… | |
… | |
16 | cede; # yield to coro |
16 | cede; # yield to coro |
17 | print "3\n"; |
17 | print "3\n"; |
18 | cede; # and again |
18 | cede; # and again |
19 | |
19 | |
20 | # use locking |
20 | # use locking |
21 | use Coro::Semaphore; |
|
|
22 | my $lock = new Coro::Semaphore; |
21 | my $lock = new Coro::Semaphore; |
23 | my $locked; |
22 | my $locked; |
24 | |
23 | |
25 | $lock->down; |
24 | $lock->down; |
26 | $locked = 1; |
25 | $locked = 1; |
… | |
… | |
90 | } 1, 2, 3; |
89 | } 1, 2, 3; |
91 | |
90 | |
92 | This creates a new coro thread and puts it into the ready queue, meaning |
91 | This creates a new coro thread and puts it into the ready queue, meaning |
93 | it will run as soon as the CPU is free for it. |
92 | it will run as soon as the CPU is free for it. |
94 | |
93 | |
95 | C<async> will return a coro object - you can store this for future |
94 | C<async> will return a Coro object - you can store this for future |
96 | reference or ignore it, the thread itself will keep a reference to it's |
95 | reference or ignore it - a thread that is running, ready to run or waiting |
97 | thread object - threads are alive on their own. |
96 | for some event is alive on it's own. |
98 | |
97 | |
99 | Another way to create a thread is to call the C<new> constructor with a |
98 | Another way to create a thread is to call the C<new> constructor with a |
100 | code-reference: |
99 | code-reference: |
101 | |
100 | |
102 | new Coro sub { |
101 | new Coro sub { |
… | |
… | |
131 | A lot can happen after the coro thread has started running. Quite usually, |
130 | A lot can happen after the coro thread has started running. Quite usually, |
132 | it will not run to the end in one go (because you could use a function |
131 | it will not run to the end in one go (because you could use a function |
133 | instead), but it will give up the CPU regularly because it waits for |
132 | instead), but it will give up the CPU regularly because it waits for |
134 | external events. |
133 | external events. |
135 | |
134 | |
136 | As long as a coro thread runs, it's coro object is available in the global |
135 | As long as a coro thread runs, its Coro object is available in the global |
137 | variable C<$Coro::current>. |
136 | variable C<$Coro::current>. |
138 | |
137 | |
139 | The low-level way to give up the CPU is to call the scheduler, which |
138 | The low-level way to give up the CPU is to call the scheduler, which |
140 | selects a new coro thread to run: |
139 | selects a new coro thread to run: |
141 | |
140 | |
… | |
… | |
203 | |
202 | |
204 | my $coro = async { |
203 | my $coro = async { |
205 | exit 1; |
204 | exit 1; |
206 | }; |
205 | }; |
207 | |
206 | |
208 | $coro->cancel; # an also accept values for ->join to retrieve |
207 | $coro->cancel; # also accepts values for ->join to retrieve |
209 | |
208 | |
210 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> |
209 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
211 | without actually exiting, and might leave C libraries and XS modules in |
210 | actually exiting, and might leave C libraries and XS modules in a weird |
212 | a weird state. Unlike other thread implementations, however, Coro is |
211 | state. Unlike other thread implementations, however, Coro is exceptionally |
213 | exceptionally safe with regards to cancellation, as perl will always be |
212 | safe with regards to cancellation, as perl will always be in a consistent |
214 | in a consistent state, and for those cases where you want to do truly |
213 | state, and for those cases where you want to do truly marvellous things |
215 | marvellous things with your coro while it is being cancelled, there is |
214 | with your coro while it is being cancelled - that is, make sure all |
|
|
215 | cleanup code is executed from the thread being cancelled - there is even a |
216 | even a C<< ->safe_cancel >> method. |
216 | C<< ->safe_cancel >> method. |
217 | |
217 | |
218 | So, cancelling a thread that runs in an XS event loop might not be the |
218 | So, cancelling a thread that runs in an XS event loop might not be the |
219 | best idea, but any other combination that deals with perl only (cancelling |
219 | best idea, but any other combination that deals with perl only (cancelling |
220 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
220 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
221 | safe. |
221 | safe. |
222 | |
222 | |
|
|
223 | Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed |
|
|
224 | automatically - just like other objects in Perl. This is not such a common |
|
|
225 | case, however - a running thread is referencedy b C<$Coro::current>, a |
|
|
226 | thread ready to run is referenced by the ready queue, a thread waiting |
|
|
227 | on a lock or semaphore is referenced by being in some wait list and so |
|
|
228 | on. But a thread that isn't in any of those queues gets cancelled: |
|
|
229 | |
|
|
230 | async { |
|
|
231 | schedule; # cede to other coros, don't go into the ready queue |
|
|
232 | }; |
|
|
233 | |
|
|
234 | cede; |
|
|
235 | # now the async above is destroyed, as it is not referenced by anything. |
|
|
236 | |
223 | =item 5. Cleanup |
237 | =item 5. Cleanup |
224 | |
238 | |
225 | Threads will allocate various resources. Most but not all will be returned |
239 | Threads will allocate various resources. Most but not all will be returned |
