Question

我在std::mutex锁定互斥锁时遇到DllMain()的死锁。下面是一个针对我的问题的最小DLL测试用例。我的实际代码执行互斥锁定，因为它使用的成员函数在正常函数期间也可以在初始化之外使用。

我认为问题是调度程序之间的死锁，如main()线程的调用堆栈和调度程序生成的另一个线程（可能）。在main()实际执行之前，似乎发生了死锁。

对于如何修复/解决死锁，我将不胜感激。

简单的DLL：

static void testFunc()
{
    std::mutex mtx;
    mtx.lock();

    mtx.unlock();
}


BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    switch (ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
        testFunc ();
        break;

    case DLL_THREAD_ATTACH:
        testFunc ();
        break;

    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

在死锁时，进程中有两个线程：

Not Flagged >   6408    0   Main Thread Main Thread msvcr110d.dll!Concurrency::details::SchedulerBase::SchedulerBase    Normal
Not Flagged     7600    0   Worker Thread   ntdll.dll!_TppWaiterpThread@4() ntdll.dll!_NtDelayExecution@8   Normal

这是main()线程的调用堆栈：

    ntdll.dll!_NtWaitForKeyedEvent@16() Unknown
    ntdll.dll!_TppWaitpSet@16() Unknown
    ntdll.dll!_TppSetWaitInterrupt@12() Unknown
    ntdll.dll!_RtlRegisterWait@24() Unknown
    kernel32.dll!_RegisterWaitForSingleObject@24()  Unknown
>   msvcr110d.dll!Concurrency::details::SchedulerBase::SchedulerBase(const Concurrency::SchedulerPolicy & policy) Line 152  C++
    msvcr110d.dll!Concurrency::details::ThreadScheduler::ThreadScheduler(const Concurrency::SchedulerPolicy & policy) Line 26   C++
    msvcr110d.dll!Concurrency::details::ThreadScheduler::Create(const Concurrency::SchedulerPolicy & policy) Line 34    C++
    msvcr110d.dll!Concurrency::details::SchedulerBase::CreateWithoutInitializing(const Concurrency::SchedulerPolicy & policy) Line 276  C++
    msvcr110d.dll!Concurrency::details::SchedulerBase::GetDefaultScheduler() Line 650   C++
    msvcr110d.dll!Concurrency::details::SchedulerBase::CreateContextFromDefaultScheduler() Line 567 C++
    msvcr110d.dll!Concurrency::details::SchedulerBase::CurrentContext() Line 399    C++
    msvcr110d.dll!Concurrency::details::LockQueueNode::LockQueueNode(unsigned int timeout) Line 616 C++
    msvcr110d.dll!Concurrency::critical_section::lock() Line 1017   C++
    msvcp110d.dll!mtx_do_lock(_Mtx_internal_imp_t * * mtx, const xtime * target) Line 65    C++
    msvcp110d.dll!_Mtx_lock(_Mtx_internal_imp_t * * mtx) Line 144   C++
    ConsoleApplicationDll.dll!std::_Mtx_lockX(_Mtx_internal_imp_t * * _Mtx) Line 68 C++
    ConsoleApplicationDll.dll!std::_Mutex_base::lock() Line 43  C++
    ConsoleApplicationDll.dll!testFunc() Line 16    C++
    ConsoleApplicationDll.dll!DllMain(HINSTANCE__ * hModule, unsigned long ul_reason_for_call, void * lpReserved) Line 29   C++
    ConsoleApplicationDll.dll!__DllMainCRTStartup(void * hDllHandle, unsigned long dwReason, void * lpreserved) Line 508    C
    ConsoleApplicationDll.dll!_DllMainCRTStartup(void * hDllHandle, unsigned long dwReason, void * lpreserved) Line 472 C
    ntdll.dll!_LdrpCallInitRoutine@16() Unknown
    ntdll.dll!_LdrpRunInitializeRoutines@4()    Unknown
    ntdll.dll!_LdrpInitializeProcess@8()    Unknown
    ntdll.dll!__LdrpInitialize@8()  Unknown
    ntdll.dll!_LdrInitializeThunk@8()   Unknown

第二个线程的调用堆栈很短：

>   ntdll.dll!_NtDelayExecution@8() Unknown
    ntdll.dll!__LdrpInitialize@8()  Unknown
    ntdll.dll!_LdrInitializeThunk@8()   Unknown

编辑1：

WinDbg确认它是加载程序锁定问题：

PRIMARY_PROBLEM_CLASS:  APPLICATION_HANG_HungIn_LoaderLock

Answer 1

检查Best Practices for Creating DLLs文档：

您永远不应该在DllMain中执行以下任务：


直接或间接调用LoadLibrary或LoadLibraryEx。这可能会导致死锁或崩溃。

与其他线程同步。这可能会导致死锁。

Answer 2

似乎使用QueueUserAPC()进行队列初始化总是在main（）之前执行，但是在可怕的加载程序锁之外执行。这看起来像是我问题的解决方案。

编辑1

经过一些测试后，如果我从DllMain()排队APC，APC方法似乎有效，但如果我从一个类的静态全局实例的ctor排队APC，它就不起作用。 IOW，对于我来说，使用APC并不能在编译器和构建模式的所有可能组合中统一使用。

从DllMain（）锁定时，Visual Studio 2012中的C ++ 11 std :: mutex死锁

2 个答案: