Bug 975947 - Fix generational GC's interaction with the barrier verifier; r=sfink

js/public/GCAPI.h

@@ -307,37 +307,22 @@ WasIncrementalGC(JSRuntime *rt);
 /*
  * Generational GC:
  *
- * Note: Generational GC is not yet enabled by default. The following functions
- *       are non-functional unless SpiderMonkey was configured with
+ * Note: Generational GC is not yet enabled by default. The following class
+ *       is non-functional unless SpiderMonkey was configured with
  *       --enable-gcgenerational.
  */
 
-/*
- * Generational GC is enabled by default. Use this method to disable it.
- */
-extern JS_FRIEND_API(void)
-DisableGenerationalGC(JSRuntime *rt);
-
-/*
- * Generational GC may be re-enabled at runtime.
- */
-extern JS_FRIEND_API(void)
-EnableGenerationalGC(JSRuntime *rt);
-
 /* Ensure that generational GC is disabled within some scope. */
 class JS_FRIEND_API(AutoDisableGenerationalGC)
 {
     JSRuntime *runtime;
+#ifdef JS_GC_ZEAL
+    bool restartVerifier;
+#endif
 
   public:
-    AutoDisableGenerationalGC(JSRuntime *rt)
-      : runtime(rt)
-    {
-        DisableGenerationalGC(rt);
-    }
-    ~AutoDisableGenerationalGC() {
-        EnableGenerationalGC(runtime);
-    }
+    AutoDisableGenerationalGC(JSRuntime *rt);
+    ~AutoDisableGenerationalGC();
 };
 
 /*

js/src/gc/RootMarking.cpp

@@ -263,6 +263,7 @@ MarkWordConservatively(JSTracer *trc, uintptr_t w)
     MarkIfGCThingWord(trc, w);
 }
 
+#ifndef JSGC_USE_EXACT_ROOTING
 MOZ_ASAN_BLACKLIST
 static void
 MarkRangeConservatively(JSTracer *trc, const uintptr_t *begin, const uintptr_t *end)
@@ -272,7 +273,6 @@ MarkRangeConservatively(JSTracer *trc, const uintptr_t *begin, const uintptr_t *
         MarkWordConservatively(trc, *i);
 }
 
-#ifndef JSGC_USE_EXACT_ROOTING
 static void
 MarkRangeConservativelyAndSkipIon(JSTracer *trc, JSRuntime *rt, const uintptr_t *begin, const uintptr_t *end)
 {
@@ -343,8 +343,6 @@ MarkConservativeStackRoots(JSTracer *trc, bool useSavedRoots)
                             ArrayEnd(cgcd->registerSnapshot.words));
 }
 
-#endif /* JSGC_USE_EXACT_ROOTING */
-
 void
 js::MarkStackRangeConservatively(JSTracer *trc, Value *beginv, Value *endv)
 {
@@ -363,6 +361,8 @@ js::MarkStackRangeConservatively(JSTracer *trc, Value *beginv, Value *endv)
 #endif
 }
 
+#endif /* JSGC_USE_EXACT_ROOTING */
+
 MOZ_NEVER_INLINE void
 ConservativeGCData::recordStackTop()
 {

js/src/gc/Verifier.cpp

@@ -368,6 +368,8 @@ typedef HashMap<void *, VerifyNode *, DefaultHasher<void *>, SystemAllocPolicy>
  */
 struct VerifyPreTracer : JSTracer
 {
+    JS::AutoDisableGenerationalGC noggc;
+
     /* The gcNumber when the verification began. */
     uint64_t number;
 
@@ -381,13 +383,10 @@ struct VerifyPreTracer : JSTracer
     char *term;
     NodeMap nodemap;
 
-    VerifyPreTracer(JSRuntime *rt) : root(nullptr) {
-        JS::DisableGenerationalGC(rt);
-    }
+    VerifyPreTracer(JSRuntime *rt) : noggc(rt), root(nullptr) {}
 
