On 20/07/2015 18:36, Stefan Hajnoczi wrote: >> > >> > i/o thread vcpu thread worker thread >> > --------------------------------------------------------------------- >> > lock_iothread >> > notify_me = 1 >> > ... >> > unlock_iothread >> > lock_iothread >> > notify_me = 3 >> > ppoll >> > notify_me = 1 >> > bh->scheduled = 1 >> > event_notifier_set >> > event_notifier_test_and_clear >> > ppoll >> > *** hang *** > I don't understand this diagram. Why is event_notifier_test_and_clear() > called by the vcpu thread? event_notifier_set() was called *after* vcpu > thread's ppoll() returned so I wouldn't expect the vcpu thread to see > the notify. > > Was there a previous notify pending?
Yes, for example a bottom half could have rescheduled itself. Paolo
