On Thu, 2012-03-08 at 16:08 -0500, Steven Rostedt wrote: > Hmm, perhaps we need a way to attach a priority to a lock. Maybe we just > need a way to set a priority of a lock with.. "A task of priority X > needs the lock, set the owner to at least X while it holds the lock", > where it doesn't care about the high priority task, it just cares about > the lock. That is, give locks a priority too (like priority ceiling). On > doing spin_trylock_rt() (no need for deadlock detection) if it fails, > gives a lock the priority of the task trying to take it. The lock will > be given a temporary priority for the duration it is held. The owner of > the lock will get that priority unless its already higher in priority. > When the lock is released, both the owner and the lock lose the > priority. > > Note, spin_trylock_rt() continues to run even on failure. > > Have cpu_chill() do a "sched_yield()" (the good kind, to put the current > FIFO task behind another FIFO task of the same priority). Then the owner > of the lock will get to run. > > The sched_yield in cpu_chill() would be needed if the owner of the lock > is blocked on the lock the high priority task has. After the high > priority task releases its lock, and calls cpu_chill(), the > sched_yield() allows the owner of the lock to run if it happens to be > blocked on the lock the high prio task held. As the cpu_chill() will be > called after that lock is released. Now put the thing on 2 cpus and both tasks can endlessly chase each other's tail, no? The yield will be useless there.. -- 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
