* Kirill Tkhai <[email protected]> [2014-06-24 11:53:52]: > We kill rq->rd on the CPU_DOWN_PREPARE stage: > > cpuset_cpu_inactive -> cpuset_update_active_cpus -> > partition_sched_domains -> > -> cpu_attach_domain -> rq_attach_root -> set_rq_offline > > This unthrottles all throttled cfs_rqs. > > But the cpu is still able to call schedule() till > > take_cpu_down->__cpu_disable() > > is called from stop_machine. > > This case the tasks from just unthrottled cfs_rqs are pickable > in a standard scheduler way, and they are picked by dying cpu. > The cfs_rqs becomes throttled again, and migrate_tasks() > in migration_call skips their tasks (one more unthrottle > in migrate_tasks()->CPU_DYING does not happen, because rq->rd > is already NULL). > > Patch sets runtime_enabled to zero. This guarantees, the runtime > is not accounted, and the cfs_rqs won't exceed given > cfs_rq->runtime_remaining = 1, and tasks will be pickable > in migrate_tasks(). runtime_enabled is recalculated again > when rq becomes online again. > > Ben Segall also noticed, we always enable runtime in > tg_set_cfs_bandwidth(). Actually, we should do that for online > cpus only. To fix that, we check if a cpu is online when > its rq is locked. This guarantees we do not have races with > set_rq_offline(), which also requires rq->lock. > > v2: Fix race with tg_set_cfs_bandwidth(). > Move cfs_rq->runtime_enabled=0 above unthrottle_cfs_rq(). > > Signed-off-by: Kirill Tkhai <[email protected]> > CC: Konstantin Khorenko <[email protected]> > CC: Ben Segall <[email protected]> > CC: Paul Turner <[email protected]> > CC: Srikar Dronamraju <[email protected]> > CC: Mike Galbraith <[email protected]> > CC: Peter Zijlstra <[email protected]> > CC: Ingo Molnar <[email protected]>
looks good to me. Reviewed-by: Srikar Dronamraju <[email protected]> -- Thanks and Regards Srikar Dronamraju -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