226 | when a thread terminates, during clean-up. |
240 | when a thread terminates, during clean-up. |
227 | |
241 | |
… | |
… | |
250 | # if we reutrn, or die or get cancelled, here, |
264 | # if we reutrn, or die or get cancelled, here, |
251 | # then the semaphore will be "up"ed. |
265 | # then the semaphore will be "up"ed. |
252 | }; |
266 | }; |
253 | |
267 | |
254 | The C<Guard::guard> function comes in handy for any custom cleanup you |
268 | The C<Guard::guard> function comes in handy for any custom cleanup you |
255 | might want to do: |
269 | might want to do (but you cannot switch to other coroutines form those |
|
|
270 | code blocks): |
256 | |
271 | |
257 | async { |
272 | async { |
258 | my $window = new Gtk2::Window "toplevel"; |
273 | my $window = new Gtk2::Window "toplevel"; |
259 | # The window will not be cleaned up automatically, even when $window |
274 | # The window will not be cleaned up automatically, even when $window |
260 | # gets freed, so use a guard to ensure it's destruction |
275 | # gets freed, so use a guard to ensure it's destruction |
… | |
… | |
273 | # if we return or die here, the description will be restored |
288 | # if we return or die here, the description will be restored |
274 | } |
289 | } |
275 | |
290 | |
276 | =item 6. Viva La Zombie Muerte |
291 | =item 6. Viva La Zombie Muerte |
277 | |
292 | |
278 | Even after a thread has terminated and cleaned up it's resources, the coro |
293 | Even after a thread has terminated and cleaned up its resources, the Coro |
279 | object still is there and stores the return values of the thread. Only in |
294 | object still is there and stores the return values of the thread. |
280 | this state will the coro object be "reference counted" in the normal perl |
|
|
281 | sense: the thread code keeps a reference to it when it is active, but not |
|
|
282 | after it has terminated. |
|
|
283 | |
295 | |
284 | The means the coro object gets freed automatically when the thread has |
296 | The means the Coro object gets freed automatically when the thread has |
285 | terminated and cleaned up and there arenot other references. |
297 | terminated and cleaned up and there arenot other references. |
286 | |
298 | |
287 | If there are, the coro object will stay around, and you can call C<< |
299 | If there are, the Coro object will stay around, and you can call C<< |
288 | ->join >> as many times as you wish to retrieve the result values: |
300 | ->join >> as many times as you wish to retrieve the result values: |
289 | |
301 | |
290 | async { |
302 | async { |
291 | print "hi\n"; |
303 | print "hi\n"; |
292 | 1 |
304 | 1 |
… | |
… | |
712 | To avoid this, it is best to put a suspended coro into the ready queue |
724 | To avoid this, it is best to put a suspended coro into the ready queue |
713 | unconditionally, as every synchronisation mechanism must protect itself |
725 | unconditionally, as every synchronisation mechanism must protect itself |
714 | against spurious wakeups, and the one in the Coro family certainly do |
726 | against spurious wakeups, and the one in the Coro family certainly do |
715 | that. |
727 | that. |
716 | |
728 | |
|
|
729 | =item $state->is_new |
|
|
730 | |
|
|
731 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
732 | yet. Those states basically consist of only the code reference to call and |
|
|
733 | the arguments, but consumes very little other resources. New states will |
|
|
734 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
735 | |
|
|
736 | =item $state->is_zombie |
|
|
737 | |
|
|
738 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
739 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
740 | C<safe_cancel>'ed or simply went out of scope. |
|
|
741 | |
|
|
742 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
743 | exited and only stores and exit status and no other resources is called a |
|
|
744 | "zombie". |
|
|
745 | |
717 | =item $is_ready = $coro->is_ready |
746 | =item $is_ready = $coro->is_ready |
718 | |
747 | |
719 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
748 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
720 | object gets destroyed, it will eventually be scheduled by the scheduler. |
749 | object gets destroyed, it will eventually be scheduled by the scheduler. |
721 | |
750 | |
… | |
… | |
737 | current Coro. |
766 | current Coro. |
738 | |
767 | |
739 | This is a rather brutal way to free a coro, with some limitations - if |
768 | This is a rather brutal way to free a coro, with some limitations - if |
740 | the thread is inside a C callback that doesn't expect to be canceled, |
769 | the thread is inside a C callback that doesn't expect to be canceled, |
741 | bad things can happen, or if the cancelled thread insists on running |
770 | bad things can happen, or if the cancelled thread insists on running |
742 | complicated cleanup handlers that rely on it'S thread context, things will |
771 | complicated cleanup handlers that rely on its thread context, things will |
743 | not work. |
772 | not work. |
744 | |
773 | |
745 | Sometimes it is safer to C<< ->throw >> an exception, or use C<< |
774 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
746 | ->safe_cancel >>. |
775 | a thread context, and is not allowed to switch to other threads. On the |
|
|
776 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
