[libc++][shared_mutex] Do we have plan to favor readers over writers?

[Jolyon0202]

libc++'s shared_mutex favor writers over readers, but libstdc++'s shared_mutex favor readers over writers defaultly.

libstdc++‘s shared_mutex use ptread_rwlock_t(PTHREAD_RWLOCK_PREFER_READER_NP defaultly), and it also support to favor writers over readers.

Official C++ Standard doesn't specify the std::shared_mutex policy. Explanation could be found in original N2406 proposal (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2406.html#shared_mutex_imp) in shared_mutex.

Do we have plan to favor readers over writers in shared_mutex?

[Jolyon0202]

ping