libstdc++/68921 add timeout argument to futex(2)

	PR libstdc++/68921
	* src/c++11/futex.cc
	(__atomic_futex_unsigned_base::_M_futex_wait_until): Use null pointer
	as timeout argument.

From-SVN: r231676

libstdc++-v3/ChangeLog

 2015-12-15  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/68921
+	* src/c++11/futex.cc
+	(__atomic_futex_unsigned_base::_M_futex_wait_until): Use null pointer
+	as timeout argument.
+
 	* include/std/functional (_Mu<_Arg, false, false>::operator()): Restore
 	accidentally-removed volatile qualifier.
 

libstdc++-v3/src/c++11/futex.cc

@@ -52,7 +52,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	// we will fall back to spin-waiting.  The only thing we could do
 	// here on errors is abort.
 	int ret __attribute__((unused));
-	ret = syscall (SYS_futex, __addr, futex_wait_op, __val);
+	ret = syscall (SYS_futex, __addr, futex_wait_op, __val, nullptr);
 	_GLIBCXX_DEBUG_ASSERT(ret == 0 || errno == EINTR || errno == EAGAIN);
 	return true;
       }