777 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
778 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
779 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
747 | |
780 | |
748 | The arguments are not copied, but instead will be referenced directly |
781 | The arguments to C<< ->cancel >> are not copied, but instead will |
749 | (e.g. if you pass C<$var> and after the call change that variable, then |
782 | be referenced directly (e.g. if you pass C<$var> and after the call |
750 | you might change the return values passed to e.g. C<join>, so don't do |
783 | change that variable, then you might change the return values passed to |
751 | that). |
784 | e.g. C<join>, so don't do that). |
752 | |
785 | |
753 | The resources of the Coro are usually freed (or destructed) before this |
786 | The resources of the Coro are usually freed (or destructed) before this |
754 | call returns, but this can be delayed for an indefinite amount of time, as |
787 | call returns, but this can be delayed for an indefinite amount of time, as |
755 | in some cases the manager thread has to run first to actually destruct the |
788 | in some cases the manager thread has to run first to actually destruct the |
756 | Coro object. |
789 | Coro object. |
… | |
… | |
760 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
793 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
761 | consequently, can fail with an exception in cases the thread is not in a |
794 | consequently, can fail with an exception in cases the thread is not in a |
762 | cancellable state. |
795 | cancellable state. |
763 | |
796 | |
764 | This method works a bit like throwing an exception that cannot be caught |
797 | This method works a bit like throwing an exception that cannot be caught |
765 | - specifically, it will clean up the thread from within itself, so all |
798 | - specifically, it will clean up the thread from within itself, so |
766 | cleanup handlers (e.g. C<guard> blocks) are run with full thread context |
799 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
767 | and can block if they wish. |
800 | context and can block if they wish. The downside is that there is no |
|
|
801 | guarantee that the thread can be cancelled when you call this method, and |
|
|
802 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
803 | C<terminate>. |
768 | |
804 | |
769 | A thread is safe-cancellable if it either hasn't been run yet, or |
805 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
770 | it has no C context attached and is inside an SLF function. |
806 | or it has no C context attached and is inside an SLF function. |
771 | |
807 | |
772 | The latter two basically mean that the thread isn't currently inside a |
808 | The latter two basically mean that the thread isn't currently inside a |
773 | perl callback called from some C function (usually XS modules) and isn't |
809 | perl callback called from some C function (usually via some XS modules) |
774 | currently inside some C function itself. |
810 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
811 | API). |
775 | |
812 | |
776 | This call always returns true when it could cancel the thread, or croaks |
813 | This call returns true when it could cancel the thread, or croaks with an |
777 | with an error otherwise, so you can write things like this: |
814 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
815 | |
|
|
816 | Why the weird interface? Well, there are two common models on how and |
|
|
817 | when to cancel things. In the first, you have the expectation that your |
|
|
818 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
819 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
820 | croaks to notify of the bug. |
|
|
821 | |
|
|
822 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
823 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
824 | relatively easy like this: |
778 | |
825 | |
779 | if (! eval { $coro->safe_cancel }) { |
826 | if (! eval { $coro->safe_cancel }) { |
780 | warn "unable to cancel thread: $@"; |
827 | warn "unable to cancel thread: $@"; |
781 | } |
828 | } |
|
|
829 | |
|
|
830 | However, what you never should do is first try to cancel "safely" and |
|
|
831 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
832 | no sense: either you rely on being able to execute cleanup code in your |
|
|
833 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
834 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
835 | direct. |
782 | |
836 | |
783 | =item $coro->schedule_to |
837 | =item $coro->schedule_to |
784 | |
838 | |
785 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
839 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
786 | of continuing with the next coro from the ready queue, always switch to |
840 | of continuing with the next coro from the ready queue, always switch to |
… | |
… | |
805 | inside the coro at the next convenient point in time. Otherwise |
859 | inside the coro at the next convenient point in time. Otherwise |
806 | clears the exception object. |
860 | clears the exception object. |
807 | |
861 | |
808 | Coro will check for the exception each time a schedule-like-function |
862 | Coro will check for the exception each time a schedule-like-function |
809 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
863 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
