Throttled tasks are invisisble to cpu-offline since they are not eligible for selection by pick_next_task(). The regular 'escape' path for a thread that is blocked at offline is via ttwu->select_task_rq, however this will not handle a throttled group since there are no individual thread wakeups on an unthrottle. Resolve this by unthrottling offline cpus so that threads can be migrated. Signed-off-by: Paul Turner Reviewed-by: Hidetoshi Seto --- kernel/sched.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) Index: tip/kernel/sched.c =================================================================== --- tip.orig/kernel/sched.c +++ tip/kernel/sched.c @@ -6269,6 +6269,30 @@ static void calc_global_load_remove(stru rq->calc_load_active = 0; } +#ifdef CONFIG_CFS_BANDWIDTH +static void unthrottle_offline_cfs_rqs(struct rq *rq) +{ + struct cfs_rq *cfs_rq; + + for_each_leaf_cfs_rq(rq, cfs_rq) { + struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); + + if (!cfs_rq->runtime_enabled) + continue; + + /* + * clock_task is not advancing so we just need to make sure + * there's some valid quota amount + */ + cfs_rq->runtime_remaining = cfs_b->quota; + if (cfs_rq_throttled(cfs_rq)) + unthrottle_cfs_rq(cfs_rq); + } +} +#else +static void unthrottle_offline_cfs_rqs(struct rq *rq) {} +#endif + /* * Migrate all tasks from the rq, sleeping tasks will be migrated by * try_to_wake_up()->select_task_rq(). @@ -6294,6 +6318,9 @@ static void migrate_tasks(unsigned int d */ rq->stop = NULL; + /* Ensure any throttled groups are reachable by pick_next_task */ + unthrottle_offline_cfs_rqs(rq); + for ( ; ; ) { /* * There's this thread running, bail when that's the only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/