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

src/futex-emulation.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_FUTEX_EMULATION_H_
 #define V8_FUTEX_EMULATION_H_
 
 #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"
 #include "src/base/platform/mutex.h"
 #include "src/handles.h"
 
 // Support for emulating futexes, a low-level synchronization primitive. They
 // are natively supported by Linux, but must be emulated for other platforms.
 // This library emulates them on all platforms using mutexes and condition
 // variables for consistency.
@@ skipping 11 matching lines @@
 
 class Isolate;
 
 class FutexWaitListNode {
  public:
   FutexWaitListNode()
       : prev_(nullptr),
         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;
   friend class FutexWaitList;
 
   base::ConditionVariable cond_;
   FutexWaitListNode* prev_;
   FutexWaitListNode* next_;
   void* backing_store_;
   size_t wait_addr_;
-  bool waiting_;
+  base::Atomic32 waiting_;
+  base::Atomic32 interrupted_;
 
   DISALLOW_COPY_AND_ASSIGN(FutexWaitListNode);
 };
 
 
 class FutexWaitList {
  public:
   FutexWaitList();
 
   void AddNode(FutexWaitListNode* node);
@@ skipping 43 matching lines @@
                                int num_waiters_to_wake, int32_t value,
                                size_t addr2);
 
   // Return the number of threads waiting on |addr|. Should only be used for
   // testing.
   static Object* NumWaitersForTesting(Isolate* isolate,
                                       Handle<JSArrayBuffer> array_buffer,
                                       size_t addr);
 
  private:
+  friend class FutexWaitListNode;
+
   static base::LazyMutex mutex_;
   static base::LazyInstance<FutexWaitList>::type wait_list_;
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_FUTEX_EMULATION_H_