810 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
864 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
811 | detect this case and return early in case an exception is pending. |
865 | that are part of Coro itself) detect this case and return early in case an |
|
|
866 | exception is pending. |
812 | |
867 | |
813 | The exception object will be thrown "as is" with the specified scalar in |
868 | The exception object will be thrown "as is" with the specified scalar in |
814 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
869 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
815 | (unlike with C<die>). |
870 | (unlike with C<die>). |
816 | |
871 | |
817 | This can be used as a softer means than C<cancel> to ask a coro to |
872 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
818 | end itself, although there is no guarantee that the exception will lead to |
873 | >to ask a coro to end itself, although there is no guarantee that the |
819 | termination, and if the exception isn't caught it might well end the whole |
874 | exception will lead to termination, and if the exception isn't caught it |
820 | program. |
875 | might well end the whole program. |
821 | |
876 | |
822 | You might also think of C<throw> as being the moral equivalent of |
877 | You might also think of C<throw> as being the moral equivalent of |
823 | C<kill>ing a coro with a signal (in this case, a scalar). |
878 | C<kill>ing a coro with a signal (in this case, a scalar). |
824 | |
879 | |
825 | =item $coro->join |
880 | =item $coro->join |
… | |
… | |
827 | Wait until the coro terminates and return any values given to the |
882 | Wait until the coro terminates and return any values given to the |
828 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
883 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
829 | from multiple threads, and all will be resumed and given the status |
884 | from multiple threads, and all will be resumed and given the status |
830 | return once the C<$coro> terminates. |
885 | return once the C<$coro> terminates. |
831 | |
886 | |
832 | =cut |
|
|
833 | |
|
|
834 | sub join { |
|
|
835 | my $self = shift; |
|
|
836 | |
|
|
837 | unless ($self->{_status}) { |
|
|
838 | my $current = $current; |
|
|
839 | |
|
|
840 | push @{$self->{_on_destroy}}, sub { |
|
|
841 | $current->ready; |
|
|
842 | undef $current; |
|
|
843 | }; |
|
|
844 | |
|
|
845 | &schedule while $current; |
|
|
846 | } |
|
|
847 | |
|
|
848 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
849 | } |
|
|
850 | |
|
|
851 | =item $coro->on_destroy (\&cb) |
887 | =item $coro->on_destroy (\&cb) |
852 | |
888 | |
853 | Registers a callback that is called when this coro thread gets destroyed, |
889 | Registers a callback that is called when this coro thread gets destroyed, |
854 | that is, after it's resources have been freed but before it is joined. The |
890 | that is, after it's resources have been freed but before it is joined. The |
855 | callback gets passed the terminate/cancel arguments, if any, and I<must |
891 | callback gets passed the terminate/cancel arguments, if any, and I<must |
856 | not> die, under any circumstances. |
892 | not> die, under any circumstances. |
857 | |
893 | |
858 | There can be any number of C<on_destroy> callbacks per coro, and there is |
894 | There can be any number of C<on_destroy> callbacks per coro, and there is |
859 | no way currently to remove a callback once added. |
895 | no way currently to remove a callback once added. |
860 | |
|
|
861 | =cut |
|
|
862 | |
|
|
863 | sub on_destroy { |
|
|
864 | my ($self, $cb) = @_; |
|
|
865 | |
|
|
866 | push @{ $self->{_on_destroy} }, $cb; |
|
|
867 | } |
|
|
868 | |
896 | |
869 | =item $oldprio = $coro->prio ($newprio) |
897 | =item $oldprio = $coro->prio ($newprio) |
870 | |
898 | |
871 | Sets (or gets, if the argument is missing) the priority of the |
899 | Sets (or gets, if the argument is missing) the priority of the |
872 | coro thread. Higher priority coro get run before lower priority |
900 | coro thread. Higher priority coro get run before lower priority |
… | |
… | |
1144 | future to allow per-thread schedulers, but Coro::State does not yet allow |
1172 | future to allow per-thread schedulers, but Coro::State does not yet allow |
1145 | this). I recommend disabling thread support and using processes, as having |
1173 | this). I recommend disabling thread support and using processes, as having |
1146 | the windows process emulation enabled under unix roughly halves perl |
1174 | the windows process emulation enabled under unix roughly halves perl |
1147 | performance, even when not used. |
1175 | performance, even when not used. |
1148 | |
1176 | |
|
|
1177 | Attempts to use threads created in another emulated process will crash |
|
|
1178 | ("cleanly", with a null pointer exception). |
|
|
1179 | |
1149 | =item coro switching is not signal safe |
1180 | =item coro switching is not signal safe |
1150 | |
1181 | |
1151 | You must not switch to another coro from within a signal handler (only |
1182 | You must not switch to another coro from within a signal handler (only |
1152 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
1183 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
1153 | you are sure you are not interrupting a Coro function. |
1184 | you are sure you are not interrupting a Coro function. |