On Fri, Mar 15, 2013 at 12:46 PM, Sebastian Huber < sebastian.hu...@embedded-brains.de> wrote:
> Hello, > > I want to port the FreeBSD kqueue implementation to another operating > system (RTEMS in this case) to improve the Erlang support. > > I have difficulties to understand the purpose of the kqueue_task. This > function runs asynchronously. It obtains some locks and wakes up the > normal kqueue channel if (kq->kq_state & KQ_TASKDRAIN) == KQ_TASKDRAIN. > This state is only set in kqueue_close(). So most of the time the > kqueue_task only obtains some locks, clears a flag (KQ_TASKSCHED) and > releases the locks? > You missed the most important thing that it does: it calls KNOTE_LOCKED to wake up any waiters sleeping on this event. I suspect that it had to be done in a separate task due to lock ordering problems with the kq_global lock. The call to wakeup() is used to synchronize with kqueue_close to ensure that kqueue_close will not free the kqueue while the task is pending. Otherwise the task could run after kq was freed and crash the system. _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
