On 01/27, Tycho Andersen wrote: > > It seems like (and the current pidfd_test enforces for some cases) Which pidfd_test ? > we > want exactly one notification for a task dying. This can't be right. EVERY user of poll_wait() or wait_event/etc must handle/tolerate the false wakeups. > I don't understand > how we guarantee this now, with all of these calls. I don't understand why do we need or even want to guarantee this. The extra wakeup must be always fine correctness-wise. Sure, it would be nice to avoid the unnecessary wakeups, and perhaps we can change wake_up_all() to pass a key to, say, only wake_up the PIDFD_THREAD waiters from exit_notify(). But certainly this is outside the scope of PIDFD_THREAD change we discuss. The changes in do_notify_parent() (I have already sent the patch) and in exit_notify() (proposed in my previous email) just ensure that, with the minimal changes, we avoid 2 do_notify_pidfd's from the same exit_notify() path. > > exit_notify() is called after exit_files(). pidfd_getfd() returns > > ESRCH if the exiting thread completes release_task(), otherwise it > > returns EBADF because ->files == NULL. This too doesn't really > > depend on PIDFD_THREAD. > > Yup, understood. It just seems like an inconsistency we might want to > fix. Not sure this worth "fixing"... Oleg.
