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=head1 NAME |
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Coro - the only real threads in perl |
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=head1 SYNOPSIS |
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use Coro; |
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async { |
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# some asynchronous thread of execution |
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print "2\n"; |
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cede; # yield back to main |
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print "4\n"; |
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}; |
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print "1\n"; |
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cede; # yield to coro |
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print "3\n"; |
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cede; # and again |
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# use locking |
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my $lock = new Coro::Semaphore; |
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my $locked; |
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$lock->down; |
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$locked = 1; |
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$lock->up; |
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=head1 DESCRIPTION |
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For a tutorial-style introduction, please read the L<Coro::Intro> |
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manpage. This manpage mainly contains reference information. |
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This module collection manages continuations in general, most often in |
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the form of cooperative threads (also called coros, or simply "coro" |
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in the documentation). They are similar to kernel threads but don't (in |
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general) run in parallel at the same time even on SMP machines. The |
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specific flavor of thread offered by this module also guarantees you that |
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it will not switch between threads unless necessary, at easily-identified |
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points in your program, so locking and parallel access are rarely an |
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issue, making thread programming much safer and easier than using other |
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thread models. |
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Unlike the so-called "Perl threads" (which are not actually real threads |
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but only the windows process emulation (see section of same name for |
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more details) ported to UNIX, and as such act as processes), Coro |
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provides a full shared address space, which makes communication between |
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threads very easy. And coro threads are fast, too: disabling the Windows |
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process emulation code in your perl and using Coro can easily result in |
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a two to four times speed increase for your programs. A parallel matrix |
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multiplication benchmark (very communication-intensive) runs over 300 |
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times faster on a single core than perls pseudo-threads on a quad core |
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using all four cores. |
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Coro achieves that by supporting multiple running interpreters that share |
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data, which is especially useful to code pseudo-parallel processes and |
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for event-based programming, such as multiple HTTP-GET requests running |
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concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
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into an event-based environment. |
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In this module, a thread is defined as "callchain + lexical variables + |
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some package variables + C stack), that is, a thread has its own callchain, |
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its own set of lexicals and its own set of perls most important global |
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variables (see L<Coro::State> for more configuration and background info). |
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See also the C<SEE ALSO> section at the end of this document - the Coro |
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module family is quite large. |
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=head1 CORO THREAD LIFE CYCLE |
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During the long and exciting (or not) life of a coro thread, it goes |
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through a number of states: |
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=over 4 |
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=item 1. Creation |
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The first thing in the life of a coro thread is it's creation - |
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obviously. The typical way to create a thread is to call the C<async |
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BLOCK> function: |
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async { |
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# thread code goes here |
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}; |
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You can also pass arguments, which are put in C<@_>: |
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async { |
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print $_[1]; # prints 2 |
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} 1, 2, 3; |
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This creates a new coro thread and puts it into the ready queue, meaning |
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it will run as soon as the CPU is free for it. |
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C<async> will return a Coro object - you can store this for future |
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reference or ignore it - a thread that is running, ready to run or waiting |
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for some event is alive on it's own. |
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Another way to create a thread is to call the C<new> constructor with a |
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code-reference: |
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new Coro sub { |
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# thread code goes here |
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}, @optional_arguments; |
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This is quite similar to calling C<async>, but the important difference is |
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that the new thread is not put into the ready queue, so the thread will |
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not run until somebody puts it there. C<async> is, therefore, identical to |
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this sequence: |
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my $coro = new Coro sub { |
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# thread code goes here |
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}; |
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$coro->ready; |
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return $coro; |
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=item 2. Startup |
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When a new coro thread is created, only a copy of the code reference |
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and the arguments are stored, no extra memory for stacks and so on is |
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allocated, keeping the coro thread in a low-memory state. |
