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

src/execution.cc

Index: src/execution.cc
diff --git a/src/execution.cc b/src/execution.cc
index d2dd41a12c6598ca170d80da314267382780e86e..b21bd8f82f81bb1811dba1526dfde0b2a47030d7 100644
--- a/src/execution.cc
+++ b/src/execution.cc
@@ -413,6 +413,11 @@ void StackGuard::RequestInterrupt(InterruptFlag flag) {
   // Not intercepted.  Set as active interrupt flag.
   thread_local_.interrupt_flags_ |= flag;
   set_interrupt_limits(access);
+
+  // If this isolate is waiting in a futex, notify it to wake up.
+  if (isolate_->futex_wait_list_node()->waiting()) {

[Jarin, 2015/08/19 05:26:05]

Could we perhaps pull the waiting() check into NotifyWake?

Then the waiting accessors could be private (and perhaps we could even pull the
waiting_ flag into the critical section and make it non-atomic).

[binji, 2015/08/19 17:36:23]

My thought here was to do a quick check to avoid taking a lock if there is no
futex waiting (which is the common case). What do you think?

+    isolate_->futex_wait_list_node()->NotifyWake();
+  }
 }