Only run CC after the GC has run at least once (bug 626768, r=gal). a=blocker

dom/base/nsJSEnvironment.cpp

@@ -148,6 +148,8 @@ static PRLogModuleInfo* gJSDiagnostics;
 static nsITimer *sGCTimer;
 static nsITimer *sCCTimer;
 
+static bool sGCHasRun;
+
 // The number of currently pending document loads. This count isn't
 // guaranteed to always reflect reality and can't easily as we don't
 // have an easy place to know when a load ends or is interrupted in
@@ -3392,8 +3394,8 @@ nsJSContext::MaybePokeCC()
 void
 nsJSContext::PokeCC()
 {
-  if (sCCTimer) {
-    // There's already a timer for GC'ing, just return
+  if (sCCTimer || !sGCHasRun) {
+    // There's already a timer for GC'ing, or GC hasn't run yet, just return.
     return;
   }
 
@@ -3477,6 +3479,7 @@ DOMGCCallback(JSContext *cx, JSGCStatus status)
     } else {
       // If this was a full GC, poke the CC to run soon.
       if (!cx->runtime->gcTriggerCompartment) {
+        sGCHasRun = true;
         nsJSContext::PokeCC();
       }
     }
@@ -3589,6 +3592,7 @@ nsJSRuntime::Startup()
 {
   // initialize all our statics, so that we can restart XPCOM
   sGCTimer = sCCTimer = nsnull;
+  sGCHasRun = false;
   sPendingLoadCount = 0;
   sLoadingInProgress = PR_FALSE;
   sPostGCEventsToConsole = PR_FALSE;

js/src/xpconnect/src/nsXPConnect.cpp

@@ -464,6 +464,18 @@ nsXPConnect::BeginCycleCollection(nsCycleCollectionTraversalCallback &cb,
         return NS_ERROR_FAILURE;
     }
 
+    static bool gcHasRun = false;
+    if(!gcHasRun)
+    {
+        JSRuntime* rt = JS_GetRuntime(mCycleCollectionContext->GetJSContext());
+        if(!rt)
+            NS_RUNTIMEABORT("Failed to get JS runtime!");
+        uint32 gcNumber = JS_GetGCParameter(rt, JSGC_NUMBER);
+        if(!gcNumber)
+            NS_RUNTIMEABORT("Cannot cycle collect if GC has not run first!");
+        gcHasRun = true;
+    }
+
 #ifdef DEBUG_CC
     NS_ASSERTION(!mJSRoots.ops, "Didn't call FinishCycleCollection?");
 

xpcom/base/nsCycleCollector.cpp

@@ -3287,7 +3287,6 @@ class nsCycleCollectorRunner : public nsRunnable
     PRBool mRunning;
     PRBool mShutdown;
     PRBool mCollected;
-    PRBool mJSGCHasRun;
 
 public:
     NS_IMETHOD Run()
@@ -3335,8 +3334,7 @@ public:
           mReply(mLock, "cycle collector reply condvar"),
           mRunning(PR_FALSE),
           mShutdown(PR_FALSE),
-          mCollected(PR_FALSE),
-          mJSGCHasRun(PR_FALSE)
+          mCollected(PR_FALSE)
     {
         NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
     }
@@ -3347,7 +3345,7 @@ public:
 
         MutexAutoLock autoLock(mLock);
 
-        if (!mRunning || !mJSGCHasRun)
+        if (!mRunning)
             return 0;
 
         nsAutoTPtrArray<PtrInfo, 4000> whiteNodes;
@@ -3388,14 +3386,6 @@ public:
         mRequest.Notify();
         mReply.Wait();
     }
-
-    void JSGCHasRun()
-    {
-        NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
-
-        MutexAutoLock autoLock(mLock);
-        mJSGCHasRun = PR_TRUE;
-    }
 };
 
 // Holds a reference.
@@ -3404,43 +3394,6 @@ static nsCycleCollectorRunner* sCollectorRunner;
 // Holds a reference.
 static nsIThread* sCollectorThread;
 
-static JSBool
-nsCycleCollector_gccallback(JSContext *cx, JSGCStatus status)
-{
-    NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
-
-    if (status == JSGC_END) {
-        if (sCollectorRunner)
-            sCollectorRunner->JSGCHasRun();
-
-        nsCOMPtr<nsIJSRuntimeService> rts =
-          do_GetService(nsIXPConnect::GetCID());
-        NS_WARN_IF_FALSE(rts, "Failed to get XPConnect?!");
-        if (rts)
-            rts->UnregisterGCCallback(nsCycleCollector_gccallback);
-    }
-
-    return JS_TRUE;
-}
-
-class nsCycleCollectorGCHookRunnable : public nsRunnable
-{
-public:
-    NS_IMETHOD Run()
-    {
-        NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
-
-        nsCOMPtr<nsIJSRuntimeService> rts =
-            do_GetService(nsIXPConnect::GetCID());
-        if (!rts) {
-            NS_RUNTIMEABORT("This must never fail!");
-        }
-
-        rts->RegisterGCCallback(nsCycleCollector_gccallback);
-        return NS_OK;
-    }
-};
-
 nsresult
 nsCycleCollector_startup()
 {
@@ -3449,17 +3402,11 @@ nsCycleCollector_startup()
 
     sCollector = new nsCycleCollector();
 
-    // We can't get XPConnect yet as it hasn't been initialized yet.
-    nsRefPtr<nsCycleCollectorGCHookRunnable> hook =
-        new nsCycleCollectorGCHookRunnable();
-    nsresult rv = NS_DispatchToCurrentThread(hook);
-    NS_ENSURE_SUCCESS(rv, rv);
-
     nsRefPtr<nsCycleCollectorRunner> runner =
         new nsCycleCollectorRunner(sCollector);
 
     nsCOMPtr<nsIThread> thread;
-    rv = NS_NewThread(getter_AddRefs(thread), runner);
+    nsresult rv = NS_NewThread(getter_AddRefs(thread), runner);
     NS_ENSURE_SUCCESS(rv, rv);
 
     runner.swap(sCollectorRunner);