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Only when it actually starts executing will all the resources be finally |
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allocated. |
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The optional arguments specified at coro creation are available in C<@_>, |
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similar to function calls. |
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=item 3. Running / Blocking |
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A lot can happen after the coro thread has started running. Quite usually, |
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it will not run to the end in one go (because you could use a function |
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instead), but it will give up the CPU regularly because it waits for |
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external events. |
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As long as a coro thread runs, its Coro object is available in the global |
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variable C<$Coro::current>. |
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The low-level way to give up the CPU is to call the scheduler, which |
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selects a new coro thread to run: |
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Coro::schedule; |
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Since running threads are not in the ready queue, calling the scheduler |
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without doing anything else will block the coro thread forever - you need |
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to arrange either for the coro to put woken up (readied) by some other |
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event or some other thread, or you can put it into the ready queue before |
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scheduling: |
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# this is exactly what Coro::cede does |
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$Coro::current->ready; |
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Coro::schedule; |
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All the higher-level synchronisation methods (Coro::Semaphore, |
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Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<< |
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Coro::schedule >>. |
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While the coro thread is running it also might get assigned a C-level |
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thread, or the C-level thread might be unassigned from it, as the Coro |
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runtime wishes. A C-level thread needs to be assigned when your perl |
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thread calls into some C-level function and that function in turn calls |
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perl and perl then wants to switch coroutines. This happens most often |
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when you run an event loop and block in the callback, or when perl |
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itself calls some function such as C<AUTOLOAD> or methods via the C<tie> |
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mechanism. |
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=item 4. Termination |
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Many threads actually terminate after some time. There are a number of |
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ways to terminate a coro thread, the simplest is returning from the |
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top-level code reference: |
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async { |
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# after returning from here, the coro thread is terminated |
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}; |
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async { |
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return if 0.5 < rand; # terminate a little earlier, maybe |
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print "got a chance to print this\n"; |
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# or here |
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}; |
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Any values returned from the coroutine can be recovered using C<< ->join |
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>>: |
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my $coro = async { |
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"hello, world\n" # return a string |
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}; |
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my $hello_world = $coro->join; |
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print $hello_world; |
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Another way to terminate is to call C<< Coro::terminate >>, which at any |
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subroutine call nesting level: |
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async { |
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Coro::terminate "return value 1", "return value 2"; |
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}; |
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And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the |
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coro thread from another thread: |
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my $coro = async { |
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exit 1; |
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}; |
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$coro->cancel; # also accepts values for ->join to retrieve |
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Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
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actually exiting, and might leave C libraries and XS modules in a weird |
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state. Unlike other thread implementations, however, Coro is exceptionally |
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safe with regards to cancellation, as perl will always be in a consistent |
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state, and for those cases where you want to do truly marvellous things |
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with your coro while it is being cancelled - that is, make sure all |
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cleanup code is executed from the thread being cancelled - there is even a |
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C<< ->safe_cancel >> method. |
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So, cancelling a thread that runs in an XS event loop might not be the |
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best idea, but any other combination that deals with perl only (cancelling |
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when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
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safe. |
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Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed |
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automatically - just like other objects in Perl. This is not such a common |
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case, however - a running thread is referencedy b C<$Coro::current>, a |
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thread ready to run is referenced by the ready queue, a thread waiting |
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on a lock or semaphore is referenced by being in some wait list and so |
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on. But a thread that isn't in any of those queues gets cancelled: |
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async { |
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schedule; # cede to other coros, don't go into the ready queue |
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}; |
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cede; |
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# now the async above is destroyed, as it is not referenced by anything. |
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=item 5. Cleanup |
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Threads will allocate various resources. Most but not all will be returned |
