From e7f685002bb0facb222ac13c21ff4a2257ab76cc Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Mon, 24 Feb 2014 15:23:39 -0800
Subject: Atomics: implement fetchAndSub on top of fetchAndAdd

Instead of looping unnecessarily on top of testAndSet.

Task-number: QTBUG-37031
Change-Id: I8120f8405eb76dccc9066749cee0a92b0f2da20e
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Sergio Ahumada <sahumada@blackberry.com>
---
 src/corelib/thread/qgenericatomic.h | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/corelib/thread/qgenericatomic.h b/src/corelib/thread/qgenericatomic.h
index 0c66d45855..aeed199c97 100644
--- a/src/corelib/thread/qgenericatomic.h
+++ b/src/corelib/thread/qgenericatomic.h
@@ -264,12 +264,8 @@ template <typename BaseClass> struct QGenericAtomicOps
     template <typename T> static inline always_inline
     T fetchAndSubRelaxed(T &_q_value, typename QAtomicAdditiveType<T>::AdditiveT operand) Q_DECL_NOTHROW
     {
-        // implement fetchAndSub on top of testAndSet
-        Q_FOREVER {
-            T tmp = BaseClass::load(_q_value);
-            if (BaseClass::testAndSetRelaxed(_q_value, tmp, T(tmp - operand)))
-                return tmp;
-        }
+        // implement fetchAndSub on top of fetchAndAdd
+        return fetchAndAddRelaxed(_q_value, -operand);
     }
 
     template <typename T> static inline always_inline
-- 
cgit v1.2.3