Unprotected multithreaded access to a variable

[wixbot]

In core.cpp, CoreApply gives the address of the cOverallProgressTicks variable to the cache thread and then uses itself when it goes to execute. The cache and execute methods go on to use it as if they weren't sharing it with each other. This could result in reporting the wrong progress.

if (pEngineState->plan.cCacheActions)
{
    // Launch the cache thread.
    cacheThreadContext.pEngineState = pEngineState;
    cacheThreadContext.pcOverallProgressTicks = &cOverallProgressTicks;
    cacheThreadContext.pfRollback = &fRollback;

    hCacheThread = ::CreateThread(NULL, 0, CacheThreadProc, &cacheThreadContext, 0, NULL);

    ...
}

// Execute.
if (pEngineState->plan.cExecuteActions)
{
    hr = ApplyExecute(pEngineState, hCacheThread, &cOverallProgressTicks, &fKeepRegistration, &fRollback, &fSuspend, &restart);
    UserExperienceExecutePhaseComplete(&pEngineState->userExperience, hr); // signal that execute completed.
}

Originally opened by rseanhall