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when a thread terminates, during clean-up. |
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Cleanup is quite similar to throwing an uncaught exception: perl will |
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work it's way up through all subroutine calls and blocks. On it's way, it |
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will release all C<my> variables, undo all C<local>'s and free any other |
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resources truly local to the thread. |
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So, a common way to free resources is to keep them referenced only by my |
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variables: |
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async { |
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my $big_cache = new Cache ...; |
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}; |
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If there are no other references, then the C<$big_cache> object will be |
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freed when the thread terminates, regardless of how it does so. |
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What it does C<NOT> do is unlock any Coro::Semaphores or similar |
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resources, but that's where the C<guard> methods come in handy: |
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my $sem = new Coro::Semaphore; |
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async { |
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my $lock_guard = $sem->guard; |
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# if we reutrn, or die or get cancelled, here, |
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# then the semaphore will be "up"ed. |
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}; |
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The C<Guard::guard> function comes in handy for any custom cleanup you |
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might want to do (but you cannot switch to other coroutines form those |
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code blocks): |
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async { |
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my $window = new Gtk2::Window "toplevel"; |
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# The window will not be cleaned up automatically, even when $window |
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# gets freed, so use a guard to ensure it's destruction |
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# in case of an error: |
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my $window_guard = Guard::guard { $window->destroy }; |
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# we are safe here |
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}; |
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Last not least, C<local> can often be handy, too, e.g. when temporarily |
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replacing the coro thread description: |
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sub myfunction { |
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local $Coro::current->{desc} = "inside myfunction(@_)"; |
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# if we return or die here, the description will be restored |
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} |
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=item 6. Viva La Zombie Muerte |
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Even after a thread has terminated and cleaned up its resources, the Coro |
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object still is there and stores the return values of the thread. |
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The means the Coro object gets freed automatically when the thread has |
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terminated and cleaned up and there arenot other references. |
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If there are, the Coro object will stay around, and you can call C<< |
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->join >> as many times as you wish to retrieve the result values: |
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async { |
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print "hi\n"; |
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1 |
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}; |
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# run the async above, and free everything before returning |
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# from Coro::cede: |
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Coro::cede; |
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{ |
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my $coro = async { |
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print "hi\n"; |
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1 |
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}; |
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# run the async above, and clean up, but do not free the coro |
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# object: |
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Coro::cede; |
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# optionally retrieve the result values |
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my @results = $coro->join; |
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# now $coro goes out of scope, and presumably gets freed |
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}; |
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=back |
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=cut |
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package Coro; |
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use common::sense; |
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use Carp (); |
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use Guard (); |
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use Coro::State; |
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use base qw(Coro::State Exporter); |
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our $idle; # idle handler |
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our $main; # main coro |
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our $current; # current coro |
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our $VERSION = 6.08; |
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|
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our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
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our %EXPORT_TAGS = ( |
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prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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); |
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our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
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|
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=head1 GLOBAL VARIABLES |
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=over 4 |
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=item $Coro::main |
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|
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This variable stores the Coro object that represents the main |
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program. While you cna C<ready> it and do most other things you can do to |
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coro, it is mainly useful to compare again C<$Coro::current>, to see |
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whether you are running in the main program or not. |
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=cut |
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# $main is now being initialised by Coro::State |
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=item $Coro::current |
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The Coro object representing the current coro (the last |
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coro that the Coro scheduler switched to). The initial value is |
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C<$Coro::main> (of course). |
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This variable is B<strictly> I<read-only>. You can take copies of the |
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value stored in it and use it as any other Coro object, but you must |
