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QReadWriteLock: extract method fastTryLock

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This removes a little bit of duplication, and reduces the temptation to
remove the first part of tryLockForX as duplicated (it should remain
there for performance reasons).

Change-Id: I7ce102ceeb03b5ab4fe026b56fbba245b4c2f310
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
David Faure 2025-04-08 23:37:14 +02:00
parent 677ee0cf7c
commit 22d4f117bd
1 changed files with 16 additions and 10 deletions
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26
src/corelib/thread/qreadwritelock.cpp
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@ -164,6 +164,14 @@ void QReadWriteLock::destroyRecursive(QReadWriteLockPrivate *d)
\sa unlock(), lockForRead() \sa unlock(), lockForRead()
*/ */
static Q_ALWAYS_INLINE bool fastTryLock(QAtomicPointer<QReadWriteLockPrivate> &d_ptr,
QReadWriteLockPrivate *dummyValue,
QReadWriteLockPrivate *&d)
{
// Succeed fast if not contended
return d == nullptr && d_ptr.testAndSetAcquire(nullptr, dummyValue, d);
}
/*! /*!
\overload \overload
\since 6.6 \since 6.6
@ -183,9 +191,8 @@ void QReadWriteLock::destroyRecursive(QReadWriteLockPrivate *d)
*/ */
bool QReadWriteLock::tryLockForRead(QDeadlineTimer timeout) bool QReadWriteLock::tryLockForRead(QDeadlineTimer timeout)
{ {
// Fast case: non contended:
QReadWriteLockPrivate *d = d_ptr.loadRelaxed(); QReadWriteLockPrivate *d = d_ptr.loadRelaxed();
if (d == nullptr && d_ptr.testAndSetAcquire(nullptr, dummyLockedForRead, d)) if (fastTryLock(d_ptr, dummyLockedForRead, d))
return true; return true;
return contendedTryLockForRead(d_ptr, timeout, d); return contendedTryLockForRead(d_ptr, timeout, d);
} }
@ -195,9 +202,9 @@ Q_NEVER_INLINE static bool contendedTryLockForRead(QAtomicPointer<QReadWriteLock
{ {
while (true) { while (true) {
if (d == nullptr) { if (d == nullptr) {
if (!d_ptr.testAndSetAcquire(nullptr, dummyLockedForRead, d)) if (fastTryLock(d_ptr, dummyLockedForRead, d))
continue; return true;
return true; continue;
} }
if ((quintptr(d) & StateMask) == StateLockedForRead) { if ((quintptr(d) & StateMask) == StateLockedForRead) {
@ -301,9 +308,8 @@ Q_NEVER_INLINE static bool contendedTryLockForRead(QAtomicPointer<QReadWriteLock
*/ */
bool QReadWriteLock::tryLockForWrite(QDeadlineTimer timeout) bool QReadWriteLock::tryLockForWrite(QDeadlineTimer timeout)
{ {
// Fast case: non contended:
QReadWriteLockPrivate *d = d_ptr.loadRelaxed(); QReadWriteLockPrivate *d = d_ptr.loadRelaxed();
if (d == nullptr && d_ptr.testAndSetAcquire(nullptr, dummyLockedForWrite, d)) if (fastTryLock(d_ptr, dummyLockedForWrite, d))
return true; return true;
return contendedTryLockForWrite(d_ptr, timeout, d); return contendedTryLockForWrite(d_ptr, timeout, d);
} }
@ -313,9 +319,9 @@ Q_NEVER_INLINE static bool contendedTryLockForWrite(QAtomicPointer<QReadWriteLoc
{ {
while (true) { while (true) {
if (d == nullptr) { if (d == nullptr) {
if (!d_ptr.testAndSetAcquire(d, dummyLockedForWrite, d)) if (fastTryLock(d_ptr, dummyLockedForWrite, d))
continue; return true;
return true; continue;
} }
if (isUncontendedLocked(d)) { if (isUncontendedLocked(d)) {