From 68f220c93b3e831a3f9b8cee0df6bd2ec69f7a11 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Fri, 13 May 2022 18:21:01 +0200
Subject: [PATCH] QReadWriteLock: fix data race in stateForWaitCondition()

The function dereferences the load()ed pointer, so it needs an acquire
fence.

Pick-to: 6.3 6.2 5.15
Change-Id: Ib951de3f00851d915fec3392cdaba64f4a994300
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/thread/qreadwritelock.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/corelib/thread/qreadwritelock.cpp b/src/corelib/thread/qreadwritelock.cpp
index d5602974a6..c60580b9f3 100644
--- a/src/corelib/thread/qreadwritelock.cpp
+++ b/src/corelib/thread/qreadwritelock.cpp
@@ -414,7 +414,7 @@ void QReadWriteLock::unlock()
 /*! \internal  Helper for QWaitCondition::wait */
 QReadWriteLock::StateForWaitCondition QReadWriteLock::stateForWaitCondition() const
 {
-    QReadWriteLockPrivate *d = d_ptr.loadRelaxed();
+    QReadWriteLockPrivate *d = d_ptr.loadAcquire();
     switch (quintptr(d) & StateMask) {
     case StateLockedForRead: return LockedForRead;
     case StateLockedForWrite: return LockedForWrite;