Better handling of presentation compiler shutdown.

of deadlocks: when the PC was asked to shutdown, all work items in the
work queue would be left pending, and no response would be set.

This commit attempts to clean up a bit better: a shutdown request clears
the work queue and all pending loaded&typed or parsed-entered requests
by setting their responses to 'MissingResponse'. review by odersky.

2 files changed, 60 insertions, 8 deletions

diff --git a/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala b/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
index 25a80bc4a6..63793fa21a 100644
--- a/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
+++ b/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
@@ -276,62 +276,98 @@ trait CompilerControl { self: Global =>
 
   abstract class WorkItem extends (() => Unit) {
     val onCompilerThread = self.onCompilerThread
+
+    /** Raise a MissingReponse, if the work item carries a response. */
+    def raiseMissing(): Unit
   }
 
   case class ReloadItem(sources: List[SourceFile], response: Response[Unit]) extends WorkItem {
     def apply() = reload(sources, response)
     override def toString = "reload "+sources
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
   case class FilesDeletedItem(sources: List[SourceFile], response: Response[Unit]) extends WorkItem {
     def apply() = filesDeleted(sources, response)
     override def toString = "files deleted "+sources
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskTypeAtItem(val pos: Position, response: Response[Tree]) extends WorkItem {
+  case class AskTypeAtItem(val pos: Position, response: Response[Tree]) extends WorkItem {
     def apply() = self.getTypedTreeAt(pos, response)
     override def toString = "typeat "+pos.source+" "+pos.show
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskTypeItem(val source: SourceFile, val forceReload: Boolean, response: Response[Tree]) extends WorkItem {
+  case class AskTypeItem(val source: SourceFile, val forceReload: Boolean, response: Response[Tree]) extends WorkItem {
     def apply() = self.getTypedTree(source, forceReload, response)
     override def toString = "typecheck"
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskTypeCompletionItem(val pos: Position, response: Response[List[Member]]) extends WorkItem {
+  case class AskTypeCompletionItem(val pos: Position, response: Response[List[Member]]) extends WorkItem {
     def apply() = self.getTypeCompletion(pos, response)
     override def toString = "type completion "+pos.source+" "+pos.show
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskScopeCompletionItem(val pos: Position, response: Response[List[Member]]) extends WorkItem {
+  case class AskScopeCompletionItem(val pos: Position, response: Response[List[Member]]) extends WorkItem {
     def apply() = self.getScopeCompletion(pos, response)
     override def toString = "scope completion "+pos.source+" "+pos.show
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
   class AskToDoFirstItem(val source: SourceFile) extends WorkItem {
     def apply() = moveToFront(List(source))
     override def toString = "dofirst "+source
+
+    def raiseMissing() = ()
   }
 
-  class AskLinkPosItem(val sym: Symbol, val source: SourceFile, response: Response[Position]) extends WorkItem {
+  case class AskLinkPosItem(val sym: Symbol, val source: SourceFile, response: Response[Position]) extends WorkItem {
     def apply() = self.getLinkPos(sym, source, response)
     override def toString = "linkpos "+sym+" in "+source
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskLoadedTypedItem(val source: SourceFile, response: Response[Tree]) extends WorkItem {
+  case class AskLoadedTypedItem(val source: SourceFile, response: Response[Tree]) extends WorkItem {
     def apply() = self.waitLoadedTyped(source, response, this.onCompilerThread)
     override def toString = "wait loaded & typed "+source
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskParsedEnteredItem(val source: SourceFile, val keepLoaded: Boolean, response: Response[Tree]) extends WorkItem {
+  case class AskParsedEnteredItem(val source: SourceFile, val keepLoaded: Boolean, response: Response[Tree]) extends WorkItem {
     def apply() = self.getParsedEntered(source, keepLoaded, response, this.onCompilerThread)
     override def toString = "getParsedEntered "+source+", keepLoaded = "+keepLoaded
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
 
-  class AskInstrumentedItem(val source: SourceFile, line: Int, response: Response[(String, Array[Char])]) extends WorkItem {
+  case class AskInstrumentedItem(val source: SourceFile, line: Int, response: Response[(String, Array[Char])]) extends WorkItem {
     def apply() = self.getInstrumented(source, line, response)
     override def toString = "getInstrumented "+source
+
+    def raiseMissing() =
+      response raise new MissingResponse
   }
+
 }
 
   // ---------------- Interpreted exceptions -------------------
diff --git a/src/compiler/scala/tools/nsc/interactive/Global.scala b/src/compiler/scala/tools/nsc/interactive/Global.scala
index 3d7d14627c..362ec1bae0 100644
--- a/src/compiler/scala/tools/nsc/interactive/Global.scala
+++ b/src/compiler/scala/tools/nsc/interactive/Global.scala
@@ -320,6 +320,22 @@ class Global(settings: Settings, reporter: Reporter, projectName: String = "")
           newTyperRun()
           minRunId = currentRunId
           demandNewCompilerRun()
+
+        case Some(ShutdownReq) =>
+          scheduler.synchronized { // lock the work queue so no more items are posted while we clean it up
+            val units = scheduler.dequeueAll {
+              case item: WorkItem => Some(item.raiseMissing())
+              case _ => Some(())
+            }
+            debugLog("ShutdownReq: cleaning work queue (%d items)".format(units.size))
+            debugLog("Cleanup up responses (%d loadedType pending, %d parsedEntered pending)"
+                .format(waitLoadedTypeResponses.size, getParsedEnteredResponses.size))
+            checkNoResponsesOutstanding()
+
+            log.flush();
+            throw ShutdownReq
+          }
+
         case Some(ex: Throwable) => log.flush(); throw ex
         case _ =>
       }