core: lock around machine actions

lib/vagrant/errors.rb

@@ -404,6 +404,10 @@ module Vagrant
       error_key(:local_data_dir_not_accessible)
     end
 
+    class MachineActionLockedError < VagrantError
+      error_key(:machine_action_locked)
+    end
+
     class MachineGuestNotReady < VagrantError
       error_key(:machine_guest_not_ready)
     end

lib/vagrant/machine.rb

@@ -1,3 +1,4 @@
+require "digest/md5"
 require "thread"
 
 require "log4r"
@@ -147,18 +148,28 @@ module Vagrant
     def action(name, extra_env=nil)
       @logger.info("Calling action: #{name} on provider #{@provider}")
 
-      # Get the callable from the provider.
-      callable = @provider.action(name)
+      # Create a deterministic ID for this machine
+      id = Digest::MD5.hexdigest("#{@env.root_path}#{@name}")
 
-      # If this action doesn't exist on the provider, then an exception
-      # must be raised.
-      if callable.nil?
-        raise Errors::UnimplementedProviderAction,
-          :action => name,
-          :provider => @provider.to_s
+      # Lock this machine for the duration of this action
+      @env.lock("machine-action-#{id}") do
+        # Get the callable from the provider.
+        callable = @provider.action(name)
+
+        # If this action doesn't exist on the provider, then an exception
+        # must be raised.
+        if callable.nil?
+          raise Errors::UnimplementedProviderAction,
+            :action => name,
+            :provider => @provider.to_s
+        end
+
+        action_raw(name, callable, extra_env)
       end
-
-      action_raw(name, callable, extra_env)
+    rescue Errors::EnvironmentLockedError
+      raise Errors::MachineActionLockedError,
+        action: name,
+        name: @name
     end
 
     # This calls a raw callable in the proper context of the machine using

templates/locales/en.yml

@@ -744,6 +744,16 @@ en:
         that the NFS client software is properly installed, and consult any resources
         specific to the linux distro you're using for more information on how to
         do this.
+      machine_action_locked: |-
+        An action '%{action}' was attempted on the machine '%{name}',
+        but another process is already executing an action on the machine.
+        Vagrant locks each machine for access by only one process at a time.
+        Please wait until the other Vagrant process finishes modifying this
+        machine, then try again.
+
+        If you believe this message is in error, please check the process
+        listing for any "ruby" or "vagrant" processes and kill them. Then
+        try again.
       machine_guest_not_ready: |-
         Guest-specific operations were attempted on a machine that is not
         ready for guest communication. This should not happen and a bug

test/unit/vagrant/machine_test.rb

@@ -208,7 +208,7 @@ describe Vagrant::Machine do
     end
   end
 
-  describe "actions" do
+  describe "#action" do
     it "should be able to run an action that exists" do
       action_name = :up
       called      = false