Method set_next_writer

benchmarks/tbb/reader_writer_lock.cpp:161–178

}

void reader_writer_lock::set_next_writer(scoped_lock *W) {
    writer_head = W;
    if (W->status == waiting_nonblocking) {
        if (rdr_count_and_flags.compare_and_swap(WFLAG1+WFLAG2, 0) == 0) {
            W->status = active;
        }
    }
    else {
        if (fetch_and_or(rdr_count_and_flags, WFLAG1) & RFLAG) { // reader present
            spin_wait_until_and(rdr_count_and_flags, WFLAG2); // block until readers set WFLAG2
        }
        else { // no reader in timing window
            __TBB_AtomicOR(&rdr_count_and_flags, WFLAG2);
        }
        spin_wait_while_geq(rdr_count_and_flags, RC_INCR); // block until readers finish
        W->status = active;
   }
}

// Acquires the reader_writer_lock for read.    If the lock is currently held by a writer,
// this reader will block and wait until the writers are done.