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Description: QReadWriteLock: fix data race on the d_ptr members
The loadRelaxed() at the beginning of tryLockForRead/tryLockForWrite
isn't enough to bring us the non-atomic write of the recursive bool.
Same issue with the std::mutex itself.
Origin: upstream, https://code.qt.io/cgit/qt/qtbase.git/commit?id=80d01c4ccb697b9d
Last-Update: 2025-12-14
--- a/src/corelib/thread/qreadwritelock.cpp
+++ b/src/corelib/thread/qreadwritelock.cpp
@@ -258,7 +258,10 @@ bool QReadWriteLock::tryLockForRead(int
d = val;
}
Q_ASSERT(!isUncontendedLocked(d));
- // d is an actual pointer;
+ // d is an actual pointer; acquire its contents
+ d = d_ptr.loadAcquire();
+ if (!d || isUncontendedLocked(d))
+ continue;
if (d->recursive)
return d->recursiveLockForRead(timeout);
@@ -365,7 +368,10 @@ bool QReadWriteLock::tryLockForWrite(int
d = val;
}
Q_ASSERT(!isUncontendedLocked(d));
- // d is an actual pointer;
+ // d is an actual pointer; acquire its contents
+ d = d_ptr.loadAcquire();
+ if (!d || isUncontendedLocked(d))
+ continue;
if (d->recursive)
return d->recursiveLockForWrite(timeout);
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