Check for thread consistency in JSCRuntime

Summary:
In the version of JSC on iOS 11, creating a JSContext on one
thread and using it on another can trigger subtle and nearly
impossible to debug reentrancy-related crashes in the VM (see
https://bugs.webkit.org/show_bug.cgi?id=186827).  In !NDEBUG builds,
check for this case and throw an exception, so it can be detected
early.

Reviewed By: amnn

Differential Revision: D13313264

fbshipit-source-id: ee85435c20e23c8520495ce743d2f91f2eeada5c

ReactCommon/cxxreact/Instance.cpp

@@ -53,6 +53,8 @@ void Instance::initializeBridge(
     m_syncCV.notify_all();
   });
 
+  // If the NativeToJsBridge ctor throws an exception, this check will
+  // likely happen before before the redbox can be rendered.
   CHECK(nativeToJsBridge_);
 }
 

ReactCommon/jsi/JSCRuntime.cpp

@@ -28,6 +28,14 @@ struct Lock {
   void unlock(const jsc::JSCRuntime&) const {}
 };
 
+#if __has_builtin(__builtin_expect)
+#define JSC_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
+#define JSC_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
+#else
+#define JSC_LIKELY(EXPR) (EXPR)
+#define JSC_UNLIKELY(EXPR) (EXPR)
+#endif
+
 class JSCRuntime : public jsi::Runtime {
  public:
   // Creates new context in new context group
@@ -191,23 +199,32 @@ class JSCRuntime : public jsi::Runtime {
   void checkException(JSValueRef exc, const char* msg);
   void checkException(JSValueRef res, JSValueRef exc, const char* msg);
 
+  void checkThreadId() {
+#ifndef NDEBUG
+    if (JSC_UNLIKELY(tid_ != std::this_thread::get_id())) {
+      // In the version of JSC on iOS 11, creating a JSContext on one
+      // thread and using it on another can trigger subtle and nearly
+      // impossible to debug reentrancy-related crashes in the VM (see
+      // https://bugs.webkit.org/show_bug.cgi?id=186827).  In !NDEBUG
+      // builds, check for this case and throw an exception, so it can
+      // be detected early.  This could be called anywhere, but for
+      // now, it's called only in a few less frequently used places to
+      // avoid unnecessary checks.
+      throw std::logic_error("Detected JSC thread hazard");
+    }
+#endif
+  }
+
   JSGlobalContextRef ctx_;
   std::atomic<bool> ctxInvalid_;
   std::string desc_;
 #ifndef NDEBUG
   mutable std::atomic<intptr_t> objectCounter_;
   mutable std::atomic<intptr_t> stringCounter_;
+  std::thread::id tid_;
 #endif
 };
 
-#if __has_builtin(__builtin_expect)
-#define JSC_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
-#define JSC_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
-#else
-#define JSC_LIKELY(EXPR) (EXPR)
-#define JSC_UNLIKELY(EXPR) (EXPR)
-#endif
-
 #define JSC_ASSERT(x)          \
   do {                         \
     if (JSC_UNLIKELY(!!(x))) { \
@@ -292,7 +309,8 @@ JSCRuntime::JSCRuntime(JSGlobalContextRef ctx)
 #ifndef NDEBUG
       ,
       objectCounter_(0),
-      stringCounter_(0)
+      stringCounter_(0),
+      tid_(std::this_thread::get_id())
 #endif
 {
 }
@@ -317,6 +335,8 @@ JSCRuntime::~JSCRuntime() {
 void JSCRuntime::evaluateJavaScript(
     std::unique_ptr<const jsi::Buffer> buffer,
     const std::string& sourceURL) {
+  checkThreadId();
+
   std::string tmp(
       reinterpret_cast<const char*>(buffer->data()), buffer->size());
   JSStringRef sourceRef = JSStringCreateWithUTF8CString(tmp.c_str());
@@ -335,6 +355,8 @@ void JSCRuntime::evaluateJavaScript(
 }
 
 jsi::Object JSCRuntime::global() {
+  checkThreadId();
+
   return createObject(JSContextGetGlobalObject(ctx_));
 }