Class: OsCtld::Lockable::Lock

Inherits:
Object
  • Object
show all
Defined in:
lib/osctld/lockable.rb

Constant Summary collapse

TIMEOUT = 
90

Instance Method Summary collapse

Constructor Details

#initialize(object) ⇒ Lock

Returns a new instance of Lock.

Parameters:

  • object (Object) 


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# File 'lib/osctld/lockable.rb', line 32

def initialize(object)
  @mutex = OsCtl::Lib::Mutex.new
  @in_held = []
  @in_queued = []
  @ex_queued = []
  @ex = nil
  @allow_inclusive_after_exclusive = false
  @cond_ex = ConditionVariable.new
  @cond_in = ConditionVariable.new
  @object = object
end

Instance Method Details

#acquire_exclusive ⇒ Object 



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# File 'lib/osctld/lockable.rb', line 118

def acquire_exclusive
  return if @mutex.owned? && @ex == Thread.current

  t = Time.now
  is_timeout = false

  LockRegistry.register(@object, :exclusive, :waiting)

  begin
    @mutex.lock(TIMEOUT)
  rescue OsCtl::Lib::Mutex::Timeout
    LockRegistry.register(@object, :exclusive, :timeout)
    raise OsCtld::DeadlockDetected.new(@object, :exclusive)
  end

  if @in_held.empty?
    @allow_inclusive_after_exclusive = false
    @ex = Thread.current
    LockRegistry.register(@object, :exclusive, :locked)

  elsif @in_held.include?(Thread.current)
    @mutex.unlock
    raise 'attempted to acquire exclusive lock while holding inclusive lock'

  else
    @ex_queued << Thread.current

    # Wait for all inclusive blocks to finish
    LockRegistry.register(@object, :exclusive, :waiting)

    loop do
      now = Time.now

      if (now - t) >= TIMEOUT
        is_timeout = true
        break

      elsif @in_held.empty? && @ex.nil?
        break
      end

      @cond_ex.wait(@mutex, TIMEOUT - (now - t))
    end

    if (!@in_held.empty? || @ex) && is_timeout
      LockRegistry.register(@object, :exclusive, :timeout)
      @mutex.unlock
      raise OsCtld::DeadlockDetected.new(@object, :exclusive)
    else
      @allow_inclusive_after_exclusive = false
      @ex = @ex_queued.shift
      LockRegistry.register(@object, :exclusive, :locked)
    end
  end
end

#acquire_inclusive ⇒ Object 



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# File 'lib/osctld/lockable.rb', line 44

def acquire_inclusive
  t = Time.now
  is_timeout = false

  sync do
    if @ex_queued.any? && !@allow_inclusive_after_exclusive
      @in_queued << Thread.current

      # Wait for the exclusive lock to finish, if there is one
      LockRegistry.register(@object, :inclusive, :waiting)

      loop do
        now = Time.now

        if (now - t) >= TIMEOUT
          is_timeout = true
          break

        elsif @ex.nil? && (@allow_inclusive_after_exclusive || @ex_queued.empty?)
          break
        end

        @cond_in.wait(@mutex, TIMEOUT - (now - t))
      end

      if (@ex || (!@allow_inclusive_after_exclusive && @ex_queued.any?)) && is_timeout
        LockRegistry.register(@object, :inclusive, :timeout)
        raise OsCtld::DeadlockDetected.new(@object, :inclusive)
      else
        @in_queued.delete(Thread.current)
        @in_held << Thread.current
        LockRegistry.register(@object, :inclusive, :locked)
      end

    else
      @in_held << Thread.current
      LockRegistry.register(@object, :inclusive, :locked)
    end
  end
end

#exclusively ⇒ Object 



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# File 'lib/osctld/lockable.rb', line 197

def exclusively
  if @mutex.owned? && @ex == Thread.current
    yield

  else
    acquire_exclusive

    begin
      yield
    ensure
      release_exclusive
    end
  end
end

#inclusively ⇒ Object 



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# File 'lib/osctld/lockable.rb', line 98

def inclusively
  return yield if @mutex.owned? && @ex == Thread.current

  held = false
  sync { held = @in_held.include?(Thread.current) }

  if held
    yield

  else
    acquire_inclusive

    begin
      yield
    ensure
      release_inclusive
    end
  end
end

#release_exclusive ⇒ Object 



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# File 'lib/osctld/lockable.rb', line 174

def release_exclusive
  unless @mutex.owned?
    raise 'expected to own the mutex, have you called acquire_exclusive first?'
  end

  # Leave exlusive block, signal waiting inclusive blocks to continue
  @ex = nil
  LockRegistry.register(@object, :exclusive, :unlocked)

  # Give the first chance to a round of inclusive locks, then exclusive
  # ones
  if @in_queued.any?
    @allow_inclusive_after_exclusive = true
    @cond_in.broadcast

  elsif @ex_queued.any?
    @allow_inclusive_after_exclusive = false
    @cond_ex.signal
  end

  @mutex.unlock
end

#release_inclusive ⇒ Object 



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# File 'lib/osctld/lockable.rb', line 85

def release_inclusive
  sync do
    @in_held.delete(Thread.current)
    LockRegistry.register(@object, :inclusive, :unlocked)

    # Start exclusive block, if there is one waiting
    if @in_held.empty? && @ex_queued.any?
      @allow_inclusive_after_exclusive = false
      @cond_ex.signal
    end
  end
end