Signal a blocked futex if the isolate is interrupted; don't busy-wait

src/futex-emulation.h

Index: src/futex-emulation.h
diff --git a/src/futex-emulation.h b/src/futex-emulation.h
index 2a07f332d56fc472d3c7fef2028573780ba3bef9..7d93df57b755f24322999f283ceca3da431e1103 100644
--- a/src/futex-emulation.h
+++ b/src/futex-emulation.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include "src/allocation.h"
+#include "src/base/atomicops.h"
 #include "src/base/lazy-instance.h"
 #include "src/base/macros.h"
 #include "src/base/platform/condition-variable.h"
@@ -39,7 +40,25 @@ class FutexWaitListNode {
         next_(nullptr),
         backing_store_(nullptr),
         wait_addr_(0),
-        waiting_(false) {}
+        waiting_(false),
+        interrupted_(false) {}
+
+  bool waiting() { return base::NoBarrier_Load(&waiting_) != 0; }
+  bool interrupted() { return base::NoBarrier_Load(&interrupted_) != 0; }
+
+  void set_waiting(bool value) {
+    base::NoBarrier_Store(&waiting_, value ? 1 : 0);
+  }
+
+  void set_interrupted(bool value) {
+    base::NoBarrier_Store(&interrupted_, value ? 1 : 0);
+  }
+
+  bool CheckInterruptedAndClear() {
+    return base::NoBarrier_CompareAndSwap(&interrupted_, 1, 0) == 1;
+  }
+
+  void NotifyWake();
 
  private:
   friend class FutexEmulation;
@@ -50,7 +69,8 @@ class FutexWaitListNode {
   FutexWaitListNode* next_;
   void* backing_store_;
   size_t wait_addr_;
-  bool waiting_;
+  base::Atomic32 waiting_;
+  base::Atomic32 interrupted_;
 
   DISALLOW_COPY_AND_ASSIGN(FutexWaitListNode);
 };
@@ -114,6 +134,8 @@ class FutexEmulation : public AllStatic {
                                       size_t addr);
 
  private:
+  friend class FutexWaitListNode;
+
   static base::LazyMutex mutex_;
   static base::LazyInstance<FutexWaitList>::type wait_list_;
 };