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not otherwise modify the variable itself. |
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|
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=cut |
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sub current() { $current } # [DEPRECATED] |
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|
384 |
root |
1.181 |
=item $Coro::idle |
385 |
root |
1.9 |
|
386 |
root |
1.181 |
This variable is mainly useful to integrate Coro into event loops. It is |
387 |
root |
1.238 |
usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
388 |
root |
1.181 |
pretty low-level functionality. |
389 |
|
|
|
390 |
root |
1.270 |
This variable stores a Coro object that is put into the ready queue when |
391 |
|
|
there are no other ready threads (without invoking any ready hooks). |
392 |
root |
1.83 |
|
393 |
root |
1.270 |
The default implementation dies with "FATAL: deadlock detected.", followed |
394 |
|
|
by a thread listing, because the program has no other way to continue. |
395 |
root |
1.238 |
|
396 |
|
|
This hook is overwritten by modules such as C<Coro::EV> and |
397 |
root |
1.285 |
C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
398 |
root |
1.248 |
coro so the scheduler can run it. |
399 |
root |
1.91 |
|
400 |
root |
1.270 |
See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
401 |
root |
1.9 |
|
402 |
|
|
=cut |
403 |
|
|
|
404 |
root |
1.275 |
# ||= because other modules could have provided their own by now |
405 |
|
|
$idle ||= new Coro sub { |
406 |
root |
1.270 |
require Coro::Debug; |
407 |
|
|
die "FATAL: deadlock detected.\n" |
408 |
|
|
. Coro::Debug::ps_listing (); |
409 |
root |
1.9 |
}; |
410 |
root |
1.8 |
|
411 |
root |
1.248 |
# this coro is necessary because a coro |
412 |
root |
1.24 |
# cannot destroy itself. |
413 |
root |
1.226 |
our @destroy; |
414 |
|
|
our $manager; |
415 |
root |
1.103 |
|
416 |
|
|
$manager = new Coro sub { |
417 |
pcg |
1.57 |
while () { |
418 |
root |
1.291 |
_destroy shift @destroy |
419 |
root |
1.103 |
while @destroy; |
420 |
|
|
|
421 |
root |
1.24 |
&schedule; |
422 |
|
|
} |
423 |
|
|
}; |
424 |
root |
1.208 |
$manager->{desc} = "[coro manager]"; |
425 |
root |
1.103 |
$manager->prio (PRIO_MAX); |
426 |
|
|
|
427 |
root |
1.43 |
=back |
428 |
root |
1.8 |
|
429 |
root |
1.248 |
=head1 SIMPLE CORO CREATION |
430 |
root |
1.8 |
|
431 |
|
|
=over 4 |
432 |
|
|
|
433 |
root |
1.13 |
=item async { ... } [@args...] |
434 |
root |
1.8 |
|
435 |
root |
1.248 |
Create a new coro and return its Coro object (usually |
436 |
|
|
unused). The coro will be put into the ready queue, so |
437 |
root |
1.181 |
it will start running automatically on the next scheduler run. |
438 |
|
|
|
439 |
|
|
The first argument is a codeblock/closure that should be executed in the |
440 |
root |
1.248 |
coro. When it returns argument returns the coro is automatically |
441 |
root |
1.8 |
terminated. |
442 |
|
|
|
443 |
root |
1.181 |
The remaining arguments are passed as arguments to the closure. |
444 |
|
|
|
445 |
root |
1.248 |
See the C<Coro::State::new> constructor for info about the coro |
446 |
|
|
environment in which coro are executed. |
447 |
root |
1.145 |
|
448 |
root |
1.248 |
Calling C<exit> in a coro will do the same as calling exit outside |
449 |
|
|
the coro. Likewise, when the coro dies, the program will exit, |
450 |
root |
1.122 |
just as it would in the main program. |
451 |
root |
1.79 |
|
452 |
root |
1.181 |
If you do not want that, you can provide a default C<die> handler, or |
453 |
|
|
simply avoid dieing (by use of C<eval>). |
454 |
|
|
|
455 |
root |
1.248 |
Example: Create a new coro that just prints its arguments. |
456 |
root |
1.181 |
|
457 |
root |
1.13 |
async { |
458 |
|
|
print "@_\n"; |
459 |
|
|
} 1,2,3,4; |
460 |
|
|
|
461 |
root |
1.105 |
=item async_pool { ... } [@args...] |
462 |
|
|
|
463 |
root |
1.248 |
Similar to C<async>, but uses a coro pool, so you should not call |
464 |
root |
1.181 |
terminate or join on it (although you are allowed to), and you get a |
465 |
root |
1.248 |
coro that might have executed other code already (which can be good |
466 |
root |
1.181 |
or bad :). |
467 |
|
|
|
468 |
root |
1.228 |
On the plus side, this function is about twice as fast as creating (and |
469 |
root |
1.248 |
destroying) a completely new coro, so if you need a lot of generic |
470 |
|
|
coros in quick successsion, use C<async_pool>, not C<async>. |
471 |
root |
1.105 |
|
472 |
root |
1.181 |
The code block is executed in an C<eval> context and a warning will be |
473 |
root |
1.108 |
issued in case of an exception instead of terminating the program, as |
474 |
root |
1.248 |
C<async> does. As the coro is being reused, stuff like C<on_destroy> |
475 |
root |
1.108 |
will not work in the expected way, unless you call terminate or cancel, |
476 |
root |
1.181 |
which somehow defeats the purpose of pooling (but is fine in the |
477 |
|
|
exceptional case). |
478 |
root |
1.105 |
|
479 |
root |
1.181 |
The priority will be reset to C<0> after each run, tracing will be |
480 |
root |
1.146 |
disabled, the description will be reset and the default output filehandle |
481 |
root |
1.248 |
gets restored, so you can change all these. Otherwise the coro will |
482 |
|
|
be re-used "as-is": most notably if you change other per-coro global |
483 |
root |
1.204 |
stuff such as C<$/> you I<must needs> revert that change, which is most |
484 |
|
|
simply done by using local as in: C<< local $/ >>. |
485 |
root |
1.105 |
|
486 |
root |
1.248 |
The idle pool size is limited to C<8> idle coros (this can be |
487 |
root |
1.204 |
adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
488 |
|
|
coros as required. |
489 |
root |
1.105 |
|
490 |
root |
1.248 |
If you are concerned about pooled coros growing a lot because a |
491 |
root |
1.133 |
single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
492 |
|
|
{ terminate }> once per second or so to slowly replenish the pool. In |
493 |
root |
1.232 |
addition to that, when the stacks used by a handler grows larger than 32kb |
494 |
root |
1.181 |
(adjustable via $Coro::POOL_RSS) it will also be destroyed. |
495 |
root |
1.105 |
|
496 |
|
|
=cut |
497 |
|
|
|
498 |
|
|
our $POOL_SIZE = 8; |
499 |
root |
1.232 |
our $POOL_RSS = 32 * 1024; |
500 |
root |
1.134 |
our @async_pool; |
501 |
root |
1.105 |
|
502 |
|
|
sub pool_handler { |
503 |
|
|
while () { |
504 |
root |
1.134 |
eval { |
505 |
root |
1.227 |
&{&_pool_handler} while 1; |
506 |
root |
1.105 |
}; |
507 |
root |
1.134 |
|
508 |
root |
1.227 |
warn $@ if $@; |
509 |
root |
1.106 |
} |
510 |
|
|
} |
511 |
root |
1.105 |
|
512 |
root |
1.181 |
=back |
513 |
|
|
|
514 |
root |
1.234 |
=head1 STATIC METHODS |
515 |
root |
1.181 |
|
516 |
root |
1.234 |
Static methods are actually functions that implicitly operate on the |
517 |
root |
1.248 |
current coro. |
518 |
root |
1.181 |
|
519 |
|
|
=over 4 |
520 |
|
|
|
521 |
root |
1.8 |
=item schedule |
522 |
root |
1.6 |
|
523 |
root |
1.248 |
Calls the scheduler. The scheduler will find the next coro that is |
524 |
|
|
to be run from the ready queue and switches to it. The next coro |
525 |
root |
1.181 |
to be run is simply the one with the highest priority that is longest |
526 |
root |
1.270 |
in its ready queue. If there is no coro ready, it will call the |
527 |
root |
1.181 |
C<$Coro::idle> hook. |
528 |
|
|
|
529 |
root |
1.248 |
Please note that the current coro will I<not> be put into the ready |
530 |
root |
1.181 |
queue, so calling this function usually means you will never be called |
531 |
|
|
again unless something else (e.g. an event handler) calls C<< ->ready >>, |
532 |
|
|
thus waking you up. |
533 |
|
|
|
534 |
|
|
This makes C<schedule> I<the> generic method to use to block the current |
535 |
root |
1.248 |
coro and wait for events: first you remember the current coro in |
536 |
root |
1.181 |
a variable, then arrange for some callback of yours to call C<< ->ready |
537 |
|
|
>> on that once some event happens, and last you call C<schedule> to put |
538 |
root |
1.248 |
yourself to sleep. Note that a lot of things can wake your coro up, |
539 |
root |
1.196 |
so you need to check whether the event indeed happened, e.g. by storing the |
540 |
root |
1.181 |
status in a variable. |
541 |
root |
1.91 |
|
542 |
root |
1.224 |
See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
543 |
root |
1.1 |
|
544 |
root |
1.22 |
=item cede |
545 |
root |
1.1 |
|
546 |
root |
1.248 |
"Cede" to other coros. This function puts the current coro into |
547 |
root |
1.181 |
the ready queue and calls C<schedule>, which has the effect of giving |
548 |
root |
1.248 |
up the current "timeslice" to other coros of the same or higher |
549 |
|
|
