Class: OsCtl::Lib::Mutex

Inherits:
Object
  • Object
show all
Defined in:
lib/libosctl/mutex.rb

Overview

Extended mutex with an optional timeout on lock

Defined Under Namespace

Classes: Timeout

Instance Method Summary collapse

Constructor Details

#initializeMutex

Returns a new instance of Mutex



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# File 'lib/libosctl/mutex.rb', line 8

def initialize
  @mutex = ::Mutex.new
  @cond = ConditionVariable.new
  @thread = nil
  @queue = 0
end

Instance Method Details

#lock(timeout = nil) ⇒ Object

Attempts to grab the lock and waits if it isn't available

Parameters:

  • timeout (Integer, nil) (defaults to: nil)

    timeout in seconds

Raises:

  • (Timeout)

    when timeout has passed while waiting for the lock



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# File 'lib/libosctl/mutex.rb', line 18

def lock(timeout = nil)
  t = Time.now
  is_timeout = false

  sync do
    if @thread
      @queue += 1

      loop do
        now = Time.now

        if @thread.nil?
          break

        elsif timeout && (now - t) >= timeout
          is_timeout = true
          break
        end

        @cond.wait(@mutex, timeout && (timeout - (now - t)))
      end

      @queue -= 1

      if @thread && is_timeout
        raise Timeout
      else
        @thread = Thread.current
      end

    else
      @thread = Thread.current
    end
  end

  nil
end

#locked?Boolean

Returns true if this lock is currently held by some thread

Returns:

  • (Boolean)


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# File 'lib/libosctl/mutex.rb', line 98

def locked?
  sync { !@thread.nil? }
end

#owned?Boolean

Returns true if this lock is currently held by current thread

Returns:

  • (Boolean)


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# File 'lib/libosctl/mutex.rb', line 103

def owned?
  sync { @thread == Thread.current }
end

#sleep(timeout = nil, lock_timeout = nil) ⇒ Object

Release the lock and sleep, then reaquire it

Parameters:

  • timeout (Integer, nil) (defaults to: nil)

    how long to sleep, in seconds

  • lock_timeout (Integer, nil) (defaults to: nil)

    timeout when reaquiring the lock, in seconds

Raises:

  • (ThreadError)

    when the current thread does not own the mutex

  • (Timeout)

    when timeout has passed while waiting for the lock



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# File 'lib/libosctl/mutex.rb', line 91

def sleep(timeout = nil, lock_timeout = nil)
  unlock
  Kernel.sleep(*(timeout ? [timeout] : []))
  lock(lock_timeout)
end

#syncObject (protected)



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# File 'lib/libosctl/mutex.rb', line 108

def sync
  @mutex.synchronize { yield }
end

#synchronize(timeout = nil) ⇒ Object

Execute a block with the lock

Parameters:

  • timeout (Integer, nil) (defaults to: nil)

    timeout in seconds

Raises:

  • (Timeout)

    when timeout has passed while waiting for the lock



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# File 'lib/libosctl/mutex.rb', line 75

def synchronize(timeout = nil)
  lock(timeout)

  begin
    yield
  ensure
    unlock
  end
end

#unlockObject

Release the lock

Raises:

  • (ThreadError)

    when the current thread does not own the mutex



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# File 'lib/libosctl/mutex.rb', line 58

def unlock
  sync do
    if @thread == Thread.current
      @thread = nil
      @cond.signal if @queue > 0

    else
      raise ThreadError, 'attempted to unlock mutex owned by another thread'
    end
  end

  nil
end