Bug 1341283 - Avoid conflicts between GC zeal behavior and cooperative multithreading context switches, r=jonco.

js/src/gc/Verifier.cpp

@@ -179,8 +179,13 @@ gc::GCRuntime::startVerifyPreBarriers()
     if (verifyPreData || isIncrementalGCInProgress())
         return;
 
-    if (IsIncrementalGCUnsafe(rt) != AbortReason::None || TlsContext.get()->keepAtoms || rt->hasHelperThreadZones())
+    if (IsIncrementalGCUnsafe(rt) != AbortReason::None ||
+        TlsContext.get()->keepAtoms ||
+        rt->hasHelperThreadZones() ||
+        rt->cooperatingContexts().length() != 1)
+    {
         return;
+    }
 
     number++;
 

js/src/shell/js.cpp

@@ -3600,6 +3600,11 @@ EvalInThread(JSContext* cx, unsigned argc, Value* vp, bool cooperative)
         return false;
     }
 
+    if (cooperative && !cx->runtime()->gc.canChangeActiveContext(cx)) {
+        JS_ReportErrorASCII(cx, "Cooperating multithreading context switches are not currently allowed");
+        return false;
+    }
+
     if (!args[0].toString()->ensureLinear(cx))
         return false;