priority. Once your coro gets its turn again it will automatically be |
550 |
root |
1.181 |
resumed. |
551 |
|
|
|
552 |
|
|
This function is often called C<yield> in other languages. |
553 |
root |
1.7 |
|
554 |
root |
1.102 |
=item Coro::cede_notself |
555 |
|
|
|
556 |
root |
1.181 |
Works like cede, but is not exported by default and will cede to I<any> |
557 |
root |
1.248 |
coro, regardless of priority. This is useful sometimes to ensure |
558 |
root |
1.181 |
progress is made. |
559 |
root |
1.102 |
|
560 |
root |
1.40 |
=item terminate [arg...] |
561 |
root |
1.7 |
|
562 |
root |
1.291 |
Terminates the current coro with the given status values (see |
563 |
|
|
L<cancel>). The values will not be copied, but referenced directly. |
564 |
root |
1.13 |
|
565 |
root |
1.247 |
=item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
566 |
|
|
|
567 |
|
|
These function install enter and leave winders in the current scope. The |
568 |
|
|
enter block will be executed when on_enter is called and whenever the |
569 |
root |
1.248 |
current coro is re-entered by the scheduler, while the leave block is |
570 |
|
|
executed whenever the current coro is blocked by the scheduler, and |
571 |
root |
1.247 |
also when the containing scope is exited (by whatever means, be it exit, |
572 |
|
|
die, last etc.). |
573 |
|
|
|
574 |
|
|
I<Neither invoking the scheduler, nor exceptions, are allowed within those |
575 |
|
|
BLOCKs>. That means: do not even think about calling C<die> without an |
576 |
|
|
eval, and do not even think of entering the scheduler in any way. |
577 |
|
|
|
578 |
|
|
Since both BLOCKs are tied to the current scope, they will automatically |
579 |
|
|
be removed when the current scope exits. |
580 |
|
|
|
581 |
|
|
These functions implement the same concept as C<dynamic-wind> in scheme |
582 |
|
|
does, and are useful when you want to localise some resource to a specific |
583 |
root |
1.248 |
coro. |
584 |
root |
1.247 |
|
585 |
root |
1.254 |
They slow down thread switching considerably for coros that use them |
586 |
|
|
(about 40% for a BLOCK with a single assignment, so thread switching is |
587 |
|
|
still reasonably fast if the handlers are fast). |
588 |
root |
1.247 |
|
589 |
|
|
These functions are best understood by an example: The following function |
590 |
|
|
will change the current timezone to "Antarctica/South_Pole", which |
591 |
|
|
requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
592 |
|
|
which remember/change the current timezone and restore the previous |
593 |
root |
1.252 |
value, respectively, the timezone is only changed for the coro that |
594 |
root |
1.247 |
installed those handlers. |
595 |
|
|
|
596 |
|
|
use POSIX qw(tzset); |
597 |
|
|
|
598 |
|
|
async { |
599 |
|
|
my $old_tz; # store outside TZ value here |
600 |
|
|
|
601 |
|
|
Coro::on_enter { |
602 |
|
|
$old_tz = $ENV{TZ}; # remember the old value |
603 |
|
|
|
604 |
|
|
$ENV{TZ} = "Antarctica/South_Pole"; |
605 |
|
|
tzset; # enable new value |
606 |
|
|
}; |
607 |
|
|
|
608 |
|
|
Coro::on_leave { |
609 |
|
|
$ENV{TZ} = $old_tz; |
610 |
|
|
tzset; # restore old value |
611 |
|
|
}; |
612 |
|
|
|
613 |
|
|
# at this place, the timezone is Antarctica/South_Pole, |
614 |
root |
1.248 |
# without disturbing the TZ of any other coro. |
615 |
root |
1.247 |
}; |
616 |
|
|
|
617 |
|
|
This can be used to localise about any resource (locale, uid, current |
618 |
|
|
working directory etc.) to a block, despite the existance of other |
619 |
root |
1.248 |
coros. |
620 |
root |
1.247 |
|
621 |
root |
1.255 |
Another interesting example implements time-sliced multitasking using |
622 |
|
|
interval timers (this could obviously be optimised, but does the job): |
623 |
|
|
|
624 |
|
|
# "timeslice" the given block |
625 |
|
|
sub timeslice(&) { |
626 |
|
|
use Time::HiRes (); |
627 |
|
|
|
628 |
|
|
Coro::on_enter { |
629 |
|
|
# on entering the thread, we set an VTALRM handler to cede |
630 |
|
|
$SIG{VTALRM} = sub { cede }; |
631 |
|
|
# and then start the interval timer |
632 |
|
|
Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
633 |
|
|
}; |
634 |
|
|
Coro::on_leave { |
635 |
|
|
# on leaving the thread, we stop the interval timer again |
636 |
|
|
Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
637 |
|
|
}; |
638 |
|
|
|
639 |
|
|
&{+shift}; |
640 |
|
|
} |
641 |
|
|
|
642 |
|
|
# use like this: |
643 |
|
|
timeslice { |
644 |
|
|
# The following is an endless loop that would normally |
645 |
root |
1.256 |
# monopolise the process. Since it runs in a timesliced |
646 |
root |
1.255 |
# environment, it will regularly cede to other threads. |
647 |
|
|
while () { } |
648 |
|
|
}; |
649 |
|
|
|
650 |
|
|
|
651 |
root |
1.141 |
=item killall |
652 |
|
|
|
653 |
root |
1.248 |
Kills/terminates/cancels all coros except the currently running one. |
654 |
root |
1.247 |
|
655 |
|
|
Note that while this will try to free some of the main interpreter |
656 |
root |
1.248 |
resources if the calling coro isn't the main coro, but one |
657 |
|
|
cannot free all of them, so if a coro that is not the main coro |
658 |
root |
1.247 |
calls this function, there will be some one-time resource leak. |
659 |
root |
1.181 |
|
660 |
root |
1.1 |
=cut |
661 |
|
|
|
662 |
root |
1.141 |
sub killall { |
663 |
|
|
for (Coro::State::list) { |
664 |
|
|
$_->cancel |
665 |
|
|
if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
666 |
|
|
} |
667 |
|
|
} |
668 |
|
|
|
669 |
root |
1.8 |
=back |
670 |
|
|
|
671 |
root |
1.248 |
=head1 CORO OBJECT METHODS |
672 |
root |
1.8 |
|
673 |
root |
1.248 |
These are the methods you can call on coro objects (or to create |
674 |
root |
1.181 |
them). |
675 |
root |
1.6 |
|
676 |
root |
1.8 |
=over 4 |
677 |
|
|
|
678 |
root |
1.13 |
=item new Coro \&sub [, @args...] |
679 |
root |
1.8 |
|
680 |
root |
1.248 |
Create a new coro and return it. When the sub returns, the coro |
681 |
root |
1.40 |
automatically terminates as if C<terminate> with the returned values were |
682 |
root |
1.248 |
called. To make the coro run you must first put it into the ready |
683 |
root |
1.181 |
queue by calling the ready method. |
684 |
root |
1.13 |
|
685 |
root |
1.145 |
See C<async> and C<Coro::State::new> for additional info about the |
686 |
root |
1.248 |
coro environment. |
687 |
root |
1.89 |
|
688 |
root |
1.6 |
=cut |
689 |
|
|
|
690 |
root |
1.241 |
sub _coro_run { |
691 |
root |
1.13 |
terminate &{+shift}; |
692 |
|
|
} |
693 |
|
|
|
694 |
root |
1.248 |
=item $success = $coro->ready |
695 |
root |
1.1 |
|
696 |
root |
1.248 |
Put the given coro into the end of its ready queue (there is one |
697 |
|
|
queue for each priority) and return true. If the coro is already in |
698 |
root |
1.181 |
the ready queue, do nothing and return false. |
699 |
|
|
|
700 |
root |
1.248 |
This ensures that the scheduler will resume this coro automatically |
701 |
|
|
once all the coro of higher priority and all coro of the same |
702 |
root |
1.181 |
priority that were put into the ready queue earlier have been resumed. |
703 |
root |
1.1 |
|
704 |
root |
1.250 |
=item $coro->suspend |
705 |
|
|
|
706 |
|
|
Suspends the specified coro. A suspended coro works just like any other |
707 |
|
|
coro, except that the scheduler will not select a suspended coro for |
708 |
|
|
execution. |
709 |
|
|
|
710 |
|
|
Suspending a coro can be useful when you want to keep the coro from |
711 |
|
|
running, but you don't want to destroy it, or when you want to temporarily |
712 |
|
|
freeze a coro (e.g. for debugging) to resume it later. |
713 |
|
|
|
714 |
|
|
A scenario for the former would be to suspend all (other) coros after a |
715 |
|
|
fork and keep them alive, so their destructors aren't called, but new |
716 |
|
|
coros can be created. |
717 |
|
|
|
718 |
|
|
=item $coro->resume |
719 |
|
|
|
720 |
|
|
If the specified coro was suspended, it will be resumed. Note that when |
721 |
|
|
the coro was in the ready queue when it was suspended, it might have been |
722 |
|
|
unreadied by the scheduler, so an activation might have been lost. |
723 |
|
|
|
724 |
|
|
To avoid this, it is best to put a suspended coro into the ready queue |
725 |
|
|
unconditionally, as every synchronisation mechanism must protect itself |
726 |
|
|
against spurious wakeups, and the one in the Coro family certainly do |
727 |
|
|
that. |
728 |
|
|
|
729 |
root |
1.297 |
=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 |
|
|
|
746 |
root |
1.248 |
=item $is_ready = $coro->is_ready |
747 |
root |
1.90 |
|
748 |
root |
1.248 |
Returns true iff the Coro object is in the ready queue. Unless the Coro |
749 |
|
|
object gets destroyed, it will eventually be scheduled by the scheduler. |
750 |
root |
1.28 |
|
751 |
root |
1.248 |
=item $is_running = $coro->is_running |
752 |
root |
1.28 |
|
