Hello, Peter. On Thu, May 04, 2017 at 03:31:22PM +0200, Peter Zijlstra wrote: > Yes we can hit an (almost) dead cfs_rq, but poking the bandwidth > variables thereof is harmless. > > unthrottle_cfs_rq() also stops doing anything much when it finds the > cfs_rq is empty, which must be the case if we're removing it.
Yeah, if you're okay with calling the functions on dead cfs_rq's, just wrapping with rcu_read_lock should be enough. > I don't know Paul's opinion on RCU GPs happening while stop_machine(), > but just in case he feels that's fair game, I did add the > rcu_read_lock() thingies. > > The lockdep assert is mostly documentation, to more easily see > it is indeed held when we get there. > > I left print_cfs_stats using the leaf list, no point in printing stuff > that's empty. > > This way we can avoid taking all RQ locks on cgroup destruction. Looks good to me. Thanks. -- tejun
