[llvm] r219638 - Removing the static destructor from ManagedStatic.cpp by controlling the allocation and de-allocation of the mutex.

[Chris Bieneman]

I’ve been having trouble reproducing this. Admittedly this is probably mostly due to my total lack of familiarity with Windows development. Any help tracking this down is greatly appreciated.

Thanks,
-Chris

> On Oct 14, 2014, at 9:30 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
> 
> On Tue, Oct 14, 2014 at 12:28 PM, Chris Bieneman <beanz at apple.com> wrote:
>> Thank you. I will also see if I can reproduce the hang.
> 
> As a data point, I am able to reproduce the hang on Windows 7 with an
> x86, MSVC-built clang by running the test suite. It is somewhere in
> the arcmt-test and c-index-test suites, judging by how many tests
> hung.
> 
> ~Aaron
> 
>> 
>> -Chris
>> 
>>> On Oct 14, 2014, at 9:11 AM, NAKAMURA Takumi <geek4civic at gmail.com> wrote:
>>> 
>>> Excuse me, I have reverted it in r219687.
>>> 
>>> It caused hangup in msc builder, probably deadlock in clang's
>>> arcmt-test and c-index-test.
>>> http://bb.pgr.jp/builders/ninja-clang-i686-msc17-R/builds/10976
>>> 
>>> I will investigate tomorrow.
>>> 
>>> 2014-10-14 7:37 GMT+09:00 Chris Bieneman <beanz at apple.com>:
>>>> Author: cbieneman
>>>> Date: Mon Oct 13 17:37:25 2014
>>>> New Revision: 219638
>>>> 
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=219638&view=rev
>>>> Log:
>>>> Removing the static destructor from ManagedStatic.cpp by controlling the allocation and de-allocation of the mutex.
>>>> 
>>>> This patch adds a new llvm_call_once function which is used by the ManagedStatic implementation to safely initialize a global to avoid static construction and destruction.
>>>> 
>>>> Modified:
>>>>   llvm/trunk/include/llvm/Support/Threading.h
>>>>   llvm/trunk/lib/Support/ManagedStatic.cpp
>>>> 
>>>> Modified: llvm/trunk/include/llvm/Support/Threading.h
>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Threading.h?rev=219638&r1=219637&r2=219638&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/include/llvm/Support/Threading.h (original)
>>>> +++ llvm/trunk/include/llvm/Support/Threading.h Mon Oct 13 17:37:25 2014
>>>> @@ -15,6 +15,10 @@
>>>> #ifndef LLVM_SUPPORT_THREADING_H
>>>> #define LLVM_SUPPORT_THREADING_H
>>>> 
>>>> +#if !defined(__MINGW__)
>>>> +#include <mutex>
>>>> +#endif
>>>> +
>>>> namespace llvm {
>>>>  /// Returns true if LLVM is compiled with support for multi-threading, and
>>>>  /// false otherwise.
>>>> @@ -33,6 +37,20 @@ namespace llvm {
>>>>  /// the thread stack.
>>>>  void llvm_execute_on_thread(void (*UserFn)(void*), void *UserData,
>>>>                              unsigned RequestedStackSize = 0);
>>>> +
>>>> +template <void (*UserFn)(void)> void llvm_call_once() {
>>>> +
>>>> +#if !defined(__MINGW__)
>>>> +  static std::once_flag flag;
>>>> +  std::call_once(flag, UserFn);
>>>> +
>>>> +#else
>>>> +  struct InitOnceWrapper {
>>>> +    InitOnceWrapper() { UserFn(); }
>>>> +  };
>>>> +  static InitOnceWrapper InitOnceVar;
>>>> +#endif
>>>> +}
>>>> }
>>>> 
>>>> #endif
>>>> 
>>>> Modified: llvm/trunk/lib/Support/ManagedStatic.cpp
>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/ManagedStatic.cpp?rev=219638&r1=219637&r2=219638&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/lib/Support/ManagedStatic.cpp (original)
>>>> +++ llvm/trunk/lib/Support/ManagedStatic.cpp Mon Oct 13 17:37:25 2014
>>>> @@ -16,16 +16,22 @@
>>>> #include "llvm/Support/Atomic.h"
>>>> #include "llvm/Support/Mutex.h"
>>>> #include "llvm/Support/MutexGuard.h"
>>>> +#include "llvm/Support/Threading.h"
>>>> #include <cassert>
>>>> using namespace llvm;
>>>> 
>>>> static const ManagedStaticBase *StaticList = nullptr;
>>>> +static sys::Mutex *ManagedStaticMutex = nullptr;
>>>> 
>>>> -static sys::Mutex& getManagedStaticMutex() {
>>>> +static void initializeMutex() {
>>>> +  ManagedStaticMutex = new sys::Mutex();
>>>> +}
>>>> +
>>>> +static sys::Mutex* getManagedStaticMutex() {
>>>>  // We need to use a function local static here, since this can get called
>>>>  // during a static constructor and we need to guarantee that it's initialized
>>>>  // correctly.
>>>> -  static sys::Mutex ManagedStaticMutex;
>>>> +  llvm_call_once<initializeMutex>();
>>>>  return ManagedStaticMutex;
>>>> }
>>>> 
>>>> @@ -33,7 +39,7 @@ void ManagedStaticBase::RegisterManagedS
>>>>                                              void (*Deleter)(void*)) const {
>>>>  assert(Creator);
>>>>  if (llvm_is_multithreaded()) {
>>>> -    MutexGuard Lock(getManagedStaticMutex());
>>>> +    MutexGuard Lock(*getManagedStaticMutex());
>>>> 
>>>>    if (!Ptr) {
>>>>      void* tmp = Creator();
>>>> @@ -83,8 +89,13 @@ void ManagedStaticBase::destroy() const
>>>> 
>>>> /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
>>>> void llvm::llvm_shutdown() {
>>>> -  MutexGuard Lock(getManagedStaticMutex());
>>>> +  {
>>>> +    MutexGuard Lock(*getManagedStaticMutex());
>>>> +
>>>> +    while (StaticList)
>>>> +      StaticList->destroy();
>>>> +  }
>>>> 
>>>> -  while (StaticList)
>>>> -    StaticList->destroy();
>>>> +  delete ManagedStaticMutex;
>>>> +  ManagedStaticMutex = nullptr;
>>>> }
>>>> 
>>>> 
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