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

src/execution.h

 // Copyright 2014 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_EXECUTION_H_
 #define V8_EXECUTION_H_
 
 #include "src/allocation.h"
 #include "src/base/atomicops.h"
 #include "src/handles.h"
 #include "src/utils.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class JSRegExp;
 
+
+// Whether to handle a DebugBreak in a function that is not normally subject to
+// debugging (e.g. a builtin).
+enum BreakInNonDebuggableFlag {
+  DontBreakInNonDebuggable,
+  BreakInNonDebuggable,
+};
+
+
 class Execution final : public AllStatic {
  public:
   // Call a function, the caller supplies a receiver and an array
   // of arguments. Arguments are Object* type. After function returns,
   // pointers in 'args' might be invalid.
   //
   // *pending_exception tells whether the invoke resulted in
   // a pending exception.
   //
   // When convert_receiver is set, and the receiver is not an object,
@@ skipping 163 matching lines @@
   }
   Address address_of_jslimit() {
     return reinterpret_cast<Address>(&thread_local_.jslimit_);
   }
   Address address_of_real_jslimit() {
     return reinterpret_cast<Address>(&thread_local_.real_jslimit_);
   }
 
   // If the stack guard is triggered, but it is not an actual
   // stack overflow, then handle the interruption accordingly.
-  Object* HandleInterrupts();
+  Object* HandleInterrupts(
+      BreakInNonDebuggableFlag flag = DontBreakInNonDebuggable);

[Michael Starzinger, 2015/08/31 21:52:21]

Hmpf! I realize that Yang suggested this approach, but this gives me the
shivers. Now execution.h contains both debugger and futex semantics. I am not
comfortable with this approach at all and would have actually preferred your
first patch set over this.

Yang, do you still think this second patch set is cleaner?

   void HandleGCInterrupt();
 
  private:
   StackGuard();
 
   bool CheckInterrupt(InterruptFlag flag);
   void RequestInterrupt(InterruptFlag flag);
   void ClearInterrupt(InterruptFlag flag);
   bool CheckAndClearInterrupt(InterruptFlag flag);
 
@@ skipping 78 matching lines @@
   friend class Isolate;
   friend class StackLimitCheck;
   friend class PostponeInterruptsScope;
 
   DISALLOW_COPY_AND_ASSIGN(StackGuard);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_EXECUTION_H_