[PATCH] D21609: [tsan] Intercept libcxx __release_shared to avoid false positive with weak_ptrs and destructors in C++

[Kuba Brecka via llvm-commits]

kubabrecka added a comment.

In http://reviews.llvm.org/D21609#465566, @dvyukov wrote:

> You are right.
>
> Then we can try:
>
>   Mutex shared_ptr_sync[kSomePrime];
>   
>   Mutex *mtx = &shared_ptr_sync[hash(o) % kSomePrime];
>   mtx.Lock();
>   Acquire(thr, pc, o);
>   Release(thr, pc, o);
>   SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_START();
>   REAL(_ZNSt3__119__shared_weak_count16__release_sharedEv)(o);
>   SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_END();
>   mtx.Unlock();
>   
>
> But I am scared by potential consequences of running user code under internal mutex...


Can we unlock before calling the user code?  It sounds to me we just need the Acquire+Release to be atomic.


http://reviews.llvm.org/D21609