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local/lib/perl5/Future/Mutex.pm  view on Meta::CPAN

future instances to represent still-pending operations that will complete at
some later time. There are occasions however, when this concurrency needs to
be restricted - some operations that, once started, must not be interrupted
until they are complete. Subsequent requests to perform the same operation
while one is still outstanding must therefore be queued to wait until the
first is finished. These situations call for a mutual-exclusion lock, or
"mutex".

A C<Future::Mutex> instance provides one basic operation, which will execute a
given block of code which returns a future, and itself returns a future to
represent that. The mutex can be in one of two states; either unlocked or
locked. While it is unlocked, requests to execute code are handled
immediately. Once a block of code is invoked, the mutex is now considered to
be locked, causing any subsequent requests to invoke code to be queued behind
the first one, until it completes. Once the initial code indicates completion
(by its returned future providing a result or failing), the next queued code
is invoked.

=cut

=head1 CONSTRUCTOR

=cut

=head2 new

   $mutex = Future::Mutex->new

Returns a new C<Future::Mutex> instance. It is initially unlocked.

=cut

sub new
{
   my $class = shift;

   return bless {
      f => Future->done,
   }, $class;

local/lib/perl5/Future/Mutex.pm  view on Meta::CPAN

=head1 METHODS

=cut

=head2 enter

   $f = $mutex->enter( \&code )

Returns a new C<Future> that represents the eventual result of calling the
code. If the mutex is currently unlocked, the code will be invoked
immediately. If it is currently locked, the code will be queued waiting for
the next time it becomes unlocked.

The code is invoked with no arguments, and is expected to return a C<Future>.
The eventual result of that future determines the result of the future that
C<enter> returned.

=cut

sub enter
{
   my $self = shift;

local/lib/perl5/IO/Async/Loop.pm  view on Meta::CPAN

If an extension C<listen> method is invoked, it will be passed a C<listener>
parameter even if one was not provided to the original C<< $loop->listen >>
call, and it will not receive any of the C<on_*> event callbacks. It should
use the C<acceptor> parameter on the C<listener> object.

=cut

=head1 STALL WATCHDOG

A well-behaved L<IO::Async> program should spend almost all of its time
blocked on input using the underlying C<IO::Async::Loop> instance. The stall
watchdog is an optional debugging feature to help detect CPU spinlocks and
other bugs, where control is not returned to the loop every so often.

If the watchdog is enabled and an event handler consumes more than a given
amount of real time before returning to the event loop, it will be interrupted
by printing a stack trace and terminating the program. The watchdog is only in
effect while the loop itself is not blocking; it won't fail simply because the
loop instance is waiting for input or timers.

It is implemented using C<SIGALRM>, so if enabled, this signal will no longer