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Details

Type: Bug
Resolution: Done
Priority: P3: Somewhat important
Fix Version/s: 5.4.0, 5.15.0 Beta2
Affects Version/s: 5.3.0
Component/s: Core: Plugins
Labels:
None

Commits:
ae6f73e8566fa76470937aca737141183929a5ec (qt/qtbase/5.14.2)

Description

QLibraryStore::findOrCreate is mutex-protected, but the caller (QPluginLoader::setFileName) then calls d->loadHints = lh and other setters on "d", which race with other theads, if the same plugin is loaded from multiple threads.

==14794== 
==14794== Possible data race during write of size 4 at 0xF5EAAC0 by thread #21
==14794== Locks held: none
==14794==    at 0x6633F78: QPluginLoader::setFileName(QString const&) (qpluginloader.cpp:356)
==14794==    by 0x6633230: QPluginLoader::QPluginLoader(QString const&, QObject*) (qpluginloader.cpp:158)
==14794==    by 0x5EBEBE7: KPluginLoader::findPlugin(QString const&) (kpluginloader.cpp:59)
==14794==    by 0x4ED91DB: KIO::Slave::createSlave(QString const&, QUrl const&, int&, QString&) (slave.cpp:461)
==14794== 
==14794== This conflicts with a previous write of size 4 by thread #12
==14794== Locks held: none
==14794==    at 0x6633F78: QPluginLoader::setFileName(QString const&) (qpluginloader.cpp:356)
==14794==    by 0x6633230: QPluginLoader::QPluginLoader(QString const&, QObject*) (qpluginloader.cpp:158)
==14794==    by 0x5EBEBE7: KPluginLoader::findPlugin(QString const&) (kpluginloader.cpp:59)
==14794==    by 0x4ED91DB: KIO::Slave::createSlave(QString const&, QUrl const&, int&, QString&) (slave.cpp:461)

Should the QLibraryStore be turned into a QThreadStorage, i.e. one store per thread?