CODEWITHSUNDEEP
cmultithreadingwinapic++17thread-synchronization
Irbis
Irbis

Reputation: 1511

Win Api - SetEvent and WaitForSingleObject, memory synchronization betweent threads

I debug a complex application which crashes and I suspect that a memory between threads is not synchronized correctly. Here is a simplified example which demonstrates a potential problem:

DWORD WINAPI ThreadFun(LPVOID lpParam)
{
    T* t = (T*)lpParam;

    WaitForSingleObject(t->startProcessing, INFINITE);

    //fill buffer with some data
    for (int i = 0; i < bufSize; ++i)
    {
        t->buf[i] = i;
    }

    return 0;
}

//Main thread
void T::Process(int* p)
{
    buf = p;
    SetEvent(startProcessing);
}

There is a logic time relation - buf is set before calling SetEvent but does it guarentee that a memory will be synchronized between threads ? Should I use win api mutexes ?

Upvotes: 2

Views: 214

Answers (1)

Anthony Williams
Anthony Williams

Reputation: 68691

SetEvent and WaitForSingleObject do provide the guarantee that writes before the SetEvent are visible after WaitForSingleObject returns. There is no need to provide anything else here.

Upvotes: 4

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