From: Kirill Tkhai Date: Wed, 25 Jun 2014 08:19:42 +0000 (+0400) Subject: sched/fair: Disable runtime_enabled on dying rq X-Git-Tag: omap-for-v3.17/fixes-against-rc2~177^2~15 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0e59bdaea75f12a7d7c03672f4ac22c0119a1bc0;p=pandora-kernel.git sched/fair: Disable runtime_enabled on dying rq 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 prevent races with unthrottle_offline_cfs_rqs() we take get_online_cpus() lock. Reviewed-by: Ben Segall Reviewed-by: Srikar Dronamraju Signed-off-by: Kirill Tkhai CC: Konstantin Khorenko CC: Paul Turner CC: Mike Galbraith Cc: Linus Torvalds Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1403684382.3462.42.camel@tkhai Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed