Summary: Fix race condition in std::atomic_store for std::shared_ptr.

[halyavin]

Summary

The function __libcpp_mutex_trylock returns true/false instead of integer
like pthread_mutex_trylock.

[halyavin]

ping

[EricWF]

Wow that's my bad. I thought I fixed up all callers of __libcpp_mutex_trylock. However it's shocking we didn't have a test that uncovered this. Do you think you can write a test for this?

[halyavin]

Unfortunately, I can't write deterministic test.

[halyavin]

Thank you. Could you commit this patch for me?

[EricWF]

Committed in r302129.

src/memory.cpp

 {
 }
 
 void
 __sp_mut::lock() _NOEXCEPT
 {
     auto m = static_cast<__libcpp_mutex_t*>(__lx);
     unsigned count = 0;
-    while (__libcpp_mutex_trylock(m) != 0)
+    while (!__libcpp_mutex_trylock(m))
     {
         if (++count > 16)
         {
             __libcpp_mutex_lock(m);
             break;
         }
         this_thread::yield();
     }