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QObject: fix memory order on load/store of signal spy callback set

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QSignalSpyCallbackSet is a set of pointers, so when we store a pointer
to it for later dereferencing, we need to use a release fence for the
store and a corresponding acquire on load, lest the two don't
synchronize with each other and we end up with a data race.

Amends a65752c71bd25bbb66bf33d3a82f7901419c5d95.

Change-Id: Ic2983d76237c5c5b00eb2a3575b10beb84d57190
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
This commit is contained in:
Marc Mutz 2019-06-20 02:13:12 +02:00
parent 08103d3a52
commit 322ac72945
1 changed files with 2 additions and 2 deletions
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4
src/corelib/kernel/qobject.cpp
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@ -82,7 +82,7 @@ Q_CORE_EXPORT QBasicAtomicPointer<QSignalSpyCallbackSet> qt_signal_spy_callback_
void qt_register_signal_spy_callbacks(QSignalSpyCallbackSet *callback_set) void qt_register_signal_spy_callbacks(QSignalSpyCallbackSet *callback_set)
{ {
qt_signal_spy_callback_set.store(callback_set); qt_signal_spy_callback_set.storeRelease(callback_set);
} }
QDynamicMetaObjectData::~QDynamicMetaObjectData() QDynamicMetaObjectData::~QDynamicMetaObjectData()
@ -3696,7 +3696,7 @@ void doActivate(QObject *sender, int signal_index, void **argv)
signal_index, argv); signal_index, argv);
} }
const QSignalSpyCallbackSet *signal_spy_set = callbacks_enabled ? qt_signal_spy_callback_set.load() : nullptr; const QSignalSpyCallbackSet *signal_spy_set = callbacks_enabled ? qt_signal_spy_callback_set.loadAcquire() : nullptr;
void *empty_argv[] = { nullptr }; void *empty_argv[] = { nullptr };
if (!argv) if (!argv)