1 files changed, 94 insertions, 0 deletions
diff --git a/lib/chef/win32/mutex.rb b/lib/chef/win32/mutex.rb
new file mode 100644
index 0000000000..b0a9ba210e
--- /dev/null
+++ b/lib/chef/win32/mutex.rb
@@ -0,0 +1,94 @@
+#
+# Author:: Serdar Sutay (<serdar@opscode.com>)
+# Copyright:: Copyright 2013 Opscode, Inc.
+# License:: Apache License, Version 2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+require 'chef/win32/api/synchronization'
+
+class Chef
+  module ReservedNames::Win32
+    class Mutex
+      include Chef::ReservedNames::Win32::API::Synchronization
+      extend Chef::ReservedNames::Win32::API::Synchronization
+
+      def initialize(name)
+        @name = name
+        # First check if there exists a mutex in the system with the
+        # given name.
+
+        # In the initial creation of the mutex initial_owner is set to
+        # false so that mutex will not be acquired until someone calls
+        # acquire.
+        # In order to call "*W" windows apis, strings needs to be
+        # encoded as wide strings.
+        @handle = CreateMutexW(nil, false, name.to_wstring)
+
+        # Fail early if we can't get a handle to the named mutex
+        if @handle == 0
+          Chef::Log.error("Failed to create system mutex with name'#{name}'")
+          Chef::ReservedNames::Win32::Error.raise!
+        end
+      end
+
+      attr_reader :handle
+      attr_reader :name
+
+      #####################################################
+      # Attempts to grab the mutex.
+      # Returns true if the mutex is grabbed or if it's already
+      # owned; false otherwise.
+      def test
+        WaitForSingleObject(handle, 0) == WAIT_OBJECT_0
+      end
+
+      #####################################################
+      # Attempts to grab the mutex and waits until it is acquired.
+      def wait
+        wait_result = WaitForSingleObject(handle, INFINITE)
+        case wait_result
+        when WAIT_ABANDONED
+          # Previous owner of the mutex died before it can release the
+          # mutex. Log a warning and continue.
+          Chef::Log.debug "Existing owner of the mutex exited prematurely."
+        when WAIT_OBJECT_0
+          # Mutex is successfully acquired.
+        else
+          Chef::Log.error("Failed to acquire system mutex '#{name}'. Return code: #{wait_result}")
+          Chef::ReservedNames::Win32::Error.raise!
+        end
+      end
+
+      #####################################################
+      # Releaes the mutex
+      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 the mutex is attempted to be acquired by other threads.")
+          Chef::ReservedNames::Win32::Error.raise!
+        end
+      end
+    end
+  end
+end
+
+