753 |
root |
1.248 |
Returns true iff the Coro object is currently running. Only one Coro object |
754 |
|
|
can ever be in the running state (but it currently is possible to have |
755 |
|
|
multiple running Coro::States). |
756 |
|
|
|
757 |
|
|
=item $is_suspended = $coro->is_suspended |
758 |
|
|
|
759 |
|
|
Returns true iff this Coro object has been suspended. Suspended Coros will |
760 |
|
|
not ever be scheduled. |
761 |
|
|
|
762 |
|
|
=item $coro->cancel (arg...) |
763 |
|
|
|
764 |
root |
1.294 |
Terminates the given Coro thread and makes it return the given arguments as |
765 |
root |
1.290 |
status (default: an empty list). Never returns if the Coro is the |
766 |
root |
1.248 |
current Coro. |
767 |
root |
1.28 |
|
768 |
root |
1.294 |
This is a rather brutal way to free a coro, with some limitations - if |
769 |
|
|
the thread is inside a C callback that doesn't expect to be canceled, |
770 |
|
|
bad things can happen, or if the cancelled thread insists on running |
771 |
root |
1.299 |
complicated cleanup handlers that rely on its thread context, things will |
772 |
root |
1.294 |
not work. |
773 |
|
|
|
774 |
root |
1.295 |
Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
775 |
|
|
a thread context, and is not allowed to switch to other threads. On the |
776 |
|
|
plus side, C<< ->cancel >> will always clean up the thread, no matter |
777 |
|
|
what. If your cleanup code is complex or you want to avoid cancelling a |
778 |
|
|
C-thread that doesn't know how to clean up itself, it can be better to C<< |
779 |
|
|
->throw >> an exception, or use C<< ->safe_cancel >>. |
780 |
|
|
|
781 |
|
|
The arguments to C<< ->cancel >> are not copied, but instead will |
782 |
|
|
be referenced directly (e.g. if you pass C<$var> and after the call |
783 |
|
|
change that variable, then you might change the return values passed to |
784 |
|
|
e.g. C<join>, so don't do that). |
785 |
root |
1.291 |
|
786 |
|
|
The resources of the Coro are usually freed (or destructed) before this |
787 |
|
|
call returns, but this can be delayed for an indefinite amount of time, as |
788 |
|
|
in some cases the manager thread has to run first to actually destruct the |
789 |
|
|
Coro object. |
790 |
root |
1.40 |
|
791 |
root |
1.294 |
=item $coro->safe_cancel ($arg...) |
792 |
|
|
|
793 |
|
|
Works mostly like C<< ->cancel >>, but is inherently "safer", and |
794 |
|
|
consequently, can fail with an exception in cases the thread is not in a |
795 |
|
|
cancellable state. |
796 |
|
|
|
797 |
|
|
This method works a bit like throwing an exception that cannot be caught |
798 |
root |
1.295 |
- specifically, it will clean up the thread from within itself, so |
799 |
|
|
all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
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>. |
804 |
root |
1.294 |
|
805 |
root |
1.295 |
A thread is in a safe-cancellable state if it either hasn't been run yet, |
806 |
|
|
or it has no C context attached and is inside an SLF function. |
807 |
root |
1.294 |
|
808 |
|
|
The latter two basically mean that the thread isn't currently inside a |
809 |
root |
1.295 |
perl callback called from some C function (usually via some XS modules) |
810 |
|
|
and isn't currently executing inside some C function itself (via Coro's XS |
811 |
|
|
API). |
812 |
|
|
|
813 |
|
|
This call returns true when it could cancel the thread, or croaks with an |
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: |
825 |
root |
1.294 |
|
826 |
|
|
if (! eval { $coro->safe_cancel }) { |
827 |
|
|
warn "unable to cancel thread: $@"; |
828 |
|
|
} |
829 |
|
|
|
830 |
root |
1.295 |
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. |
836 |
|
|
|
837 |
root |
1.248 |
=item $coro->schedule_to |
838 |
root |
1.229 |
|
839 |
root |
1.248 |
Puts the current coro to sleep (like C<Coro::schedule>), but instead |
840 |
root |
1.229 |
of continuing with the next coro from the ready queue, always switch to |
841 |
root |
1.248 |
the given coro object (regardless of priority etc.). The readyness |
842 |
|
|
state of that coro isn't changed. |
843 |
root |
1.229 |
|
844 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
845 |
|
|
uses for this one. |
846 |
|
|
|
847 |
root |
1.248 |
=item $coro->cede_to |
848 |
root |
1.229 |
|
849 |
root |
1.248 |
Like C<schedule_to>, but puts the current coro into the ready |
850 |
root |
1.229 |
queue. This has the effect of temporarily switching to the given |
851 |
root |
1.248 |
coro, and continuing some time later. |
852 |
root |
1.229 |
|
853 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
854 |
|
|
uses for this one. |
855 |
|
|
|
856 |
root |
1.248 |
=item $coro->throw ([$scalar]) |
857 |
root |
1.208 |
|
858 |
|
|
If C<$throw> is specified and defined, it will be thrown as an exception |
859 |
root |
1.248 |
inside the coro at the next convenient point in time. Otherwise |
860 |
root |
1.222 |
clears the exception object. |
861 |
|
|
|
862 |
|
|
Coro will check for the exception each time a schedule-like-function |
863 |
|
|
returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
864 |
root |
1.295 |
>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
865 |
|
|
that are part of Coro itself) detect this case and return early in case an |
866 |
|
|
exception is pending. |
867 |
root |
1.208 |
|
868 |
|
|
The exception object will be thrown "as is" with the specified scalar in |
869 |
|
|
C<$@>, i.e. if it is a string, no line number or newline will be appended |
870 |
|
|
(unlike with C<die>). |
871 |
|
|
|
872 |
root |
1.295 |
This can be used as a softer means than either C<cancel> or C<safe_cancel |
873 |
|
|
>to ask a coro to end itself, although there is no guarantee that the |
874 |
|
|
exception will lead to termination, and if the exception isn't caught it |
875 |
|
|
might well end the whole program. |
876 |
root |
1.208 |
|
877 |
|
|
You might also think of C<throw> as being the moral equivalent of |
878 |
root |
1.248 |
C<kill>ing a coro with a signal (in this case, a scalar). |
879 |
root |
1.208 |
|
880 |
root |
1.248 |
=item $coro->join |
881 |
root |
1.40 |
|
882 |
root |
1.248 |
Wait until the coro terminates and return any values given to the |
883 |
root |
1.143 |
C<terminate> or C<cancel> functions. C<join> can be called concurrently |
884 |
root |
1.292 |
from multiple threads, and all will be resumed and given the status |
885 |
root |
1.248 |
return once the C<$coro> terminates. |
886 |
root |
1.40 |
|
887 |
root |
1.248 |
=item $coro->on_destroy (\&cb) |
888 |
root |
1.101 |
|
889 |
root |
1.284 |
Registers a callback that is called when this coro thread gets destroyed, |
890 |
root |
1.293 |
that is, after it's resources have been freed but before it is joined. The |
891 |
|
|
callback gets passed the terminate/cancel arguments, if any, and I<must |
892 |
|
|
not> die, under any circumstances. |
893 |
root |
1.101 |
|
894 |
root |
1.293 |
There can be any number of C<on_destroy> callbacks per coro, and there is |
895 |
|
|
no way currently to remove a callback once added. |
896 |
root |
1.284 |
|
897 |
root |
1.248 |
=item $oldprio = $coro->prio ($newprio) |
898 |
root |
1.31 |
|
899 |
root |
1.41 |
Sets (or gets, if the argument is missing) the priority of the |
900 |
root |
1.284 |
coro thread. Higher priority coro get run before lower priority |
901 |
|
|
coros. Priorities are small signed integers (currently -4 .. +3), |
902 |
root |
1.41 |
that you can refer to using PRIO_xxx constants (use the import tag :prio |
903 |
|
|
to get then): |
904 |
root |
1.31 |
|
905 |
|
|
PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
906 |
|
|
3 > 1 > 0 > -1 > -3 > -4 |
907 |
|
|
|
908 |
|
|
# set priority to HIGH |
909 |
root |
1.248 |
current->prio (PRIO_HIGH); |
910 |
root |
1.31 |
|
911 |
root |
1.284 |
The idle coro thread ($Coro::idle) always has a lower priority than any |
912 |
root |
1.248 |
existing coro. |
913 |
root |
1.31 |
|
914 |
root |
1.248 |
Changing the priority of the current coro will take effect immediately, |
915 |
root |
1.284 |
but changing the priority of a coro in the ready queue (but not running) |
916 |
|
|
will only take effect after the next schedule (of that coro). This is a |
917 |
|
|
bug that will be fixed in some future version. |
918 |
root |
1.31 |
|
919 |
root |
1.248 |
=item $newprio = $coro->nice ($change) |
920 |
root |
1.31 |
|
921 |
|
|
Similar to C<prio>, but subtract the given value from the priority (i.e. |
922 |
root |
1.284 |
higher values mean lower priority, just as in UNIX's nice command). |
923 |
root |
1.31 |
|
924 |
root |
1.248 |
=item $olddesc = $coro->desc ($newdesc) |
925 |
root |
1.41 |
|
926 |
|
|
Sets (or gets in case the argument is missing) the description for this |
927 |
root |
1.284 |
coro thread. This is just a free-form string you can associate with a |
