While researching a bug I came across something that might be a bug in the pa_once logic, but this stuff is tricky, so I might also be missing something. Imagine this: * Thread 1 runs pa_once_begin, succeeds and starts running the payload (i e the code that should only run once). * Thread 2 starts running pa_once_begin, but only the first row. We're now right *before* pa_atomic_inc(&control->ref) but *after* pa_atomic_load(&control->done). * Thread 1 finishes the payload, runs pa_once_done which sets control->done and frees the mutex. * Thread 2 continues, pa_once_begin succeeds and the payload is now run a second time! -- David Henningsson, Canonical Ltd. http://launchpad.net/~diwic
