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#
# thread.rb - thread support classes
# $Date: 2006-12-31 07:02:22 -0800 (Sun, 31 Dec 2006) $
# by Yukihiro Matsumoto <matz@netlab.co.jp>
#
# Copyright (C) 2001 Yukihiro Matsumoto
# Copyright (C) 2000 Network Applied Communication Laboratory, Inc.
# Copyright (C) 2000 Information-technology Promotion Agency, Japan
#
unless defined? Thread
raise "Thread not available for this ruby interpreter"
end
unless defined? ThreadError
class ThreadError < StandardError
end
end
if $DEBUG
Thread.abort_on_exception = true
end
class Thread
#
# Wraps a block in Thread.critical, restoring the original value upon exit
# from the critical section.
#
def Thread.exclusive
_old = Thread.critical
begin
Thread.critical = true
return yield
ensure
Thread.critical = _old
end
end
end
class Mutex
def initialize
@owner = nil
end
# Check and only allow it to be marshal'd if there are no waiters.
def marshal_dump
raise "Unable to dump locked mutex" unless @waiters.empty?
1
end
# Implemented because we must since we use marshal_load PLUS we need
# to create AND prime @lock. If we didn't do this, then Marshal
# wouldn't prime the lock anyway.
def marshal_load(bunk)
initialize
end
def locked?
Rubinius.locked?(self)
end
def try_lock
# Locking implies a memory barrier, so we don't need to use
# one explicitly.
if Rubinius.try_lock(self)
@owner = Thread.current
true
else
false
end
end
def lock
Rubinius.memory_barrier
if @owner == Thread.current
raise ThreadError, "Recursively locking not allowed"
end
Rubinius.lock self
@owner = Thread.current
Rubinius.memory_barrier
return self
end
def unlock
Rubinius.memory_barrier
if @owner != Thread.current
raise ThreadError, "Not owner, #{@owner.inspect} is"
end
@owner = nil
Rubinius.unlock self
end
def synchronize
lock
begin
yield
ensure
unlock
end
end
end
#
# ConditionVariable objects augment class Mutex. Using condition variables,
# it is possible to suspend while in the middle of a critical section until a
# resource becomes available.
#
# Example:
#
# require 'thread'
#
# mutex = Mutex.new
# resource = ConditionVariable.new
#
# a = Thread.new {
# mutex.synchronize {
# # Thread 'a' now needs the resource
# resource.wait(mutex)
# # 'a' can now have the resource
# }
# }
#
# b = Thread.new {
# mutex.synchronize {
# # Thread 'b' has finished using the resource
# resource.signal
# }
# }
#
class ConditionVariable
#
# Creates a new ConditionVariable
#
def initialize
@waiters = []
end
#
# Releases the lock held in +mutex+ and waits; reacquires the lock on wakeup.
#
def wait(mutex, timeout=nil)
Rubinius.lock(self)
begin
wchan = Rubinius::Channel.new
begin
mutex.unlock
@waiters.push wchan
Rubinius.unlock(self)
signaled = wchan.receive_timeout timeout
ensure
mutex.lock
Rubinius.lock(self)
unless signaled or @waiters.delete(wchan)
# we timed out, but got signaled afterwards (e.g. while waiting to
# acquire @lock), so pass that signal on to the next waiter
@waiters.shift << true unless @waiters.empty?
end
end
if timeout
!!signaled
else
self
end
ensure
Rubinius.unlock(self)
end
end
#
# Wakes up the first thread in line waiting for this lock.
#
def signal
Rubinius.lock(self)
begin
@waiters.shift << true unless @waiters.empty?
ensure
Rubinius.unlock(self)
end
self
end
#
# Wakes up all threads waiting for this lock.
#
def broadcast
Rubinius.lock(self)
begin
@waiters.shift << true until @waiters.empty?
ensure
Rubinius.unlock(self)
end
self
end
end
#
# This class provides a way to synchronize communication between threads.
#
# Example:
#
# require 'thread'
#
# queue = Queue.new
#
# producer = Thread.new do
# 5.times do |i|
# sleep rand(i) # simulate expense
# queue << i
# puts "#{i} produced"
# end
# end
#
# consumer = Thread.new do
# 5.times do |i|
# value = queue.pop
# sleep rand(i/2) # simulate expense
# puts "consumed #{value}"
# end
# end
#
# consumer.join
#
class Queue
#
# Creates a new queue.
#
def initialize
@que = []
@que.taint # enable tainted comunication
self.taint
@waiting = []
@waiting.taint
@mutex = Mutex.new
@resource = ConditionVariable.new
end
#
# Pushes +obj+ to the queue.
#
def push(obj)
@mutex.synchronize do
@que.push obj
@resource.signal
end
end
#
# Alias of push
#
alias << push
#
# Alias of push
#
alias enq push
#
# Retrieves data from the queue. If the queue is empty, the calling thread is
# suspended until data is pushed onto the queue. If +non_block+ is true, the
# thread isn't suspended, and an exception is raised.
#
def pop(non_block=false)
while true
@mutex.synchronize do
#FIXME: some code in net or somewhere violates encapsulation
#and demands that a waiting queue exist for Queue, as a result
#we have to do a linear search here to remove the current Thread.
@waiting.delete(Thread.current)
if @que.empty?
raise ThreadError, "queue empty" if non_block
@waiting.push Thread.current
@resource.wait(@mutex)
else
retval = @que.shift
@resource.signal
return retval
end
end
end
end
#
# Alias of pop
#
alias shift pop
#
# Alias of pop
#
alias deq pop
#
# Returns +true+ if the queue is empty.
#
def empty?
@que.empty?
end
#
# Removes all objects from the queue.
#
def clear
@que.clear
end
#
# Returns the length of the queue.
#
def length
@que.length
end
#
# Alias of length.
#
alias size length
#
# Returns the number of threads waiting on the queue.
#
def num_waiting
@waiting.size
end
end
#
# This class represents queues of specified size capacity. The push operation
# may be blocked if the capacity is full.
#
# See Queue for an example of how a SizedQueue works.
#
class SizedQueue < Queue
#
# Creates a fixed-length queue with a maximum size of +max+.
#
def initialize(max)
raise ArgumentError, "queue size must be positive" unless max > 0
@max = max
@queue_wait = []
@queue_wait.taint # enable tainted comunication
@size_mutex = Mutex.new
@sem = ConditionVariable.new
super()
end
#
# Returns the maximum size of the queue.
#
def max
@max
end
#
# Sets the maximum size of the queue.
#
def max=(max)
@size_mutex.synchronize do
@max = max
@sem.broadcast(@size_mutex)
end
max
end
#
# Pushes +obj+ to the queue. If there is no space left in the queue, waits
# until space becomes available.
#
def push(obj)
while true
@size_mutex.synchronize do
@queue_wait.delete(Thread.current)
if @que.size >= @max
@queue_wait.push Thread.current
@sem.wait(@size_mutex)
else
return super(obj)
end
end
end
end
#
# Alias of push
#
alias << push
#
# Alias of push
#
alias enq push
#
# Retrieves data from the queue and runs a waiting thread, if any.
#
def pop(*args)
retval = super
@size_mutex.synchronize do
if @que.size < @max
@sem.broadcast
end
end
return retval
end
#
# Alias of pop
#
alias shift pop
#
# Alias of pop
#
alias deq pop
#
# Returns the number of threads waiting on the queue.
#
def num_waiting
@waiting.size + @queue_wait.size
end
end
# Documentation comments:
# - How do you make RDoc inherit documentation from superclass?
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