928 |
root |
1.248 |
coro. |
929 |
root |
1.150 |
|
930 |
root |
1.248 |
This method simply sets the C<< $coro->{desc} >> member to the given |
931 |
root |
1.280 |
string. You can modify this member directly if you wish, and in fact, this |
932 |
|
|
is often preferred to indicate major processing states that cna then be |
933 |
|
|
seen for example in a L<Coro::Debug> session: |
934 |
|
|
|
935 |
|
|
sub my_long_function { |
936 |
|
|
local $Coro::current->{desc} = "now in my_long_function"; |
937 |
|
|
... |
938 |
|
|
$Coro::current->{desc} = "my_long_function: phase 1"; |
939 |
|
|
... |
940 |
|
|
$Coro::current->{desc} = "my_long_function: phase 2"; |
941 |
|
|
... |
942 |
|
|
} |
943 |
root |
1.150 |
|
944 |
root |
1.41 |
=cut |
945 |
|
|
|
946 |
|
|
sub desc { |
947 |
|
|
my $old = $_[0]{desc}; |
948 |
|
|
$_[0]{desc} = $_[1] if @_ > 1; |
949 |
|
|
$old; |
950 |
root |
1.8 |
} |
951 |
root |
1.1 |
|
952 |
root |
1.233 |
sub transfer { |
953 |
|
|
require Carp; |
954 |
|
|
Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
955 |
|
|
} |
956 |
|
|
|
957 |
root |
1.8 |
=back |
958 |
root |
1.2 |
|
959 |
root |
1.234 |
=head1 GLOBAL FUNCTIONS |
960 |
root |
1.92 |
|
961 |
|
|
=over 4 |
962 |
|
|
|
963 |
root |
1.97 |
=item Coro::nready |
964 |
|
|
|
965 |
root |
1.248 |
Returns the number of coro that are currently in the ready state, |
966 |
root |
1.181 |
i.e. that can be switched to by calling C<schedule> directory or |
967 |
root |
1.248 |
indirectly. The value C<0> means that the only runnable coro is the |
968 |
root |
1.181 |
currently running one, so C<cede> would have no effect, and C<schedule> |
969 |
|
|
would cause a deadlock unless there is an idle handler that wakes up some |
970 |
root |
1.248 |
coro. |
971 |
root |
1.97 |
|
972 |
root |
1.103 |
=item my $guard = Coro::guard { ... } |
973 |
|
|
|
974 |
root |
1.243 |
This function still exists, but is deprecated. Please use the |
975 |
|
|
C<Guard::guard> function instead. |
976 |
root |
1.103 |
|
977 |
|
|
=cut |
978 |
|
|
|
979 |
root |
1.243 |
BEGIN { *guard = \&Guard::guard } |
980 |
root |
1.103 |
|
981 |
root |
1.92 |
=item unblock_sub { ... } |
982 |
|
|
|
983 |
|
|
This utility function takes a BLOCK or code reference and "unblocks" it, |
984 |
root |
1.181 |
returning a new coderef. Unblocking means that calling the new coderef |
985 |
|
|
will return immediately without blocking, returning nothing, while the |
986 |
|
|
original code ref will be called (with parameters) from within another |
987 |
root |
1.248 |
coro. |
988 |
root |
1.92 |
|
989 |
root |
1.282 |
The reason this function exists is that many event libraries (such as |
990 |
|
|
the venerable L<Event|Event> module) are not thread-safe (a weaker form |
991 |
root |
1.238 |
of reentrancy). This means you must not block within event callbacks, |
992 |
root |
1.181 |
otherwise you might suffer from crashes or worse. The only event library |
993 |
root |
1.282 |
currently known that is safe to use without C<unblock_sub> is L<EV> (but |
994 |
|
|
you might still run into deadlocks if all event loops are blocked). |
995 |
root |
1.92 |
|
996 |
root |
1.274 |
Coro will try to catch you when you block in the event loop |
997 |
|
|
("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
998 |
|
|
only works when you do not run your own event loop. |
999 |
|
|
|
1000 |
root |
1.92 |
This function allows your callbacks to block by executing them in another |
1001 |
root |
1.248 |
coro where it is safe to block. One example where blocking is handy |
1002 |
root |
1.92 |
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
1003 |
root |
1.181 |
disk, for example. |
1004 |
root |
1.92 |
|
1005 |
|
|
In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
1006 |
|
|
creating event callbacks that want to block. |
1007 |
|
|
|
1008 |
root |
1.181 |
If your handler does not plan to block (e.g. simply sends a message to |
1009 |
root |
1.248 |
another coro, or puts some other coro into the ready queue), there is |
1010 |
|
|
no reason to use C<unblock_sub>. |
1011 |
root |
1.181 |
|
1012 |
root |
1.183 |
Note that you also need to use C<unblock_sub> for any other callbacks that |
1013 |
|
|
are indirectly executed by any C-based event loop. For example, when you |
1014 |
|
|
use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
1015 |
|
|
provides callbacks that are the result of some event callback, then you |
1016 |
|
|
must not block either, or use C<unblock_sub>. |
1017 |
|
|
|
1018 |
root |
1.92 |
=cut |
1019 |
|
|
|
1020 |
|
|
our @unblock_queue; |
1021 |
|
|
|
1022 |
root |
1.105 |
# we create a special coro because we want to cede, |
1023 |
|
|
# to reduce pressure on the coro pool (because most callbacks |
1024 |
|
|
# return immediately and can be reused) and because we cannot cede |
1025 |
|
|
# inside an event callback. |
1026 |
root |
1.132 |
our $unblock_scheduler = new Coro sub { |
1027 |
root |
1.92 |
while () { |
1028 |
|
|
while (my $cb = pop @unblock_queue) { |
1029 |
root |
1.227 |
&async_pool (@$cb); |
1030 |
root |
1.105 |
|
1031 |
root |
1.227 |
# for short-lived callbacks, this reduces pressure on the coro pool |
1032 |
|
|
# as the chance is very high that the async_poll coro will be back |
1033 |
|
|
# in the idle state when cede returns |
1034 |
|
|
cede; |
1035 |
root |
1.92 |
} |
1036 |
root |
1.105 |
schedule; # sleep well |
1037 |
root |
1.92 |
} |
1038 |
|
|
}; |
1039 |
root |
1.208 |
$unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
1040 |
root |
1.92 |
|
1041 |
|
|
sub unblock_sub(&) { |
1042 |
|
|
my $cb = shift; |
1043 |
|
|
|
1044 |
|
|
sub { |
1045 |
root |
1.105 |
unshift @unblock_queue, [$cb, @_]; |
1046 |
root |
1.92 |
$unblock_scheduler->ready; |
1047 |
|
|
} |
1048 |
|
|
} |
1049 |
|
|
|
1050 |
root |
1.271 |
=item $cb = rouse_cb |
1051 |
root |
1.224 |
|
1052 |
root |
1.238 |
Create and return a "rouse callback". That's a code reference that, |
1053 |
|
|
when called, will remember a copy of its arguments and notify the owner |
1054 |
root |
1.248 |
coro of the callback. |
1055 |
root |
1.224 |
|
1056 |
|
|
See the next function. |
1057 |
|
|
|
1058 |
root |
1.271 |
=item @args = rouse_wait [$cb] |
1059 |
root |
1.224 |
|
1060 |
root |
1.238 |
Wait for the specified rouse callback (or the last one that was created in |
1061 |
root |
1.248 |
this coro). |
1062 |
root |
1.224 |
|
1063 |
root |
1.238 |
As soon as the callback is invoked (or when the callback was invoked |
1064 |
|
|
before C<rouse_wait>), it will return the arguments originally passed to |
1065 |
root |
1.258 |
the rouse callback. In scalar context, that means you get the I<last> |
1066 |
|
|
argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
1067 |
|
|
statement at the end. |
1068 |
root |
1.224 |
|
1069 |
|
|
See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
1070 |
|
|
|
1071 |
root |
1.92 |
=back |
1072 |
|
|
|
1073 |
root |
1.8 |
=cut |
1074 |
root |
1.2 |
|
1075 |
root |
1.283 |
for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
1076 |
|
|
my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
1077 |
|
|
|
1078 |
|
|
*{"Coro::$module\::new"} = sub { |
1079 |
|
|
require "Coro/$module.pm"; |
1080 |
|
|
|
1081 |
|
|
# some modules have their new predefined in State.xs, some don't |
1082 |
|
|
*{"Coro::$module\::new"} = $old |
1083 |
|
|
if $old; |
1084 |
|
|
|
1085 |
|
|
goto &{"Coro::$module\::new"}; |
1086 |
|
|
}; |
1087 |
|
|
} |
1088 |
|
|
|
1089 |
root |
1.8 |
1; |
1090 |
root |
1.14 |
|
1091 |
root |
1.224 |
=head1 HOW TO WAIT FOR A CALLBACK |
1092 |
|
|
|
1093 |
root |
1.248 |
It is very common for a coro to wait for some callback to be |
1094 |
|
|
called. This occurs naturally when you use coro in an otherwise |
1095 |
root |
1.224 |
event-based program, or when you use event-based libraries. |
1096 |
|
|
|
1097 |
|
|
These typically register a callback for some event, and call that callback |
1098 |
root |
1.248 |
when the event occured. In a coro, however, you typically want to |
1099 |
root |
1.224 |
just wait for the event, simplyifying things. |
1100 |
|
|
|
1101 |
|
|
For example C<< AnyEvent->child >> registers a callback to be called when |
1102 |
|
|
a specific child has exited: |
1103 |
|
|
|
1104 |
|
|
my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
1105 |
|
|
|
1106 |
root |
1.248 |
But from within a coro, you often just want to write this: |
1107 |
root |
1.224 |
|
1108 |
|
|
my $status = wait_for_child $pid; |
1109 |
|
|
|
1110 |
|
|
Coro offers two functions specifically designed to make this easy, |
1111 |
|
|
C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
1112 |
|
|
|
1113 |
|
|
The first function, C<rouse_cb>, generates and returns a callback that, |
1114 |
root |
1.248 |
when invoked, will save its arguments and notify the coro that |
