… | |
… | |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
418 | C<pthread_atfork> which is even faster). |
418 | C<pthread_atfork> which is even faster). |
419 | |
419 | |
420 | The big advantage of this flag is that you can forget about fork (and |
420 | The big advantage of this flag is that you can forget about fork (and |
421 | forget about forgetting to tell libev about forking) when you use this |
421 | forget about forgetting to tell libev about forking, although you still |
422 | flag. |
422 | have to ignore C<SIGPIPE>) when you use this flag. |
423 | |
423 | |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | environment variable. |
425 | environment variable. |
426 | |
426 | |
427 | =item C<EVFLAG_NOINOTIFY> |
427 | =item C<EVFLAG_NOINOTIFY> |
… | |
… | |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
683 | and C<ev_loop_destroy>. |
683 | and C<ev_loop_destroy>. |
684 | |
684 | |
685 | =item ev_loop_fork (loop) |
685 | =item ev_loop_fork (loop) |
686 | |
686 | |
687 | This function sets a flag that causes subsequent C<ev_run> iterations to |
687 | This function sets a flag that causes subsequent C<ev_run> iterations |
688 | reinitialise the kernel state for backends that have one. Despite the |
688 | to reinitialise the kernel state for backends that have one. Despite |
689 | name, you can call it anytime, but it makes most sense after forking, in |
689 | the name, you can call it anytime you are allowed to start or stop |
690 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
690 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
691 | sense after forking, in the child process. You I<must> call it (or use |
691 | child before resuming or calling C<ev_run>. |
692 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
693 | |
|
|
694 | In addition, if you want to reuse a loop (via this function of |
|
|
695 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
692 | |
696 | |
693 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
697 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
694 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
698 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
695 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
699 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
696 | during fork. |
700 | during fork. |
… | |
… | |
2028 | |
2032 | |
2029 | The relative timeouts are calculated relative to the C<ev_now ()> |
2033 | The relative timeouts are calculated relative to the C<ev_now ()> |
2030 | time. This is usually the right thing as this timestamp refers to the time |
2034 | time. This is usually the right thing as this timestamp refers to the time |
2031 | of the event triggering whatever timeout you are modifying/starting. If |
2035 | of the event triggering whatever timeout you are modifying/starting. If |
2032 | you suspect event processing to be delayed and you I<need> to base the |
2036 | you suspect event processing to be delayed and you I<need> to base the |
2033 | timeout on the current time, use something like this to adjust for this: |
2037 | timeout on the current time, use something like the following to adjust |
|
|
2038 | for it: |
2034 | |
2039 | |
2035 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2040 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
2036 | |
2041 | |
2037 | If the event loop is suspended for a long time, you can also force an |
2042 | If the event loop is suspended for a long time, you can also force an |
2038 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2043 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2039 | ()>. |
2044 | ()>, although that will push the event time of all outstanding events |
|
|
2045 | further into the future. |
2040 | |
2046 | |
2041 | =head3 The special problem of unsynchronised clocks |
2047 | =head3 The special problem of unsynchronised clocks |
2042 | |
2048 | |
2043 | Modern systems have a variety of clocks - libev itself uses the normal |
2049 | Modern systems have a variety of clocks - libev itself uses the normal |
2044 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
2050 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
… | |
… | |
2907 | |
2913 | |
2908 | Prepare and check watchers are often (but not always) used in pairs: |
2914 | Prepare and check watchers are often (but not always) used in pairs: |
2909 | prepare watchers get invoked before the process blocks and check watchers |
2915 | prepare watchers get invoked before the process blocks and check watchers |
2910 | afterwards. |
2916 | afterwards. |
2911 | |
2917 | |
2912 | You I<must not> call C<ev_run> or similar functions that enter |
2918 | You I<must not> call C<ev_run> (or similar functions that enter the |
2913 | the current event loop from either C<ev_prepare> or C<ev_check> |
2919 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2914 | watchers. Other loops than the current one are fine, however. The |
2920 | C<ev_check> watchers. Other loops than the current one are fine, |
2915 | rationale behind this is that you do not need to check for recursion in |
2921 | however. The rationale behind this is that you do not need to check |
2916 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2922 | for recursion in those watchers, i.e. the sequence will always be |
2917 | C<ev_check> so if you have one watcher of each kind they will always be |
2923 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2918 | called in pairs bracketing the blocking call. |
2924 | kind they will always be called in pairs bracketing the blocking call. |
2919 | |
2925 | |
2920 | Their main purpose is to integrate other event mechanisms into libev and |
2926 | Their main purpose is to integrate other event mechanisms into libev and |
2921 | their use is somewhat advanced. They could be used, for example, to track |
2927 | their use is somewhat advanced. They could be used, for example, to track |
2922 | variable changes, implement your own watchers, integrate net-snmp or a |
2928 | variable changes, implement your own watchers, integrate net-snmp or a |
2923 | coroutine library and lots more. They are also occasionally useful if |
2929 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
3263 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3269 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3264 | of course. |
3270 | of course. |
3265 | |
3271 | |
3266 | =head3 The special problem of life after fork - how is it possible? |
3272 | =head3 The special problem of life after fork - how is it possible? |
3267 | |
3273 | |
3268 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3274 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3269 | up/change the process environment, followed by a call to C<exec()>. This |
3275 | up/change the process environment, followed by a call to C<exec()>. This |
3270 | sequence should be handled by libev without any problems. |
3276 | sequence should be handled by libev without any problems. |
3271 | |
3277 | |
3272 | This changes when the application actually wants to do event handling |
3278 | This changes when the application actually wants to do event handling |
3273 | in the child, or both parent in child, in effect "continuing" after the |
3279 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3897 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3903 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3898 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3904 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3899 | |
3905 | |
3900 | // my_ev.h |
3906 | // my_ev.h |
3901 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3907 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3902 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3908 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3903 | #include "../libev/ev.h" |
3909 | #include "../libev/ev.h" |
3904 | |
3910 | |
3905 | // my_ev.c |
3911 | // my_ev.c |
3906 | #define EV_H "my_ev.h" |
3912 | #define EV_H "my_ev.h" |
3907 | #include "../libev/ev.c" |
3913 | #include "../libev/ev.c" |