[futex] Allow debugger to break in the middle of a futexWait

test/cctest/test-debug.cc

Index: test/cctest/test-debug.cc
diff --git a/test/cctest/test-debug.cc b/test/cctest/test-debug.cc
index c6a889664f79451c73687fb49dfe5ebd5ed7d33f..f4e539a5fb884a93ee39f38fed7f9436b9bdf5bd 100644
--- a/test/cctest/test-debug.cc
+++ b/test/cctest/test-debug.cc
@@ -36,6 +36,7 @@
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/frames.h"
+#include "src/futex-emulation.h"
 #include "src/utils.h"
 #include "test/cctest/cctest.h"
 
@@ -7624,3 +7625,146 @@ TEST(DebugBreakInLexicalScopes) {
       "x * y",
       30);
 }
+
+
+Barriers futex_barriers;
+
+
+class FutexV8Thread : public v8::base::Thread {
+ public:
+  FutexV8Thread(void* sab_data, size_t sab_size)
+      : Thread(Options("V8Thread")), sab_data_(sab_data), sab_size_(sab_size) {}
+  void Run();
+  v8::Isolate* isolate() { return isolate_; }
+
+ private:
+  v8::Isolate* isolate_;
+  void* sab_data_;
+  size_t sab_size_;
+};
+
+
+class FutexDebuggerThread : public v8::base::Thread {
+ public:
+  explicit FutexDebuggerThread(v8::Isolate* v8_isolate, void* sab_data,
+                               size_t sab_size)
+      : Thread(Options("DebuggerThread")),
+        v8_isolate_(v8_isolate),
+        sab_data_(sab_data),
+        sab_size_(sab_size) {}
+  void Run();
+
+ private:
+  v8::Isolate* v8_isolate_;
+  void* sab_data_;
+  size_t sab_size_;
+};
+
+
+static void FutexMessageHandler(const v8::Debug::Message& message) {
+  static char print_buffer[1000];
+  v8::String::Value json(message.GetJSON());
+  Utf16ToAscii(*json, json.length(), print_buffer);
+  if (IsBreakEventMessage(print_buffer)) {
+    // Check that we are inside the futex.
+    int source_line = GetSourceLineFromBreakEventMessage(print_buffer);
+    CHECK(source_line == 1);
+    futex_barriers.barrier_2.Wait();
+  }
+}
+
+
+void FutexV8Thread::Run() {
+  const char* source =
+      "var i32a = new Int32Array(sab);\n"
+      "Atomics.futexWait(i32a, 0, 0, Infinity)\n";
+
+  v8::Isolate::CreateParams create_params;
+  create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+  isolate_ = v8::Isolate::New(create_params);
+  futex_barriers.barrier_3.Wait();
+  {
+    v8::Isolate::Scope isolate_scope(isolate_);
+    DebugLocalContext env(isolate_);
+    v8::HandleScope scope(isolate_);
+    v8::Debug::SetMessageHandler(&FutexMessageHandler);
+    v8::Handle<v8::ObjectTemplate> global_template =
+        v8::ObjectTemplate::New(env->GetIsolate());
+    global_template->Set(
+        v8::String::NewFromUtf8(env->GetIsolate(), "sab"),
+        v8::SharedArrayBuffer::New(isolate_, sab_data_, sab_size_));
+
+    v8::Handle<v8::Context> context =
+        v8::Context::New(isolate_, NULL, global_template);
+    v8::Context::Scope context_scope(context);
+
+    CompileRun(source);
+  }
+  futex_barriers.barrier_4.Wait();
+  isolate_->Dispose();
+}
+
+
+void FutexDebuggerThread::Run() {
+  v8::Isolate::CreateParams create_params;
+  create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+  v8::Isolate* debug_isolate = v8::Isolate::New(create_params);
+  {
+    v8::Isolate::Scope isolate_scope(debug_isolate);
+    DebugLocalContext env(debug_isolate);
+    v8::HandleScope scope(debug_isolate);
+    v8::Handle<v8::SharedArrayBuffer> sab(
+        v8::SharedArrayBuffer::New(debug_isolate, sab_data_, sab_size_));
+
+    i::Handle<i::JSArrayBuffer> i_sab = v8::Utils::OpenHandle(*sab);
+    i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(debug_isolate);
+    // Spin loop until v8 thread is waiting on futex.
+    while (true) {
+      i::Object* num_waiters =
+          i::FutexEmulation::NumWaitersForTesting(i_isolate, i_sab, 0);
+      if (num_waiters->IsSmi() && i::Smi::cast(num_waiters)->value() > 0) {
+        break;
+      }
+    }
+
+    v8::Debug::DebugBreak(v8_isolate_);
+    futex_barriers.barrier_2.Wait();
+
+    i::FutexEmulation::Wake(i_isolate, i_sab, 0, 1);
+    {
+      const int kBufferSize = 1000;
+      uint16_t buffer[kBufferSize];
+      const char* command_continue =
+          "{\"seq\":0,"
+          "\"type\":\"request\","
+          "\"command\":\"continue\"}";

[Yang, 2015/08/27 06:27:25]

Please do not use the JSON protocol for tests anymore. Chrome does not use it.
Use the JS API instead.

[binji, 2015/08/31 21:25:18]

What is the JS API for continue? All I could find was
DebugCommandProcessor.prototype.continueRequest_ in debug.js, which seems to be
only dispatched from the JSON protocol as well.

+
+      v8::Debug::SendCommand(v8_isolate_, buffer,
+                             AsciiToUtf16(command_continue, buffer));
+    }
+    futex_barriers.barrier_4.Wait();
+  }
+  debug_isolate->Dispose();
+}
+
+
+TEST(FutexDebugging) {
+  i::FLAG_harmony_sharedarraybuffer = true;
+  i::FLAG_harmony_atomics = true;
+
+  size_t size = 16;
+  v8::ArrayBuffer::Allocator* array_buffer_allocator =
+      CcTest::array_buffer_allocator();
+  void* data = array_buffer_allocator->Allocate(size);
+
+  FutexV8Thread v8_thread(data, size);
+
+  // Create a V8 environment
+  v8_thread.Start();
+  futex_barriers.barrier_3.Wait();
+  FutexDebuggerThread debugger_thread(v8_thread.isolate(), data, size);
+  debugger_thread.Start();
+
+  v8_thread.Join();
+  debugger_thread.Join();
+}