224 | |
3224 | |
3225 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3226 | just the default loop. |
|
|
3227 | |
|
|
3228 | =head3 Queueing |
3225 | =head3 Queueing |
3229 | |
3226 | |
3230 | C<ev_async> does not support queueing of data in any way. The reason |
3227 | C<ev_async> does not support queueing of data in any way. The reason |
3231 | is that the author does not know of a simple (or any) algorithm for a |
3228 | is that the author does not know of a simple (or any) algorithm for a |
3232 | multiple-writer-single-reader queue that works in all cases and doesn't |
3229 | multiple-writer-single-reader queue that works in all cases and doesn't |
… | |
… | |
3331 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3328 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3332 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3329 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3333 | embedding section below on what exactly this means). |
3330 | embedding section below on what exactly this means). |
3334 | |
3331 | |
3335 | Note that, as with other watchers in libev, multiple events might get |
3332 | Note that, as with other watchers in libev, multiple events might get |
3336 | compressed into a single callback invocation (another way to look at this |
3333 | compressed into a single callback invocation (another way to look at |
3337 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3334 | this is that C<ev_async> watchers are level-triggered: they are set on |
3338 | reset when the event loop detects that). |
3335 | C<ev_async_send>, reset when the event loop detects that). |
3339 | |
3336 | |
3340 | This call incurs the overhead of a system call only once per event loop |
3337 | This call incurs the overhead of at most one extra system call per event |
3341 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3338 | loop iteration, if the event loop is blocked, and no syscall at all if |
3342 | repeated calls to C<ev_async_send> for the same event loop. |
3339 | the event loop (or your program) is processing events. That means that |
|
|
3340 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3341 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3342 | zero) under load. |
3343 | |
3343 | |
3344 | =item bool = ev_async_pending (ev_async *) |
3344 | =item bool = ev_async_pending (ev_async *) |
3345 | |
3345 | |
3346 | Returns a non-zero value when C<ev_async_send> has been called on the |
3346 | Returns a non-zero value when C<ev_async_send> has been called on the |
3347 | watcher but the event has not yet been processed (or even noted) by the |
3347 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
4369 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4369 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4370 | |
4370 | |
4371 | =item EV_ATOMIC_T |
4371 | =item EV_ATOMIC_T |
4372 | |
4372 | |
4373 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4373 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4374 | access is atomic with respect to other threads or signal contexts. No such |
4374 | access is atomic and serialised with respect to other threads or signal |
4375 | type is easily found in the C language, so you can provide your own type |
4375 | contexts. No such type is easily found in the C language, so you can |
4376 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4376 | provide your own type that you know is safe for your purposes. It is used |
4377 | as well as for signal and thread safety in C<ev_async> watchers. |
4377 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4378 | in C<ev_async> watchers. |
4378 | |
4379 | |
4379 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4380 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4380 | (from F<signal.h>), which is usually good enough on most platforms. |
4381 | (from F<signal.h>), which is usually good enough on most platforms. |
4381 | |
4382 | |
4382 | =item EV_H (h) |
4383 | =item EV_H (h) |
… | |
… | |
5120 | =item Processing ev_async_send: O(number_of_async_watchers) |
5121 | =item Processing ev_async_send: O(number_of_async_watchers) |
5121 | |
5122 | |
5122 | =item Processing signals: O(max_signal_number) |
5123 | =item Processing signals: O(max_signal_number) |
5123 | |
5124 | |
5124 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5125 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5125 | calls in the current loop iteration. Checking for async and signal events |
5126 | calls in the current loop iteration and the loop is currently |
|
|
5127 | blocked. Checking for async and signal events involves iterating over all |
5126 | involves iterating over all running async watchers or all signal numbers. |
5128 | running async watchers or all signal numbers. |
5127 | |
5129 | |
5128 | =back |
5130 | =back |
5129 | |
5131 | |
5130 | |
5132 | |
5131 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5133 | =head1 PORTING FROM LIBEV 3.X TO 4.X |