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Marc A. Lehmann


Coro - coroutine process abstraction


 use Coro;

 async {
    # some asynchronous thread of execution

 # alternatively create an async process like this:

 sub some_func : Coro {
    # some more async code



This module collection manages coroutines. Coroutines are similar to threads but don't run in parallel.

In this module, coroutines are defined as "callchain + lexical variables + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own callchain, it's own set of lexicals and it's own set of perl's most important global variables.


This coroutine represents the main program.

$current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value is $main (of course).


The coroutine to switch to when no other coroutine is running. The default implementation prints "FATAL: deadlock detected" and exits.


Static methods are actually functions that operate on the current process only.

async { ... } [@args...]

Create a new asynchronous process and return it's process object (usually unused). When the sub returns the new process is automatically terminated.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

Calls the scheduler. Please note that the current process will not be put into the ready queue, so calling this function usually means you will never be called again.


"Cede" to other processes. This function puts the current process into the ready queue and calls schedule, which has the effect of giving up the current "timeslice" to other coroutines of the same or higher priority.

terminate [arg...]

Terminates the current process with the given status values (see cancel).

# dynamic methods


These are the methods you can call on process objects.

new Coro \&sub [, @args...]

Create a new process and return it. When the sub returns the process automatically terminates as if terminate with the returned values were called. To make the process run you must first put it into the ready queue by calling the ready method.


Put the given process into the ready queue.

$process->cancel (arg...)

Temrinates the given process and makes it return the given arguments as status (default: the empty list).


Wait until the coroutine terminates and return any values given to the terminate or cancel functions. join can be called multiple times from multiple processes.

$oldprio = $process->prio($newprio)

Sets (or gets, if the argument is missing) the priority of the process. Higher priority processes get run before lower priority processes. Priorities are small signed integers (currently -4 .. +3), that you can refer to using PRIO_xxx constants (use the import tag :prio to get then):

       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH

The idle coroutine ($Coro::idle) always has a lower priority than any existing coroutine.

Changing the priority of the current process will take effect immediately, but changing the priority of processes in the ready queue (but not running) will only take effect after the next schedule (of that process). This is a bug that will be fixed in some future version.

$newprio = $process->nice($change)

Similar to prio, but subtract the given value from the priority (i.e. higher values mean lower priority, just as in unix).

$olddesc = $process->desc($newdesc)

Sets (or gets in case the argument is missing) the description for this process. This is just a free-form string you can associate with a process.


 - you must make very sure that no coro is still active on global
   destruction. very bad things might happen otherwise (usually segfaults).

 - this module is not thread-safe. You should only ever use this module
   from the same thread (this requirement might be losened in the future
   to allow per-thread schedulers, but Coro::State does not yet allow


Support/Utility: Coro::Cont, Coro::Specific, Coro::State, Coro::Util.

Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, Coro::SemaphoreSet, Coro::RWLock.

Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket, Coro::Select.

Embedding: Coro:MakeMaker


 Marc Lehmann <schmorp@schmorp.de>