Class: ReservedNames::Win32::Mutex

Inherits:
Object
  • Object
show all
Includes:
Chef::ReservedNames::Win32::API::Synchronization
Defined in:
lib/chef/win32/mutex.rb

Constant Summary

Constants included from Chef::ReservedNames::Win32::API::Synchronization

Chef::ReservedNames::Win32::API::Synchronization::DELETE, Chef::ReservedNames::Win32::API::Synchronization::INFINITE, Chef::ReservedNames::Win32::API::Synchronization::MUTEX_ALL_ACCESS, Chef::ReservedNames::Win32::API::Synchronization::MUTEX_MODIFY_STATE, Chef::ReservedNames::Win32::API::Synchronization::READ_CONTROL, Chef::ReservedNames::Win32::API::Synchronization::SYNCHRONIZE, Chef::ReservedNames::Win32::API::Synchronization::WAIT_ABANDONED, Chef::ReservedNames::Win32::API::Synchronization::WAIT_FAILED, Chef::ReservedNames::Win32::API::Synchronization::WAIT_OBJECT_0, Chef::ReservedNames::Win32::API::Synchronization::WAIT_TIMEOUT, Chef::ReservedNames::Win32::API::Synchronization::WRITE_DAC, Chef::ReservedNames::Win32::API::Synchronization::WRITE_OWNER

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name) ⇒ Mutex

Returns a new instance of Mutex.



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# File 'lib/chef/win32/mutex.rb', line 27

def initialize(name)
  @name = name
  create_system_mutex
end

Instance Attribute Details

#handle ⇒ Object (readonly)

Returns the value of attribute handle.



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# File 'lib/chef/win32/mutex.rb', line 32

def handle
  @handle
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/chef/win32/mutex.rb', line 33

def name
  @name
end

Instance Method Details

#release ⇒ Object

Releases the mutex



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# File 'lib/chef/win32/mutex.rb', line 72

def release
  # http://msdn.microsoft.com/en-us/library/windows/desktop/ms685066(v=vs.85).aspx
  # Note that release method needs to be called more than once
  # if mutex is acquired more than once.
  unless ReleaseMutex(handle)
    # Don't fail things in here if we can't release the mutex.
    # Because it will be automatically released when the owner
    # of the process goes away and this class is only being used
    # to synchronize chef-clients runs on a node.
    Chef::Log.error("Can not release mutex '#{name}'. This might cause issues \
if other threads attempt to acquire the mutex.")
    Chef::ReservedNames::Win32::Error.raise!
  end
end

#test ⇒ Object

Attempts to grab the mutex. Returns true if the mutex is grabbed or if it's already owned; false otherwise.



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# File 'lib/chef/win32/mutex.rb', line 39

def test
  WaitForSingleObject(handle, 0) == WAIT_OBJECT_0
end

#wait ⇒ Object

Attempts to grab the mutex and waits until it is acquired.



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# File 'lib/chef/win32/mutex.rb', line 45

def wait
  loop do
    wait_result = WaitForSingleObject(handle, 1000)
    case wait_result
    when WAIT_TIMEOUT
      # We are periodically waking up in order to give ruby a
      # chance to process any signal it got while we were
      # sleeping. This condition shouldn't contain any logic
      # other than sleeping.
      sleep 0.1
    when WAIT_ABANDONED
      # Previous owner of the mutex died before it can release the
      # mutex. Log a warning and continue.
      Chef::Log.trace "Existing owner of the mutex exited prematurely."
      break
    when WAIT_OBJECT_0
      # Mutex is successfully acquired.
      break
    else
      Chef::Log.error("Failed to acquire system mutex '#{name}'. Return code: #{wait_result}")
      Chef::ReservedNames::Win32::Error.raise!
    end
  end
end