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Thread::Semaphore(3)
NAME
  Thread::Semaphore - thread-safe semaphores

SYNOPSIS
      use Thread::Semaphore;
      my $s = new Thread::Semaphore;
      $s->down;	  # Also known as the semaphore P operation.
      # The guarded section is here
      $s->up;	  # Also known as the semaphore V operation.

      # The default semaphore value is 1.
      my $s = new Thread::Semaphore($initial_value);
      $s->down($down_value);
      $s->up($up_value);

DESCRIPTION
  Semaphores provide a mechanism to regulate access to resources. Semaphores,
  unlike locks, aren't tied to particular scalars, and so may be used to
  control access to anything you care to use them for.

  Semaphores don't limit their values to zero or one, so they can be used to
  control access to some resource that there may be more than one of. (For
  example, filehandles.) Increment and decrement amounts aren't fixed at one
  either, so threads can reserve or return multiple resources at once.

FUNCTIONS AND METHODS
  new
  new NUMBER
	  "new" creates a new semaphore, and initializes its count to the
	  passed number. If no number is passed, the semaphore's count is set
	  to one.

  down
  down NUMBER
	  The "down" method decreases the semaphore's count by the specified
	  number, or by one if no number has been specified. If the
	  semaphore's count would drop below zero, this method will block
	  until such time that the semaphore's count is equal to or larger
	  than the amount you're "down"ing the semaphore's count by.

	  This is the semaphore "P operation" (the name derives from the
	  Dutch word "pak", which means "capture" -- the semaphore operations
	  were named by the late Dijkstra, who was Dutch).

  up
  up NUMBER
	  The "up" method increases the semaphore's count by the number
	  specified, or by one if no number has been specified. This will
	  unblock any thread blocked trying to "down" the semaphore if the
	  "up" raises the semaphore count above the amount that the "down"s
	  are trying to decrement it by.

	  This is the semaphore "V operation" (the name derives from the
	  Dutch word "vrij", which means "release").

Index for Section 3

Alphabetical listing for T

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