Bug 900598 - Make sure not to collect the atoms compartment when exclusive threads are present (r=bhackett)

js/src/jsgc.cpp

@@ -2773,6 +2773,15 @@ BeginMarkPhase(JSRuntime *rt)
     for (ThreadDataIter iter(rt); !iter.done(); iter.next())
         keepAtoms |= iter->gcKeepAtoms;
 
+    /*
+     * We don't scan the stacks of exclusive threads, so we need to avoid
+     * collecting their objects in another way. The only GC thing pointers they
+     * have are to their exclusive compartment (which is not collected) or to
+     * the atoms compartment. Therefore, we avoid collecting the atoms
+     * compartment when exclusive threads are running.
+     */
+    keepAtoms |= rt->exclusiveThreadsPresent();
+
     if (atomsZone->isGCScheduled() && rt->gcIsFull && !keepAtoms) {
         JS_ASSERT(!atomsZone->isCollecting());
         atomsZone->setGCState(Zone::Mark);
@@ -4352,6 +4361,8 @@ gc::IsIncrementalGCSafe(JSRuntime *rt)
     for (ThreadDataIter iter(rt); !iter.done(); iter.next())
         keepAtoms |= iter->gcKeepAtoms;
 
+    keepAtoms |= rt->exclusiveThreadsPresent();
+
     if (keepAtoms)
         return IncrementalSafety::Unsafe("gcKeepAtoms set");
 

js/src/vm/Runtime.h

@@ -765,6 +765,14 @@ struct JSRuntime : public JS::shadow::Runtime,
 #endif
     }
 
+    bool exclusiveThreadsPresent() const {
+#ifdef JS_THREADSAFE
+        return numExclusiveThreads > 0;
+#else
+        return false;
+#endif
+    }
+
     /* Default compartment. */
     JSCompartment       *atomsCompartment;