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QSemaphore: move suspect increment of waiter count

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We might return false a few lines down, without decreasing the count.

Change-Id: I0a90c07f279860987e41539e9d5f3b5d2cb15207
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Mårten Nordheim 2021-03-25 13:58:00 +01:00
parent c87847db87
commit 9211d04730
1 changed files with 3 additions and 3 deletions
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6
src/corelib/thread/qsemaphore.cpp
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@ -246,13 +246,13 @@ template <bool IsTimed> bool futexSemaphoreTryAcquire(QBasicAtomicInteger<quintp
// we need to wait // we need to wait
quintptr oneWaiter = quintptr(Q_UINT64_C(1) << 32); // zero on 32-bit quintptr oneWaiter = quintptr(Q_UINT64_C(1) << 32); // zero on 32-bit
if (futexHasWaiterCount) { if (futexHasWaiterCount) {
// increase the waiter count
u.fetchAndAddRelaxed(oneWaiter);
// We don't use the fetched value from above so futexWait() fails if // We don't use the fetched value from above so futexWait() fails if
// it changed after the testAndSetOrdered above. // it changed after the testAndSetOrdered above.
if ((quint64(curValue) >> 32) == 0x7fffffff) if ((quint64(curValue) >> 32) == 0x7fffffff)
return false; // overflow! return false; // overflow!
// increase the waiter count
u.fetchAndAddRelaxed(oneWaiter);
curValue += oneWaiter; curValue += oneWaiter;
// Also adjust nn to subtract oneWaiter when we succeed in acquiring. // Also adjust nn to subtract oneWaiter when we succeed in acquiring.