1115 |
root |
1.224 |
created the callback. |
1116 |
|
|
|
1117 |
|
|
The second function, C<rouse_wait>, waits for the callback to be called |
1118 |
|
|
(by calling C<schedule> to go to sleep) and returns the arguments |
1119 |
|
|
originally passed to the callback. |
1120 |
|
|
|
1121 |
|
|
Using these functions, it becomes easy to write the C<wait_for_child> |
1122 |
|
|
function mentioned above: |
1123 |
|
|
|
1124 |
|
|
sub wait_for_child($) { |
1125 |
|
|
my ($pid) = @_; |
1126 |
|
|
|
1127 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
1128 |
|
|
|
1129 |
|
|
my ($rpid, $rstatus) = Coro::rouse_wait; |
1130 |
|
|
$rstatus |
1131 |
|
|
} |
1132 |
|
|
|
1133 |
|
|
In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
1134 |
|
|
you can roll your own, using C<schedule>: |
1135 |
|
|
|
1136 |
|
|
sub wait_for_child($) { |
1137 |
|
|
my ($pid) = @_; |
1138 |
|
|
|
1139 |
root |
1.248 |
# store the current coro in $current, |
1140 |
root |
1.224 |
# and provide result variables for the closure passed to ->child |
1141 |
|
|
my $current = $Coro::current; |
1142 |
|
|
my ($done, $rstatus); |
1143 |
|
|
|
1144 |
|
|
# pass a closure to ->child |
1145 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
1146 |
|
|
$rstatus = $_[1]; # remember rstatus |
1147 |
|
|
$done = 1; # mark $rstatus as valud |
1148 |
|
|
}); |
1149 |
|
|
|
1150 |
|
|
# wait until the closure has been called |
1151 |
|
|
schedule while !$done; |
1152 |
|
|
|
1153 |
|
|
$rstatus |
1154 |
|
|
} |
1155 |
|
|
|
1156 |
|
|
|
1157 |
root |
1.17 |
=head1 BUGS/LIMITATIONS |
1158 |
root |
1.14 |
|
1159 |
root |
1.217 |
=over 4 |
1160 |
|
|
|
1161 |
root |
1.219 |
=item fork with pthread backend |
1162 |
|
|
|
1163 |
|
|
When Coro is compiled using the pthread backend (which isn't recommended |
1164 |
|
|
but required on many BSDs as their libcs are completely broken), then |
1165 |
root |
1.248 |
coro will not survive a fork. There is no known workaround except to |
1166 |
root |
1.219 |
fix your libc and use a saner backend. |
1167 |
|
|
|
1168 |
root |
1.217 |
=item perl process emulation ("threads") |
1169 |
|
|
|
1170 |
root |
1.181 |
This module is not perl-pseudo-thread-safe. You should only ever use this |
1171 |
root |
1.238 |
module from the first thread (this requirement might be removed in the |
1172 |
root |
1.181 |
future to allow per-thread schedulers, but Coro::State does not yet allow |
1173 |
root |
1.217 |
this). I recommend disabling thread support and using processes, as having |
1174 |
|
|
the windows process emulation enabled under unix roughly halves perl |
1175 |
|
|
performance, even when not used. |
1176 |
|
|
|
1177 |
root |
1.296 |
Attempts to use threads created in another emulated process will crash |
1178 |
|
|
("cleanly", with a null pointer exception). |
1179 |
|
|
|
1180 |
root |
1.248 |
=item coro switching is not signal safe |
1181 |
root |
1.217 |
|
1182 |
root |
1.272 |
You must not switch to another coro from within a signal handler (only |
1183 |
|
|
relevant with %SIG - most event libraries provide safe signals), I<unless> |
1184 |
|
|
you are sure you are not interrupting a Coro function. |
1185 |
root |
1.217 |
|
1186 |
root |
1.221 |
That means you I<MUST NOT> call any function that might "block" the |
1187 |
root |
1.248 |
current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
1188 |
root |
1.217 |
anything that calls those. Everything else, including calling C<ready>, |
1189 |
|
|
works. |
1190 |
|
|
|
1191 |
|
|
=back |
1192 |
|
|
|
1193 |
root |
1.9 |
|
1194 |
root |
1.266 |
=head1 WINDOWS PROCESS EMULATION |
1195 |
|
|
|
1196 |
|
|
A great many people seem to be confused about ithreads (for example, Chip |
1197 |
root |
1.267 |
Salzenberg called me unintelligent, incapable, stupid and gullible, |
1198 |
root |
1.266 |
while in the same mail making rather confused statements about perl |
1199 |
|
|
ithreads (for example, that memory or files would be shared), showing his |
1200 |
|
|
lack of understanding of this area - if it is hard to understand for Chip, |
1201 |
|
|
it is probably not obvious to everybody). |
1202 |
|
|
|
1203 |
|
|
What follows is an ultra-condensed version of my talk about threads in |
1204 |
root |
1.281 |
scripting languages given on the perl workshop 2009: |
1205 |
root |
1.266 |
|
1206 |
|
|
The so-called "ithreads" were originally implemented for two reasons: |
1207 |
|
|
first, to (badly) emulate unix processes on native win32 perls, and |
1208 |
|
|
secondly, to replace the older, real thread model ("5.005-threads"). |
1209 |
|
|
|
1210 |
|
|
It does that by using threads instead of OS processes. The difference |
1211 |
|
|
between processes and threads is that threads share memory (and other |
1212 |
|
|
state, such as files) between threads within a single process, while |
1213 |
|
|
processes do not share anything (at least not semantically). That |
1214 |
|
|
means that modifications done by one thread are seen by others, while |
1215 |
|
|
modifications by one process are not seen by other processes. |
1216 |
|
|
|
1217 |
|
|
The "ithreads" work exactly like that: when creating a new ithreads |
1218 |
|
|
process, all state is copied (memory is copied physically, files and code |
1219 |
|
|
is copied logically). Afterwards, it isolates all modifications. On UNIX, |
1220 |
|
|
the same behaviour can be achieved by using operating system processes, |
1221 |
|
|
except that UNIX typically uses hardware built into the system to do this |
1222 |
|
|
efficiently, while the windows process emulation emulates this hardware in |
1223 |
|
|
software (rather efficiently, but of course it is still much slower than |
1224 |
|
|
dedicated hardware). |
1225 |
|
|
|
1226 |
|
|
As mentioned before, loading code, modifying code, modifying data |
1227 |
|
|
structures and so on is only visible in the ithreads process doing the |
1228 |
|
|
modification, not in other ithread processes within the same OS process. |
1229 |
|
|
|
1230 |
|
|
This is why "ithreads" do not implement threads for perl at all, only |
1231 |
|
|
processes. What makes it so bad is that on non-windows platforms, you can |
1232 |
|
|
actually take advantage of custom hardware for this purpose (as evidenced |
1233 |
|
|
by the forks module, which gives you the (i-) threads API, just much |
1234 |
|
|
faster). |
1235 |
|
|
|
1236 |
|
|
Sharing data is in the i-threads model is done by transfering data |
1237 |
|
|
structures between threads using copying semantics, which is very slow - |
1238 |
|
|
shared data simply does not exist. Benchmarks using i-threads which are |
1239 |
|
|
communication-intensive show extremely bad behaviour with i-threads (in |
1240 |
|
|
fact, so bad that Coro, which cannot take direct advantage of multiple |
1241 |
|
|
CPUs, is often orders of magnitude faster because it shares data using |
1242 |
|
|
real threads, refer to my talk for details). |
1243 |
|
|
|
1244 |
|
|
As summary, i-threads *use* threads to implement processes, while |
1245 |
|
|
the compatible forks module *uses* processes to emulate, uhm, |
1246 |
|
|
processes. I-threads slow down every perl program when enabled, and |
1247 |
|
|
outside of windows, serve no (or little) practical purpose, but |
1248 |
|
|
disadvantages every single-threaded Perl program. |
1249 |
|
|
|
1250 |
|
|
This is the reason that I try to avoid the name "ithreads", as it is |
1251 |
|
|
misleading as it implies that it implements some kind of thread model for |
1252 |
|
|
perl, and prefer the name "windows process emulation", which describes the |
1253 |
|
|
actual use and behaviour of it much better. |
1254 |
|
|
|
1255 |
root |
1.9 |
=head1 SEE ALSO |
1256 |
|
|
|
1257 |
root |
1.181 |
Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
1258 |
root |
1.152 |
|
1259 |
|
|
Debugging: L<Coro::Debug>. |
1260 |
|
|
|
1261 |
|
|
Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
1262 |
root |
1.67 |
|
1263 |
root |
1.238 |
Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
1264 |
root |
1.235 |
L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
1265 |
root |
1.67 |
|
1266 |
root |
1.238 |
I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
1267 |
root |
1.181 |
|
1268 |
root |
1.238 |
Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
1269 |
root |
1.235 |
a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
1270 |
|
|
L<Coro::Select>. |
1271 |
root |
1.152 |
|
1272 |
root |
1.181 |
XS API: L<Coro::MakeMaker>. |
1273 |
root |
1.67 |
|
1274 |
root |
1.238 |
Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
1275 |
root |
1.1 |
|
1276 |
|
|
=head1 AUTHOR |
1277 |
|
|
|
1278 |
root |
1.66 |
Marc Lehmann <schmorp@schmorp.de> |
1279 |
root |
1.64 |
http://home.schmorp.de/ |
1280 |
root |
1.1 |
|
1281 |
|
|
=cut |
1282 |
|
|
|