why __thread thread_id()

[James Peach]

Hi Yunkai,

I'm looking at the reclaimable freelist code, and this jumped out at me:

        static inline pthread_t thread_id(void)
        {
          static __thread pthread_t tid;

          return tid?tid:(tid = pthread_self());
        }

Why does this need to cache the thread ID in thread local storage?

J