On Fri, 9 Jul 2010, Darren Hart wrote: > The requeue_pi mechanism introduced proxy locking of the rtmutex. This creates > a scenario where a task can wake-up, not knowing it has been enqueued on an > rtmutex. In order to detect this, the task would have to be able to take either > task->pi_blocked_on->lock->wait_lock and/or the hb->lock. Unfortunately, > without already holding one of these, the pi_blocked_on variable can change > from NULL to valid or from valid to NULL. Therefor, the task cannot be allowed > to take a sleeping lock after wakeup or it could end up trying to block on two > locks, the second overwriting a valid pi_blocked_on value. This obviously > breaks the pi mechanism. > > This patch increases latency, while running the ltp pthread_cond_many test > which Michal reported the bug with, I see double digit hrtimer latencies > (typically only on the first run after boo): > > kernel: hrtimer: interrupt took 75911 ns Eewwww. There must be some more intelligent and less intrusive way to detect this. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
