https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83638
--- Comment #2 from mikulas at artax dot karlin.mff.cuni.cz --- >From performance point of view it doesn't matter if the lock is taken inside the kernel or inside the gcc library. If the userspace wants to optimize different code paths for lockless atomics and for locked atomics, atomic_is_lock_free should return false, to indicate that the atomic operation is as costly as taking a lock.