     ~VerifyPreTracer() {
         js_free(root);
-        JS::EnableGenerationalGC(runtime);
     }
 };
 

js/src/jsfriendapi.cpp

@@ -930,11 +930,18 @@ JS::DisableIncrementalGC(JSRuntime *rt)
     rt->gcIncrementalEnabled = false;
 }
 
-extern JS_FRIEND_API(void)
-JS::DisableGenerationalGC(JSRuntime *rt)
+JS::AutoDisableGenerationalGC::AutoDisableGenerationalGC(JSRuntime *rt)
+  : runtime(rt)
+#ifdef JS_GC_ZEAL
+  , restartVerifier(rt->gcVerifyPostData)
+#endif
 {
 #ifdef JSGC_GENERATIONAL
     if (IsGenerationalGCEnabled(rt)) {
+#ifdef JS_GC_ZEAL
+        if (restartVerifier)
+            gc::EndVerifyPostBarriers(rt);
+#endif
         MinorGC(rt, JS::gcreason::API);
         rt->gcNursery.disable();
         rt->gcStoreBuffer.disable();
@@ -943,15 +950,18 @@ JS::DisableGenerationalGC(JSRuntime *rt)
     ++rt->gcGenerationalDisabled;
 }
 
-extern JS_FRIEND_API(void)
-JS::EnableGenerationalGC(JSRuntime *rt)
+JS::AutoDisableGenerationalGC::~AutoDisableGenerationalGC()
 {
-    JS_ASSERT(rt->gcGenerationalDisabled > 0);
-    --rt->gcGenerationalDisabled;
+    JS_ASSERT(runtime->gcGenerationalDisabled > 0);
+    --runtime->gcGenerationalDisabled;
 #ifdef JSGC_GENERATIONAL
-    if (IsGenerationalGCEnabled(rt)) {
-        rt->gcNursery.enable();
-        rt->gcStoreBuffer.enable();
+    if (runtime->gcGenerationalDisabled == 0) {
+        runtime->gcNursery.enable();
+        runtime->gcStoreBuffer.enable();
+#ifdef JS_GC_ZEAL
+        if (restartVerifier)
+            gc::StartVerifyPostBarriers(runtime);
+#endif
     }
 #endif
 }

js/src/shell/js.cpp

@@ -6203,8 +6203,9 @@ main(int argc, char **argv, char **envp)
 
     JS_SetGCParameter(rt, JSGC_MAX_BYTES, 0xffffffff);
 #ifdef JSGC_GENERATIONAL
+    Maybe<JS::AutoDisableGenerationalGC> noggc;
     if (op.getBoolOption("no-ggc"))
-        JS::DisableGenerationalGC(rt);
+        noggc.construct(rt);
 #endif
 
     size_t availMem = op.getIntOption("available-memory");

js/src/shell/jsheaptools.cpp

@@ -155,15 +155,11 @@ class HeapReverser : public JSTracer, public JS::CustomAutoRooter
     /* Construct a HeapReverser for |context|'s heap. */
     HeapReverser(JSContext *cx)
       : JS::CustomAutoRooter(cx),
+        noggc(JS_GetRuntime(cx)),
         runtime(JS_GetRuntime(cx)),
         parent(nullptr)
     {
         JS_TracerInit(this, runtime, traverseEdgeWithThis);
-        JS::DisableGenerationalGC(runtime);
-    }
-
-    ~HeapReverser() {
-        JS::EnableGenerationalGC(runtime);
     }
 
     bool init() { return map.init(); }
@@ -172,6 +168,8 @@ class HeapReverser : public JSTracer, public JS::CustomAutoRooter
     bool reverseHeap();
 
   private:
+    JS::AutoDisableGenerationalGC noggc;
+
     /* A runtime pointer for use by the destructor. */
     JSRuntime *runtime;