Messages in this thread Patch in this message | | | Date | Tue, 03 May 2011 02:28:58 -0700 | From | Paul Turner <> | Subject | [patch 12/15] sched: migrate throttled tasks on HOTPLUG |
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Throttled tasks are invisible 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 <pjt@google.com> --- kernel/sched.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)
Index: tip/kernel/sched.c =================================================================== --- tip.orig/kernel/sched.c +++ tip/kernel/sched.c @@ -6145,6 +6145,32 @@ 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(). @@ -6170,6 +6196,9 @@ 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
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