Llvm thread sanitizer and qmutex



  • Hallo,

    we make heavy use of Qt in our software and are now trying to use llvm thread sanitizer for debugging. Unfortunately the sanitizer doesn't seem to recognize QMutex as a locking mechanism.
    The example below warns about a race condition because the member "data" is accessed in two threads. If you use a boost::mutex instead, the warning disappears. If "data" is a global variable, the false warning is not shown also.

    What are the differences between the two mutex variants? Shouldn't both use pthread_mutex internally on a linux system? Are there any experiences in debugging Qt programs with llvm thread sanitizer?

    Thanks in advance,
    Benjamin

    @#include <QtConcurrentRun>
    #include <QMutex>
    #include <iostream>
    #include <boost/thread/mutex.hpp>

    //int data;

    class TestClass
    {
    public:
    void fun()
    {
    QMutexLocker autoMutex(&mutex);
    //boost::mutex::scoped_lock bautoMutex(bmutex);
    data = 1;
    }
    private:
    int data;
    QMutex mutex;
    boost::mutex bmutex;
    };

    int main()
    {
    TestClass *tc = new TestClass;

    QFuture<void> t1 = QtConcurrent::run(tc, &TestClass::fun);
    QFuture<void> t2 = QtConcurrent::run(tc, &TestClass::fun);

    t1.waitForFinished();
    t2.waitForFinished();

    return 0;
    }@


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    I would advise to bring this topic on the interest mailing list. You'll find there Qt's developers/maintainers (this forum is more user oriented)



  • Thanks for this tip. My question was answered on the interest mailing list:
    http://lists.qt-project.org/pipermail/interest/2014-March/011479.html


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